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LIBRARY
Michigan State
University

 

 

 

This is to certify that the
thesis entitled

PROCESSING AND MECHANICAL PROPERTY TESTING
OF PAPER FIBER AND HIGH DENSITY POLYETHYLENE

COMPOSITES

presented by

'Thirayuth-‘Chotipatoomwan

has been accepted towards fulﬁllment
of the requirements for

Master om degree in waging

4&3.» 2.2%

Major professor

Date Dec 8 98

0-7639 MS U is an Afﬁrmative Action/Equal Opportunity Institution

 

 

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DATE DUE DATE DUE DATE DUE

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1!” clam“

PROCESSING AND MECHANICAL PROPERTY TESTING OF PAPER FIBER AND
HIGH DENSITY POLYETHYLENE COMPOSITES

By

Thirayuth Chotipatoomwan

A THESIS

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

MASTER OF SCIENCE
School of Packaging

1998

ABSTRACT
PROCESSING AND MECHANICAL PROPERTY TESTING OF PAPER FIBER AND
HIGH DENSITY POLYETHYLENE COMPOSITES
By

T hirayuth Chotipatoomwan

The utilization of waste paper can be increased by combining paper ﬁbers with
thermoplastics like High Density Polyethylene (HDPE) into a composite material. Two
kinds of paper ﬁbers, mixed and deinked paper ﬁbers, were used as ﬁllers in composites.
The mechanical and physical properties were studied by varying the ﬁber content and
using different kinds of ﬁbers at the same processing conditions. HDPE and paper ﬁbers
were combined in a twin-screw extruder to form the composite, and then compression
molded. Tensile properties, Izod impact strength and water absorption were evaluated
following ASTM standard procedures. The dispersion of ﬁbers was seen by scanning
electron microscope (SEM). The results Show that the addition of paper ﬁbers to HDPE
causes a decrease in tensile strength and impact strength, but an increase in tensile
modulus. Water was more absorbed due to the addition of paper ﬁbers. SEM showed
that the ﬁbers did not disperse in the matrix very well.

Mixed paper ﬁber composites gave better results in strength when compared with
deinked paper ﬁber composites. Composite strength was lower than aspen wood ﬁber

composites from prior experiments, but water absorption was lessened.

To my parents , Pattama and Chuan Chotipatoomwan

iii

ACIG‘IOWLEDGEMENTS

First of all, I would like to thank my major professor, Susan Selke, PhD. (School
of Packaging, Michigan State University), and my committee members, Jack Giacin, PhD.
(School of Packaging, Michigan State University) and Indrek S. Wichman,
PhD.(Department of Mechanical Engineering, Michigan State University), for their

guidance and assisstance.

I also would like to thank Michael J. Rich from the Composite Materials and
Structures Center for his instruction and use of the extruder, Richard Schalek, PhD. for his
assistance with the Scanning Electron Microscope (SEM), and Phil Culcasi for his

instuction in use of Instron.

Lastly, my special thank goes to my two lovely sisters, Pattra Maneesin and Rujida

Leepipattanawit, for their help in statistical analysis and providing a lot of information.

iv

TABLE OF CONTENTS

LIST OF TABLES ....................................................................... vii
LIST OF FIGURES ...................................................................... viii
INTRODUCTION ........................................................................ 1
CHAPTER 1
LITERATURE REVIEW ................................................................ 7
Background on composite materials. ............................................... 7
Reinforcement ......................................................................... 7
Polymer matrix ......................................................................... 9
Interface ............................................................................... 1]
Prediction of properties .............................................................. 12
Prior research .......................................................................... 21
CHAPTER 2
MATERIALS AND METHODS ....................................................... 27
Materials ............................................................................... 27
Methods ............................................................................... 29
CHAPTER 3
RESULTS AND DISSCUSSION ...................................................... 33
Results - Tensile strength ............................................................ 33
Results - Modulus of elasticity ..................................................... 35
Results - Yield strength .............................................................. 37
Results - % Elongation at break ..................................................... 39
Discussion - Tensile strength ........................................................ 41
Results - Izod impact strength ....................................................... 47
Discussion - Izod impact strength ................................................... 49
Results - Water absorption ........................................................... 50
Discussion - Water absorption ....................................................... 52
Results - Comparison of wood and paper ﬁber reinforced HDPE composites
(at 40% ﬁber and 60% HDPE) ..................................................... 54
Discussion - Comparison of wood and paper ﬁber reinforced HDPE composites
(at 40% ﬁber and 60% HDPE) .................................................... 57
SUMMARY AND CONCLUSIONS ................................................... 62

RECOMMENDATION FOR FUTURE RESEARCH .............................. 64

APPENDIX A ............................................................................. 65
APPENDIX B ............................................................................. 71
REFERENCES ........................................................................... 77

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8.

Table 9.

Table 10.

Table 11.

Table 12.

Table 13.

Table 14.

Table 15.

LIST OF TABLES

Recovered Paper (Thousand tons) ....................................... 3
Apparent Recovery and Utilization Rates (1992) ....................... 3
Results of Tensile Strength ................................................ 33
Results of Modulus of Elasticity .......................................... 3 5
Results of Yield Strength .................................................. 37
Results of % Elongation at Break ......................................... 39
Results of Izod Impact Strength ........................................... 47
Results of Water Absorption ............................................... 50
Comparison of Wood and Paper Fiber Composites ..................... 56
Data Tensile Strength ........................................................ 65
Data Modulus of Elasticity .................................................. 66
Data Yield Strength .......................................................... 67
Data % Elongation at Break ................................................ 68
Data Izod Impact Strength .................................................. 69
Data Water Absorption ....................................................... 7O

vii

LIST OF FIGURES

Figure 1. Tensile Strength .............................................................. 34
Figure 2. Modulus of Elasticity ........................................................ 36
Figure 3. Yield Strength 38
Figure 4. % Elongation at Break ...................................................... 40
Figure 5. Dispersion of Mixed Paper Fibers at 10% ................................ 43
Figure 6'. Dispersion of Mixed Paper Fibers at 40% ................................ 44
Figure 7. Dispersion of Deinked Paper Fibers at 10% ............................. 45
Figure 8. Dispersion ofDeinked Paper Fibers at 40% ...... 46
Figure 9. Izod Impact Strength ........................................................ 48
Figure 10. Water Absorption ............................................................ 51
Figure 11. Mixed Paper Fibers .......................................................... 59
Figure 12. Deinked Paper Fibers ........................................................ 60
Figure 13. Aspen Wood Fibers ......................................................... 61

viii

INTRODUCTION

Nowadays, paper products and packages are in high use in industrial, commercial,
and residential applications. Consequently, these cause us a lot of trouble in decreasing
the amount of ﬁber resources used because wood ﬁbers and pulps are the main sources for
paper manufacturing. Moreover, controlling the high quantity of paper wastes is also
needed to reduce the environmental problems, such as the concern over the volume of
solid waste being directed to landﬁll sites.

In the United States, all types of solid wastes amount to about 60,415 pounds of
waste per person per year (Selke, 1994). These solid wastes are classiﬁed as water
pollutants, industrial waste, wastewater treatment, air pollutants, oil spills, mining,
demolition waste, agricultural waste, hazardous waste, and municipal solid waste (MSW).

Packaging wastes are one part of MSW, about 1/3 of the total, and paper and
paperboard are the highest percentage of this part. Paper products have traditionally been
disposed to landﬁlls, and this is becoming increasingly expensive with landﬁll space
becoming less available. The recycling of recovered paper, not a new phenomenon, could
be the way to solve these problems. There are two measures about which we are
concerned. Utilization and recovery rates are the factors which tell about the materials
effect on the environment. The higher percentage they are, the less problem it is.

First of all, the utilization rate is measured from the amount of wastepaper used in

the production of a speciﬁc product, or product sector, or by the industry.

Utilization rate = Waste paper used (tonsLx 100 (1)
Paper or board production (tons)

For example, the consumption of paper and board ﬁom around the world in 1992
was 245.6 million tons, but the amount of wastepaper consumption was only 96 million
tons (Mckinney, 1995). These means that the utilization rate is about 31%.

Another factor is the recovery rate, which is a measure of recovery of wastepaper ,

and is given as a proportion of the total paper and board consumption.

Recovery rate = Wastepaper recovered (ton_s) x 100 (2)
Apparent consumption of paper and board (tons)

Because of the high volume of solid waste and the lack of adequate ﬁber sources,
many countries have introduced programs, legislation and regulations to promote waste
ﬁber recycling. Therefore, the paper recovery rate has increased each year.

Two primary indices, recovery and utilization rates, are used to compare the level
of recycling in various countries. The difference between these indices is that the
utilization rate is the comparison of the amount of secondary ﬁber used in paper/board
production with the total ﬁber used, whereas recovery rate is the comparison of
wastepaper recovered for reuse with paper consumed (Smook, 1992). These two indices
do not need to be equivalent, and depend on major factors, such as the amount of forest
resources, and the paper industry in each country. For example, Sweden is the leading

paper exporting country, so the utilization rate is understandably less (Smook, 1992).

Table 1. Recovered Paper (Thousand tons)

 

 

 

 

Country 1989 1994
Canada 1652 2458
Finland 684 1472
France 2877 3514

Germany 5663 9758

Italy 1452 2278
Japan n/a 14908
Norway 157 297
Portugal 291 3
Spain 1591 1816
Sweden 890 990
Switzerland nla 754
Turkey n/a 425
United Kingdom 2880 4048
United States 24664 35100

 

 

 

 

Source : OECD 1997

Table 2. Apparent Recovery and Utilization Rates (1992)

 

 

Country Utilization (91) Recovery (9%)
USA 33.1 38.7
Germany 52.1 50.6
Japan 52.7 51.1
The Nethertands 70.5 54.7
Sweden 14.3 49.7
Australia 45.8 36.8
South Korea 69.6 43.2
UK 60.2 33.9
Denmark 96.6 37.6

 

 

 

 

Source : McKinney 1995

In Japan, the wastepaper recovery rate ﬁom 1953 to 1991, increased from 19.6%
to 50.8% (McKinney, 1995) because of the lack of forest resources. The United States
has a lower recovery rate. In 1994, the recovery rate was just 40% (OECD, 1997).
However, this is slightly above the world average.

Even if the utilization rate is high, it does not mean that paper ﬁber can be

processed many times in a recycling system, because signiﬁcant losses of both ﬁber

substance and strength occur during each recycling. It is considered that a ﬁber can be
recycled only four times before the loss in some quality, such as ﬁber substance and
strength ( Smock, 1992). The eﬁ‘ect of multiple recycling operations on ﬁber
characteristics had been studied from the late 1960’s to the late 1970’s. Smock
summarized results ﬁom one study on the effect of repeated recycling of newsprint on
individual ﬁber strength and on the bonding strength between ﬁbers. Both strength types
were decreased, and the bonding between ﬁbers was dramatically lost. With each drying
and slushing cycle, the ﬁbers become less ﬂexible and less permeable to water, and
therefore do not conform as well as virgin ﬁbers. Cumulative loss of hemicellulose from
the ﬁber surfaces also contributes toward reduced bonding.

Besides ordinary waste paper, waste polymer-coated paper is a concern, especially
paper coated with LDPE which is used to produce such products as aseptic packages,
paper milk cartons, frozen food boxes, and paper plates and cups.

In 1992, researchers at the USDA Forest Service Forest Products Laboratory
(FPL) were aware of the problems associated with LDPE. Then, they considered the
ways to reuse these materials. Finally, there were three ways which were proposed: (a)
burning it for fuel, (b) drying and separating the paper ﬁber from the LDPE so that each
material could be recycled using existing technologies, and (c) making a ﬁber/plastic
composite of the material (English and Schneider, 1994)

However, the ﬁrst and second options were not chosen because of environmental
concerns and the difﬁculty in separation. The FPL researchers decided making a paper

ﬁber/plastic composite was the most attractive option.

Generally, in composite materials, wood and paper ﬁber have been used as a

reinforcing ﬁber in therrnosetting plastics. On the other hand, thermoplastics, like LDPE,

have recently been mixed with wood and paper ﬁber also. Moreover, several billion

pounds of ﬁllers and reinforcements are used annually in the plastic industry (Katz and

Milewski, 1987).

There are many reasons that a ﬁber/plastic composite was produced.

1)

2)

3)

Material cost saving : As plastic materials have relatively high cost, the ﬁbers
which have low cost can help by reducing the quantity of plastic used.
Improving some physical properties of thermoplastics : The addition of wood
or paper to therrnoplastics increases stiffness and strength and reduces creep.
This material can be used in automotive, building, appliance, and other

applications.

However, there are still some drawbacks occurring from this material also. For

example:

1)

2)

3)

Possibility of degradation of ﬁbers : ﬁbers can lose their properties due to high
temperatures in processing.

Limited type of thermoplastics: just some kinds of therrnoplastics can be used
with agro-ﬁbers, for example polyethylene (PE), polypropylene (PP), polyvinyl
chloride (PVC), and polystyrene (PS), because it is diﬁicult to mix ﬁbers with
thermoplastic due to their high melting points and high solution viscosities.
Moisture absorption: by nature, ﬁbers can absorb moisture, and this can result
in swelling of the ﬁbers. However, the absorption of moisture by the ﬁbers is

minimized in the composite due to encapsulation by the polymer.

The primary objective of this research was to utilize the wastepaper in the form of
paper ﬁbers in the process of composite materials, resulting in manufacturing cost savings,
decreasing of environmental problems, and improvement of properties in the composites.

As the cost of HDPE resin is higher than that of the ﬁber, and the quantity of
HDPE used in the composite decreases as the ﬁber ratio increases, the cost can be cut
down in this way. Moreover, the amount of wastepaper can be reduced by using it as a
raw material in this kind of composite.

However, some properties are changed by adding paper ﬁbers into the HDPE
matrix. In this research, tensile strength, yield strength, % elongation, modulus of
elasticity, and Izod impact strength were tested by comparing the eﬂ‘ects on the composite
of two kinds of paper ﬁbers, high-grade deinked and mixed paper ﬁbers.

Moisture absorption and dispersion of ﬁbers in the matrix are important to know.
Even though the ﬁbers are encapsulated by the polymer matrix, they can swell up by
absorbing moisture outside. ASTM 570-81 determines the amount of moisture (in
percentages) that the materials absorb as a function of time. To see how ﬁbers disperse in
the composites, scanning electron microscopy (SEM) can be used to show how ﬁbers are
mixed into the polymer matrix.

Lastly, data on aspen wood ﬁbers from the earlier experiments by JoAnna Denise
Childress (1991), were compared with the results from paper ﬁbers, as they both
functioned as the reinforcement in composites. The comparison between the ﬁbers was

made at the ratio of 40% by weight in HDPE.

CHAPTER 1
LITERATURE REVIEW
1) Background on composite materials

Generally, a structural composite consists of three phases. One of the phases is the
reinforcement, which is usually discontinuous, stiﬁ‘er, and stronger. The continuous
phase, which is less stiﬂ‘ and weaker, is called the matrix. Finally, the interface is the
chemical or other interactions between the reinforcement and the matrix.

Each phase has diﬁ‘erent roles that depend on the application and type of the
composite materials. In this project, the chosen reinforcement, paper ﬁbers, is usually in
the form of short ﬁbers, and it provides stiﬂ‘ness, whereas the matrix is the main load-
bearing constituent governing the mechanical properties of the material. Additionally, the
matrix can protect the ﬁber ﬁ'om abrasion and the effects of the environment. The
interface can play an important role in controlling the failure mechanisms, fracture

toughness, and overall stress-strain behavior of the material.

2) Reinforcement
Paper ﬁbers made from waste papers are used as the reinforcement in these
experiments. Waste papers have been divided into ﬁve grades by the American Forest &
Paper Association (OECD, 1997).
a) Mixed paper : Mixed papers, super mixed papers, ofﬁce papers (if not deinked or of
suitable quality to be used as a pulp substitute), telephone directories, magazines and

catalogues, recycled boxboard cuttings, tissue paper converting scrap if predominately

composed of recycled ﬁber, mill wrappers, specialty grades and all other grades not
elsewhere speciﬁed.

b) Newspapers : Old newspapers (ONP), special news (including deinked quality)
overissue news, white blank news, ground-wood computer printout publication blanks,
mixed ground-wood and ﬂyleaf Shavings, coated ground-wood sections.

c) Corrugated : Old containers both corrugated and solid ﬁber, container plant cuttings,
kraﬁ paper and bags, kraft bag clippings, carrier stock and carrier stock clippings.

d) Pulp substitutes : Unprinted paper and board that has not been coated or adulterated in
any way; included in this category are tabulating cards, white and semi-bleached
sheets, cuttings, shavings, or trimmings.

e) High-grade deinked : Bleached chemical grade ofﬁce papers and computer printout to
be deinked, bleached sulphite and sulphate cuttings including tissue paper converting
scrap if predominantly composed of bleached chemical pulp ﬁber, coated book stock.
Printed grades, if deinked, are reported as high grade deinking.

In this case, ﬁbers from mixed paper and from high grade deinked paper were
compared in mechanical properties when they were combined in composites. Moreover,
the effects of ﬁber content, ﬁber length, dispersion, and ability of water absorption were
investigated.

Reinforcing ﬁbers are classiﬁed into three categories, which are particulate,
continuous, and discontinuous ﬁbers (Daniel and Ishai, 1994).

Particulate composites: They consist of particles of various sizes and shapes randomly

dispersed within the matrix. Because of the randomness of particle distribution, these

composites can be regarded as quasi-homogeneous on a scale larger than the particle size

and spacing and quasi-isotropic. Particulate composites may consist of either nonmetallic
or metallic particles in nonmetallic or metallic matrix. Examples include concrete and
glass reinforced with mica ﬂakes.

Discontinuous or short ﬁber composites: They contain short ﬁbers or whiskers as the
reinforcing phase. These short ﬁbers, which can be fairly long compared with the
diameter, can be either all oriented along one direction or randomly oriented. In the ﬁrst
instance, the composite material tends to be markedly anisotropic, or orthotrOpic, but in
the second, it can be regarded as quasi-isotropic.

Continuous ﬁber composites: They are reinforced by long continuous ﬁbers and are the
most efﬁcient ﬁom the point of view of stiffness and strength. The continuous ﬁbers can
be all parallel, can be oriented at right angles to each other, or can be oriented along
several directions.

As paper ﬁbers are a kind of short ﬁbers, they are classiﬁed as discontinuous
ﬁbers. Addition of short ﬁber reinforcement to thermoplastic materials can be used to
enhance physical properties and performance characteristics. There are many factors that
inﬂuence the properties of composites, such as ﬁber type, length of ﬁber, length to
diameter ratio, ﬁber alignment, interface, matrix resin morphology, processing procedures

and environmental effects.

3) Polymer matrix
A polymer is deﬁned as a long-chain molecule containing one or more repeating
units of atoms, joined together by strong covalent bonds (Mallick, 1988). In general, they

are divided into two broad categories, thermoplastics and therrnosets. These two kinds of

matrices have both advantages and disadvantages, when they are reinforced into
composite materials.

Thermoset polymers in composites normally give thermal stability and chemical
resistance. They also exhibit much less creep and stress relaxation than thermoplastic
polymers. Then, thermosetting materials are particularly suitable as composite materials
due to their relative ease of fabrication and good adhesion characteristics. However, their
disadvantages are their limited storage life (before the ﬁnal shape is molded) at room
temperature, long fabrication time in the mold, and low strains to failure which also cause
them to have low impact strength.

On the other hand, thermoplastic polymers in composites will give high impact
strength and fracture resistance, which in turn impart excellent damage tolerance
characteristics to the composite materials. Moreover, thermoplastic polymers have higher
strains to failure, so they provide a better resistance to matrix microcracking in composite
laminates. Even though thermoplastic polymers have a lot of advantages, they still have
been developed slowly compared to therrnoset matrices (Mallick, 1988). Because of their
high melt or solution viscosities, incorporation of continuous ﬁbers into therrnoplastics is
diﬁicult.

From several experiments, it was determined that some polymers are susceptible to
reinforcement, others are not. Especially, it is diﬁcult to incorporate continuous ﬁbers
into most thermoplastics, such as polycarbonate and nylon, due to their high melt and
solution viscosities (Mallick, 1988). This means the requirements for ﬁller particle size

depend upon the polymer matrix type.

10

4) Interface

Berlin et al (1986) studied the eﬁ‘ect of adhesion at the interface in composites,
which is divided into two categories. First, in the case of good adhesion between the
matrix and ﬁbers, the maximum stress that can be transmitted from the matrix to the ﬁber
is equal to the shear yield point of the matrix, “cm, for a plastic matrix, and equal to the
shear strength of the matrix for a brittle material. Secondly, in the case of poor adhesion,
the maximum stress transmissible from the matrix to the ﬁber will be smaller than tm and
equal to the strength of adhesion (Berlin et al, 1986).

In the complete absence of adhesion, a very small stress applied to the matrix
would cause detachment of the matrix material from the ﬁber surface with the formation
of voids. No Stresses at all would be transmitted to the ﬁber in this case.

The mechanism of stress transfer at the interface in composites is much more
complex. It is important to distinguish between normal stress and shear stress. Shear
stresses will transmit tensile stress to the ﬁbers along the ﬁber orientation. Normal
stresses arise on the side surfaces of the ﬁbers due to the residual thermal stresses in the
composite and the different Poisson’s ratios (v) of the matrix and ﬁber.

In continuous ﬁber-reinforced composites, the resistance to shear between the
matrix and ﬁber has a relatively small eﬁ‘ect on the composite strength under tension along
the ﬁbers. However, it does have a certain eﬁ‘ect at stresses close to the ultimate stress,
when the weaker ﬁbers begin to break and stress transmission through the matrix begins to
play an important role. When tension is applied across the ﬁbers, it is not the resistance to

shear but the resistance to separation (Cmf) which begins to play the major role.

11

In general, at high ratios of ﬁbers in composites, the strength of reinforced
composites will depend on our, the maximum values of tensile stress in the composites (0})
will decrease because a matrix can come oﬂ‘ the transversely oriented ﬁbers and the
resultant voids will initiate crack development and, therefore, the composites will not have
a high mechanical strength.

Berlin et al (1986) classiﬁed three factors that needed to be considered: void size,
void content, and the stress causing dewetting, which causes the ﬁbers to not adhere to
the matrix. The void Size is determined by the ﬁller particle size. The smaller the
particles, the smaller will be the voids resulting from dewetting of the matrix. The void
content is determined by the volume fraction of the ﬁller. Finally, the stress required to
cause dewetting depends on the adhesion strength between the ﬁller particles and the

matrix.

5) Prediction of properties
Theoretically, calculations for tensile strength, modulus, and other properties of
ﬁber-reinforced composites are based on the ﬁber volume ﬁaction in the material, which

can be determined ﬁom Equation 3 (Bean et al, 1986).

Vr = WP’Dr (3)
(WI/pf) + (l’wfypm

where: W; = ﬁber weight ﬁaction
(1 'Wf) = matrix weight fraction

pf = ﬁber density

12

p... = matrix density

The composite density (pc) is another factor related to the ﬁber weight fraction

(Wf). It can be calculated by the following equation.

1 (4)

(Win/pr) + (l-Wr)/Pm

During the processing of composites, air or other volatiles may be trapped in the

pa:

material. This can cause voids, which will affect the mechanical properties of the

composite materials. Void content can be estimated by Equation 5.
V‘, = QsLQ (5)

p.
where: Vv = volume fraction of voids

theoretical density (as calculated in equation 4)

pc
actual density, measured experimentally on composite specimen

p
A high void content (% by volume) usually leads to lower fatigue resistance,

greater susceptibility to water diffusion, and increased variation in mechanical properties

In the case of anisotropic materials under uniaxial tension along a direction, the

axial and transverse deformation (strain) are given by Equations 6 and 7 respectively

(Berlin et al, 1986).

ex =_q& (6)
Ex
63 =-_v33<13 (7)
E,

where: (I" = axial normal stress

E = axial modulus in x-direction

l3

vxy = Poissons ratio associated with loading in the x-direction and strain in the y-
direction
Additionally, Poisson’s ratio (vxy) can be estimated by Equation 8

v3 = m (8)
E,

where: m, = shear coupling coefﬁcient (the ﬁrst subscript denotes normal loading in the

x-direction; the second subscript denotes shear strain)

Normally, ﬁber-reinforced composites are microscopically inhomogeneous and
orthotropic (Mallick, 1988). Thus, the mechanics of ﬁber-reinforced composites are far
more complex than those of conventional materials. Predictions of mechanics of ﬁber-
reinforced materials are divided into two diﬂ‘erent approaches.

1) The micromechanics approach: Equations describing the elastic and thermal
characteristics of a lamina, which is the incorporation of a large number of ﬁbers into a
thin layer of matrix, are based on micromechanics formulations.

2) The macromechanics approach: The studied material is assumed to be homogeneous.
Equations of orthotropic elasticity are used to calculate stresses, strains, and
deﬂections.

Mallick (1988) considered the mechanics of ﬁber-matrix interactions in a
unidirectional lamina. Then, he proposed the basic assumption, in which ﬁbers are
distributed throughout the matrix and bonded to the matrix perfectly, and voids cannot
occur. Applied loads are used in either the longitudinal or transverse direction. As
continuous parallel ﬁbers were used to study longitudinal tensile loading, bonding between

the ﬁbers and matrix is assumed to be perfect.

14

Then, er = 6... = 6c (9)
where Ef, em, e, are the longitudinal strains in the ﬁbers, matrix, and composite
respectively. Since both ﬁbers and matrix are elastic, the stresses can be shown to be the
following (Mallick, 1988):
of = E363=Erec (10)
om= Emem=Emec (11)
When a tensile force is applied on a composite material, it will be shared by the
ﬁber and matrix. The total force (PC) can be written as:
Pc = Pf+ Pm (12)
Since the force or load is equal to stress (0' ) x area (A), so equation 12 can be
rewritten as
cr.~.Ac = OrAr+ omAm (13)

01'

0c = 413:4“ 9:35:33 (14)
Ac Ac

where oc = average tensile stress in the composite
A; = net cross-sectional area for the ﬁbers
A... = net cross-sectional area for the matrix
The total area of the composite will be the area of the ﬁbers plus matrix:
Ac = Ar+ Am (15)
Since Vf= Ag’Ac and V... = Am/Ac, from equation 14

(3c = Ofo+ 0'me

15

= Gfo + o...(l-Vf) (16)
Since modulus of elasticity equals the ratio of stress and strain,
E = o/ e (17)
then, the longitudinal modulus for the composite can be written as:
cc = Efo€f+ Emeem (18)
Equation 18 can be rewritten in the form of the rule of mixtures as equation 19.
E.=B3v3+1~:..(1-v3) (19)

Birley et a1 (1992) said the rule of mixtures gave an upper-bound limit for stifﬁiess,
which is related directly to the volume ﬁ'action (Vf) of the reinforcement phase. Fiber
content is calculated on a weight fraction basis with loading up to 40% (by weight) being
typical. In general, the longitudinal modulus is actually less than that predicted by equation
19.

Wherever stresses are applied at an angle to the ﬁber-axis, the modulus diminishes
to a value between the limits deﬁned by equation 19, and an equivalent expression for the
transverse modulus.

E= 1 (20)
ONE) + (Var/Em)

 

Calculating ﬁom equation 20 is usually inaccurate and pessimistic. Then, it can be

shown that a semi-empirical modiﬁcation of equation 20 yields (Birley, et al, 1992).

I = 1 [ Vt/Ef+ anm/Em] (21)
Et Vf + 7]th

 

where m = the stress partition parameter, for which experimental data has shown 0.5 to

be an accurate representation.

16

In general, the ﬁber failure strain is lower than the matrix failure strain. Mallick
(1988) assumed that all ﬁbers had the same length, and the tensile rupture of ﬁbers
precipitated the tensile rupture in the composites, Thus, using equation 16, the
longitudinal tensile strength (cm) of a unidirectional continuous composite can be
estimated as:

om = (3me + om’(1-Vf) (22)
where Of“ = ﬁber tensile strength (assuming a single value for all ﬁbers)
om’ = matrix stress at the ﬁber failure strain ( at em = er“)

In the case of discontinuous parallel ﬁbers, tensile load is transferred to these ﬁbers
by a shearing mechanism between the ﬁbers and matrix. Since the matrix has a lower
modulus, the longitudinal strain in the matrix is higher than that in adjacent ﬁbers.

If a perfect bond is assumed between the two constituents, the difference in
longitudinal strains creates a shear stress distribution. The normal stress distribution in a

discontinuous ﬁber is calculated by the following equation.

= 4t (23)

(1r

as

where Cf = longitudinal stress in ﬁber at a distance x from one of its ends

I shear stress at the ﬁber/matrix interface

df ﬁber diameter
To determine the normal stress distribution in the ﬁber at either one of its ends,
equation 23 can be derived into the following equation (Mallick 1988):

Cf = i] tdx (24)
dr

Normally, the interfacial shear stress is assumed to be constant. Then,

17

O'f = 4TI'X (25)
dr

where t; = interfacial shear stress
A composite lamina contains discontinuous ﬁbers, the ﬁber stress is not uniform.
It is zero at the ends and builds up linearly to the maximum value at the central portion of

the ﬁber. Then, the maximum ﬁber stress can be estimated by equation 26.

(00m = ZTIL’I (26)
dr

where x = L./2 = load transfer length at each ﬁber end. For a given ﬁber diameter and
ﬁber/matrix interfacial condition, a critical ﬁber length (L) is calculated from equation 26
as
Lc = gag; (27)
2t;
where of“ = ultimate ﬁber strength
Lc = minimum ﬁber length required for the ﬁber stress to be equal to the ﬁber
ultimate strength at its midlength.

This ultimate value is also valid when stress is transferred due to ﬁiction between
the matrix and ﬁbers. The critical length of ﬁbers can be used to predict the failure of
composites by comparing it to the ﬁber length (14‘).

I When L; < LC, the maximum ﬁber stress may never reach the ultimate ﬁber strength.
In this case, either the ﬁber/matrix interfacial bond or the matrix may fail before ﬁbers

achieve their potential strength.

18

I When L: > Le, the maximum ﬁber stress may reach the ultimate ﬁber strength over
much of its length. However, over a distance equal to LJ2 from each end, the ﬁber
remains ineﬂ‘ective.

The critical length can be controlled by increasing or decreasing Ti. A matrix
compatible coupling agent may increase Ti, which in turn decreases L. If Lc can be
reduced relative to L; through paper coupling agents, effective reinforcement can be
achieved without changing the ﬁber length.

To investigate impact behavior, it is assumed that the addition of solid ﬁllers to
plastic matrices makes composites more brittle, if the ﬁller content (by volume) is around
or above 0.2 (Berlin, et al, 1986).

As impact strength is deﬁned as the capacity to absorb and dissipate energies under
impact shock loading (Mallick, 1988), the energy-absorbing mechanisms in the composite
included the following conditions:

1) Utilization of the energy required to debond the ﬁbers and pull them completely out of
the matrix.

2) Use of a weak interface between the ﬁber and the matrix.

In most ﬁber-reinforced plastics, a signiﬁcant part of the energy absorption during
impact takes place through the ﬁber pullout process. The largest amount of energy
involved, and so the greatest toughness, occurs when the length of the ﬁbers is equal to
the critical length (Le). The variation of impact strength with ﬁber length was calculated
by using a model based on condition 1. Fibers shorter than Lc will be pulled out from the
matrix rather than broken when a crack passes through the composite. The fracture

energy will largely be a combination of the work needed to debond the ﬁbers from the

19

matrix and the work done against ﬁiction in pulling the ﬁbers out of the matrix. The
fracture energy (U) arising from ﬁber pullout is given by equation 28 and 30.
For L < Lc

U3 = LU (28)
12d

where d = the ﬁber diameter
t = the interfacial ﬁiction stress
v = the volume fraction of the ﬁber
Hence, U1 oc l/L2 for L< Lc
when L = Lc, the energy reaches a maximum and will have a value:

Um = 25L: (29)
12d

In case of L > Le, only a portion of the ﬁbers will pull out, and then the energy is
given by

U2 = £93 (30)
12dL

The impact energy or strength decreases as:
U; at 1/L
This decrease in impact strength for composites will happen with the ﬁber length
shorter than the critical length. However, the impact strength of composites is found to

increase linearly with the weight fraction of ﬁber (Devi et al, 1997).

20

Prior research

There are a lot of studies on the properties of composites. Most ﬁllers in the
research reviewed here, were from natural resources like wood ﬁbers, such as jute, sisal,
and pineapple leaf, including paper ﬁber. Several kinds of polymer matrices,
thermoplastics and therrnosets, were combined into the composites. The ﬁber, matrix, and
the adhesion between them can affect the mechanical properties of composites.

Gogoi (1989) investigated the effects of ﬁber pre-treatment, screw conﬁguration
of a twin-screw extruder, and compounding temperature on the mechanical properties of
the composite. Aspen ﬁbers were combined with recycled high density polyethylene, and
mixing conditions were varied. The tensile strength decreased gradually with increasing
ﬁber content, whereas the tensile modulus increased with ﬁber content. The impact
strength was decreased compared to that of recycled HDPE, but ﬂexural strength was
increased when the ﬁbers were added.

Raj et al (1990) investigated the effect of aging on mechanical properties of linear
low density polyethylene (LLDPE)-glass ﬁber, mica, and wood ﬁber composites. The
effect of aging on mechanical properties of composites was examined under diﬁ‘erent
conditions: (1) exposure at 105 C for 7 days; and (2) immersion in boiling water for 4 hrs.
Sarnples with glass ﬁbers showed the best results with regard to tensile strength,
elongation, and fracture energy. LLDPE with mica produced poor results compared to
wood ﬁber composites. Dimensional stability of LLDPE-wood ﬁber composites, after

boiling water treatment, was inferior to mica and glass ﬁber composites.

21

Felix and Gatenholm (1991) studied the nature of adhesion in composites of
modiﬁed cellulose ﬁbers and polypropylene. Cellulose ﬁbers were surface modiﬁed with
polypropylene-maleic anhydride copolymer. Then, the modiﬁed ﬁbers were compounded
with polypropylene, and composites with various amount of ﬁbers were manufactured by
injection molding. All mechanical properties were improved when treated ﬁbers were
used. Scanning electron microscopy (SEM) showed improved dispersion, wetting of
ﬁbers, and adhesion. The study found that the surface modifying agent is covalently
bonded to the ﬁbers through esteriﬁcation. The degree of esteriﬁcation is enhanced by
activating the modifying agent before ﬁber treatment.

Raj et al (1992) studied mechanical properties of polyethylene-organic ﬁber
composites. The selected organic ﬁbers were obtained from blending peanut hulls and
pecan shells. Composites were made by using a compression-molding technique. Studies
of variations in molding temperature (145-180 °C) and ﬁber concentration (040% by
weight) were correlated to the mechanical properties of the composites (tensile strength,
elongation, fracture energy, modulus, and impact strength). In untreated nut shell
composites, tensile strength decreased steadily as the ﬁber content increased due to poor
bonding between the untreated ﬁber and polymer. Polyisocyanate was used as a coupling
agent to improve tensile strength, but it had no effect on the modulus of the composites.
Both untreated and isocyanate-treated composites had low impact strength values; ﬁrrther
composite matrix modiﬁcation would be necessary to maintain or improve impact
strength.

Joseph et al (1993) investigated tensile properties of short sisal-reinforced

polyethylene composites. Sisal is a ligonocellulosic like jute, coir, and pineapple, and it is

22

of particular interest for use as a reinforcement in therrnoset matrices, because it has high
impact strength besides having moderate tensile and ﬂexural properties compared to other
lignocellulosic ﬁbers. A preliminary investigation showed that sisal ﬁber could also be
used as a reinforcement in a thermoplastic matrix and that it performed better than did
wood ﬁbers. The inﬂuence of the processing method and the effect of ﬁber content, ﬁber
length, and orientation on tensile properties of the composite were evaluated. The tensile
properties of the composites showed a gradual increase with ﬁber content. The properties
also increased with ﬁber length, to a maximum at a ﬁber length of about 6 mm.
Unidirectional alignment of the short ﬁbers achieved by an extnrsion process enhanced the
tensile strength and modulus of the composites along the axis of ﬁber alignment by more
than twofold, compared to randomly oriented ﬁber composites.

Karmaker et al (1994) studied the inﬂuence of water uptake on the mechanical
properties of jute ﬁber-reinforced polypropylene. Being hydrophilic, jute ﬁbers absorb a
high amount of water, causing swelling of the ﬁbers. As polypropylene left some gaps
when it was shnrnk by heat, the swelling of the jute ﬁbers could ﬁll these gaps. Then, it
could give positive results on the mechanical properties of the composites and result in
higher shear strength between ﬁbers and matrix during fracture.

George ct a1 (1995) studied composites of short pineapple leaf ﬁber reinforced low
density polyethylene, which were prepared by two different methods, melt-mixing and
solution-mixing methods. Tensile properties of melt-mixed and solution-mixed
composites were compared. Solution-mixed composites showed better properties than
melt-mixed composites. The inﬂuence of ﬁber length, ﬁber loading, and orientation on the

mechanical properties was also evaluated. Considering the overall mechanical properties

23

and processability characteristics, a ﬁber length of 6 mm was found to be the optimum
length of pineapple leaf ﬁber for reinforcement in low density polyethylene (LDPE). The
mechanical prOperties were enhanced and elongation at break reduced with increasing
ﬁber loading. Longitudinally oriented composites showed better properties than randomly
and transversely oriented composites. A comparison of the properties of the pineapple
leaf ﬁber (PALF)-reinforced LDPE composites with those of other cellulose-ﬁber-
reinforced LDPE system indicated superior performance of the PALF-LDPE composites.

Marcovich et al (1996) used sawdust, obtained from Eucaliptus saligna, or calcium
carbonate as ﬁllers, and combined them with an unsaturated polyester matrix. The
ultimate strength, elongation, and water absorption decreased with the addition of ﬁllers.
On the other hand, Young’s modulus was increased. The dynamic mechanical properties
were used to determine the inﬂuence of the moisture content on the performance of the
material.

Herrera-Franco and Aguilar-Vega (1997) studied the effect of cellulosic ﬁber,
obtained from henequen (Agrave fourcroydes), combined with LDPE. The reinforcing
ﬁbers were used with three diﬂ‘erent types of surface treatment: without any treatment,
preirnpregnation with a solution containing 2% by weight of LDPE in xylene at 130 C
under reﬂux for one hour conducted under a nitrogen atmosphere, and using a silane
coupling agent applied at a concentration of 1% by weight in carbon tetrachloride at 70 C
with dicumile peroxide as the catalyst. The concentration of randomly oriented ﬁbers in
the composite ranged between 0 and 30% by volume. The tensile strength and Young’s
modulus were increased with the addition of ﬁbers. However, strain values were

decreased, and the thermal behavior of the composite matrix was affected.

24

Preimpregnation of the cellulosics in a LDPE-xylene solution and the use of a silane
coupling agent resulted in a small increment in the mechanical properties of the
composites. The shear properties of the composites also increased with increasing of ﬁber
content and ﬁber surface treatment. It was also found that the ﬁber surface treatment
improves ﬁber dispersion in the matrix.

Devi et al (1997) used pineapple leaf ﬁber (PALF) as a polymer reinforcement
because it is rich in cellulose, relatively inexpensive, and abundantly available. This study
investigated the tensile, ﬂexural, and impact behavior of PALF-reinforced polyester
composites as a function of ﬁber loading, ﬁber length, and ﬁber surface modiﬁcation.
Increase in ﬁber content increased tensile strength and Young’s modulus of the
composites, as well as elongation at break. The mechanical properties were optimum at a
ﬁber length of 30 mm. The speciﬁc ﬂexural stiffness of the composite was about 2.3 times
greater than that of neat polyester resin. The impact strength was increased with increase
in ﬁber content, also. To improve the tensile strength, silane A172-treated ﬁbers were
combined into composites. The PALF polyester composite possessed superior mechanical
properties compared to other cellulose-based natural ﬁber composites.

Oksman and Clemons (1998) studied the mechanical properties and morphology of
impact modiﬁed polypropylene (PP)-wood ﬁber composites. PP has poor impact
properties, especially at low temperatures. The impact properties were improved through
the use of two diﬁ'erent ethylene/propylene/diene terpolymers (EPPM) and one maleated
styrene-ethylene/butylene-styrene triblock copolyrner (SEBS-MA) as impact modiﬁers in
the PP/wood ﬁber systems. All three elastomers increased the impact strength of the

PP/wood ﬁber. Maleated polypropylene (MAPP) was used as a compatibilizer. Addition

25

of MAPP alone did not affect the impact properties but it had a positive effect when used
together with elastomers. In tensile tests, MAPP showed a negative effect on the
elongation at break but a positive effect on tensile strength. MAPP ﬁrrther enhanced
adhesion between wood ﬂour and impact-modiﬁed PP systems. The impact modiﬁers
were found to decrease the stiﬂhess of the composites. Scanning electron microcopy
showed that maleated EPDM and SEBS had a stronger afﬁnity for wood surfaces than did
the unmodiﬁed EPDM. The maleated elastomers were expected to form a ﬂexible

interface around the wood particles, giving the composites better impact strength.

26

CHAPTER 2
MATERIALS AND METHODS
Materials

The composite materials consisted of two parts, the polymer matrix and the
reinforcement or ﬁller.
1) Polymer matrix

High Density Polyethylene (HDPE) supplied by Paxon was chosen as the polymer
matrix. HDPE resins were combined with paper ﬁbers using a co-rotating twin screw
extruder. The temperature of the extruder was set at 150°C in each zone in order to be
higher than the HDPE melting point, which is between 130 and 135°C.

For other properties, HDPE has a glass transition temperature of -120°C, and the
density is above 0.945 g/cc. Moreover, HDPE is highly crystalline, being between 65 and
90% crystalline.

As HDPE has a highly crystalline structure, it tends to have good stiﬂiiess, good
moisture barrier properties, a high melting point and high tensile strength compared to
some other kinds of plastics like low-density polyethylene (LDPE). HDPE is also a

hydrophobic and non-polar thermoplastic.
2) Reinforcements or Fillers

There were two kinds of paper ﬁbers supplied by Interﬁbe which were used as

reinforcements in the composite materials.

27

LL?»

5U

a) Mixed paper ﬁber

b) High-grade deinked paper ﬁber

Mixed paper is paper of varied quality; included in this category are ofﬁce waste,
boxboard cuttings and mill wrappers. Deinked paper has been through a deinking process,
resulting in paper ﬁber which is white and has more brightness than mixed paper ﬁber.

Normally, the structure of paper ﬁber is polar, hydrophilic ﬁbers, while the
structure of a polymer matrix like HDPE is hydrophobic. It is known that the hydrophilic
cellulosic ﬁbers have little adhesion to the hydrophobic thermoplastic matrix. It is also
known that the high viscosity of the matrix during composite fabrication hinders the paper
ﬁber impregnation and, therefore, results in poor ﬁber-matrix interaction (Herrera-Franco
and Aguilar-Vega, 1997).

The ﬁber cannot get mixed very well without adding some kind of coupling agent,
such as silane. The ﬁber has an inﬂuence on the properties of the composites. Especially,
factors like ﬁber content, ﬁber length, ﬁber orientation and types of ﬁbers inﬂuence the

strength and properties of the composite, as will be detailed in the next chapter.

28

Methods
1) Processing of composites

The paper ﬁbers and HDPE resins were combined by using a co-rotating twin

screw extruder (W emer-Pﬂeiderer ZSK 30). The extruder was set as follows:
Compounding speed = 120 rpm
Compounding % load = 90 %
Discharge temperature = 150°C

The feed rate varied depending upon the ratio of paper ﬁbers in the composite
materials. The ratios of paper ﬁbers used in the experiment were 0%, 10%, 20%, 30%
and 40%. Loading greater than 40% could not be achieved because of the limited
efﬁciency of the extruder.

The extruder has 6 processing zones. In each zone, the temperature was set at
150°C. The water as a coolant was run to maintain the temperature throughout the
process. HDPE resins were fed into the extruder at zone 1. In zone 2, the resins were
melted and passed to zone 3 for combining with the paper ﬁbers. The reason why the
ﬁbers were fed in zone 3 is to reduce ﬁber damage and gain ﬁber distribution. In zone 4,
5, and 6, the ﬁbers mixed with the HDPE completely. The extrudate emerged from zone
6, and was cut into approximately 6 inch sections.

The extruded materials were compressed into sheets by a Carver laboratory press

compression molding machine, model M. The extrudates were assembled between two

29

5!

USE

“'3'

iii

"1 .
1.3 *

iFtis

Elm

“VIII

chrome plates and a frame. There were two sizes of ﬁ'ames, 15x 15x0.25 cm and
12.7x12.7x0.3175 cm

. The ﬁrst size of frame was used to prepare samples for the tensile property tests,
whereas the second was used to prepare samples for the impact test and water absorption.
Mylar sheets, made from polyethylene terephthalate (PET), were placed between the
frame and chrome plates to minimize problems with sticking. This conﬁguration was
called a “sandwich”.

The sandwich was placed between both platens where the temperature was set at
150°C, the recommended temperature for HDPE. Hydraulic pressure at 30,000 psi was
used to press the sandwich for 5 minutes. Then, it was cooled to 50°C, using cooling
water. After the composite sheets were set completely, they were cut into the desired
Shapes, such as a dumbbell shape for tensile testing and a rectangular shape

(0.5x2.5x0. 125 in) for Izod impact testing, and water absorption testing.

2) Tensile properties

Following ASTM D63 8-90, Tensile Standard Test Method for Tensile Properties
of Plastics, the test specimens of reinforced composite were prepared in the dimensions of
type I. The specimens were shaped by using Tensilkut equipment into the dumbbell shape.

An Instron testing machine, model no.4201, was used at the ambient conditions
(23 °C, 50% RH), with the parameters as follows: load cell capacity of 1000 lbs, pre-load
value of 5 lbs, and cross head speed of 0.5 in/min. The specimens were gripped on both
ends by the cross heads. The results of tensile strength, % elongation, modulus of

elasticity and yield strength were calculated as outlined in the standard.

30

3) Izod impact strength

Izod impact strength was determined following ASTM D256-90b, Standard Test
Methods for Impact Resistance of Plastics and Electrical Insulating Materials. The
specimens were cut in the dimension of 0.5x2.5x0.125 in and notched by the TMI
notching cutter. The angle of notch was 22 ‘/2° i ‘/2° and the depth of notch was 0.1 inch,
according to the standard. The specimens were tested by using a TMI 43 -I IZOD impact
tester with 5-lb pendulum. They were held as a vertical cantilever beam and were broken
by a single swing of the pendulum. When the sample failed, it was necessary to consider
its type of failue. The types of failures were classiﬁed following the ASTM standard, as
type C (Complete break), H (Hinge break), PC (Partial break), or NB (Non-break).
Finally, the machine reported the test data for all samples, including the mean and standard

deviation.

4) Water absorption

To test water absorption, the method used was ASTM D570-81, Standard Test
Method for Water Absorption of Plastics. The specimens were cut in the dimensions of
2.5x0.5 in, and sandpaper was used to smooth the edges of the specimens to prevent
water absorption ﬁom the uneven surface.

The specimens were dried in an oven at 50:3 °C for 24 hours, cooling them in the
desicator, and then immediately weighing them to the nearest 0.001 g. Next, the
conditioned specimens were placed in boiling distilled water for 2 hours, and they all were

immersed completely under water. Finally, they were dried and weighed to the nearest

31

0.001 g immediately. The percentage of water absorption was calculated by the following

equation.

% water absorption = gain in weight (g) x 100 (31)
conditioned wt. (g)

5) Comparison of mechanical properties between paper ﬁbers and wood ﬁbers

Several former experiments concentrated on mechanical property testing of wood .
ﬁber reinforced thermoplastics. Paper ﬁbers as the reinforcements were compared to
wood ﬁbers in composites when they were fed in the same ratio, 40%, and in the same
kind of polymer matrix, HDPE.

As the results of the comparison were related to the structure of the ﬁbers and
composites, a scanning electron microscope (SEM) and other equipment were used to
show the structure, dispersion, and adhesion of ﬁbers and polymer matrix in the composite

materials.

32

[11,
r!

C0

CHAPTER 3
RESULTS AND DISCUSSION

Results - Tensile Strength

The results of tensile strength measurements are tabulated in Table 3, and graphed
in Figure 1. Statistical analysis at 95% by the least signiﬁcant diﬂ‘erence method (LSD)
showed that there was no signiﬁcant difference between the unreinforced material and
composites with 10% or 20% ﬁber content. However, the difference was signiﬁcant at
ﬁber contents of 30% and 40%, for both kinds of ﬁbers.

In comparing the effects of the two different kinds of paper ﬁbers in the
composites, statistical analysis showed that there was no signiﬁcant difference in the
tensile strength.

AS can be seen in Figure 1, tensile strength tended to decrease when the ﬁbers
were added to the composites. Thus, pure HDPE samples have the highest tensile
strength.

( See Appendix A for data and Appendix B for statistical analysis )

Table 3. Results of Tensile Strength

 

 

 

 

 

 

 

Tensile strength
Materials Mean (PSI) SD (PSI)
0%ﬁber 3882 576.8
10%ﬁber 3679 216.75
20%fiber 3553 107.76
30%ﬁber 3199 372.49
40%ﬁber 3059 230.81
10%ﬁber (deinked) 3710 187.24
20%ﬁber (deinked) 3532 110.81
30%ﬁber (deinked) 3251 166.51
40%ﬁber (deinked) 3262 21 3.8

 

33

 

scale 2858..

89.52: .358

63:33 8:88

€3.53: 3:38

*0?

$8

Seesaw

$9

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Fibercontantm

e Strength

Tensil

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rgure

F

34

Results - Modulus of Elasticity

The results for modulus of elasticity are tabulated in Table 4 and presented
graphically in Figure 2. Statistical analysis at 95% by LSD method, comparing the eﬁ‘ect
of paper ﬁbers on modulus of elasticity, conﬁrmed that there was no signiﬁcant diﬁ'erence
between 0%, 10%, and 20% ﬁber content for both kinds of ﬁbers, but the difference was
signiﬁcant at 30% and 40%. Moreover, statistical analysis showed that there was no
diﬂ‘erence between the two different kinds of paper ﬁbers.

As can be seen in Figure 2, the modulus of elasticity tended to increase when either
kind of ﬁbers was added. The composite with 40% deinked paper ﬁber had the highest
modulus of elasticity.

( See Appendix A for data and Appendix B for statistical analysis )

Table 4. Results of Modulus of Elasticity

 

 

 

 

 

 

 

Modulus
Materials Mean (KPSI) SD (KPSI)
0%ﬁber 110 47.89
10%ﬂber 127 37.76
20%fiber 192 74.42
30%ﬂber 223 72.48
40%ﬁber 347 74.68
10%tiber (deinked) 139 25.65
20%ﬁber (deinked) 177 16.23
30%ﬁber (deinked) 303 16.86
40%ﬁber (deinked) 402 81.13

 

35

 

10%flber (deinked)

Fiber content (18)

Figure 2. Modulus of Elasticity

36

 

Result - Yield Strength

The results for yield strength are tabulated in Table 5 and presented graphically in
Figure 3. From statistical analysis at 95% by the LSD method, there was no signiﬁcant
difference in yield strength of most samples except for 30% mixed paper ﬁber.

From Figure 4, pure HDPE gave the best result.

decreased the strength. Statistical analysis conﬁrmed that there was not any effect from

using the different kinds of ﬁbers.

The addition of paper ﬁbers

( See Appendix A for data and Appendix B for statistical analysis )

Table 5. Results of Yield Strength

 

 

 

 

 

 

Yield

Materials Mean (PSI) SD (PSI)

0%ﬂber 3850.11 571.56

10%ﬂber 2258.33 1240.33

20%ﬂber 2771.3 1082.59

30%fiber 1549.91 1084.6

40%ﬂber 2191.78 n/a
10%ﬁber (deinked) 3424.96 240.5
20%ﬁber (deinked) 2379.7 1279.56
30%ﬂber (deinked) 2409.75 1234.23
40%ﬂber (deinked) 2868.1 1014.38

 

37

 

 

93.53 .358

93:33 .858.

 

Fiber content (it)

Figure 3. Yield Strength

38

Results - Elongahion at Brea_k

Results for elongation at break are shown in Table 6 and presented graphically in

Figure 4. The addition of ﬁbers of both kinds signiﬁcantly decreased the percent

elongation at break.

Statistical analysis at 95%, by the LSD method, showed that pure HDPE was
statistically different from every composite, and it gave the highest value, which is about

26.96 %. When the two kinds of ﬁbers were compared, statistical analysis showed that

there was no signiﬁcant difference.

( See Appendix A for data and Appendix B for statistical analysis )

Table 6. Results of Elongation at Break

 

 

 

 

 

 

Elongation
Materials Mean (%) SD (%)
0%ﬁber 26.96 8.07
10%fiber 6.72 0.93
20%ﬁber 5.64 1 .02
30%ﬁber 3.08 1 .85
40%ﬁber 1 .31 0.22
10%ﬁber (deinked) 8.55 0.31
20%ﬁber (deinked) 6.44 0.93
30%ﬁber (deinked) 2.44 0.66
40%ﬁber (deinked) 1.61 0.71

 

39

 

meanest (deinked)

Fiber contort! (%)

Figure 4. % Elongation at Break

40

20%iiher (deinked)

3:
3:,
3
5

 

manor (deinked)

Discussion - Tensile Properties

The results of tensile testing have been used to determine the mechanical strength
of composites. These data are useful for qualitative characterization and development. In
the experiment, tensile strength, tensile modulus, yield strength and elongation at break
were determined, and interpreted in light of several inﬂuences, such as the effect of
adhesion at the ﬁber-matrix interface, ﬁber concentration, and ﬁber length.

At 40% ﬁber content for both kinds of paper ﬁbers, mixed and deinked paper
ﬁbers, the tensile strength is relatively low. The higher ﬁber loading the samples have, the
lower strength values they have. On the other hand, tensile modulus is increased with the
addition of paper ﬁbers.

As the tensile strength and tensile modulus of the composite are inﬂuenced by the
ﬁber loading and the adhesion at the ﬁber matrix interface, it indicates that the addition of
ﬁbers causes the composite to have poor adhesion at the interface because the hydrophilic
cellulosic ﬁbers have no adhesion to the hydrophobic thermoplastic matrix. In addition,
the high viscosity of the matrix during composite fabrication hinders proper ﬁber
irnpregation, and therefore results in poor-ﬁber matrix interaction. (Herrera-Franco and
Aguilar-Vego, 1997).

Yield strength and elongation have the same result as the tensile strength. The
percentage of elongation of the paper ﬁber reinforced composites decreases with the
increase in ﬁber loading. For example, at 40% ﬁber loading, the value of elongation at
break was very low due to the poor interaction between ﬁbers and the matrix, and it was

statistically signiﬁcantly different ﬁ'om the pure HDPE.

41

When the effects on tensile properties of the two kinds of paper ﬁbers, at the same
content in composites, were compared, statistical analysis showed no signiﬁcant
difference. However, the raw data for tensile strength suggested that the composite of
deinked paper ﬁbers had lower strength than that of mixed paper ﬁbers. It is known that
dieinking processes change the properties of paper ﬁbers, besides removing ink. For
example, the ﬁber length of deinked paper ﬁber is shorter than that of mixed paper ﬁbers.
As the length is shortened, the strength of the paper ﬁbers is decreased.

As shown in Figures 5 to 8, the dispersion of the mixed and deinked paper ﬁbers at
10% and 40% content in HDPE was investigated by SEM. The ﬁbers were found to
disperse randomly and not to be well mixed in the matrix. For instance, from Figure 6, at
a magniﬁcation of 115 times, it can be seen that there is a bunch of dense ﬁber in one area,
while few ﬁbers are found in another area. This random dispersion contributes to the low

strength of the composite.

42

 

Figure 5. Dispersion of Mixed Paper Fiber Composites at 10%

43

 

Figure 6. Dispersion of Mixed Paper Fiber Composites at 40%

44

 

Figure 7. Dispersion of Deinked Paper Fiber Composites at 10%

45

 

Figure 8. Dispersion of Deinked Paper Fiber Composites at 40%

46

Results - Izod Impact Strength
Results determined from Izod impact strength testing are summarized in Table 7

and presented graphically in Figure 9. They showed that the pure HDPE sample gave the
best result in Izod impact strength, and it was statistically signiﬁcantly different from the
other samples. In addition, the characteristic type of break differed. Pure HDPE resulted
in a partial break, whereas the other composites resulted in complete breaks.

From Figure 9, the addition of ﬁbers of both kinds can be seen to have resulted in
decreasing Izod impact strength. Statistical analysis at 95% by the LSD method
conﬁrmed that at 0% ﬁber, the result was statistically different from the samples with
10%, 20%, 30% and 40% ﬁber. However, there was no signiﬁcant difference between the
two kinds of ﬁbers at the same content.

(See Appendix A for data and Appendix B for statistical analysis )

Table 7. Results of Izod Impact Strength

 

 

 

 

 

 

Materials Mean (ftlb/in) SD (ftlbfin) Classify
0%fiber 1.730 0.108 Partial
10%ﬁber 0.653 0.023 Complete
20%ﬂber 0.604 0.051 Complete
30%ﬂber 0.488 0.048 Complete
40%fiber 0.407 0.065 Complete
10%ﬂber (deinked) 0.629 0.040 Complete
20%ﬁber (deinked) 0.556 0.022 Complete
30%ﬁber (deinked) 0.468 0.025 Complete
40%ﬁber (deinked) 0.368 0.062 Complete

 

47

 

 

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rgure

F

48

Discussion - Izod Impgct Strength

This test method is used to determine the resistance to breakage by ﬂexural shock
of composites. The notch on the samples was made to concentrate the stress, minimize
the deformation, and direct the fracture to the part of the specimen behind the notch.

Generally, it is assumed that the inclusion of ﬁllers to plastic matrices makes the
composite more brittle. However, this is not always this way. As regards ﬁlled
composites, the parameters of fracture are largely determined by the properties of the
polymer matrix, since most of the energy required to fracture the material is used for
straining and ﬁacturing of the polymer matrix (Berlin et al, 1986). For brittle matrices, the
introduction of a dispersed ﬁller increases the surface energy of material fracture: This
means that the ﬁller can improve the impact strength of the composites. On the other
hand, for non-brittle polymer matrices, the ﬁller reduces the surface energy due to the
decrease of the volume fraction of matrix in the plastic zone. Therefore, the impact
strength decreases with the addition of ﬁllers.

In this investigation, when paper ﬁbers were added to the polymer matrix, HDPE,
the impact strength decreased due to the ductile nature of HDPE. This means that the
paper ﬁbers make the composites more brittle. Statistical analysis showed a signiﬁcant

difference in the results when ﬁbers were added.

49

Results - Water Absorption

The results of water absorption are tabulated in Table 8 and presented graphically
in Figure 12. Statistical analysis at 95% by LSD method conﬁrmed that there was a
signiﬁcant difference among the samples, which had different content of paper ﬁbers.
From Figure 12, it can be seen that the addition of the ﬁbers increased the percentage of

water absorption for both kinds of paper ﬁbers. At 40% mixed paper ﬁber, the water

absorbed, was highest.

When comparing the eﬂ‘ect of using different kinds of paper ﬁbers, mixed and

deinked paper ﬁbers, statistical analysis showed a signiﬁcant difference between pairs of

samples at the same percentage of paper ﬁbers, except at 10% ﬁber.

(See Appendix A for data and Appendix B for statistical analysis )

Table 8. Results of Water Absorption

 

 

 

 

 

Materials mean (%) SD (%)
0%ﬁber 0 0
10%ﬁber 0.090746 0.015206
20%ﬁber 0.214712 0.020299
30%fiber 0.229 0.010234
40%ﬁber 0.717783 0.053387
10%ﬂber (deinked) 0.066394 0.003862
20% ﬁber (deinked) 0.15311 0.005326
30% ﬁber (deinked) 0.51812 0.028953
40% ﬁber (deinked) 0.621157 0.031183

 

50

 

 

9%... 8.. 8n

 

9:83 .8: .8“

258. 8:8.

itFIbercontont

Figure 10. Water Absorption

51

Discus_sion - Water absorption

This test method, following ASTM D 570-81, is used to determine the relative rate
of water absorption, and has two chief ﬁanctions. First of all, it is a guide to the proportion
of water absorbed by a material and consequently, in those cases where the relationships
between moisture and electrical or mechanical properties, dimensions, or appearance have
been determined, as a guide to the effects of exposure to water or humid conditions on
such properties. Secondly, it is used as a control test on the unifomrity of a product.

Results showed that the higher the content of paper ﬁbers in the composite, the
higher the amount of water it absorbed. Statistical analysis showed that the inclusion of
paper ﬁbers gave a signiﬁcant difference in the results, compared to pure HDPE materials.
As the structure of the paper ﬁber is hydrophilic, it does not adhere very well to the
hydrophobic structure of the thermoplastic matrix, such as HDPE. After processing of the
composites, the thermal shrinkage of the matrix results in a gap surrounding the ﬁber.
Then, the composite materials can take up a large amount of water because the hydroxyl
groups in the ﬁber structure interact with the surrounding water. This causes swelling of
the ﬁbers which can ﬁll the gap between the ﬁbers and the polymer matrix. This can result
in a decrease in mechanical properties.

The higher the amount of ﬁbers the composite has, the more gaps can occur.
Thus, at 40% ﬁber, the water is absorbed easily compared to pure HDPE, and to
composites, with lower contents of ﬁbers.

When comparing how well the different kinds of ﬁbers can absorb water, it seems

that mixed paper ﬁbers can absorb a greater amount of water than the deinked paper ﬁbers

52

(except at 30% ﬁber). Bierrnann (1993) explained that to disperse ink during the deinking
process, it requires using a vehicle, which is commonly vegetable oil. The effect of the oil,
which is a hydrophobic structure, would cause a partial reduction in the water absorption

efﬁciency of the ﬁbers.

53

Results - Comparison of wood ﬁber (Aspen ﬁbers) an_dpgper ﬁber (Mixed a_nd
deinkethpaper ﬁbers) reinforced HDPE comﬂsites (pt 40% ﬁber and 60% HDPE)

Paper ﬁber-reinforced HDPE composites were compared to wood ﬁber-reinforced
HDPE composites ﬁ’om prior experiments by Childress (1991). To investigate the
properties of composites, she used aspen hardwood ﬁber combined with HDPE. Several
kinds of additives were used to improve the properties. In this case, the composite of
40% aspen without using any additives was selected to compare to the composites with
40% of both paper ﬁbers. Moreover, they all were compared to the properties of pure
HDPE. The tensile modulus of the wood ﬁber composites is not so much diﬂ‘erent from
that of the HDPE materials, but lower than that of the paper ﬁber composites. Decreases
in the tensile strength, % elongation at break, and Izod impact strength resulted with the
addition of the ﬁbers, so the HDPE samples were expected to have the highest values of
all properties, whereas the paper ﬁber composites gave the lowest values. This means that
the composites of the paper ﬁbers could be the most brittle materials, and the HDPE
could be the toughest materials. For water absorption, the wood ﬁber composites
absorbed more water than the paper ﬁber composites, whereas the pure HDPE did not
absorb water at all.

From Figures 11, 12, and 13, a scanning electron microscope (SEM) was used to
show the stnrctures of mixed paper ﬁbers, deinked paper ﬁbers, and aspen wood ﬁbers.
As can be seen, both kinds of paper ﬁber structures are similar. They are ﬂat and
entangled, whereas the aspen ﬁbers quite look quite straight. The ﬁber length was

compared among the three kinds of ﬁbers, as follows:

54

Mixed paper ﬁbers : 450 um < Length < 1mm
Deinked paper ﬁbers : Length < 450 um

Aspen wood ﬁbers : Length > 1 mm

55

 

 

 

 

 

 

 

 

 

 

 

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56

Discussion - Comparison of Properties of Wood and nger Fiber Compom

Childress (1991) described the natural characteristics of aspen ﬁbers as polar in
nature and hydrophilic. In the processing, the ﬁbers were in the form of thermomechanical
pulp (TMP). This mechanical pulping process is one in which the ﬁbers retain most of
their lignin and natural waxes. Aspen wood ﬁber length is typically 0.7 - 3 mm.

For paper ﬁbers, they are also polar and hydrophilic. In the processing, both kinds
of papers, mixed and deinked paper ﬁbers, pass through a pulping system to remove
contaminants, such as plastic laminates, adhesives, waxes, etc. However, there is a
difference in processing between the paper ﬁbers: deinked paper ﬁbers also have to pass
through the deinking process to remove ink in order to get good printing quality.

The effects of both paper ﬁbers on physical properties were already discussed.
Therefore, at this point, only the effects of aspen wood ﬁbers compared to paper ﬁbers on
physical properties will be explained.

The signiﬁcant difference between wood and paper ﬁbers is the ﬁber length:
George et a] (1995) explained that the strength of ﬁber-reinforced composites depends on
the degree to which an applied load is transmitted, and the extent of load transmittance is
a function of ﬁber length and magnitude of the ﬁber-matrix interfacial bond. The short
ﬁbers will debond from the matrix easily and the composite will fail at a low load. When
the ﬁber length is long, the stressed composites will lead to breaking of ﬁbers and a high
composite strength. Figures 11, 12, and 13 Show SEM photographs of the wood and
paper ﬁbers. As can be seen, aspen wood ﬁbers are much longer in length than paper

ﬁbers, so the strength of the wood ﬁber composites is expected to be higher.

57

As can be seen in Table 9, the paper ﬁber composites have high tensile strength,
and their stiffness is improved as compared to the aspen wood ﬁber composite and HDPE
materials. Their water absorption decreases. The only loss is the impact strength, which
they are expected to reduce. For the wood ﬁber composites, the tensile strength is as least
as good, and they are expected to be more brittle and stiﬂ‘er in comparison to the HDPE
materials. The wood ﬁber composites are the best for absorbing the water.

Smook (1992) explained the effect of recycling of the wastepaper on the ﬁber
strength and on the bonding strength between ﬁbers. The strength decreases and the
bonding between ﬁbers shows a more dramatic loss. These factors can support why paper
ﬁber composites have lower strength than wood ﬁber composites.

For % water absorption, Smook (1992) said that, in recycling processes, with each
drying and slushing cycle, the ﬁbers become less ﬂexible and less permeable to water, and
therefore do not conform as well as virgin ﬁbers. Thus, aspen wood ﬁbers can absorb

water better than paper ﬁbers.

58

 

Figure 13. Mixed Paper Fibers

59

 

Figure 14. Deinked Paper Fibers

60

 

Figure 15. Aspen Wood Fibers

61

Summary and Conclusions

Paper ﬁber reinforced HDPE composites were prepared by the twin-screw
extruder and compression molding at ratios of 0%, 10%, 20%, 30% , and 40% ﬁber.
Mixed and deinked paper ﬁbers were used as ﬁllers to determine whether the deinking
process had an effect on the mechanical properties of the composite materials.

Properties of ﬁber-reinforced composites depend on many factors like ﬁber-matrix
adhesion, volume fraction of ﬁber, ﬁber aspect ratio, and ﬁber orientation as well as the
stress transfer efficiency of the interface.

Mechanical properties of composites were studied which included tensile stress,
tensile modulus, yield strength, and % elongation. Tensile modulus increased when either
mixed or deinked paper ﬁbers were added. The worst result for composite strength was at
40% ﬁber which was due to the low values for tensile strength and % elongation at break.

Izod impact strength of the composites decreased greatly, as is expected for tough
materials such as HDPE. Water absorption increased with increasing ﬁber content.

Statistical analysis of the properties showed little effect of the kind of the ﬁber on
the properties of the composites. However, the deinking process can reduce the ﬁber
length of deinked paper ﬁbers and deinked paper ﬁbers will be shorter than the length of
mixed paper ﬁbers, as can be seen by the SEM photographs shown in Figures 11 and 12.
Because the length of deinked paper ﬁber is just slightly Shorter, so its strength is a little

bit weaker than the strength of mixed paper ﬁbers.

62

When the properties were compared to composites of aspen wood ﬁbers, the paper
ﬁber composites gave poorer results in terms of the tensile modulus, % elongation at
break, and Izod impact strength because they were more brittle and easier to break.

This method is a potential way to reduce the amount of waste paper, which can
cause a lot of problems in the environment. Even though a high amount of paper ﬁbers
can be used to make composite materials, which will increase the utilization rate for
recycled papers, composite properties are reduced because of the lack of interfacial
bonding between the HDPE matrices and the paper ﬁbers, due to the difference of their
potential bonding properties, hydrophobic and hydrophilic. If the bonding was improved,

the properties of paper ﬁber-reinforced HDPE composites would be better.

63

Recommendation for Future Research

AS the incompatibility of the ﬁbers and the matrix, including poor dispersion of the
ﬁbers in the matrix, causes adhesion between them in the composites to be relatively poor,
so it causes the mechanical and physical properties to have poor results.

To improve the bonding at the interface, coupling agents should be investigated to
improve dispersion, adhesion, and compatibility for a system containing hydrophilic
cellulose and a hydrophobic matrix.

Moreover, there are several other kinds of paper ﬁbers to be investigated for use in
the composite as a ﬁller. Ifthis can be successful, it will be a great opportunity to increase

paper recycling in the future.

64

Table 10. Tensile Strength Data

APPENDIX A

 

 

 

 

ensile strength (PSI)
Materials 1 2 3 4 5 Mean SD
0%fiber 2867 4177 4002 4281 4083 3882 576.8
10%ﬁber 3719 3969 3753 3564 3390 3679 216.75
20%ﬁber 3539 3655 3673 3459 3441 3553 107.76
30%ﬂber 2882 2990 3287 3810 3026 3199 372.49
40%ﬁber 2798 2986 3343 3254 2915 3059 230.81
10%ﬁber deink 3976 3776 3734 3558 3507 3710 187.24
20%ﬂber deink 3594 3527 3383 3674 3480 3532 1 10.81
30%ﬁber deink 3149 3366 3008 3338 3395 3251 166.51
40%ﬂber deink 3063 3006 3467 3432 3344 3262 213.8

 

 

 

 

 

 

 

 

65

 

Table 11. Modulus of Elasticity Data

 

 

 

IModulus of Elasticity
(KPSI)
Materials 1 2 3 4 5 Mean SD
0%ﬁber 166 157 62 82 83 110 47.89
10%ﬂber 176 89 155 120 94 127 37.76
20%tiber 112 229 281 117 219 192 74.42
30%ﬁber 318 285 171 165 176 223 72.48
40%tiber 317 379 422 384 232 347 74.68
10%ﬂber (deinked) 166 142 107 119 161 139 25.65
20%ﬁber (deinked) 185 150 172 184 192 177 16.23
30%fiber (deinked) 298 304 330 296 285 303 16.86
40%fiber (deinked) n/a 388 461 292 465 402 81 .13

 

 

 

 

 

 

 

 

 

66

 

Table 12. Yield Strength Data

 

 

 

 

ﬁeld Strength (PSI)
Materials 1 2 3 4 5 Mean SD
0%ﬂber 2852.76 4173.9 3993.71 4267 3963.17 3850.11 571.56
10%ﬁber 2982.83 828.36 988.79 3350.51 3141.15 2258.33 1240.33
20%tiber 3347.86 3488.48 875.5 2890.77 3253.88 2771.3 1082.59
30%fiber 858.39 n/a 3168.76 1097.01 1075.49 1549.91 1084.6
40%ﬂber 1077.44 nla 3306.12 nla nla 2191.78 nla
10%ﬂber (deinked) 3830.3 3452.95 3233.05 3316.69 3291.83 3424.96 240.5
20%ﬁber (deinked) 3388.39 3254.28 3297.43 1008.95 949.48 2379.7 1279.56
30%ﬂber (deinked) 1063.78 3340.85 1054.35 3221.53 3368.21 2409.75 1234.23
40%ﬂber (deinked) nla 1351.28 3463.69 3388.26 3269.19 2868.1 1014.38

 

 

 

 

 

 

 

 

67

 

Table 13. Elongation at Break Data

 

 

 

 

Elongation at break
(%)
Materials 1 2 3 4 5 Mean SD
0%tiber 19.76 20.76 30.47 24.52 39.29 26.96 8.07
10%ﬁber 5.65 7.7 5.95 6.72 7.6 6.72 0.93
20%fiber 6.89 5.38 4.14 6.14 5.66 5.64 1.02
30%ﬂber 1.44 2.09 4.79 5.35 1.71 3.08 1.85
40%fiber 1.13 1.27 1.53 1.08 1.54 1.31 0.22
10%fiber (deinked) 8.13 8.43 8.85 8.85 8.5 8.55 0.31
20%ﬂber (deinked) 7.05 7.67 6 6.2 5.3 6.44 0.93
30%fiber (deinked) 2.36 3.12 1.4 2.86 2.45 2.44 0.66
40%ﬂber (deinked) 1.17 0.83 1.38 2.52 2.17 1.61 0.71

 

 

 

 

 

 

 

 

68

 

Table 14. Izod Impact Strength Data (ft-lbfrn)

 

 

 

Materials 1 2 3 4 5 Mean SD
0%ﬂber 1.609 1.86 1.635 1.808 1.737 1.730 0.108
10%ﬁber 0.677 0.635 0.657 0.625 0.672 0.653 0.023
20%fiber 0.683 0.583 0.613 0.597 0.544 0.604 0.051
30%ﬂber 0.538 0.477 0.534 0.469 0.423 0.488 0.048
40%ﬁber 0.394 0.522 0.372 0.366 0.382 0.407 0.065
10%ﬁber (deinked) 0.662 0.597 0.678 0.622 0.588 0.629 0.040
20%ﬁber (deinked) 0.555 0.542 0.588 0.564 0.531 0.556 0.022
30%fiber (deinked) 0.433 0.488 0.458 0.494 0.469 0.468 0.025
40%ﬁber (deinked) 0.403 0.413 0.423 0.3 0.3 0.368 0.062

 

 

 

 

 

 

 

 

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70

APPENDIX B

One-Way Analysis of Variance of Tensile Strength
Data: Tensile Strength
Level codes: Treatment

Means plot: LSD C onﬁdence level: 95 Range test: LSD

Analysis of variance

 

Source of variation Sum of Squares d.f. Mean square F-ratio Sig. level

 

 

Between groups 30694200 8 383677.50 4.904 .0004 ~
Within groups 28162900 36 78230.28
Total (corrected) 58857100 44

0 missing value(s) have been excluded.

Multiple range analysis for Tensile Strength

 

Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
40% ﬁber 5 30592000 X

30% ﬁber 5 3 199.0000 XX

30% deink ﬁber 5 32512000 XX

40% deink ﬁber 5 32624000 XX

20% deink ﬁber 5 35316000 XX

20% ﬁber 5 3553,4000 XX

10% ﬁber 5 36790000 X

10% deink ﬁber 5 37102000 X

0% ﬁber 5 38820000 X

 

71

One-Way Analysis of Variance of Elongation
Data: Elongation

Level codes: Treatment
Means plot: LSD Conﬁdence level: 95 Range test: LSD

Analysis of variance

 

Source of variation Sum of Squares d.f. Mean square F—ratio Sig. level

 

 

Between groups 2503.1938 8 312.89923 38.898 .0000
Within groups 289.5901 36 8.04417
Total (corrected) 2792.7839 44

0 missing value(s) have been excluded.

Multiple range analysis for Elongation

 

Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
40% ﬁber 5 1.3100000 X

40% deink ﬁber 5 1.6140000 X

30% deink ﬁber 5 2.4380000 XX

30% ﬁber 5 3.0760000 XXX
20% ﬁber 5 5.6420000 XXX
20% deink ﬁber 5 6.4440000 XX
10% ﬁber 5 6.7240000 X
10% deink ﬁber 5 8.5520000 X
0% ﬁber 5 26.960000 X

 

72

One-Way Analysis of Variance of Yield

Data: Yield

Level codes: Treatment
Means plot: LSD Conﬁdence level: 95 Range test: LSD

Analysis of variance

 

Source of variation Sum of Squares d.f. Mean square F-ratio Sig. level

 

Between groups 17091387 8 21364234 1.941 .0889
Withingroups 34121633 31 11006978

 

Total (corrected) 51213020 39
3 missing value(s) have been excluded.

Multiple range analysis for Yield

 

Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
30% ﬁber 4 1549.9125 X

40% ﬁber 2 2191.7800 XX

10% ﬁber 5 2258.3280 XXX

20%deink ﬁber 5 2379.7060 XXX

30%deink ﬁber 5 2409,7440 XXX

20% ﬁber 5 2771.2980 XXXX

40% deink ﬁber 4 2868,1050 XXXX

10% deink ﬁber 5 3424.9640 XXX

0% ﬁber 5 3850.1080 X X

 

73

One-Way Analysis of Variance of Modulus of Elasticity

Data: Modulus of Elasticity

Level codes: Treatment
Means plot: LSD Conﬁdence level: 95 Range test: LSD

Analysis of variance

 

Source of variation Sum of Squares d.f. Mean square F-ratio Sig. level

 

 

Between groups 396504.35 8 49563.043 16.541 .0000
Within groups 104870.20 35 2996.291
Total (corrected) 501374.55 43

1 missing value(s) have been excluded.

Multiple range analysis for Modulus of Elasticity

 

Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
0% ﬁber 5 1 10.00000 X

10%ﬁber 5 126.80000 XX

10%deink ﬁber 5 139.00000 XX

20%deink ﬁber 5 176.60000 XXX

20% ﬁber 5 191.60000 XX

30% ﬁber 5 223.00000 X

30%deink ﬁber 5 302.60000 X

40% ﬁber 5 346.80000 XX

40%deink ﬁber 4 401.50000 X

 

74

One-Way Analysis of Variance of Impact Strength

Data: Impact Strength
Level codes: Treatment

Means plot: LSD Conﬁdence level: 95 Range test: LSD

 

Source of variation Sum of Squares d.f. Mean square F-ratio Sig. level

 

 

Between groups 6.8738856 8 .8592357 277.430 .0000
Within groups .1114964 36 .0030971
Total (corrected) 6.9853820 44

0 missing value(s) have been excluded.

Multiple range analysis for Impact Strength
Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
40% deink ﬁber 5 .3678000 X

40% ﬁber 5 .407 2000 XX

30% deink ﬁber 5 .4684000 XX

30% ﬁber 5 .4882000 XX

20% deink ﬁber 5 .5560000 XX

20% ﬁber 5 .6040000 XX

10%deink ﬁber 5 .6294000 X

10% ﬁber 5 .653 2000 X

0% ﬁber 5 1.7298000 X

 

75

One-Way Analysis of Water Absorption (%)

Data: Water Absorption (%)
Level codes: Treatment
Means plot: LSD Conﬁdence level: 95 Range test: LSD

Analysis of variance

 

Source of variation Sum of Squares df. Mean square F-ratio Sig. level

 

 

Between groups 1.6398826 8 .2049853 338.381 .0000
Within groups .0109041 18 .0006058
Total (corrected) 1.6507866 26

18 missing value(s) have been excluded.

Multiple range analysis for Water absorption

 

Method: 95 Percent LSD

 

Level Count Average Homogeneous Groups
0% ﬁber 3 .0000000 X

10%deink ﬁber 3 .0663 940 X

10% ﬁber 3 .0907457 X

20%deink ﬁber 3 . 1531097 X

20% ﬁber 3 .2147117 X

30% ﬁber 3 .2290327 X

30%deink ﬁber 3 .5181193 X

40%deink ﬁber 3 .6211570 X

40% ﬁber 3 .7177827 X

 

76

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