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ABSTRACT

THE RECYCLING OF PLASTIC WASTES
IN PACKAGING

BY

Yugo Suzuki

The technology of plastic waste disposal has been
researched and developed to overcome the nuisance disposal
problem, and many results have already appeared on the
market. There are several chemical approaches: stabilized
plastics for recycling, blends of different sorts of plas-
tics, and bio- or chemically degradable plastics.

Engineering methods are reviewed briefly to compare
with these chemical approaches.

Landfill has played a great role in disposal because
of its cost advantage. However, facing a land shortage,
incinceration and pyrolysis will come to be much appreci-
ated and they are now being employed to dispose of a lot
of wastes including plastics.

-After the oil crisis in 1973, prices of petroleum
products increased at an incredibly high rate, and so
reclamation has been reconsidered both from the economical

and environmental points of view.

Yugo Suzuki

It is likely that we need a long time before we
will establish a valuable technology of polymer blending.
A successful example of high density polyethelene milk
bottle recycling gives us only a small market and a small
profit even now. However, it will be a great aid for a
petroleum-inclined economy to develop reclamation and blend;
technologies.

For a new technology to be adopted in a community
and economic market, economics are very important. The
total cost estimation and the prediction of disposal meth-
ods in future indicate to us very interesting solutions.
The pyrolysis for the collected refuse and the biodegrad-
able plastic developed for non-collected refuse will give

us an outstanding result without high costs or pollution.

THE RECYCLING OF PLASTIC WASTES

IN PACKAGING

BY

Yugo Suzuki

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
School of Packaging

1974

Ti. \Ill‘r' I“

4‘ (Ill 5'

TABLE OF CONTENTS

Page
LIST OF TABLES . . . . . . . . . . . . . iv
LIST OF FIGURES . . . . . . . . . . . . . vi
1. PLASTICS IN PACKAGING . . . . . . . . . 1
2. RECYCLING SYSTEMS FOR PLASTICS . . . . . . 4
2.1. Introduction to Recycling . . . . . . 7
2.2. Disposal of Plastics . . . . . . . . 10
2.2.1. Landfill . . . . . . . . . 10
2.2.2. Incineration . . . . . . . . 11
2.2.3. Pyrolysis . . . . . . . . . 13
3. CHEMICAL APPROACH TO DISPOSAL . . . . . . . 18
3.1. Stabilization of Polymers . . . . . . 19
3.1.1. Background Theory . . . . 19
3.1.2. Ultraviolet Absorbents . . . . 21
3.1.3. Antioxidant . . . . . . . . 23
3.2. Polymer Blend . . . . . . . . 26
3.2.1. Background on Polymer Blends . . 26
3.2.2. Research on the Blend . . . . . 27
3.2.3. Properties of Blend . . . 28
3. 2. 4. Copolymers and Blend Polymers . . 34
3. 2.5. Examples of the Blend . . . . . 35
3.3. Biodegradation . . . . . . . . 46
3. 3.1. Basic Data of Biodegradation . . 47
3. 3. 2. Biodegradable Polymers . . . . 54

3. 3. 3. Particular Approach to
Biodegradability . . . . . . 58
3.4. Chemical Degradation . . . . . . . 60

3.4.1. Background of Chemical
Degradation . . . . . 60

3.4.2. New Developments in Accelerated

Degradation . . . . . . . 63

ii

Page

4. DISCUSSION AND CONCLUSION . . . . . . . . 76
4.1. Discussion of Waste Disposal System . . . 76
4.2. Conclusion . . . . . . . . . . . 87

4.2.1. Cost Estimation of Disposal . . . 87
4.2.2. Movement of Disposal in the
Future . . . . . . . . . 94

iii

LI ST OF TABLES

Table Page
2.1. Plastics Production, 1970 . . . . . . 4
2.2. Plastics in Packaging, 1970 . . . . . . 5
2.3. Composition of Residential Solid Wastes,

1970 . . . . . . . . . . . . . 5
2.4. Waste Disposal Methods . . . . . . . 10
2.5. Combustion of Packaging Wastes . . . . . 12
2.6. Pyrolysis of Plastics . . . . . . . . 14
3.1. Heat Stability of Copolymer; PS+(5) . . . 25
3.2. Heat of Mixing . . . . . . . . . . 32
3.3. Solubility Parameter d . . . . . . . 33
3.4. Mixing State of Rubbers . . . . . . . 34
3.5. MX 224.04 Blend with PVC and PE . . . . 38
3.6. Compatibility of Thermoplastics in the

Ultrasonics . . . . . . . . . . 42
3.7. Scrapped Plastics and CPR . . . . . . 43
3.8. Biodegradability of Commercial Plastics . . 48
3.9. Biodegradability of Additives . . . . . 50
3.10. Biodegradability of Straight Chain

Hydrocarbons . . . . . . . . . . 50
3.11. Effect of Branching . . . . . . . . ' 51
3.12. Effect of MW on Biodegradability . . . . 52
3.13. Biodegradability of Pyrolyzed PE . . . . 52
3.14. Biodegradability of PS . . . . . . . 53

iv

Biodegradability of Pyrolyzed PS

Biodegradability of Polyester

Biodegradability of Comonomers .

Maximal Growth Rating of Fungus Mixture
Polyurethanes and Polyesters

Examples of Easily Oxidized Polymers .

Advantages and Disadvantages in Waste
Disposal

Cost Estimation of Disposal (S/ton) in

1970

Page

0 O 53
. . 54
O O 55
on

. . 56
. . 62
. . 77
O O 93

l. PLASTICS IN PACKAGING

Packaging has long enjoyed first place as a mar-
ket for plastics; One-fifth of all the plastics produced
in the United States is consumed by the packaging industry,
though it is expected to drop into second place, yielding
to building and construction (1). But this does not mean
a decline in demand or growth. Still the growth rate is
expected to be around 10% per year in the next decade in

spite of the predicted low GNP growth rate (1).

 

 

 

 

 

 

 

 

 

 

 

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' (adhesives,
—— closures,
1975 1980 1985 coating)

Figure l.l.--P1astics in Packaging; Growth by
1985 (l).

There are two main motivating factors for the increase of
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thggwgther.materials. New technologies such as copoly-

merization, coextrusion, laminating and alloying have

expanded into plastic packaging, and there is active

research in new materials development and processing

 

 

 

 

improvement.
710
P(3)
C (4)
(l) Polyethylene (PE)
b (2) (2) Polyvinylchloride (PVC)
(3) Polystyrene (PS)
425 (4) Others
I (4) 385
’ Cu)
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_ <1) _ (2)
175
3 3
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Bottles Injection Thermoformed Foam
and molded containers containers
tubes containers

Figure 1.2.--Rigid Plastic Packaging Market in
1970 (2). (In millions of pounds.)

Surely there are problems. One is today's "stag-
flation"; that is, the average growth rate for packaging
is linked to the growth of the Net National Product (Gross
National Product adjusted for inflation) which is weak
at this time. Secondly, litter control singles out plas-
tic packaging for special treatment, and makes ecology
one of today's tough issues. Third, the high price of
crude oil and tight supply of resin for all thermoplastics

raises their cost radically, making them less competitive.

LIST OF REFERENCES
(1) Modern Plast., p. 85 (Oct. 1973).

(2) Modern Plast., p. 25 (Aug. 1971).

GENERAL REFERENCES
Modern Plast., p. 38 (Feb. 1974).
Plast. World, p. 60 (Mar. 1973).
Environmental Sci. & Tech., p. 894 (Oct. 1973).

Modern Plast., p. 50 (Mar. 1970).

2. RECYCLING SYSTEMS FOR PLASTICS

The excellence of plastics as industrial materi-
als is recognized as well as their economic superiority,
and in the future they are expected to rank with steel as
a major industrial material. But the environmental ques-
tions about plastics and the oil crisis of October 1973

have put a shadow of doubt over their glorious future.

TABLE 2.1.--Plastics Production, 1970 (3).

~4-

 

% Billions of Lbs.

PS 17.1 3.35
PVC 19.4 3.80
PE 30.6 6.00
Phenolics 5.5 1.07
PP 5.1 1.01
Others 22.3 4.37

Total 100.0 19.60

 

TABLE 2.2.--P1astics in Packaging, 1970 (3).
of pounds.)

(In millions

 

 

 

 

 

 

 

PE PVC PS PP Other Total
Adhesives -_ 41 —- -- 10 51
Bottles and tubes 584 65 18 -- 40 707
Coatings 400 143 -- -- 57 600
Closures 42 12 10 19 31 114
. Film and sheet 1,250 197 10 85 53 1,595
Containers 150 -- 730 -- 17 897
Miscellaneous -- _:: _:: _::D _32_ 23
Total 2,426 458 768 104 231 3,987
TABLE 2.3.-~Composition of Residential Solid Wastes,
1970'(4).
Paper products 43.8%
Food 18.2
Metals 9.1
Glass and ceramics 9.0
Garden wastes 7.9
Plastics, rubber, and leather 3.
Textiles 2.7
Wood 2.5
Rock, ash, etc. 3.7

 

In the data announced in 1970 (4), the composition
of plastics, rubber, and leather wastes is only 3.0% of
residential solid waste in the United States, and this
composition is similar for other industrialized countries
such as England, France, and Japan as indicated by statis-
tical data.

The troubles with waste plastics are (l) the quan-
tity has increasedrapidly with production rates, while
the disposal techniques did not follow this expansion;

(2) the research effort for plastics was limited mainly
to production, molding, and applications, rather than
disposal; (3) the use cycle time for plastics is short in
urban areas and they are disposed with other residential
solid wastes; and (4) the chemical conformation of waste
plastics is such that they do not degrade in biological
systems without treatment. Nowadays, urban refuse is dis-
posed by landfill or incinceration. There has been
criticism of plastic wastes in incinceration due to the
HCl produced by burning polyvinylchloride (PVC) and dam-
age to incincerators from the high temperatures produced
in plastics combustion.

World affairs since last October, the so-called
oil crisis (high cost of crude oil supply), changed the
problem with plastics refuse to another one.

Plastics have as high an energy of combustion as

petroleum and they have good chemical conformation. That

has demonstrated to us that plastics are another precious
resource even after use. Therefore the reclamation of
waste plastics should receive a good deal of research
effort. The reason that less than 5% of total refuse
collected as urban solid waste is so much criticized,
especially by environmentalists, is that plastics are
(l) particularly inert materials, littered everywhere
people move and gather, and highly visible; (2) found in
disposable and short-lived products, especially for pack-
ages and containers which are colorful eye-catchers that
are felt to be unnatural; and (3) a rapidly increasing
waste component in this decade tjunmfl1 they are still a
small minority.

The trend of plastics in city life is that
(1) plastic packages and containers have increased with
automation, self—service systems, and the mobility of
people, and with the market competition among retailers;
(2) consumers appreciate that plastic packages are

shatterproof, sanitary, and transparent.

2.1. Introduction to Recycling

 

The disposal of plastic wastes has briefly been
considered. In the issue of disposal technology, each
method was authorized unless it contributed another kind
of pollution, but the oil crisis has dramatically changed
this easygoing approach to .recyclability of precious

natural resources. All the effort to reuse, recycle, and

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reclaim cannot be economically justified, so only a proper
disposal technology can be applied. Considering the envi-
ronment a system (H? complete recycling either through
material reuse, pyrolysis or incinceration with heat recovery
is desirable. A product must not just have disposability
but recyclability, which means we create a new concept of
material rotation; we do not throw away urban refuse,
thinking it only useless. A recycling system should have
complete technology to separate the useful resources, to
classify into each material, and to remake it into another
product.

In general, the market value of wastes depends on
space and time, where and when they exist, as well as on
their intrinsic value; accordingly, widely dispersed materi-
als become less valuable. If collection, classification,
and remanufacturing methods and mature markets for a product
are once established, a total recycling system built in
the community really works. Examples of this already
developed are recycling for paper, aluminum cans, and glass
containers. The same problems as with plastics are dis-
cussed in other recycling systems such as rubber (tires),
glass, fibers, and waste oils. In consideration of the
recycling process, we do not only develop a new technology.
Just as important are product innovations and the develop-
ment of markets for recycled products. Some help from

legislation and cooperation between governmental units

10

and plastics industries will be needed considering both

the environment and energy affairs in these days.

2.2. Disposal of Plastics

 

2.2.1. Landfill

 

Landfills are the most common disposal method of.
urban refuse; 90% of United States and United Kingdom
wastes is landfilled (5). Landfills are classified as
open landfill and sanitary landfill, but only sanitary

landfills are now legal in the United States.

TABLE 2.4.--Waste Disposal Methods.

 

 

U.K.
France (1972) U.K. (1972) (Estim. 1980) U.S.A
Incin. 30% 10% 20% 9%
Compost. l3 -- l
Landfill 57 90 80 90

 

Reclaimed land from a high quality landfill opera-
tion has more than 890 kg/cu.m (55 lb/cu.ft.) density,
while common landfill is about 475”600 kg/cu.m and some
inferior lands have less than 300 kg/cu.m. The densities
of various plastics are around 0.8~l.0 g/cu.cm (800"1000
kg/cu.m) which indicates that many plastics theoretically
satisfy the density condition (6). Mixed plastics in the

soil of landfills do not present problems for the reclaimed

11

land, because most plastics are not naturally degradable

or unstable, but the low friction coefficient of plastics
sometimes makes them slippery, so usage in construction of
heavy buildings is not advisable without special precau-
tions. Recently even in the United States, which has a
great deal of land, many cities cannot get enough space for
landfill, and so other develOped areas such as in Europe
and Japan, can no longer depend on this major method of

disposal.

2.2.2. Incinceration

 

The easiest and most practical engineering method
for disposal, working all over the world, is incinceration.
The principle of combusion is not so difficult. Nowadays
the combustion heat in an incincerator is used to make
steam which is distributed to the community as a heat
source.

About 20% of U.S. incincerators are the heat
recycling type, where incoming air is warmed by exhaust
gases. Larger plants,amore than 600 tons per day) use
the waterfall furnace, where the circulating water is
heated around the furnace. Fumed gases released from
chambers include toxic ones such as hydrogen chloride (HCl),
carbon monoxide (CO), sulfur dioxide (802), and nitrogen
oxides (NOx); the technology for treating them is available

and claimed in many patents, but still not completed for

practical use. Some people indicate that an improved

12

device attached to the incincerator or improved furnace
designs such as the double chambers work well to minimize
toxics. But still these are very expensive and energy-
consuming methods for market competition. The removal of
HCl originated from combusting PVC is hard even for a mod-
ern technology without a large investment. As heat sources
plastics show superior properties, high combustion energy
and flammability, particularly PE, PP, and PS, but not PVC:

among the popular plastics.

TABLE 2.5.--Combustion of Packaging Wastes.

 

 

Ignition °C Cal. Kcal/Kg

PE 340 11,100
PP 350 11,050
PVC 390 5,060
PS 350 10,170
Phenols 520-540 5,850
Melamines 475-500 4,260
'6 “Uretanes 310 4,450
I Corrugated paper 4,130
Paper cartons 4,300
Textiles 4,470
Hardwood, oak 4,830

Softwood, pine 5,090

 

13

Mixed combustion of household refuse, above all
with wet garbage that is carried out by many local govern-
ments, is aided by the high energy of plastics. The ratio
of plastics can be controlled to keep temperatures constant
and to generate the same amount of heat per hour during a

long run.

2.2.3. Pyrolysis

 

The flow chart of pyrolysis of plastic wastes is
presented, which shows these four branches: (1) tar,
(2) water soluble mixture, (3) organics, and (4) gas mix-
ture. Much equipment and many pilot plants have been
developed for plastic pyrolysis, and each plant is proud

of its excellent capacity to dispose of refuse.

 

[Raw WasteQ

 

Separation JNon-Combustible]

Ti

9%Waterl

 

 

 

 

[Combustible]

 

 

 

[Dried Wastes]

~ l

‘ L 4
[Water] [MethanoI] Tar [Acetic Acid] [Organics]

 

 

 

 

 

 

 

 

Figure 2.2.-—Flow Chart of Pyrolysis.

14

TABLE 2.6.--Pyrolysis of Plastics (8).

_..-

Temp. of

 

Pyrol. (°C) Liquid (%) Gas (%) Residue (%)
PE 465 89.2 7.9 0,5
PE 470 93.6 6.0 0,4
PP 460 91.0 7.6 0,2
PP 550 94.7 5.0 0,3
PS 465 96.5 0.4 3.2
PS 530 97.8 0,9 1.9

 

Some companies have been developing the pyrolysis
technology and running experiments with pilot plants. Not
so long from now commercial plants for community needs
will be running, while some small plants are already in
commercial use. A lot of information about pyrolysis is
available and every paper claims superiority for its own
method. Some examples are (9):

(l) Destrugas process (Denmark): This works for
fuel gas, has a capacity of 18 ton/day, and the following
pyrolyzed product composition of solid, liquid, and gas,
and can easily be scaled up. Eighty percent of product
gases ii; burned in the plant and the remaining 20% is
supplied to the outside community.

(2) Union Carbide process: Controlling the pyroly-

 

sis temperature and time, this process can select the

15

product composition among wax, grease, oil, and even gas.

The process consists of a premelting process and a pyroly-
sis furnace, hence HCl from PVC can be removed at a stage

of preheating.

(3) Monsanto process: This is developed for the

 

purpose of urban refuse disposal, and has four stages:
crushing, pyrolysis, gas purification, and residue treat-
ment. Ninety-four percent of the gas is released in a low
oxidation state and purified at high temperatures, removing
toxic gases and washing out particles with water.

(4) Lentz converter process: A closed rotary kiln

 

as a furnace is operated at around 1,200 °F. Steam, vola-
tile oil, carbon dioxide, and carbon are converted from
plastics, then the steam and carbon dioxide are removed.
The volatile oil includes hydrogen, methane, and propylene,
which have the heat capacity to generate 400,000 kw of
electricity per day.

With relation to these methods, a tire reclamation
process is running in the U.S. Bureau of Mines and U.S.
Rubber Reclaiming Company, which claim to produce many
chemicals as well as hydrocarbons (10).

It is said that pyrolysis is more favorable than
incineration among experts, because (1) a closed system
is possible to minimize air pollution; (2) a large-scale
plant and recycled heat can decrease the investment and

running cost; (3) recycled gas is reformed to raw materials

16

for other processes; (4) urban refuse is reduced to less
than 50% by volume, so post treatment becomes easier.

The result in San Diego after three years of experience
indicates that (l) the volume of wastes was decreased to
50% of starting; (2) a new energy supply Wasw39t neces-
sary; (3) the remaining ash or other materials are favor-
able to landfills; (4) recycled gas and oil are available
for new products for the market; (5) on a large scale, it

is estimated that the total cost of building and operating'

is about 65% of that of an incinceration plant.

LIST OF REFERENCES
(3) Modern Plast., p. 65 (Jan. 1971).
(4) Chem. Eng., p. 155 (Jan. 21, 1971).
(5) Europlast., p. 66 (Mar. 1973)

(6) Plst. Handbook (1970); Indust. Material, 22(5):
41 (1971).

(7) Plst. Handbook (1970).

(8) M. Ichikawa, H. Ando, Applied Phys. (Japan), 40:
1268 (1971).

(9) DeBell & Richardson, Inc., "Plastic Waste Disposal
Practices," Manufacturing Chemists Assoc. (1972).

(10) Environmental Sci. & Tech., 12(3): 188 (1973).

GENERAL REFERENCES
Modern Plast., p. 76 (Oct. 1973).
W. Herber, Chem. Eng., p. 66 (Jan. 10, 1972).

P. A. Witt, Chem. Eng., p. 62 (Oct. 4, 1971).

17

T. Kagiya, Plaspia (Japan), 2(12) (1973).
Chem. Eng., p. 56 (June 14, 1971).

Chem. Eng., p. 88 (June 15, 1970).
Package Eng., p. 46 (Dec. 1972).

A. E. Higgins, The Chem. Engineer, p. 217 (Apr. 1974).
G. Applegate, The Chem. Engineer, p. 222 (Apr. 1974).
J. Skitt, The Chem. Engineer, p. 55 (Apr. 1974).

G. Cheater, The Chem. Engineer, p. 85 (Apr. 1974).
Chem. Eng., p. 68 (Apr. 6, 1970).

Europlast., p. 66 (Mar. 1973).

J. A. Fife, Envir. Sci. & Tech., p. 310 (1973).

C. Hulswitt, Chem. Eng., p. 80 (May 15, 1972).

Chem. Eng., p. 56 (Dec. 15, 1969).

E. R. Kaiser, First National Conference on Packaging
Waste (Sept. 22, 1969).

3. CHEMICAL APPROACH TO DISPOSAL

We have now come to the point to discuss the chemi-
cal approach to the recycling of plastics found in
collected solid waste and litter.

Since the birth of synthetic plastics, research
chemists have devoted themselves to the stabilization of
plastics against heat and light. Tough and clear plastics
were their dream for a long time. To apply this idea in
the recycling of plastics, and how we can make a stable
plastic through its use and reclamation, is the Chemist's
big interest now.

The techniques of polymer blending are some of the
most difficult areas and, therefore, only less advanced
technology has been developed there. However, once it is
developed we would not need a classification process, which
is another difficult technique even for modern technology
except the human eye.

Littered plastics are a main target at which a lot
of environmentalists and ecologists throw sharp accusa-
tions. If plastics would disappear before their eyes it
would be a big relief for all these people unless they pay
attention to the toxicity of the degraded plastics. They

will no longer hurt the beautiful scenery around us.

18

19

There are two methods to degrade plastics:
biodegradation and chemical degradation. Biodegradation
is literally a degradation by bio-organisms and chemical
degradation is a photodegradation kn? ultraviolet (UV)

energy, or an oxidation with an oxidizer.

3.1. Stabilization of Polymers

 

3.1.1. Background Theory

 

Synthetic polymers require stabilizers to be
processed into products, and the stability of physical and
chemical properties of plastics depends on these stabiliz-
ers and the prOper technique of using them. The ideas of
stabilization and of degradation are opposite, however
the chemical approach to each is similar. The chemical
bonds in polymers generally have an energy of about 40-90
kcal/mole, corresponding to about 720-320 pm of wave
length. Carbon-carbon, carbon-hydrogen and carbon-halogen
bonds are generally 65-85 kcal/mole and typical carbon-
carbon bonds in polymers are about EM) kcal/mole. Carbon-
hydrogen bonds are somewhat more reactive, especially when
the hydrogen is tertiary or alpha to an activating group
such as C=C. On the other hand, a bond energy of 40-90
kcal/mole corresponds to the visible and ultraviolet light
region. This indicates that polymers are degradable in
the natural environment and commercial plastics need sta-

bilizers for most applications. Commercial plastics

20

undergo a lot of thermal processes that cause oxidation of
the polymer chain and branches, and degrade or color them.
So we need various kinds of stabilizers for various poly-
mers, above all heat resistant ones.

An outstanding new development of stabilizers has
not been seen in recent years, because commercial sta-
bilizers were developed in the 19505 and they have been
effective enough as market needs. Stronger polymers are
not realistic or hopeful, because here you see the physical
limitation of bond energy: 40-90 kcal/mole. The more we
add additives for strength, the less plastic polymers
become. This is a dilemma for the chemist.

Factors of polymer degradation are classified
(1) oxidation by UV light, (2) oxidation by heat, (3) oxi-
dation catalysis by transition metals, (4) oxidation with
ozone, (5) thermodegradation, (6) degradation by radiation;
(1)-(3) are important. In Time samples of vinyl polymers,

degradation from oxidation is indicated by [l].

R R

R R
' thu'A I
W —CH2 l-CHZ—M-T'T' W -('2—CH2 —CH2 W
2
H n H

21

R R
I
r—+ fW[-C|Z-CH2]—é=0 +HO-CH2—-—-
H
T T
r--> AN [—(|3—CH2 .—CH2NV+ oooa [l]
H n

 

I I
‘“-> NV l:-<f—<3H2 I‘CHZAN + °H
000

This kind of oxidation is generally seen in vari-
ous kinds of polymers, so to maintain the physical strength
of polymers, we have to overcome these degradation reactions
under environmental conditions. Such ideas are applied
to stabilizers. Stabilizers have to deactivate the oxida-
tion radical or absorb the UV energy that causes the

oxidation.

3.1.2. Ultraviolet Absorbents

 

The UV absorbent absorbs UV light but does not
drive other reactions. Many data of experiments indicate
these three types of compounds are effective as UV absorb-
ents: [l] oxybenzophenone, [2] phenylsalicylates,

[3] 2-(2'oxypheny1)benzotriazoles.

22

 

 

o
o
[11 \r'a L,
. ‘—1—— /..
R C450 ' R C
CI <31
\ x x
O O\_"
.2. /\ ”(I .
H I
: N//"" R
C 2: o .__
O _-

These three absorb UV energy to become enoles and
release heat to return to the starting compounds, which
means they have the function of an energy exchanger between
photo and thermal energy. In blending of these compounds,
compatibility with polymers, volatility at molding, and
deformation by heat or migration to the outer system is
influenced by R or X, which are the secrets covered by
many patents. Any mixing methods cannot perfectly overcome
these defects. Recent developments concentrated in making
chemical bonds between polymers and additives by graft

c0polymerization or other polymerization methods (11, 12).

23

We find some marketed copolymerization methods that
are better than the mixing method, and that support perfect

dispersion, which is very important for stabilizers.

3.1.3. Antioxidant

 

An antioxidant requires a molecular structure
that is able to catch reactive radicals and become inert
after the combination. Some representative antioxidants,
known to exist as stable radical compounds, are [l] hin-

dered phenols, [2] aromatic amines shown in the figure.

 

t-Bu RO . t-Bu
2 .
Hobinr—p o /. CH3 + ROOH [1]
t—Bu
t-Bu

as Lo 2., W‘Q“
\\ // \\ ' //

Reactions with stabilized radicals are not
expected, because they are protected by large components.
But radicals emerging from polymers are comparatively
easy to recombine with stabilized radicals to make inert
products. The mixing of antioxidants has the same tech-
nical problems as UV absorbents, therefore high molecular
weight antioxidants with high molecular modifiers are

devised such as [3] and [4] (13).

24

OH OH
H2
t-Bu I C /.l t-Bu [ 3]
\ \\
H3 CH3
HZ—‘THZ n
CH2
HO
CI
t-Bu CH3

But the perfect dispersion is an ideal state to
receive the complete effect of the stabilizers. And
this indicates that chemically bonded (e.g., graftcopoly-
merization) additives are more desirable than conventional
mixing methods. Copolymerization with a vinyl compound,
which has an antioxidant in it, is a very favorable method
considering its ideal dispersion. This method contains
some other applications such as degraders and other

stabilizers (14).

HO O OOCHZCHZOCH=CH2 [5]

 

25

TABLE 3.1.--Heat Stability of Copolymer; PS+(SJ.

 

[n]

 

 

ime 0 (Hr) 20 144 240
PS 0.43 0.42 0.40 0.38
PS+(5] 0.41 0.42 0.42 0.41

 

 

Other stabilizers are proposed in the plastic
market, polymer types such as polysiloxane, which not
only work effectively as antioxidants, but are less vola-
tile and do not migrate. However the market share of
these compounds is still small. The development of sta-
bilizers is moving toward graftpolymerization (15) or
copolymerization, but these procedures are available only
in the laboratory. Even now many additives on the market

are modified compounds of [3] or [4].

LIST OF REFERENCES

(11) . Fertig et al., J. Appl. Polym. Sci., 10: 663 (1966).

J

(12) J. Fertig §E_al., J. Appl. Polym. Sci., 9: 903 (1965).
(13) R. Yamamoto, Meeting of Japan Rubber Ins. (1969).
(14) M. Kato, Y. Nakano, J. Polym. Sci. B, 10: 2230 (1972).

(15) F. Bayer, Chem. Abst., 65: 17, 151 (1966).

GENERAL REFERENCES

J. Luston et al., J. Polym. Sci. Polym. Sympo.,
40: 33 (1973).

26

G. Scott et al., J. Polym. Sci. Polym. Sympo.,
40: 67 (1973).

A. V. Kotova et al., J. Polym. Sci. Polym. Sympo.,
40: 87 (1973).

L. Omelka et al., J. Polym. Sci. Polym. Sympo.,
40: 105 (1973).

O. N. Karpukhin et al., J. Polym. Sci. Polym. Sympo.,
40: 145 (1973).

J. Pospisil et al., J. Polym. Sci. Polym. Sympo.,
40; 163 (1973).
P. Vink, J. Polym. Sci. Polym. Sympo., 40: 169 (1973).

A. A. Ivanov et al., J. Polym. Sci. Polym. Sympo.,
40: 175 (1973).

J. M. Nielsen, J. Polym. Sci. Polym. Sympo., 40:
189 (1973).

A. Bank et al., J. Polym. Sci. Polym. Sympo., 40:
199 (1973).

J. Pospisil et al., J. Polym. Sci. Polym. Sympo.,
42} 209 (1973).

B. Baum and R. D. Deanin, Polym-Plast. Tech. Eng.
£(l): l (1973).

M. Kato, High Polymer (Japan), 21(242): 254 (1972).

3.2. Polymer Blend

 

3.2.1. Background on
Polymer Blends

 

 

The polymer blend is a mixture of different kinds
of polymers. Since the various properties of the blend
polymers depend on compatbility, state of dispersion and
the mixture state, we have to think not only of the mix-
ture of polymers but of the mixture of additives and

moreover of macromolecular reactions.

27

From the micro point of View, c0polymers are a
mixture of more than one polymer and, of course, homo-
polymers are also a mixture of various molecular weights
and lengths. However, the one type of polymer, such as
HDPE for blow molding, will have a similar molecular dis-
tribution from various sources.

The mixture of the polymer molecules, if it is
thoroughly mixed (one molecule surrounded by another kind
of polymer molecule) has definitely different properties,
but this is hard to obtain. The polymer blends that have
been produced consist of molecular dispersions from 1 u

‘to a few hundred 0.

3.2.2. Research on the Blend

The approach to the blend is quite old, for
instance natural rubber with natural resins, rubber with
asphalt, or phenolic rubber with phenol polymers. Then
other combinations were studied, but they have not been
successful untiltflmaintroduction of ABS (polyacryloni-
trilbutadienestyreneterpolymer).

In the production process, polymer blending is
carried out at the final molding process to meet the
particular market needs. At this time raw material makers
are starting to pay attention not only to the new tech-
nology but to the innovating treatment of recycling

plastics.

28

The blend polymers must have compatibilities
between polymers, meanwhile other incompatible combinations
should be investigated, since they sometimes have inter-
esting properties as raw materials. We cannot neglect
them because they may be needed for purposes of recycling
and industrial materials. For example, incompatible
blends indicate a phase separation phenomenon and may be
applicable as a material for some important parts of
several electronics products. Most scientists have
researched only pure materials, even though natural poly—
mers and materials are not pure. For example, wood and

bamboo are composed of different structures and materials.

3.2.3. Pr0perties of Blend

 

(a) Factors of mixture: In the case of a mixture

 

of more than one polymer, it is necessary to know the
properties of the polymers and the mixing methods as well
as the mixing ratio.

(1) Property of a polymer

a. Chemical conformation, configuration,
stereoregularity, solubility parameter
d (16), phase separation.

b. Degree of polymerization.

c. Crystallinity (HDPE, LDPE)

d. Reactivity of polymer; reaction between
polymers, reaction between polymers and
additives (cross linking).

(2) State of polymer
Solid--plastics, fibers, rubber emulsion

(latex).
Liquid--liquid polymer (oligomer).

29

(b) Density of blend polymer: In the sample of

 

roll blended polystyrene (PS) and polymethylmethacrylate
(PMMA), the corelation between the blend ratio and density
tells us that an actual density is lower than an arithmetic
average (17). Evidence of this poor compatibility is shown
in a whitened film. The expansion of the volume is caused
by the incompatible phase of polymers; the larger the
contact surface, the greater the expansion. On the other
hand, if two polymers come close enough, the density will

be greater than the arithmetic average.

1.19

 

1.17
1.15
.13
.11
.09
.07
.05

(125°

P‘ P‘ h‘ F‘ H

 

 

 

 

0 20 40 6O 80 100
PMMA PS

Figure 3.1.--Density of Polymer Blend PMMA+PS.

(c) Transparency: The transparency of the blend

 

polymer does not depend much on the refraction of the
materials. The refraction of PMMA is 1.49; PS, 159; and
PVC, 1.54; but blended PVC-PS is white, while PVC-PMMA is
clear. This mainly is the result of the proximity or

closeness of the polymers.

30

(d) Physical property: The physical property of

 

the blend is affected by the contact surface and the ten-
sile strength of the blend depends on the degree of
deformation given to the dispersed phase. Suppose a dis-
continuous phase B dispersed in a continuous phase A does
not deform when A is charged by physical power. This
shows that the compatibility between A-B is much smaller
than the phase strength of B. The blend which does not
transmit a load between A-B has the lower strength. How-
ever, if a chemical bond is formed between A-B, it must
have stronger properties than without it, because of the
increase of the molecular weight (18). The main factor

in impact resistance is whether impact energy is absorbed
by the blend. Deformation is also one of the important
factors in absorbing the energy. However, the impact time
is always so short that the deformation is an elastic one,
therefore we should form the elastic element in the blend
polymers. The toughness of materials needs a good balance
between load and deformation when considering the impact
resistance.

(e) Precipitation in cosolvents: The precipitation

 

test is a method to precipitate two polymers in a solvent
in which a precipitizer is added to measure their compati-
bility. The interaction between two polymers shifts a
precipitation curve as shown at Figure 3.2 (b), but non-
interaction between them indicates no clear shift at

Figure 3.2 (a) (19).

31

 

 

 

 

 

 

 

 

BdPMMA
Blend PVC
NR
1+;.1 LllLi
(a) PVC-NR (THF sol.) (b) PMMA-Cellulosenitrate (cu)
(MEX sol.)

Figure 3.2.--Precipitation Curve.

(f) Phase separation: Two polymers dissolved in

 

a solvent sometimes separate into multiple phases. A
polymer which has a big clinging energy to itself results
in the separation phenomenon because this energy excludes
other polymers in the solvent.

(9) Measuring thegglass transition temperature:

 

On measuring the glass transition temperature of the blend
polymer, some examples show different transition tempera-
tures from those of the pure polymers. The glass transi-
tion temperature is the point at which the thermal activity
is frozen. When there are two transition temperatures,

the interaction energy between the two polymers is not
great enough to shift the temperature curves. In general,
a compatible blend gives a different thermal property

from any of the pure polymers.

(h) Heat of mixing: For the mixing of materials,

 

whether it is endothermic or exothermic depends on the

thermal prOperties of the phase change. In the case that

the mixing is exothermic, blending is easy.

32

From the

thermodynamic characteristics the solubility parameter,

d, of polymers is obtained (21).

TABLE 3.2.--Heat of Mixing (20).

 

Heat of Mix.

 

P P

olymer l olymer 2 Solvent (cal/mol)
PB PS Benzene 0.3
PB NR Benzene 0.3
NR SBR (Styrenebutadiene) Benzene -O.3
Butylcellulose PS Anone -l.3
Bytylcellulose PS Chloroform -3.9
Nitrocellulose Acetylcellulose Acetone +5.9
Nitrocellulose PVA Acetone +0.9
Acetylcellulose PVA Acetone -2.9
Polymethylacrylate Polybutylacrylate Acetone 0.0
Polymethylacrylate PMMA Acetone —2.5
Polybutylacrylate Polybutylmethacrylate Acetone -0.6
PVA (Polyvinylacetate) PMMA Acetone -l.0

 

33

TABLE 3.3.--Solubility Parameter d (21).

 

 

d
Polymer (call/Z/cm2/3) Polymer d
PE 7.7~8.35 Polypropylacrylate 9.05
PP 8.2~9.2 Polybutylacrylate 8.8~9.1
Polyisobutene 7.8~8.1 Polyisobutylacrylate 8.7~11.0
PB 8.1~8.6 PMMA 9.l~12.8
PS 8.5~9.3 Polyethylmethacrylate 8.7~9.0
PVC 9.4~10.8 Polybutylmethacrylate 8.2~10.0
Polyvinylidenechloride 9.9~12.2 Polybenzylmethacrylate 9.8~10.0
Polyvinylbromide 9.5 Polyacrylonitrile 12.5"15.5
Polychlortrifluorethylene 7.2~7.9 Polymethacrylonitrile 10.7
Polytetrafluoroethylene 6.2 Polymethylenoxide 10.2~ll.0
Polychloroprene 8.2~9.25 Polytetramethylenoxide 8.55
PVA 9.35~11.05 Polypropyloxide 7.55~9.9
Polyvinylpropyonate 8.8 Polyethylensulfite 9.0~9.5
Polymethylacrylate 9.7~10.4 Polydimethylcyloxane 7.3~7.6
Polyethylacrylate 9.25~9.4 Polyepychlorhydrine 9.4
Polyisoprene 7.9~10.0 Polyethyleneterphthalate9.7~10.7

 

(i) Mixing state: The experimental methods to

 

determine the mixing state are (l) measuring the refraction:
transparency or phase microscopy; (2) polymer crystallinity:
electrosc0py or X-ray refraction; (3) glass transition
temperature: Tg.

We can judge whether two certain polymers are

soluble or not by the phase separation method or by the

34

heat of mixing measurement. Also, we can judge by the
value of the solubility parameter, d. A phase separation
may not appear in a polymer-polymer mixture, because of

the high viscosity of the polymers. Examples of the mixing
state of rubbers are described in Table 3.4 which reveals
the relation between dispersed particles and the solubility

parameters (21).

TABLE 3.4.--Mixing State of Rubbers.

 

 

Rubbers Diameter of Particle d
(u)
NR/SBR 2 8.15/8.54
Polychloroprene/SBR ' 0.5 ' 9.38/8.54
Buna 85/NR 0-5 8.65/8.15
PB/NR 0.5 8.38/8.15
CisBR/NR 0.5 8.38/8.38
NR/Polyisoprene 2 8.15/8.15
NR/Butyl rubber l 8.15/7.87
SBR/BR 2 8.54/8.38

 

3.2.4. Copolymers and Blend Polymers

 

A copolymer has the different segments or compo-
nents in the molecular chain, while the blend polymer is
the mixture of the different molecules. The random
copolymer has the intermolecular plasticization phenomenon

related to the random configuration, while the blend of

35

the different segments shows various phenomena such as
repulsion and adsorption. It is a good advantage for the
blend to add a third copolymer that has the same segments
as blending polymers, and a good affinity to both polymers
in the blend. However, it is impossible to synthesize all
of these copolymers now. And so we set up a reaction in
the blend; that is, a polymer reaction in the blended
polymer. A chemical reaction needs a very short distance
between reacting sites, therefore some techniques are
devised to force functional sites closer together in the
polymer blend. If the polymer has a dipole moment and a
good tendency to come closer, we do not have to form a

new bond. In some cases, heat, light, or a reagent is added
to initiate the reaction between the less compatible phases.
The conversion of this reaction does not have to reach up
to 100%, because products can still contribute to a desir-

able property such as elongation strength.

3.2.5. Examples of the Blend

 

PVC blends.--The purpose of the blend is to improve

 

processability, to improve plasticity, to improve physical
and chemical properties, and to reduce cost, but the
improvement of impact resistance is the main consideration
in industrial research. However, in this section we are
concerned with the multimixtures for the reclamation of

the recycled plastics.

36

A high impact resistant PVC is marketed such as
described in this summary.

(1) An ABS blend with PVC or an MBS (polymethyl-
methacrylate-PB-PS) blend with PVC: ABS and MBS are the
most familiar blends with PVC, that are produced by a post
polymerization method or graft polymer blend method. The
good impact resistance of the blend depends on the graft
ratio, graft components, and rubber particles. Trans-
parent MBS-PVC is not unusual for certain market needs
(24, 25).

(2) EVA blend: The copolymer EVA [PE-polyvinyl-
acetate (PVA)] has a variable compatibility with PVC due
to the PVA content. When more PVA is added, more com-
patibility with PVC is given to EVA, and the blend is
more transparent and more highly impact resistant. So
far a high PVA content of EVA has appeared in the market
for blending with PVC, and it is said that crosslinked
PVC with EVA has outstandingly high impact resistance.

(3) Chlorinated PE (CPE): The history of chlor-
inated PE began in the 19505, however it is only lately
that CPE received wide application in industry, for
instance "Placon CPE" of Allied Chemicals, "Tyrine" of
Dow Chemicals, and "Holoflex" of ICI (27).

The physical and chemical properties of chlorinated
polyethylene depend on the distribution of chlorine, degree

of chlorination, distribution of molecular weights, and

37

crystallinity. It is said that non-crystalized CPE with
35% chlorine is most favorable for PVC blending.

In View of the fluctuating market, it is unwise to
invent a new polymer for a single use, therefore an
improvement of the general purpose polymers by way of the
polymer blend methods and the graft c0polymerization method
has attracted wide attention. Recent trends of blending
are toward multicomponent systems, which are the mixture
of the intermediate graft copolymers to retain the charac-
teristics of blending component polymers (28, 29).

A good product is the nonflammable PE blend with
CPE proposed by Dow's "MX2243.04," where CPE has 36% of C1,
1740 lb/sq.in of tensile strength, 69% of elongation,

lll lb/sq.in of tear strength (30).

In Table 3.5, they describe remarkably improved
tear strength of the blended PVC and PE.

(4) EVA/PVC graftpolymer: Bayer Chem. (Germany)
developed 1:1 PVC/grafted EVA, that has more impact
resistance than EVA blended with PVC and better weather
resistance, but not tensile strength (31).

This graft polymer is available to produce both
hard and soft PVCs Without changing the plasticizer.

ABS and MBS do not have good weather resistance
because of the double bonds in the main chains, so EVA

without double bonds in the main chains takes their place.

38

TABLE 3.5.--MX 2243.04 Blend with PVC and PE.

 

 

 

Blend Pol er Additives Tensile Elongation Tear Melt Viscosity
ym (%) (lb/inz) (%) (lb/inz) (poises)
—- -- 1740 690 111 3660
-- A120 1910 775 128 3820
-- T110 1860 760 156 3770
20% PVC -- 1730 550 163 3890
20% PVC A120 1540 400 161 4060
20% PVC T110 2220 480 194 4015
20% LDPE -— 1600 725 180 2310
20% LDPE A120 1260 610 178 2560
20% LDPE T110 1410 650 209 2375
10% HDPE -- 2090 740 207 3355
10% HDPE A120 1580 635 187 3650
10% HDPE T110 1970 720 221 3445
A : Calsium acetate.
1
T1: Talc.

In the PVC group such multicomponent plastics as PVC-PVC/
polycarbonate, PVC-EVA-CPE, PVC-EVA-SBR, PVC-EVA-PMMA,
PVC-PVC/PE-ABS, PVC-PVC/PE-PB, PVC-PE chlorosulfonate-AS,
PVC-polychloroprene-AS, PVC-PVC/PE-CPE have been devel-
oped(33), and PVC-PE-CPE 1&3 reported to have better impact
resistance than PVC-ABS (34). The high flowing PVC-PP
copolymer or low molecular weight PVC such as postchlorina-

ted PVC:h5under development to be blended for heat

resistance improvement (35, 36).

39

PS blends.--In addition to the high impact resist-

 

ance, efforts for improving ABS and MBS were aimed at
. getting high heat resistance and better transparency and
a processability of foamed plastic (37). Since low weather
resistance is the major defect for the high impact polymers,
the sunlight resistant plastics such as PS and AS
(acrylonitrile-styrene) are coated on ABS or MBS (38).

The blend of ABS with polycarbonate ("Cycoloy" of
Marbon Co.) shows better impact resistance and process-
ability than polycarbonate, and better weather resistance
than ABS (39). However, PS/PB (polybutadiene) block
copolymer (by Shell Chem. Co.) has almost the same com-
patibility with PS as the blended PS/PB, and the same

stress—strain curve as PB rubber (40).

Olefin blends.--The poor properties of PE are

 

stress cracking, low weather resistance, and poor printing
ability, and those of PP are low weather resistance, impact
resistance at lower temperatures, and poor dyeing ability.
Polyvinylbutylol and polyethyleneisophtalate as
well as synthetic rubbers are blended with PE to improve
stress cracking. A graft copolymer of PE with diene or
vinyl is impact resistant. A halogenated copolymer blend
is devised to lower the inflammability of polyolefins,
though incompatibility is a severe problem. PP has
improved impact resistance by adding butylrubber, polyiso-

butylene, EPrubber (ethylenepropylene), and polybutene-l

40

(alkylrubber); however, due to the research development
ethylene/butene-l, EVA, propyleneoxide rubber, ethylene/
acrylate, polybutadiene or ethylene/propylene block
copolymer are mixed to create even better impact resist-
ance nowadays. Also, the multiblend systems such as
PP-polyisoprene-PE, PP-PE-EPT, PP-polyisobutylene-EVA

are proposed to mend impact resistance of PP. A dyeing
ability of PP is crucial when it is formed to fibers, and
so vinylpyridinanuiepoxy-polymer which have significant
dyeing ability are blended. The particular blend such as
PE-Nylon-polymer with metal ion has properties both of PE
and of nylon. The other blends such as CPE-AS blended with
butyl rubber or PMMA, and CPE-EVA,EVA-PS are suggested for

the impact resistance improvement of PP (41).

Other polymer blends.--The aliphatic polyamide

 

blended with aromatic polyester has been attempted to pro-
duce a new fiber.

PMMA is blended with EVA/MMA (methylmethacrylate)
graft c0polymer or PMMA-EVA blend to raise impact resist-
ance. Polycarbonate blended with polyacrylate or PE-PS
has improved cracking resistance and impact resistance
(42). Polyacetal mixed with ABS, PB or polybutene is
stable against heat and impact. Polycarbonate, polyace-
tate or polyamide blended with PE and their grafted
copolymers with PE show the good processability and impact

resistance (43).

41

Ultrasonic welding.--The ultrasonic welding (20,000

 

cycle/sec) of plastics is applied toiflmaprocess to connect
parts in plastic manufacturing. The material should be a
thermoplastic which gets the frictional heat being generated
between the two plastics to be joined. This results in a
molten flowing and fusion<xftwo parts into a permanent bond.
The compatibility between two components isaacrucial one for
this process, and melting temperatures are also significant,
because this is a kind of heat process. The data of the
compatibility of thermoplastic materials shown in Table 3.6
is applied for the polymer blend and the possibility of the
manufacturing development. The mass scale process of ultra-
sonic welding will be developed to treat a vast amount of
plastics at once, however many barriers are predicted at

this time of the beginning of the research (44).

3.2.6. Future of Blending

 

The aim of the polymer blend is mainly to improve
physical properties such as high impact resistance. (Nuacom-
patibility of additives such as plasticizers, pigments and
filler has been paid less attention than that of polymers.
However, from this time on, polymeric additives will be
developed to reform the additive system and enhance the
physical properties of the polymers. The application of the
polymer blends in metals, woods, glasses (glassfibers),
cement and paper industries will be further studied in the

future.

TABLE 3.6.--Compatibility of Thermoplastics

42

(44) in the Ultrasonic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Welding.

w

4.)

m

:

O>4 4)

.QO 4.:

H .4 o m

m .4 > c

o m m m o

m m ‘\ m n

F. m o o u H m

o m H -H -H m m d

m a 0 r4 r4 H a o z

\. \. u >1 >1 >4 0 x \.

“”8868 8328.888:
Q Q m a d g 2 m z m m m m m m

ABS 6 O O O O O O O O
ABS/Polycarbonate O O O O O O O O
PVC/ABS alloy 0 O O O O O O
Acetal O
Acrylics O O O O O O O O
Acrylic/PVC O O O O O O 0
AS 0 O O O O O O O
Butylates 6
Nylon O
Polycarbonate O O 6
PE 6
PST 0 O O O
PPO 6
PVC 0 O 6
SAN/NAS O O O O O O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 denotes compatibility.

0 denotes some but not all grades and compositions
compatible.

 

43

Japan Steel Works disclosed a plastics recycling
installation with a capacity of 440 lb/hr. In this pilot
plant, waste plastics are composed generally of 40% of LDPE,
10% of HDPE, 10% of PP, 15% of PS, 15% of PVC, and 8% of
thermoset or other plastics. The remaining 2% is made up of
non-ferrous metals and other wastes. This plant consists of
crushing, separating of heavy materials, grinding, magnetic
separating, washing and pelletizing, in which polymixture
pellets were produced at a cost of about 3¢/lb in 1973; how-
ever, the mechanical strength is not good enough to meet the
market needs (45). As shown in Figure 3.3, plastics made by
blending methods have desperately poor comatibilities to
build a mass recycling system and to produce a wide market
root.

There will be big barriers to pass over before we
will have completed the technology to blend these commer-

' cial plastics successfully.

TABLE 3.7.--Scrapped Plastics and CPE (46).

 

 

Elong. (%) Tensile (psi) Impact (psi)
100% scrap 11 1,450 0
15% CPE 11.7 1,715 0.45
17.5% CPE 12.7 1,690 0.54
20% CPE 15.7 1,715 0.76
22.5% CPE 17.7 1,712 1.5
25% CPE 20 1,600 1.6

27.5% CPE 22 1,600 2.83

 

44

 

Tensile (lb/inz)

 

 

 

 

 

 

Elong. (%)
HDPE Young (10 x lb/inz)
. 2
3204 Module (lb/1n )
73.5
0.829
2245
'—
2150 2210
15.1 ’ 38.9
0.901 0.935
236 ‘ 568

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2320
1.87
,1.24
22.2
3930 2710 1.27 2720 ) 3510
2.20 1.40 ’1.65 1.77‘ .12.0
1.79 1.935 4413.4; 1.84 1.705
43.2 18.9 26.3 345
. . . — b
5470 5920 5970 6020 7460
2.27__ 1.86 1.87 2.14 56.7
2.41 3.19 3.20 2.82 2.24
‘ 62.0l ‘55.1 _ ‘ 55.1 . , 64.5 . . 2615
PS 1 PVC

Figure 3.3.--Properties of the Blended PE, PS and
PVC (46).

(16)
(17)

(18)
(19)
(20)
(21)

(22)
(23)
(24)

(25)
(26)
(27)

(28)

(29)

(30)
(31)
(32)
(33)
(34)
(35)
(36)

(37)

45

LIST OF REFERENCES

P. A. Small, J. Appl. Chem., 3: 71 (1953).

V. N. Kuleznev, Akad. Nauk., 24: 1858 (1962).
K. Foto, H. Fuji, Plast. Age, 3: 77 (1969).

Plastic Age, 3: 15 (1969).

K. Ichihara, H. Inoue, Chem. Eng. Japan, 33: 193 (1969).
G. L. Stonimski, J. Polm. Sci., 32; 625 (1958).

D. W. Van Krevelen, "Properties of polymers, corela-
tion with chemical structure," Elsevier Publishing,

p. 140 (1972).

Y. Minoura et al., Macromol., 13: 770 (1963).

K. Furuya, Chem. Ind. (JPN), 13: 13 (1963).

A. W. Carlson, T. A. Jones, J. R. Martin, Modern Plast.,
33: 155 (Sept. 1967).

R. D. Deanin, SPE Journ., 33: 90 (1967).
U.S. Patent, 2657188, 3126545; U.K. Patent, 927174.
R. R. Blanchard et al., SPE J., 33(1): 74 (1968).

D. R. Paul et al., Polym. Eng. & Sci., 13(3): 202
(1973).

D. R. Paul et al., Polym. Eng. & Sci., 13(4): 308
(1973).

J. Aoki, Rubber Digest (JPN), 13(6): 49 (1972).

W. Gobel, PVC & Polym., 3(2): 30 (1968).

A. Ogawa, Plastics (JPN), 39(4): 1 (1969).

G. Natt EE_31., Rubber Chem. Tech., 33: 1667 (1967).
K. Goto, Rubber Ind. (JPN), 33: 17 (1969).

R. D. Deanin, SPE J., 33(5): 50 (1967).

G. C. Pordingel, British Plast., 33(4) (1967).

B. D. Gesner, J. Appl. Polym. Sci., 11: 2499 (1968).

46

(38) C. B. Bucknall et al., J.A.P.S., 13: 831 (1968).

(39) C. W. Childan et al., Rubber Chem. Tech., 40: 1183
(1967). ——'

(40) R. E. Cunningham EE_31., J.A.P.S., 13: 23 (1968).
(41) K. Goto gE_§1., Rubber Digest, 13(4): 33 (1971).
(42) Japan patent 43-18620, 43-16854, 43-16300, 43-24540.
(43) H. Horie, Rubber Ins. (JPN), 33(10) (1969).

(44) J. R. Sherry, Plast. Design & Processing, p. 10
(April 1974).

(45) Modern Plast., p. 35 (Sept. 1973).

(46) D. R. Paul et al., Polym. Eng. Sci., 13(12): 157
(1972).

 

GENERAL REFERENCES
J. E. Hauk, Modern Plast., p. 39 (Aug. 1971).
J. A. Bryson, Plastics, 33; 107 (Dec. 1961).

N. E. Davenport, Brit. Plast., 33: 549 (1959).

3.3. Biodegradation

 

Biodegradation is a process of degradation initi-
ated by living organisms or by products directly derived
from such organisms. There are many reports indicating
that general purpose commercial plastics such as PE, PP,
PVC, and PS are not biodegradable. However, some reports
revealed that even such kinds of polymers are degradable
by a few strains of bacteria. These biodegradation phe-

nomena are crucial for plastic manufacturers.

47

The biodegradation reaction is generally classi-
fied as:

(l) degradation of polymers including biode—
gradable copolymer and hetero chain polymer,

(2) degradation of the low molecular weight
polymer,

(3) biotic attack to the impurities, such as
additives, fillers, and plasticizers.

With the significant mechanism in the degradation
context, it is

(1) simple oxidation,

(2) hydrolysis,

(3) other reactions by microorganisms,

(4) stresscracking,

(5) attack by insects, rodents, and marine

creatures.

3.3.1. Basic Data of Biodegradation

 

The biodegradability of commercial plastics has
been investigated by many researchers by ASTM test,
D-l924, and D—2676T; which requires 3—week exposure to
the environment, then assigned growth ratings as shown (47):

Growth ratings: 0--no growth

l--trace (less than 10% covered)
2--1ight growth (10 U330% covered)
3-—medium growth (30 to 60%)
4--heavy growth (60 to 100%)

Table 3.8 indicates that most commercial plastic
products are resistant to bio-attack, although some samples

are susceptible. No growth was seen on the samples

extracted with toluene, which explains that the

48

TABLE 3.8.-~Biodegradability of Commercial Plastics.

 

Plastics

M

Growth Rating

 

rwaH

\lO‘U‘l

8.
9.
10.

ll.
12.
l3.

14.
15.
l6.

l7.
l8.
19.

20.
21.

22”

23.
24.
25.

26.
27.
28.

29.
30.

PE household wrap
Sample 1, extracted with toluene

PVC-epoxidized soybean oil plasticizer

(3) extracted with toluene

PP
PS
PE terephthalate

Polyvinylidenechloride
ABS
ABS-Polycarbonate blend

Butadiene-acrylonitrile rubber
AS
Rubber modified PS

Styrene—butadiene blockcopolymer
PMMA
Rubbermodified PMMMA

PET (Polyethyleneterephthalate)
Polycyclohexanedimethylterephthalate
Bisphenol A polycarbonate

Bisphenol A polysulfone
Poly (4-methyl-l-pentene)
Polyisobutylene

Chlorosulfonated PE
Celluloseacetate or butylate
Nylon-6, nylon-66, nylon 12

Polyurethane
Polyvinyl butylal
Polyformaldehyde

Polyvinylethylether
Polyvinylacetate

o<5c> c>o+d IHFJH HHQFJN

GOO

GOO

GOO

 

49

polymermolecule itself is not attacked, but most commer-
cial plastic samples have biodegradable additives. Some
papers did not explain even whether additives in the
polymer are extracted or not, but stated only the conclu-
sion of their experiments.

The antioxidants and the ultraviolet absorbents
are definitely resistant to bioreaction and do not allow
any growth on the test samples. But the slip agents and
plasticizers are receptive to biodegradation, since some
of them have amide, phosphate, and ester groups in their
structures. PVC, which contains many additives, is easily
attacked by bacteria in the air, which is supported by
the result of the experimental data in Table 3.9.

The effects of the molecular weight of a polymer
and of branching are important to biodegradation, and a
number of investigations have been reported in papers.
Interesting results are given in Table 3.10. It is observed
that when the molecular weight increased from 451 to 507
the growth rating had drastically shifted from 4 to 0,
which confirms that the biotic reaction must have a high
degree of specificity. Branching hydrocarbons are also
resistant to biodegradation as seen in the petroleum pro-
tein reaction where only normal parafins (no branching)
are consumed by the fungi.

Even in the low molecular weight region, branched

samples do not indicate biodegradability, while straight

50

TABLE 3.9.-~Biodegradability of Additives (47).

 

Additive

Growth Rating

 

Antioxidant
Hindered phenol
Nonylphenol phosphate

Slip agent
C22 primary amide
C13 II
Olealylpalmitliamide

UV absorbents
2-hydroxy-4 dodecycloxy benzophenone
P-octylphenyl salicylate

Plasticizers
Di-Z-ethylhexylphthalate
Tricresil phosphate
Epoxidized soybean oil
Aliphatic polyester

00 N454:-

nubhao

 

TABLE 3.10.--Biodegradability of Straight Chain Hydro-

carbons (47).

 

 

Compound Formula MW Growth Rating

1. Dodecane C12H26 170 4
2. Hexadecane C16H34 226 4
3. Octadecane C18H38 255 4
4. Docosane C22H46 311 4
5. Tetracosane C24H50 339 4
6. Octacosane C28H58 395 4
7. Dotriacontane C32H66 451 4
8. Hexatriacontane C36H74 507 0
9. Tetracontane C4OH82 563
10. Tetratetracontane C44H90 620

 

51

chain hydrocarbons give a growth rating of 4 as shown in

Tables 3.10 and 3.11.

The result from these data is supported by LDPE

samples, in which the structure of the polymer is simi-

larly branching to the samples of Table 3.11.

TABLE 3.11.--Effect of Branching (47).

 

Growth Rating

 

Compound of Structure MW
2, 6, ll-trimethyldodecane C171132
f? <.=
C-C-C-C-C-C-C-C-C-C—C—C 212

2, 6, ll, 15-tetramethy1hexadecane C20H42

(I: I
(C-C‘C-C-C-C-C-C)2 283

Squalane C30H62

33 <5?
(C'C'C-C-C-C—C~C~C-C-C-Ch. 423

 

Since HDPE is linear and non-branching, the lower

molecular weight samples 1 and 2 in Table 3.12 are as

degradable as the low molecular weight straight chain

olefins (47).

TABLE 3.12.--Effect of MW on Biodegradability (47).

52

 

 

MW Growth Rating
1. HDPE 10,970 2
2. HDPE 13,800 2
3. HDPE 31,600 0
4. HDPE 52,500 0
5. HDPE 97,300 1
6. LDPE 1,350 1
7. LDPE 2,600 3
8. LDPE 12,000 2
9. LDPE 21,000 1
10. LDPE 28,000 1

 

Also, in the experimental data of Table 3.12, LDPE indi-
cates the same trend as observed in HDPE except 6 and 7,
where 6 is branching and greasy, while 7 is straight
chained crystalline sample.

The same kind of discussion is described with the
pyrolyzed HDPE and LDPE in Table 3.13, in which the lower

molecular weight is favorable on biodegradability.

TABLE 3.13.-~Biodegradability of Pyrolyzed PE (47).

 

Pyrolysis Temp. °C Viscosity av. MW Growth Rating

 

HDPE Control 123,000 0
HDPE 400 16,000 1
HDPE 400 8,000 1
HDPE 500 3,200 3
HDPE 535 1,000 3
LDPE Control 56,000 0
LDPE 400 19,000 1
LDPE 450 12,000 1
LDPE 500 2,100 2
LDPE 535 1,000 3

 

53

Notice the growth rating of PS shown in Tables 3.14 and
3.15 is different from PE because of its aromatic pendant

--benzene.

TABLE 3.14.--Biodegradabi1ity of PS (47).

 

Average MW Growth Rating

 

214,000
62,000
44,000
19,000
14,000

5,900
2,100
600

00000000

 

TABLE 3.15.--Biodegradability of Pyrolyzed PS (47).

 

 

Pyrolysis Temp. °C Average MW Growth Rating
Control 220,000 1
400 93,000 1
450 68,000 0
500 26,000 0
535 4,000 0

 

The only degradable synthetic high polymers are those
having aliphatic ester linkages in the main chain. The
biodegradability oftflmapolymer in which the pendant compo-
nent is composed of esters such as polyvinylacetate is

different from the main chain polyesters.

54

TABLE 3.16.--Biodegradabi1ity of Polyester (47).

 

 

Esters Reduced Growth

VlSC. Rating
1. Caprolactone polyester 0.7 4
2. Pivalactone polyester 0.1 0
3. Polyethylene succinate 0.24 4
4. Polytetramethylene succinate 0.59 1
5. Polytetramethylene succinate 0.08 4
6. Polyhexamethylene succinate 0.91 4
7. Polyhexamethylene fumarate 0.25 2
8. Polyhexamethylene fumarate 0.78 2
9. Polyethylene adipate 0.13 4
10. Polyethylene terephthalate High 0
11. Polycyclohexanedimethano1 terephthalate High 0
12. Polybisphenol A carbonate High 0

 

Since polyester does not have a simple formation
like PE and PS, the discussion of its biodegradability
has to cover different aspects. However, it may be summa-
rized that this is the copolymer which has the bioreactive

comonomer .

3.3.2. Biodegradable Polymers

Biodegradable copolymers and heterochain polymers.--
An attempt to synthesize a biodegradable copolymer has not
much been carried out, and some specialists say it is still
very hard to predict the completion of this technology.
Especially,commercia1 polymers such as PE, PP, and PS are
not treated by this method. A few biosensitive comonomers

which have hydoxide, acid, and ester branches are tested

55

for the purpose of degradation; however, the result indi-
cates that only a negligibly small growth is allowed on

the samples.

TABLE 3.17.--Biodegradabi1ity of Comonomers (47).

 

 

Comonomer % Comonomer Growth Rating
1. PE Vinyl acetate 18, 33, 45 1
Vinyl alcohol 13, 70 0
Acrylic acid 15 0
Sodium acrylate 20 0
Ammonium acrylate 20 0
Ethyl acrylate 18 0
Dodecyl acrylate 25 1
Carbon monoxide 6, 8 0
2. PS Acrylic acid 16 0
Sodium acrylate 16 0
Dimethyl itaconate 30 0
Ethyl acrylate 50 0
Acrylonitrile 28 0
Methacrylonitrile 87 0
Dodecyl acrylate 15 0

 

As mentioned above, the biodegradable c0polymers are con-
sidered very hard to synthesize, because they have the
carbon chains which are inactive to microbial reaction

even when they contain some amount of biosensitive branches.
The branch, even if it is consumed by bacteria, does not

make the main chains biodegradable. But heterochain

56

copolymers (they may not be classified as copolymers,
actually) such as polyester, polyurethane, and nylon,

are comparatively sensitive to biodegradation and so they
may have a big potential for future development.

Darby and Kaplan examined the biodegradability of
diols, polyesters, and urethanes, and as the experimental
result, they indicated that polyesters support heavy
growth on samples in a few weeks, as shown in Table 3.18

(48).

TABLE 3.18.--Maximal Growth Rating of Fungus Mixture on Polyurethanes
and Polyesters.

 

 

 

 

Polymer
Diol Monomer
TDI MDI
l. Ethyleneglycol 2 0 1
2. 1.3--Propanol 2 1 2
3. 1.4-—Butanediol 4 2 2
4. 2.3--Butanediol 4 2 O
5. 2—Methy1—1.4-butanediol 4 2 1
6. 2.2-Dimethy1-1.3-propanediol 3 2 O
7. 2.3-Dimethy1-2.3-butanediol 2 0 1
8. Diethylene glycol 2 1 l
9. Triethylene glycol 2 1 1
10. Polypropylene glycol (MW 400) 2 2 2
11. Polypropylene glycol (MW 1320) 2 3 2
12. Bis (4—hydroxyphenyl) dimethylsilane 1 0 O
Polyesters
1. Polyethyleneglycoladipate 4 4 4
2. Poly-1.3-propanedioladipate 4 4 4
3. Poly-1.4-butanedioladipate 4 4 4

 

TDI: Tolylendiisocyanate.
MDI: Methylenediisocyanate.

57

Generally speaking, nylon is resistant to fungal
attack, but its monomers are sensitive. However, some
reports mentioned that even nylon is biodegradable in the
soil burial test.

On the other hand, since most natural polymers
such as natural rubber and cellulose are biodegradable,
modified natural polymers have been applied as thermo-
plastics. For example, hydroxypropyl cellulose (brand
name is Klucel) does not only show thermoplastic proper-
ties, but is soluble in water below 45°C, biodegradable,
non—caloric, and non-nutritive when digested (49).

Amylose starch film is edible, water-dispersible,
and mechanically strong. When adopted as a packaging
material, its fermented starch also provides modified
cellulose which is thermoplastic, water soluble, and

easily modified with acid to make polyesters (50).

Impurities for biodegradability.--Many fillers,

 

plasticizers, and modifiers such as oligomeric esters for
PVC mixed in the plastics are regarded as biodegradable.

In 1973, a very simple but practical method was discovered
by Griffin. He mixed only starches to control the biodegra-
dation rate of commercial plastics. In his report,

starches are added from 20 to 50 wt. % to the polymer (51).
The physical properties are reported not worse than
expected, moreover even high molecular weight polymers

are degradable as well as low molecular weight ones. He

58

mentioned that the biodegradability depends on the surface
condition of the polymers exposed to air and all the
plastics could be biodegradable by the surface reforma-
tion with the readily decomposed starches. When plastics
are manufactured most of commercial ones are processed
with plasticizers such as oligomeric esters and alcohols.
However, these additives are not stable to the bioreaction,
and therefore commercial plastics are sometimes decomposed
while stored if Griffin's proposal is right. The examples
of highly biodegradable plasticizers are di-Z-ethylhexyl
azelate, di-n-hexyl adipate, di—isooctyl adipate,
tetrahydrofurfuryl oleate, triethylene glycol, epoxidized
soybean oil, and bytyl ricinolate (52).

3.3.3. Particular Approach
to Biodegradability

 

 

A practical approach was carried out by Wallhauser,
who has studied the behavior of composting of urban refuse
with the systematic treatment in a bioreaction vessel.
Collected refuse is bioreacted in aerated cells at 65-85°C
for 10-20 days and the finished compost remains as a
byproduct. In his data this method shows a few defects
such as a long reaction time, non-continuous process, and

high cost of disposal (53).

LIST OF REFERENCES

(47) J. E. Potts et al., "Degradability of polym. & plast.
meeting," London, p. 121 (Nov. 1973).

 

59

(48) R. T. Darby et al., Microbiol., 16: 900 (1968).
(49) J. M. Rossman, Packaging Eng., p. 54 (July 1971).

(50) G. A. Politis et al., Packaging Eng., p. 59 (Apr.
1971).

(51) C. J. L. Griffin, "Degradability meeting," London,
p. 15-1 (Nov. 1973).

(52) W. Summer, Corrosion Tech., p. 19 (Apr. 1964).

(53) K. H. Wallhauser, "Degradability meeting," London,
p. 17-1 (Nov. 1973).

GENERAL REFERENCES

H. J. Hueck, "Degradability meeting," London,
p. ll-l (Nov. 1973).

D. E. Hugh, "Degradability meeting," London (Nov.
1973).

 

E. Kuster et al., "Degradability meeting," London
(Nov. 1973).

N. Nykvist, "Degradability meeting," London (Nov.
1973).

F. Rodriguez, Chem. Tech., p. 409 (July 1971).
Europlast., p. 78 (Oct. 1972).
Package Eng., p. 32 (Oct. 1972).

A. Agarwal et al., Popular plast., Fiber & Polymers I
(India) (Oct. 1971).

Modern Package., p. 39 (July 1972).

Modern Package., p. 72 (June 1973).

Plastics Design & Processing, p. 23 (Nov. 1973).
Chem. & Eng., p. 37, (Sept. 11, 1972).

Chem. Eng., p. 68 (Oct. 15, 1973).

60

3.4. Chemical Degradation

 

3.4.1. Background of
Chemical Degradation

 

The factors influencing photochemical degradation
reactions are (1) factors external to the polymer and'
(2) inner factors of the conformation of the polymer. The
external factors are light, oxygen, ozone, corrosive gas
like nitrogen oxide, and impurities mixed in the polymer.
The internal factors affecting the degradation reaction
are the conformation of polymers. The reaction processes
'of the chemical degradation contain radical or non-radical
pathways. The first example of the radical degradation

reaction is a spontaneous oxidation called auto-oxidation.

RH——————+ R- Initiation

R' + O-—-——> ROO- .
ROO' +2RH-———-+ ROOH + R° J Propagation

2R°-——-—-+
ROO° + R'-———+- Termination
2ROO°-————+

 

The second one is the radical initiation with peroxides and

halogenated compounds, and the third one is the reaction

of photosensitizers. One of them is a radical initiator

like benzophonone which extracts hydrogen from a molecule.

Another one is an oxygen-sensitizer like methylene blue.
The decomposition step of polymer hydroperoxides

and peroxides is so slow that light, or heavy metals or

their salts are added in the reaction system as catalysts.

61

.mmmooum coflumomummouu.w.m whomflh

 

pmpmnmmo —

 

um>HMDMOIcoz
Godumcasuma

 

fl

fiGOH UMGHQHOU mm T

 

 

 

 

mamumfi
:OAuwmcwuu
souosm
umsamumo
coflummmmoum coflumfluflcH
, Auoumuuucu Hmouomuv
_ 811%

 

_

(1; HmowpmnhwWHmmoupmm

Hmoflcmm N0 + aouosm #umssaom

0cm mxouwm NO Hmfihaom drlllll|||\\\\\

 

 

 

Amo+

N

oz .mcouov couonm

62

The chemical degradation without the production of
any toxic degraded products needs some particular configu-

rations in main chains, as described in Table 3.19.

TABLE 3.19.--Examples of Easily Oxidized Polymers..

 

 

Configuration Polymers
I
—C—C—C— PP, HDPE, EP rubber
R
III ..
—C—C=C— Polydiolefin, SBR, NBR, ABS
I
u?
—C—N— Polyethyleneimine

_c_o_c Polyether

O
| .

—C—- Polyvinylether
H

H
_%_$_fi_ Polyamide, polyurethane
O

 

63

In general the polymer which has a pi bond or a

lone pair in the main chain is photosensitive

_ | l I I 41
—‘C=C_' _C:C_, "N-N-I (Ezo I C=S ’ —O_’ _

Photosensitive structure

---—CH2 —CH2 j—CHZ —<:H2 ----

/\

Norrish Type I Norrish Type II
I l
—CH2—CH2—CH2—i— CHZ—C—CHz—CH2---
+ ' +
CHZ—CH2--- ---CH2=CH2

for example, the Norrish Type II reaction in ethylene-
carbonmonoxide copolymer is common when it is photode-
graded (54).

3.4.2. New Developments in
Accelerated Degradation

Photosensitive polymers.--Guillet has established

 

the authoritative technology of the photodegradable copoly-
mer with vinylketone at wave length, 300-350 mu, where
vinylketon is copolymerized with many kinds of vinylcomono-
mers, and the degradability is controlled by light exposure
time from a few days to 6 months depending on comonomers.

He explains that there are no changes on chemical and

64

physical properties and no side effects on heat stability
of polymers even if modified with vinylketon. The cost
increase is only minimal (he claims) because of low con-
tent of vinylketon, hence Guillet has licensed with
Ecoplastic (Canada) and Royal Packaging Ind. (Holland)

to distribute his know-how in the market (55).

Such companies as Union Carbide, Eastman Kodak,
Ethylene Plastique and Mitsubishi have applied Guillet's
method to copolymerize ketoniccarbonyl into polymer main
chains (56).

As presented in Figure 3.5, Kato modified vinyl-
ketone with aminoacetophenone (MAA) and 2, 6-di-tert-
butylaminomethylphenyl (TBAP) which he explains more
degradable and controllable when mixed with antioxidants
(57).

Eastman Kodak has a patent of ethylene-carbonmon-
oxide c0polymer for temporary food packages. The company
claims that when 8% of carbonmonoxide is copolymerized
with ethylene, the wrapper is decomposed by the end of
the fourth day.

Ethylene Plastique also developed ethylene-
carbonmonoxide copolymer containing 0.2-9% of carbon-
monoxide, which is applied as coating materials, and
this copolymer, when copolymerized at 2% content of
carbonmonoxide, gets badly cracked and torn after 2-3

months (58).

65

H3
'CH2=C—c0-—NH /-\ CO—CH3, CH2=CH—CO—NH—CH2 "Bu
, TBAP
MAA (aminoacetophenone) t-Bu H
Ketone derivatives (2.6-di-tert-butylamiuo

-ethy1 phenyl)

 

Control

 

25 50 75 100

Time (hr.)

(A) 2.5 mol % of phenyl-B-naphthylamine

(B) 2.5 mol % of 2.6-di-tert-butyl-p—cresol

(C) 2.5 mol % of 4.4'-thio—bis-(6-ter-butyl-m-cresol)
(D) 0.5 mol % of 2.6—di-tertbutyl-p-cresol

(E) 2.5 mol % of 2-(octadecyloxylcarbonylethylethyl) sulfide

Figure 3.5.--Controllability of Degradation of
PMMA—MVK (56 mol %) Copolymer in Toluene.

66

Mitsubishi has studied the copolymerization of
methylvinyl ketone to such polymers as PS, PVC, PE, PP,
and PMMA, and when 0.3%-10% of methylvinyl ketone is

added, the gradual degradation was obtained (59).

Low stable polymers.-—Takeuchi presents an example

 

of the polymer which has a low stability to light. As
shown in Figure 3, 6-syndiotactic 1, 2-polybutadiene is
photo degradable without any sensitizers, and controllable
with stabilizers. It is suitable for food packaging
materials because of nontoxicity, and the service life of
this polybutadiene film can be controlled by a proper

selection and combination of stabilizers (60).

  
   
  
 
 

 

0 i
3; stabilizer (a)
§ _20 _ abilizer (b)
4.) .
r6 -
g _ stabilizer (c)
H —40
m D-
14..
O h
o -60
m
c
m
6 -80 - Unstabilized
_l n l

 

 

 

O 2 4 6 810
Exposure time (days)

Figure 3.6.--Weathering Test of Syndiotactic
1,2-Polybutadiene Film by Outdoor Exposure.

67

Mitsui Toatsu Chem. develOped the same type of
00polymer as Takeuchi's of styrene and butadiene by
1,2-polymerization method. Now it is surveyed in the
market to set a good reputation and to get more informa-

tion for Suntax, the brand name of this copolymer (61).

 

 

 

 

 

PS
5:: 100 \ .H S_ummer
E ( Winter
(8 Winter (low sensitive)
§ 50 Winter (high sensitive)
4.)
8 ' Summer (low)
3 S_uuer (high)
04 0 l l L

 

10 20 30
Exposure time (days)

Figure 3.7.--Degradation Rate of Suntax in Seasons.

Poly (1,3-pheny1ene iSOphthalamide) (PPIPA) is not
a general purpose plastic but its fibers and papers are
marketed by Du Pont by the trade name Nomex, and enjoys a
good reputation. Du Pont explains that it is remarkably
susceptible to UV degradation, because it absorbs most of
the energy of sunlight in the wavelength range of 355 mu
'to 400 mu. According to the disclosed data, Nomex retains
only half of the original breaking strength and one-third
of elongation strength, and discolors noticeably after 100

hour exposure in an Atlax xenon arc weatherometer (62).

68

ll /NH

‘c U—LL’ _Q/II. + °NH :.|

(02 1
Photo oxidation of PPIPA . Oxidation
fioz other reactions
0
AK

COOH

Photosensitive additives.--On the pathway of radi-

 

cal reactions, the additives form free radicals which pull
out hydrogen from the polymer chains directly or indi-
rectly through an intermediate hydroperoxide, and then they
make polymers break down.

Scott suggests the effective photosensitizers such
as iron stearate at 1.3% content and iron dibutyldithio-
carbamate at 0.013%, and also refers to cobalt, copper,
chromium, manganese and cerium metal salts, and numerous
other anti-oxidants. In his paper, he reported on the
photodegradation of LDPE, HDPE, PP, PS, high impact PS,
polyvinylchloride-acetate and PVC. The effect of
prooxidants on the UV degradation of polyolefin is shown
in Figure 3.8, where the carbonyl index in the polymer is

related to the physical properties of the plastic; that

69

 

   

  

 

 

 

30 h
5 (BF 200 hr)
0 -5
_g 8.5 x 10
>«
a
0
.Q
5.;
m
U

10

No additive
1 , (BF21000 hr)

 

50 100 150 200
Irradiation time (hr)

Figure 3.8.--UV Degradation of LDPE Containing
Fe(III)-acetylacetonate, conc. [Moles/100 9] (BF = Brittle
Fracture).

is, the high carbonyl index polymer rapidly loses its
strength and becomes brittle (63). Also, it is well known
that metal ions such as aqueous ferric chloride catalyze
the photodegradation. Scott mentions that metal ion
chloride initiates the photooxidation of PP. According to
the feature of a magazine, he has patents of these photo-
sensitizers all over the world and is licensing with many
manufacturers including U.S. companies (63).

AB Tetrapack developed a new type of plastic for
packaging which decomposes rapidly when discarded outdoors

but retains its strength inside. In this plastic, the

70

additive has double bonds which are attacked by oxygen and
light, and decompose the polymer chains. Also they dis-
closed the data that LDPE makes crosslinks between chains
with the ultraviolet ray energy; however, the additives
such as parafin, oleic acid, and soya oil blended in the
LDPE film inhibit this crosslinking reaction and cause a
more rapid decomposition (64, 65).

Princeton Chemical Research invented the easily
decomposing film of polybutene-l used on farms, where they
devised a balanced combination of antioxidants, UV absorb-
ents, and other additives. Since polybutene-l is
susceptible to UV degradation, UV may not always be
necessary. In any event, Princeton Chemical will soon be
marketing a polybutene-l version called Ecolan. In spite
of the expensive monomer costs of polybutene-l compared to
ethylene, they believe that the overall cost of polybutene-l
mulch will be almost the same as that of PE mulch consid-
ering the high labor costs to dispose of the non-degradable
PE mulch after use.

Eastman Kodak disclosed the application of pro-
oxidant additives with pacifying agents (e.g., carbon
black) to LDPE, PP, and polybutene films. Eastman's
prooxidants include cobalt, acetate, copper oleate, manga-
nese stearate, manganous dodecyl acetoacetate and cobalt

acetyl acetonate (67).

71

Mobil Oil Co. also developed an additive system
for polybutene-l. They prepared 30 mil plaques and 2 mil
films and produced bags from polybutene-l films with mixed
compounds containing an oxidation catalyst of cobalt, which
is a free radical producer (polyterpene) and a UV light
sensitizer (benzophenone). After exposure outdoors for
30 days, all samples containing prooxidants,except those
mixed with 2.5% carbon black, had degraded. Within 13
days, the bags containing 1000 ppm of cobalt octoate and
0.05% ionol broke and in 31 days they disappeared com-
pletely. However, as explained before, polybutene-l is
inherently more unstable than PE, therefore without any
prooxidant, polybutene-l still degrades within 3 months.
On exposure to sunlight, the principal reaction in poly-
butene-l is a kind of chain scission, while crosslinking
reactions occur simultaneously in PE (68).

ICI presented the additives of ketone and its
derivatives which should be mixed at around 0.001 to 10%
in polyolefins. This ketone is composed of the structure

Rl—(CO)—R2, where R1 and R2 are aliphatic or aromatic and

ketone derivatives are R3—C—R4, also aliphatic and aromatic
for R3 and R4, X is sulfur, oximino, imino, hydrazone or
their derivatives. They claim that this polymer is avail—
able for disposable packages, containers, and cups (69).

ICI established one more technique of degradable

polyolefins with ferrocene and its derivatives at 0.01 to

72

2%. They also devised the degradable PE with 0.01 to 10%
of poly (4 methylpentene-l) and 0.001 to 2% of photosensi-
tizer, and this polyolefin is applied for various kinds

of films and packages (70).

Another method is discussed by Dow Chemical where
PE is mixed with absorbents such as aliphatic and aromatic
ketones, aromatic ammonia, quinones and aldehydes. They
explain that this PE is available for many purposes such
as disposable kitchen goods, packages, and items for
farms (71).

Societe Anonym Ethylene Plastique (France) is
working on polyaromatic chloride at 2% to a-polyolefins
(72).

Mitsubishi thought about new sensitizers for poly-
olefins such as 3—benzylidenephthalide or its derivatives,
and 3-(a-cyanobenzylidene)-phthalide or its derivatives
and imidine compounds, which are sensitive to sunlight and
other lights of no longer than 400 mu, and so available

for the plastics for indoor furniture and packages (73).

X
1
2c B
/ C\Y
A l
\\\ ,/ benzylidenephthalide

0:0

73

They also invented the degradable polyolefins with
sensitizers such as modified ethylene, which is princi-

pally modified with aromatic carbonyl (74).

R —X—C—R aromatic carbonyl ethylene
1_@ g 2

(R1,R2: aromatic ring, X: hydrocarbon)

Sumitomo Chem. concentrated in quinone compounds,
transition metals and metals such as Cu, Ag, Zn, Cd, at
0.01 to 10% applied for almost all the polymers (75).

Kagiya added various kinds of carbonyl compounds
to the polymer, particularly halogenated carbonyls and
their metallic salts such as ferric chloride to PVC, PS,
and PE by his own experimental method, where plastic
films are dipped into solutions of carbonyl compounds. He
found that films so treated lost tensile strength and dura-
bility on exposure to UV radiation and in atmospheric
oxygen at room temperature. He researched more of this UV
radiation method, for example, methylacetylene and tetra-
fluoroethylene which are light sensitive when mixed into
PE causing bridge formation between polymer chains. But
both techniques are not practical yet to be used in manu-
facturing processes which generally require simple and
marketable methods (76).

We can find many reports and papers of degradable

plastics, and they are indicating a lot of techniques of

74

additive system and degradable copolymers, however, they
are not completely ready for an industrial application and

market needs.

LIST OF REFERENCES

(54) A. W. Birley et al., "Degradability meeting," London,
p. 1-1 (Nov. 1973). '

 

(55) J. E. Guillet, "Degradability meeting," London (Nov.
1973).

(56) B. Baum et al., Polym.—Plast. Tech. Eng., 2(1): 1
.(1973).

(57) M. Kato, "Degradability meeting," London (Nov. 1973).
(58) U.K. Patent 1128793 (1968).
(59) Plast. Ind. News (Japan), 1(17): 166 (1971).

(60) Y. Takeuchi et al., "Degradability meeting," London,
p. 9-1 (Nov. 1973).

(61) Mitsui Toatsu Chem. pamphlet.

(62) D. W. Wiles, "Degradability meeting," London, p. 2-1
(Nov. 1973).

(63) G. Scott, "Degradability meeting," London (Nov. 1973).
(64) Modern Packaging, p. 21 (May 1973).

(65) Package Eng., p. 14 (June 1971).

(66) U.S. Patent 3590528.

(67) U.S. Patent 3454510.

(68) U.S. Patent 3525510.

(69) Japan Patent 47-9585.

(70) Japan Patent 48-14738.

(71) Japan Patent 48-17842.

(72)
(73)
(74)
(75)

(76)

75

Japan Patent 47-9588.
Japan Patent 47-21440.
Japan Patent 48-17841.
Japan Patent 47-27244.
T. Kagiya, "Degradability meeting," London, p. 8-1
(Nov. 1973).
GENERAL REFERENCES

R. Ranby et al., "Degradability meeting," London,
p. 3-1 (Nov. 1973).

C. S. Hocking, "Degradability meeting," London
(Nov. 1973).

L. J. Taylor, Chem. Tech., p. 552 (Sept. 1973).

4. DISCUSSION AND CONCLUSION

4.1. Discussion of Waste Disposal System

 

We have discussed the technologies of polymer sta-
bilization, polymer blending, biodegradation, and chemical
degradation as a chemical approach to the waste plastic
disposal problems. And also we have briefly mentioned
chemical engineering methods such as landfills, incinera—
tion, and pyrolysis. We have now come to conclude our
discussions; what is the most favorable technology to
overcome the so-called plastic pollution surrounding our
community? The new technology of plastic waste disposal,
of course, should not result in secondary or another type
of pollution or contamination.

Let us consider the advantages and disadvantages of
various disposal methods from the point of social, economic,
and environmental aSpects, as shown in Table 4.1.

The degradablepflasticsnmst certainly be of great
benefit to our environment as far as the degraded products
are not another nuisance. The research work with the
degraded plastics is surprisingly delayed compared with
the efforts to develop degradable plastics, and there are
few reports of how these degraded plastics react in the
soil. Above all, biodegradable plastics have a lot of
unknown areas; what kind of bioreaction, bioorganism or

76

77

TABLE 4.1.--Advantages and Disadvantages in Waste Disposal.

 

 

Disposal Advantage Disadvantage
(1) Degradation 'no collection 'cost-up
in littering °beauty in environment “processability

(2)

(3)

(4)

(5)

Recycling

Incineration

Pyrolysis

Landfill

'go to natural cycle

“save resource
'products
°beauty in environment

°heat
'high temperature
°volume reduction

°products

°no fuel

°no toxic gas (closed
system)

'lower cost

°residues available

°c1aimed land
°easiest method
'low cost

°high price

'short life

°low strength

°food contamination

'ground water contamination
°hygiene (biodegradable)
°littering behavior
°resource loss

'products limited
°low demand in market
°difficult technology
'low property
'difficult collection
'high cost

‘toxic gas (open system)
'furnace collapse

'gas recycle system-~costtuJ
°1oss of resource

°difficult technology
'separation system
+cost up

°natura1 resource loss
'ground water contamination
°wide land needed

 

 

I l . 4‘ 1|!!.lllnll .i
illll ll I'll"!

78

bioproduct is harmful or not for the human environment.
Optimistically speaking, if we can produce edible proteins
from the waste plastics, it would be a great benefit for
human life. However, the various compositions of recycled
plastic yield multiple bioreactions and bioorganisms,
meanwhile for example, petro-protein is cultivated only
innnormal parafins of petroleum.

The presence of degradable plastics in refuse may
give rise to flammable gases such as methane, and toxic
or undesirable products which might contaminate the ground-
water. And therefore we should take precautions to prevent
the formation of such contaminants, particularly as low?”
molecular organic chlorides from degraded PVC.

. The manufacturers of degradable plastics have to
invest more for the process to produce these plastics and
they will be faced with problems of processability of
easily degradable plastics and with the necessity of
increasing their assortments. Furthermore, the use of
sensitizers like metal complexes which accelerate the
degradation reaction may cause even more pollution prob-
lems, and so more scientific controversy should be made
by both consumers and health authorities.

All photodegradable plastics will be more expensive
than their unmodified ones because of the higher cost of
the modifier. So far a few degradable brands have been

available in the market, however they get less demand

 

 

Infill!“ ‘1‘

III 1|.‘l. ll .

79

than their sales forecasts, and so they do not get to the
break-even point.

The public will have to be warned of the limited
shelf life of degradable containers, and more, we do not
yet know exactly whether the physical and other mechanical
properties of degradable plastics are inferior to those
of unmodified plastics, and degraded products of containers
impart undesirable smells or colors, and in particular
whether they can support the growth of micro-organisms,
which would be very objectionable for reasons of hygiene.

-The reclamation by way of polymer blending is cer-
tainly one of the most difficult methods, and so it has
been the least advanced or most neglected method.

In the blend, the compatibility, which is the defi-
nite obstacle before the practical reclamation method by
way of blending different types of polymers, is very
crucial to recycle waste plastics and this compatibility
between low affinity polymers cannot be improved more
than the physical limitation.

In the metallurgical industry, metals can make more
excellent metal alloys with physical strength and elec-
trical properties greater than each component, and they
can produce the same quality of steel from scrap as from
iron ores. Meanwhile, in the plastic world, only a few
examples of polymer alloys are available in the market

such as ABS and high impact resistant PS. Of course,

80

they are not included in a category of the plastic dis-
posal, but of the improvement of mechanical properties.
Even if a thorough mixture is acquired in the multiple
polymer blend system, the deterioration of various prop-
erties is too big to compete with non-blend materials.
However hard the recycling by way of stabilization and
polymer blend is, we should not forget those methods have
outstanding potential in the plastic recycling system.

.The plastics, usually polyolefins, HDPE, LDPE, and
PP, are probably the largest source of refuse material in
the form of reject film. Oxidation is the mode of break-
down of HDPE and LDPE resulting from continued recycling-—
a breakdown that leads to an increase in the melt flow
index. On the other hand, PE is not sensitive to contami—
nants and can be readily recycled without too many
problems.

It is said that favorable regrind levels for PP are
about a10%blendwithvirgin polymerdepending on the
thermal history of the material. Recycling results in an
increase in the melt flow index reflected by a decrease in
molecular weight and a fall-off of impact strength. PP is
also susceptible to contamination promoting degradation,
which is signified by a noticeable increase in the brittle-
ness of moldings and an increase of over 30% in the melt
flow index of the recycled material compared with that of

the virgin one. PS can be readily processed but with a

81

reduction in some physical properties, a tendency for
colors to become opaque, and with contamination by other
materials.

Reworked PVC can be used in proportions up to
100%, but on continued recycling, the stabilizer, necessary
for processing and an effective length of service life,
becomes exhausted and plastics readily degrade. The
presence of degraded material promotes the further degra-
dation of other materials with which it is blended and PVC
is also susceptible to contamination.

Clear non-degraded reground ABS plastic can be
mixed with virgin pellets of the same grade in any propor-
tion. A fall-off in physical properties, particularly
impact strength, and a darkening of the material are indi-
cations of continuously reworked ABS.

The original water white color of acrylics tends
to deteriorate slightly with repeated reworking, and when
the molded color is critical, rework should be limited.
Acrylics are not compatible with other molding materials
and contamination results in a loss of transparency and
coloring effects.

As mentioned above, a stabilizer, especially one
that is non-volatile and stable during reprocessing, is
required to rework most plastics with less deterioration

in the mechanical properties. From now on, polymeric

82

stabilizers with antioxidants and UV absorbents will be
the goal of research in this area.

There is Optimism with regard to several projects
of stabilized plastics and plastic blending to reuse
consumer plastics as they are--without attempting to sort
plastics by polymer types. But some selectivity is
usually still necessary to remove nonplastic items--except
in the case of certain industrial wastes.

For instance, PVC and PE are essentially incompat-
ible and their combined scrap is useless to manufacturers.
However, if we introduce chlorinated PE as a compatibilizer
for PVC-PE, it will require extensive research to develop
the new technology.

Paul has done this research (28) and a chlorinated
PE producer, Dow Chemical, has conducted similar experi-
ments and both efforts indicate that this material, added
to mix plastics at 10 to 30% levels, can act as a mutual
binder, enabling such blends as PVC-PS-PE and PS-PV to
be reprocessed conventionally for selected commercial
products.

Introducing this mutual binder into the compat-
ibilizers for all the waste plastics, there could be
interesting methods to modify polymers with fluorine,
bromine, and iodine (by fluorination, bromination, and
iodination) as well as chlorine to make each plastic
compatible-—to produce mutual compatibilizers among waste

plastics.

83

Furthermore, if we can add general substrates to
waste plastics, which could change incompatible plastics
into compatible ones, we would be able to develop mutual
compatibilizers without blending other binds. This method
might be established by special techniques such as radi-
ation reactions and other sophisticated methods.

At least two entrepreneurial groups are known to
be engaged in developing chemical additives that also
function as compatibilizers. One of them asserts that
their proprietary agents work as process aids, speeding
cycle times when high-nitrile and other difficult materials
are blow molded. Many other chemical companies also are
reported to be investigating similar compatibilizing
chemicals. One foresees the day, not many years off, when
entire new families of compatibilized compounds will be
used.

A more direct method of reprocessing various mix-
tures of plastics has been developed by such companies in
Japan as Japan Steel Works and Mitsubishi Petrochemicals.
As briefly mentioned before, the machine reportedly can
rework any mixture of PE, PP, PS, ABS, PVC, polyester,
and even nylon-—in molded part, film, or fiber form.
Depending upon end-use specifications, this machine will
accept up to 50% nonplastic materials including glass,

paper, cloth, etc.

84

In England, Regal Packaging, Ltd., has designed a
system for pressure forming pellets from sheets rolled
from mixed waste. Royal Kent Co. has launched a similar
program, using an air classification system to retrieve
plastic from municipal refuse.

Summarizing these two technologies--stabilization
and blending with a compatibilizer-~the recycling route
shown in Figure 4.1 will be likely soon after the comple-
tion of the search for an effective compatibilizer which
is now under investigation. A direct method of reproces-
sing recycled plastics with mechanical blending has been
almost developed by some companies, and there are only a
few problems left with this mechanical process.

In any event, both the stabilizer and compatiblizer
will be polymer types, considering volatility, stability
against heat, and compatibility.

Incineration is a common method adopted by a lot
of local governments to dispose of daily household refuse.
Due to the advanced technology, controlled combustion
systems and improved furnace materials have been found to
cope with the high temperatures released from plastics
burning. Conventional furnaces have not endured high
temperatures and could not remove molten viscous plastics
clinging to their walls.

When plastics are burned, toxic emitted gases such

as HCl, NOX, and C0 are troublesome from the environmental

85

 

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86

and public health point of view. The HCl removal equipment
has been available for more than 10 years in the incinera-
tion plant, and a highly concentrated HCl solution is made
as a byproduct with a remarkably low cost.

On the other hand, the method to lower NOx in the
emitted gases, particularly when the incinceration is
operated at high temperatures like other combustion facili-
ties such as the inner combustion engine of the automobile,
is much more difficult. For the furnace to burn indus—
trial wastes and plastics at high temperatures, it is hard
to absorb emitted NOX at chimney from the standpoint of
both technology and economy.

W;W“' Heat of steam delivered from an incincerator is
supplied to the community as a heat source for homes and
factories.

’Considering the reclamation of plastics, if once
incinerated, there is no hope to recycle a natural carbon
resource except remaining ash which is used for limited
purposes such as landfills and compostings.

Pyrolysis is not a completed method for the dis-
posal of urban refuse, but has attracted a lot of attention
recently, because it is a closed system which can avoid
another pollution.

According to the disclosed information, it reclaims

organic compounds at controlled pyrolyzing temperatures,

87

and moreover once the pyrolysis plant starts up, no more
fuel is fed to the plant because the pyrolysis reactions
are exothermic.
Pyrolyzed products can be controlled by catalysts
such as Fe203,
Landfills dispose of about 90% of urban refuse in

FeCl3, NiClz, etc.

many countries and they claim lands along seashores in
some areas.

As described before, the densities of many plas-
tics are fortunately close to soil, around 0.8-l.0 g/cm3,
and the non-corrosive property of carbon chaim polymers
in the real environmental condition is favorable for land-
fills in spite of their frictional smoothness to cause
partial landslides.

Landfills are the method to use volume properties
of plastics not energy properties, and so it is quite hard
to compare their benefits with technologies which use the

heat energy of waste plastics.

4.2. Conclusion

 

4.2.1. Cost Estimation
of Disposal

 

 

Since the waste disposal technology is concerned
with the social factors, any cost estimation should be
considered, whether by a private handling corporation or
a governmental organization, to minimize the total con-

sumption of precious capital and energy. The total cost

 

| (.I .l

88

is fluctuating at this time of soaring inflation and rapid
technical innovation. Above all the scale merit of a new
disposal plant when built on.a large scale reduces the
installation cost and running cost per unit, and so we
should not regard the cost estimation as a solid and

fixed one but an index to compare proposed disposal meth-

ods and find the less expensive one.

Costs of modified plastics.--Some amount of higher

 

cost is predicted for producing such modified plastics as
developed by Scott or Guillet, and to manufacture sta—
bilized plastics. For instance, Ecolite, PE copolymer
with Vinylcarbonyl at 0.02 to 2%, is wholesaled at $27.5
to $29.0, which originally sold at $25 when unmodified,

so there is a 10-16% increase (79). It could be esti-
mated that modifying comonomer costs 5-8 times as much as
main monomer. According to this assumption, degradable

PE developed by Guillet costs $18-$30/ton more, and that by
Scott, $2-$3/ton more than unmodified PE which cost

around $200/ton in 1970. Of course, if a vast amount of
demand emerges in the market, mass production would reduce
these costs. By the same assumption as above, stabilizers
in PE are mixed at 1-2% level and they cost 3-8 times as
much as ethylene monomer, which adds $10—$30/ton in cost

to PE pellets.

III-II I! l {1‘ I

89

Collection systems.--Solid waste disposal is

 

primarily a management decision, not a technical one. It
is said that the collection and transportation costs
account for up to 90% of all waste disposal costs (77),
and so a small technical improvement here should open
vast new areas for economical dumping. The Solid Waste
Office of the Environmental Protection Agency (U.S.)
reports collection and transportation costs ranging from
$1 to $420/ton (78).

Here is an interesting assumption. A 20 cu.yd.
truck with rear compactor and a three-man crew costs $150/
day to operate when fuel, amortization, and maintenance
are figured in. The average truck is driven about 50 miles
a day, disposing of two 4-ton loads. Thus Operating costs
are about $19/ton. If a new dump site 10 miles further
away is needed, the increased travel time is more than
1.5 hour at 25 miles/hr. So only 1.5 loads a day, or
6 tons, could be collected, raising the collection cost
close to $26/ton. The $7 difference could be applied to

a secondary transportation and landfilling (77).

Separation.--Stabilized plastics may be recycled

 

in an exclusive circulation for their reclamation, but

waste plastics are generally recycled in a random manner.
In the total disposal system the separation

process is to select plastics from other urban refuse and

to classify them into each group such as PE, PP, PS, etc.

90

As far as we have investigated, the classification
of plastics is the hardest technology in the plastics
industry, and so far only one example that may be successful
in the reusing process does not require separation--that
is, recycling only HDPE milk bottles, which are circulated
in a small community.

Since the proposed separation methods such as air
classification and the sink-float method that are actually
the separation of plastics from other refuse are at an
experimental stage, we can hardly estimate their instal-
lation and operation costs, but we assume that they are

not far from other processes such as pyrolysis (78).

Disposal.--Sanitary landfill is a solid waste
handling method which disposes of up to 90% of urban
refuse in developed countries. In Figure 4.2, we have
good estimates of sanitary landfill costs with cover
materials purchased at $1.50/cy.yd. and in the same figure,
we recognize the total cost of incinceration is about $7/
ton at 1,000 ton/mo. disposal capacity, and also a cost
estimation is given for pyrolysis assuming that it has a
similar trend to incinceration.

According to the test result for pyrolysis, the
total disposal cost is about $10/ton at a 1,000 ton/mo.
capacity plant (corresponding to a city population of

100,000) (78).

 

  
 
 
    

8 20 ' Pyr lysis

.p

a 15 -

7’ Incineration
g 10 W

8 5 - Landfill

 

 

l l J

10 10 10 10 10
Waste (ton/mo.)

 

Figure 4.2.--Cost Estimation with Tonnage, 1970.

Sale value of new products.--Landfill reclaims new

 

lands when the dump sites are acquired along the seashore
or the lake shore. The price of land varies a lot depend-
ing on where it is located. In this cost prediction to
compare the relative values, we assume a temporary value
of the reclaimed land. gi~o
Incineration produces steam and remaining ash used
for landfills which make only a small amount of profit.
On the other hand, pyrolyzed municipal refuse provides
organic liquids andehich could be reclaimed for other
raw materials. In the available data, these raw materials
are valued at as much as $20-$30/ton, depending on the
forms of chemical compounds (78). Suppose that the
reclaimed products sell at a price of one—third of the
products of virgin plastics and the profit rate is 25%

of the sales price, considering this raw material is

cheap, but the product quality is inferior.' The profit

III | ll ll!) I III. 'lll'l' ll" ‘IJ I I .....

of products is about $15/ton for the case of PE, where the

price of virgin PE is assumed to be $180/ton in 1970.

Conclusions from the cost estimation.--The total

 

cost estimation of disposal methods indicates very inter-
esting results. Inmengineering methods, pyrolysis is_more
recommended than the other two methods as far as the cost
estimation is concerned, and pyrolysis is also praised
from the environmental point of View because of its closed
operation which discharges less pollution.

In the reuse technology, if we consider these two
points--that the recycling circle of plastic is very
small and the blending technology is not completed yet--
the total cost assumption is not accurate; however, we
assume here that it is not so high if compared with other
methods.

Considering its cost competitiveness and chemical
toxicity, there is a remarkable innovation in the degradable
plastics, which is developed by Griffin. In an1 interview
Griffin explained that the starch blended in plastics did
not result in a cost increase, because the starch sold at
a price 1/2-1 times as high as ethylene monomer.

This starch degradable plastic does not appear in
the market yet, but it will be likely to get a good repu-
tation, especially as farm materials, judging from its
cost and non—toxic additives. The other two methods, pre-

sented in Table 4.2, are more expensive and toxic than

93

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94

Griffin's, although each of them claims to have more
effective degradability than others.

Our conclusion with waste plastic disposal is that
(1) plastics circulatedwith urban refuse should be dis-
posed of by pyrolysis and (2) those plastics out of the
collection should be made environmentally degradable.

Hence there are lots of exceptional cases from
our assumption; we, of course, must think about a detailed
plan to come up with various problems which may occur in
our environment. However, as we have predicted, the solu-
tions to the disposal problem will be these two methods--
pyrolysis and degradable plastics, judging from the cost
analysis and environmental situation within the next
decade.

4.2.2. Movement of Disposal
in the Future

 

The plastic reclamation by way of the separation
from urban refuse is not carried out in a plastic society—-
the reasons are (l) the classification of a tiny ratio of
plastics, about 3%, from huge amounts of urban refuse is
very difficult, considering its technology and the economic
benefits; (2) recycled products cannot compete with virgin
ones in a real market. In any way, the necessary terms to '
which we should pay attention for the successful recycling
of plastics are:

l. sanitation--recycled plastic cannot be sup-
plied in the food market.

95

2.‘ cost--cost competition with virgin plastics
should be improved, especially collection
and reclamation should definitely be cheap.

3. supply of refuse--urban refuse must be sup-
plied with stable quality and quantity for
a long term.

4. composition--recycled materials must not
have random composition, particularly incom-
patible ones should not be included.

5. market root--a solid and profitable market
for recycled plastics should be developed.

We will expend a lot of investments and efforts before we
solve this hard question--waste plastic disposal.

Considering general aspects of the disposal method,
the basic technology has progressed more rapidly than its
followers; in other words, the hardware has moved faster
than the software which is defined in this discussion as
the controlled disposal system, administration of the
government's litter control or regulation by law and public
or private organization for waste disposal.

Meanwhile, more improvement in the hardware is
expected in such cases as the recycling-inclined plastic
developed by Monsanto, which is a nitrile based, light,
safe, easy-storing, and recyclable polymer. And Monsanto
claims it has low energy consumption while processing and
recycling, meeting the recent energy shortage demands (80).

There is a very interesting proposal from the U.S.
Atomic Energy Commission, which suggests a promising method
of treatment of municipal refuse with fusion-powered elec-

trical generating stations of the future.

96

The plasma produced during nuclear fusion is so
hot that anything fed into it becomes dissociated and
ionized. The wastes are fed into the immensely hot plasma
produced for the fusion of deuterium. This magnetically
bottled plasma is around 50 million °C, a temperature that
obviously causes any solid not just to vaporize but to dis-
sociate into its elements and to ionize. When treating
typical refuse, these elements would include oxygen
(44%), carbon (33%), iron (6.6%), hydrogen (4.8%),
silicon (4.6%), aluminum, copper, sodium, magnesium, and
other elements with significant reuse value.

All of this is still very conceptual, because
nuclear fusion is a long way from being commercial, but
the potential attractions of this waste-disposal route
would likely far outweigh the cost of the high energy
level required. Furthermore, this new waste disposal
concept is good in that, unlike many other disposal tech-
niques, it does not introduce any pollution of its own,
and there is very little energy loss because the process
takes place at very high temperatures.

We hope the plasma will overcome the nuisance,
waste disposal problem, not far away from now, because it
must be a more perfect technology than mankind has ever

experienced (81, 82).

(77)
(78)
(79)
(80)
(81)

(82)

97

LIST OF REFERENCES
Chem. Eng., p. 155 (June 21, 1971).
Chem. Eng., p. 62 (Oct. 4, 1971).
Package Eng., p. 33 (Oct. 1972).
Environmental Sci. & Tech., 8(2) (Feb. 1974).
Modern Plast., p. 50 (Mar. 1970).

Chem. Eng., p. 56 (Dec. 15, 1969).

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