A COMPARATIVE STUDY OF THE USE OF PLASTIC AND GLASS BEADS IN PAVEMENT LANE MARKING Thesis for degree of Master of Science Michigan State College Charles Richard Buckham I951 THESI: 0-169 This is to certify that the thesis entitled A COMPARATIVE STUDY OF THE USE OF PLASTIC AND GLASS BEADS IN PAVEl‘viEi‘lT LANE MARKING presented by CHARLES RICHARD BUCKHAM has been accepted towards fulfillment of the requirements for Wit-40.7w Major professor Date September 21, 1951 T-H -—-——. fi.‘____ 11—1”?— p. 73?. t—Mflrrsa— —... ~ A COKPARATIVL STUDY CF TFL US: CF PLASTIC AND CIASS BEADS IN FAVETLET LAKE TAQKIHG By Charles Richard Euckham A anIS ’— Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of LESTER OF SCIENCE Department of Civil Engineering 1951 ACE} ICILE'JD C" YE ITS The author of this paper wishes to express his sincere thanks to Mr. B. W. Pocock, Head Research Engineer of the X'chigan State Highway Department Testing Laboratory, located in East Lansing. His interest in this project, his guidance, encouraaement and sug— gestions were all greatly appreciated by me. The suscestions offered by Mr. Wm. Martin and Mr. K. Brown, Chemist and Chemical Engineer respectively, Jere also very much ap- preciated. The author wishes to thank hr. B. Preston, Head Physicist of the Highway'Testing Laboratory, for his generous advice and assist- ance on the reflectivity tests conducted for fliis paper. I wish to thank once again each of the men whose mares appear above for their splendid cooperation and help. Their sincere in- terest and guidance made possible the successful completion of this paper. TABLE OF CONTENTS CHAPTER I Introduction Foreword Theory of Reflection Requirements of a Suitable Material CHAPTER II General Fraperties Gradation Color Imperfections Excessive Air Odor Effect of Temperature Effect of'Weathering Effect of Expansion and Contraction Chemical Stability Cost CHAPTER III ti cal Properties Reflectivity Tests Definition of Terms Apparatus Panels Procedure Test Results CHAPTER IV Strength PrOperties Crushing Strength wear Test Procedure Results CHAPTER V Conclusions Summary Page 66 7h 7 5 77 79 VII VIII XI XII XIIeA XIII XIIIeA XIV xv TABDSCK“CCEEIHS Sieve Analysis of Sieve Analysis of Sieve Analysis of Bead Imnerfections Plexielas Beads Polystyrene Reads Cataphote Type I Beads Reflectivity Results of Plexielas Reads Reflectivity Results of Plexiglas Be a #60 and Retained on a # O A, . PaSSIng ads Sieve Reflectivity Results of Plexig as Reads P3351“? a #70 and Retained on a #30 Sieve Reflectivity Results of Plexiglas Beads Passing a fiSO and Retained on a #130 Sieve Reflectivity Results of Plexiglas After a 5 Day Naphtha Bath Re lectivity Results of Plexiglas After a 5 Day Gasoline Bath Reflectivity Results of Plexiglas B After a 5 Day Calcium Chloride Bath T :38 Beads ‘~ads eads Reflectivity Results of Red Polystyrene Beads Reflectivity Results of Orange Polystyrene Beads Reflectivity Results of Polystyrene Reflectivity Results of Polystyrene Using Saturated Panels Reflectivity Results of Polystyrene After a 5 Day Nauhtha Bath Reflectivity Results of Polystyrene After a 5 Day Gasoline Bath Reflectivity Results of Polystyrene After a 5 Day Calcium Chloride Bath Reflectivity Results of Glass Beads Reflectivity Results of Glass Beads (90 Hour Reflux) Beads Beads Beads Beads Reads Cataphote Type I Catanhote Type I Reflectivity Results of White 1950 Highway Paint Average Crushing Strength of Plexiglas Beads Average Crushing Strength of Polystyrene Beads Average Crushing Strength of Cataphoe Type I Glass Beads Page 13 1h 15 18 DA 60 7O 72 73 Figures: 10. 11. 12. 11+. 15. 16 . 17. 18. 190 20. TABLE OF CONTENTS Specular Reflection Reflex Reflection Specular Reflection.with Irregular Particles Plexiglas Beads Before Traffic Abrasion Glass Beads After Traffic Abrasion 3M Glass Beads 3M Glass Beads (Improved) Plexiglas Beads Polystyrene Beads Glass Beads in Benzene Plexiglas Beads in Cedar Oil Polystyrene Beads in Cedar Oil Reflectivity Test Apparatus Specific Intensity of Plexiglas Beads Specific Intensity of Plexiglas and Polystyrene Beads Specific Intensity of Polystyrene Beads Relation of Bead Size to Light Intensity Relation of Bead Number to Specific Intensity Crushing Strength.Apparatus ‘Wear Test Results Page Page 1 CHAPTER I IHTPCQUCTICN FOREWORD The scientific advancements made by man in the last few dec- ades in developing pavement markings, has undoubtedly played a major role in reducing the number of accidents each year that occur on the American highways. We have certainly come a long way in the struggle for better pavement marking in the last few years. Evidences of traffic reg— ulation are apparent in the pages of Roman history and in the New herld we find traces f traffic marking dating back to the fifth century in the land of the Incas. This marking consisted of the placing of colored stones in the center of the highway and prevent— ed many a tribal squabble through a definite system of traffic reg- ulation. In the year 1911 Mr. Edward Hines, then County Road Commissioner of'Wayne County, Michigan, first conceived the idea of using a painted center-line on pavements. Since this time, man has contin— ually been improving the paints that are used for this purpose. The Michigan State Highway Department, in the year 1939, in an attempt to provide excellent night time illumination as well as day time illumination, began experimenting with small glass spheres placed on wet marking paint, flius producing a reflectorized paint. With the aid of these glass beads 2h hour visibility is obtained. The use of such beads make the center-line appear nearly three times more visible at night than a plain painted center-line. These beads range in size from 0.0165" to 0.0029" in diameter. The Michigan State Highway Department has divided glass beads, for Page 2 use in pavement marking, into two groups-~namely Type I and Type II. Type I bead is intended for application on the surface of traffic’ paint films. Type II bead is intended.to be mixed in traffic paints. cAccording to the Michigan State Highway Department Specifications for glass beads "Type I shall be capable of firm embedment in the pavement marking paint with the upper surfaces of the glass beads exposed. Type II shall display the required reflective preperties after traffic has worn off the paint film sufficiently to expose the surface of the beads." Type I bead is placed on the surface of the paint for immediate reflectivity and Type II is placed in the paint for continued reflectivity. The Type II bead is not used gen— erally today on Michigan highways. However, Type I is used on all center-line markings made today. The author of this paper was searching for a Type II plastic bead which possibly might be more effective and more economical than is the glass bead. The object of this thesis was to determine whether plastic beads might be more satisfactory and more economical, as a lane marking material, than glass beads. THEORY OF RETIECTICN r—h These spheres, Type I, are deposited evenly on a wet pigment binder (paint) and are held firmly by the paint as it dries. The beads reflect the light from a car's headlights back to the driv- er's eye; thereby making the center—line appear to be luminous. A ray of light from the vehicle's headlight enters the sphere and is immediately bent at an angle determined by the refractive index of the material. From here the light ray strikes the mirrored surface of the sphere which is partially embedded in the paint or pene— trates and strikes the pigment beyond and is returned in a path parallel to the incident ray back to the driver's eye. This is sometimes known as "reflex" reflection. It should be noted that the light ray is returned to its source and not necessarily in the opposite direction at an angle equal to the angle of incidence which is true in specular or mirror reflection. In the case of a perfect sphere, specular reflection follows practically the same path as reflex reflection. This reflected ray of light carries the color of the paint in which it is embedded back to the driver's eye; thereby making the center—line appear to be luminous or have the same hue as in the daytime. When the light ray from the car's headlight enters the bead, it is concentrated to a point of great intensity at the back of the sphere. This bright point of light is then reflected back to its original source thereby, with the aid of thousands of such spheres, lighting up several hundred feet of center-line. Inasmuch as the distance between the entering and reflected Page h ray is but a fraction of the diameter of the glass sphere, which in turn may be as small as .002 inches, the two rays are for all prac— tical purposes almost coincident. Figure 1 shows the result of a light ray from a glass or mir- rored surface and is know as "specular reflection". Figure 2 illustrates "reflex reflection" and Figure 3 "specu- lar reflection" with irregular particles. In Figure 3 ray "S" is the result of specular reflection and ray "R" is reflex reflection. It should be noted that neither ray is returned upon a path parallel or close to the entering ray. These two rays are known as "wild" rays and serve no functional . purpose in pavement marking. It is for this reason that true spheres are essential for better control of the returned rays. Page 5 k r h~ N I '\. pt I i J . . \ .1, 4 ,. ,, f“ . I , V : J I . / ,1 L, i [I/ft _c , . a a - . Furii/ 5/491» A); u" * 3 . / ”73’. 1' , H h“ ‘ /»\/ ’ I, 7/ / /" V . ‘ - i ./ i . .f ”It, 1- 7 fl... A ‘ffi ‘ 1' ‘ I r‘: '\l A ~ / r v. ; “ ,/A i .. ‘ - , w / ’5 .. j , ... ‘ ‘l‘r— l'fir / , k/ / ’1 / _ I ., /"‘5, ’ V , , , , , F/G i: xx"; / A; : /<-z. i ,z- ( , /§f‘flfi Z‘ / [7 ‘1 4” 1'1-V/x—‘X v f ,“L " i I 'I’/'\ [171" {:(’L .4111? 1173/7/17, up; "941,1“ fi-fi \fi é’/ L!" .. , '( \ i . // / / / ’1 x /, / ’ I I I.“ \ ./ x-‘l' Ara: f; F; ‘ ».:// /’/€1~'.-‘£-.;-L 1. 2- F/J. .5 3/25 s (it 1.- x}. x 1m; "/01 a Page 6 REQUIREKEHTS OF A SUITABLE VATFWLRL The beaded material used to increase the reflecting power of highway marking paints must meet very rigid requirements. One of the first requirements is obviously that the bead will not dissolve in the paint vehicle. Many plastics are attacked by certain organ- ic substances which are used in the manufacturing of paints. The degree of solubility is also a very important factor. It must be remembered that glass beads are soluble, to a slight extent, in water yet are used.teday as a reflecting medium. The melting or flowing point of the bead material must be such that they will withstand summer temperature. It is not,an uncommon occurrence to have pavement temperatures of lhhoF at times during the summer months. Therefore, obviously beads which are to be used in this manner must be capable of withstanding temperatures of at least lthF. . To be of value as a center-line marking material the beads must have an index of refraction of at least 1.50. An index of re- fraction greater than 1.50 is very desirable with a possible maxi- mum of 1.90. All beads must be perfectly spherical in shape. If the beads are not spherical in shape the light rays from the automobile's head lights will be dispersed in all directions and not returned to the driver's eye, which obviously is necessary if the material is to be of any value. Plastic beads are found to be much more per- fectly shaped than are glass beads. Very few "out of rounds" are found when working with plastic beads. Page 7 If the beads are to withstand heavy trucks and cars rolling over them day after day they must have an average crushing strength of 7.5 kilograms for Type I and 2.5 kilograms for Type II. The test used to determine the average crushing strength of beads is explained on page 66. The beads must not have enough color to impart a noticeable daytime hue to white marking paint. The surface of the beads must be free from film mars, scratches and pits. When placed under a microscope (3X) at least 90 per cent of the beads (by count) must be free from excessive air inclusions, dark particles; spherical in shape and free from milkiness.l To obtain a long and lasting life, various sizes of beads are used. The larger beads are lost to traffic first, followed by suc- cessively smaller sizes. It is for this reason that the beads must have a fairly wide range of diameters. Beads of uniform size would be of little value if used as a center-line marking material. Another point that must be carefully considered is the differ- ence in expansion rates of the paints and beads. Will the paint expand faster than the bead, thereby losing all bond between the bead and itself; or will the bead contract faster than the paint, thus being loosened and lost? The specific gravity of the bead is also an important factor. Whether or not the bead will float or sink when applied to the paint medium is of prime importance. If the bead is too light it will never sink into the paint and thus the life of the bead will 1Michigan State Highway Specifications Page 8 be materially shortened as the top layer of paint is worn away. When dealing with plastics, the possibility of the beads be- ing attacked by gasoline and oil from passing care must be care- fully weighed and checked. The reflectivity of the material, according to the Hichigan State Highway Department 1951 Specifications for glass beads, must be at least 1.0 candle power per foot candle per square foot at 00 entrance angle. In other words the specific intensity must be equal to 1.0 CP/FCxFTZ. The procedure used to determine the reflectivity of beads is given on page hl. To be of value as a center—line marking material the bead must meet all the above requirements. The author, after extensive searching for suitable plastics for this use, narrowed the field to two plastics-—namely Methyl Methacrylate (Plexiglas) and Polysty- rene (Styron). Plexiglas is made by the Rohm and Haas Chemical Com- pany of Philadelphia, Pennsylvania, and Styron is manufactured by the Dow Chemical Company of Midland, Michigan. As a control for the tests run on these two plastics the author chose today's accepted material-—glass beads. All major tests were run first on the glass beads to establish a means of control or comparison of the two "foreign" materials Styron and Plexiglas. Page 9 CHAPTER II GENERAL PROPERTIES GRADATION If proper film.thickness is used, full reflective value of the line is not secured until it has been under traffic, and ve- hicular abrasion has uncovered spheres initially covered by the wet paint film. Depending entirely upon the amount and kind of traffic, this period may be a few days or it may be several months. The spheres are graded in such a way as to provide constant reflectivity during the entire life of the highway marking. Theoretically the paint film.can wear to about .OOh inches in thickness (enough to retain the smallest sphere of .009 inches diameter) and will still be reflective. .A paint film of .OOh inches is so thin that it can readily be seen through.1 Figure h, page 11, shows a picture of the Plexiglas bead before any traffic of any kind has passed over it. Notice that none of the beads have been pried loose. Figure 5, page 12, shows a photograph of Type I glass beads which have been subjected to several months wear by traffic at the intersection of M 25 and Mi29 north of Mount Clemens. Notice.how the larger beads have been pulled out by passing vehicles and how continued reflectivity is now dependent upon the smaller beads. .As has been stated before, it is for this reason that a uniform gradation is very poor if the beads are to be used for center- line marking purposes. The sieve analysis for Plexiglas, Polystyrene, and glass 1 Prismo Bulletin hh}, Prismo Glass Corporation. Page 10 beads;are given in Tables I, II, and III respectively. gig. h Plexiglas Beads in White Paint Hagnified 10 Times Page ll e 8 u 3 “In t m 1W v 6 8 r 6 t a m .m P. 6 t Glass; Beads in Magnified 10 Times Fifi". 5 Sieve Analysis of Plexiglas Beads TABLE I Page 13 The total weight of beads used in sieves (10, 20, 30, hO) was 103.0. 100, 1140, 200) was 196.5. ing a sample splitter. Sieve No. 10 20 30 no 60 ?0 80 100 lhO 200 Pan Grams 0.0 0.1 0.h 0.9 22.5 L0.0 117.0 10.0 5.0 0.7 0.2 % Retained 0.0 0.1 0.5 1.h 11.5 32.h 92.0 97.0 99.5 100.0 100.0 100.0 99.9 99.5 98.6 88.5 67.6 8.0 3.0 0.5 0.0 0.0 The total'weight of beads used in sieves (60, 70, 80, These two samples were obtained by us- % Passing Page 1h TABLE II Sieve Analysis of Polystyrene Beads The total weight of beads used in this test was 120.9 grams—- Obtained by using a sample splitter; thereby insuring a represent- ative sample. Sieve No. Grams % Petained 1 Passing *20 0.u ‘ 0.3 99.7 *30 0.5 0.7 99.3 *hO 1.9 2.3 97.7 50 13.9 13.8 86.2 60 19.h 29.9 70.1 70 30.9 55.h hh.6 80 32.2 82.1 17.9 100 10.1 90.h 9.6 200 10.9 99.b 0.6 Pan 0.? 100.0 0.0 * Clusters of smaller beads melted together. Page 15 TABLE III Sieve Analysis of Cataphote Type I Beads The total weight of beads used in this test was 559 grams- obtained by using a sample splitter; thereby insuring a represent- ative sample. Sieve No. Egfllg S Retained % Passing 20 0 0.0 100.0 30 79 lb.1 85.9 ho 176 h5.5 hh.5 50 17h 76.7 23.3 100 128 99.6 0.). 200 2 100.0 0.0 Page 16 CCICR According to the specifications the beads must be colorless to the extent that they do not impart a noticeable daytime hue to white pavement marking paint. Both the Plexiglas and Styron beads can best be described as to color by saying that they look exactly like salt or sugar grains. 0n the other hand, glass beads are slightly more transparent than either plastic bead. However, both Plexiglas and Styron are con- sidered to be transparent. From the author's point of view the plastic beads meet the present Michigan State Highway Department Specifications as far as color is concerned. It must be remem- bered however, that neither plastic bead is as transparent as the glass bead. INPERFECTICNS To be useful as a center-line marking material the bead shall contain not less than 90 per cent (by microscopic count) perfect spheres, free from film, scratches, pits, milkiness, dark particles, and excessive air inclusions. The surface of the spheres must be smooth and lustrous. Approximately 1,000 beads were checked under a microscope for the above named imperfections. It was found that both plastic beads contained practically no misshaped or "out of round" beads. The author also discovered that both Styron and Plexiglas contained much less air inclusion per 1,000 beads than was found in glass beads. The results of the beads Checked by the author are shown in Table IV. The author would like to comment on the count made on the Page 17 Plexiglas beads. If any air bubbles at all were found in a bead it was immediately rejected as an imperfect bead. However, on both the Polystyrene and glass beads only excessive air was ruled as reason for rejection. It is for this reason that the Plexiglas bead shows a slightly higher imperfection rate than does the Poly— styrene. Actually placing the three types of beads in decreasing order of perfection they would range (1) Plexiglas, (2) Polysty- rene, and (3) glass. The Polystyrene beads seemed to contain a greater number of beads with surface mars or scratches. Another method of determining the number of imperfect beads is to place a representative sample under a microscope and take a picture of them. In this way the number of out of round beads and the number containing excessive air may readily be determined. Figures 6, 7, 8 and 9 are four pictures which were used by the author to determine the number of imperfect beads. The first of the pictures, Figure 6, shows a rather poor sample of Minnesota Mining and Manufacturing Company beads. Figure 7 shows a fairly good samp- le of 3M beads. In Figure 8 is shown a picture of Plexiglas and in Figure 9 is a picture of the Polystyrene beads. BgelB TABLE IV Bead Imperfections Polystyrene Plexiglas Trial Total Imperfect Total Imperfect 1 127 . S 2h3 13 2 1h8 b 93 b 3 119 3 102 6 h 220 10 220 10 5 168 6 159 7 6 101 3 lbh 6 7 1&1 5 86 5 8 111 h 219 8 ' 9 138 6 52 3 lo .21 .2. .252 1 Total 1,379 h9 1,L1h 63 5% Imperfect 2 % anerfect : b9(100 _, p 63(100) _ a —13‘7'9‘l - 3’5" "11.111— — ["5" W. CANVL 3.-..v. 1.9.1va0... ”CNN”: M. .. .... AV Jaw. .mzfitWAv. mew. .1510... r. ....3. vAV . . 6 “av. . A‘r; 0 VJ“. AJve. . .v .MJV. v. 3 away. v. . .3... 93 Av. .. 3.... _ c. .. . “1.9.1.. J .A—V/ .w QC... A_‘m c Anv. 1 a, 3. we... ..a..;..! ...... mm... o. . . Aw AV.. MAW vAVAV. .~ .... 4 . . .... ... c... C. anxiefl .. av . z :. A$.A..’.u. ..- .1. . ..-... . A. 3 x. . ... c. 1.”. a. .. S w e B s w l G M . 3 3. Magnified 10 Times m e B S 8 a 1 G M Z/ d 9 v 0 m. m I Magnified 10 Times Fig. 7 Fig. 8 Plexiglas Beads Magnified 180 Times Fig. 9_ Pblyetyrene Beads magnified 180.T1mes Page 25 EXCESSIVB AIR Just what is "excessive air"? A test used to determine ex- cessive air is given below. The specific gravity, using a pyonomet— er, is run on the whole beads as received from the factory. Next the beads, approximately 250 grams, are crushed in a ball mill using a load of 550 grams of nominally B/h inch flint pebbles. Tumbling is continued for h hours. Approximately 10 grams of the powdered material passing a No. 325 sieve is used to run a new specific gravity. The per cent of voids by volume was computed by the formula shown'below. Voids in $1: (s3 gr of Plexiglas - sp yr of whole bead) lOO sp gr of Plexiglas The per cent voids must be less than 2%. Another method of determining excessive air, i to place the 0] beads in a liquid of the same index of refraction the beads them- .0.) U) selves and look at them under a microscope. Any air bubbles which misht be entrapped in the bead will show up as black dots. In Figures 10, 11 and 12 are three pictures of glass, Plexi— glas, and Polystyrene beads placed in liquids of the same index of refraction as themselves. Notice the difference between the number of black dots contained in the Minnesota Mining and Manufacturing Company beads and the num- ber entrapped in the Polystyrene beads. 1-5) Fig. 10 5M Glass Beads in Benzene (n PageZh magnified 85 Times . —— \ ’WR; ‘-.’ Fig. 11'" Plexi’glas Beads in Cedar Oi magnified 180 Times l ...-0. ..‘ (n:l.5 1)“ Page 25 .' . t ‘r ( v I v. C 3!. g . ... . C ' C .‘ ...l \ V“ \v v a .f‘ ‘,. .1! ' ’ . 1.. . \ 5" - l C O Fig. 12 Polystyrene Beads in Cedar Oil (n:l.51) magnified 180 Times Page 26 ——'~—I Page 27 CDCH Both Plexiglas beads and Styron beads have very peculiar odors. The Plexiglas beads can best be described as smelling something like witch-hazel. The Styron beads smell like an or- ange peeline that has just started to ferment. It should be stat- ed however, that these odors are not very strong and therefore are not objectionable. The presence of any odor would seem to indicate that there is some sort of chemical decomposition occuring in the beads. IJFFECT CF T13: .P'l-JPJXTURE A few grams of Plexiglas beads were placed in a container and boiled for one minute. The beads were immediately checked under a microscope and it was observed that they had begun to elongate. An increase in the amount of air bubbles present was also observed. Boiling was continued for 15 minutes and the beads were again checked under the micrOSCOpe. By this time the beads had disinte- grated into fine thread—like pieces. In the summertime it is not uncommon for pavement temperature to reach lthP in Michigan. It is for this reason that the beads must stand up under temperatures of lthF. The heat distortion temperature of Plexiglas, using A.S.T.M. D—6h8-h5 T test conditions and increaing the temperature %00 per minute with a load of 26h psi was found to be 62°C (1Lhof).l 1Rohm and Haas testing labOratory. Page 28 The distortion temperature of Styron is about 7200. Therefore it is seen that both plastic beads are suitable for marking mat- erials in Michigan as far as temperatures are concerned. Page 29 EFFECT(IT?&ATWEBIHG Plexiglas beads are superior to Styron beads in that they do not turn yellow as quickly with age. Plexiglas beads do turn yel— low slightly upon being exposed to the weather for a long time. Styron beads however, have a greater tendency than do the Plexi- glas. However, since the life expectancy of any one bead is lim- ited, it is doubtful whether this slight yellowing would effect the reflectivity to a considerable extent. EFFECT OF EXPANSION AND CCNTRACTION The expansion and contraction rates of the beads and the paints must be such that the bead is not loosened by a change in tempera- ture. The test used by the author to determine the difference in expansion and contraction rates is given below. A small panel, four by four inches, was made up containing both the paint and Plexiglas beads. This panel was allowed to dny thoroughly before testing started. The panel was then placed under a microscope and a few of the beads were loosened with a probe which served as a suitable instrument for removing individual beads. Next the panel was placed in an oven (lthF) and allowed to remain there for 12 hours. It was then removed to a microscope and again indiv- idual beads were loosened with a probe. It was found that the beads were not loosened noticeably by an increase in temperature to lhhoF. Next the panel was placed in a deep freeze and held at nega- tive 20F for 12 hours. The panel was again removed to a microscope and beads pried loose with a probe. It was found.that a temperature of negative 20F did make a slight difference in the ease with which Page 30 the beads could be loosened. However, the difference was so small the author believes it would be practically negligible in the field. CHEVICAL STABILITY many plastics that would make excellent center-line marking materials can not be used for this purpose because they are at— tacked by chemical solvents which are found in the paints. The mat- erial must be resistant to attack by gasoline, motor oil, or calcium chloride which are often found on the road surface. When calcium chloride comes in contact with water, it forms hydrochloric acid. Therefore the material must resist this acid. One of the first stepstaken by the author was to check the ac- tion of the paint vehicle on Plexiglas beads. Since about 50 per cent of the paint vehicle is composed of naphtha, the first test for chemical stability consisted of placing 5.60 grams of beads in a test tube and filling the remainder of the tube with naphtha. These beads were allowed to soak for two days. The tube was shaken at various intervals throughout the two day test. Next, the naph- tha.was very carefully evaporated wifli an electric fan leaving only the beads. No loss in weight of the beads was observed after the two days immersion in naphtha. Four and oneehalf grams of beads were next placed in another test tube and enough paint vehicle,off the top of the 1950 yellow highway paint, added to fill the remainder of the tube. The beads were allowed to soak for 15 hours after which the vehicle was fil- tered off and the remaining beads rinsed clean with naphtha since it had previously been proven that naptha does not affect the beads. Page 51 The loss in weight due to 15 hours immersion in the paint vehicle was found to be negligible. In still another test tube 6 grams of Plexiglas beads were covered with gasoline and shaken intermittently for h8 hours and again no loss of weight was observed. The Plexiglas head is not attacked by gasoline. However, it should be noted that it is not the loss in weight which is of interest but rather how the paint vehicle, gasoline, calcium chloride and naphtha affects the reflectivity of the beads. Page 32 COST When considering materials to be used in such large quanti- ties as is required for this type of work, the cost is naturally of prime importance. The cost of glass beads is between 10 cents and 20 cents per pound. The cost of Plexiglas beads used by the author to conduct his tests is 70 cents per pound. The Polystyrene beads cost 89 cents per pound. This is a development price and is subject to re- view if a specific order comes in. At first glance, the difference of 50 to 60 cents per pound between the glass and Plexiglas beads seems to disqualify immediate- ly Plexiglas for this use. However, since the specific gravity of glass beads is between 2.65 and 2.89 and the specific gravity of Plexiglas is between 1.16 and 1.20, it is evident.that better than twice as many Plexiglas beads per pound are obtained as glass beads. The specific gravity of Polystyrene is 1.05 as compared to 2.63 for the glass beads. Let us assume the specific gravity of the glass beads to be 2.65 and the specific gravity of the Plexiglas beads to be 1.16. Let us also assume the price of glass beads to be 10 cents per pound and that of Plexiglas beads to be 70 cents per pound. Using these figures, it may easily be shown that the cost per pound to obtain the same number of beads (which is after all what we are interested in), is 10 cents for glass beads and 31 cents for Plexiflas. 7O(-%L%g )-:_O.31 cents Thus it is seen that Plexiglas beads cost approximately three times Page 35 as much as do glass beads. By similar computation it was found that Polystyrene beads are three and one—half times as expensive as class. 89( :ZLZ-g-g ) :_- 0.35 cents. However, it is believed by the audior that increased produc- tion of the beads might reduce this difference in pri 9. Obviously, at today's (1951) prices it is far more economical to use glass beads than it is to use plastic beads of the tvpes tested by the author. Page 3h CHAPTER III 0 TICAL PROPERTIES REFLELC TIV [TY TLS TS The prime interest is in reflectivity and not in loss of weight. It is for this reason that reflectivity panels were made using beads which had been subjected to five days of soaking in naphtha and in a saturated solution of calcium chloride. In the wintertime the beads would be exposed to a saturated solution of calcium chloride. It is for this reason that the author ran re— flectivity tests on beads so exposed. It was found that the naph— tha decreased the reflectivity to 0.8 as compared to 1.1 of the original bead. The saturated solution of calcium chloride de- creased the specific intensity from 1.1 to 0.8. Page 35 DEFINITION OF TETTS USED IN HBTIECTIVITY TESTS Inverse Square Law: The illumination of any surface varies inversely as the square of the distance from the source. (The illuminated surface must be perpendicular to the direction in which the light is travelling). Illumination: Illumination.= luminous intensity in candles square of distance from source When the unit of length used is one foot, the unit of illumination is called the foot candle. Specific Intensity: Specific intensity is the unit of reflectivity and may be de- fined as the apparent candlepower of the reflector, per foot-candle of illumination falling on it, fer unit area of reflecting surface. Apparent Candlenower: Apparent candlepower of a reflector is its luminous intensity expressed as the equivalent intensity of a point source producing an equal illumination at the same distance. Mathematically, it is the product of the illumination, in foot—candles, returned by the re- flector to the point of measurement, and the square of the distance from that point to the reflector, in feet. . Angle of Incidence or Entrance Angle: Angle of incidence or entrance angle is the angle between the direction at which light strikes the reflecting surface and a normal to the surface at that point. Divergence Angle: Divergence angle is the angle between the direction at which Page 36 incident light strikes the reflecting surface and the direction from which the reflected light is seen or measured. For long range reflectors, such as would be used for center- 1ine markings, most of the reflected light must be conserved with— in a cone whose divergence angle is not more than 20 minutes. A divergence angle of 20 minutes corresponds to a distance of about 300 feet ahead of the vehicle. Page 57 APl-murusl The eduipment used for the reflectivity tests as shown in Figure 13 consisted of (l) a goniometer, for supporting the spec- imen— (2) a bank of lights, for illuminating it—-(3) a photo- electric cell and accessories for measuring the lijht reflected and (h) a separate foot—candle meter for measuring incident light. The base of the goniometer is marked off in degrees. Left and right ang_es of incidence are established by turning the goniometer on its base. Right and left incidence angles of O, 10, 20, and 30 degrees were used by the author in his tests for reflectivity. The light source consisted of a bank of four equally spaced General Electric No. hSlS sealed beam lamps arranged in a group a- round a metal tube extending through the center of the cluster. Each lamp may be turned in any direction, as well as moved lateral- ly toward or away from the axis of the metal tube. The angle of di- vergence is controlled by radial displacement of the lamps from the tube. If the distance from the reflecting surface to the receptor photocell is exactly 50 feet and the center of each lamp exactly 3% inches from the center of the photocell, a divergence angle of 20 minutes is obtained. A divergence angle of 20 minutes is used for all Michigan State Highway Department routine testing. It was al- . so used by the author. The lamps have individual switches and also a master foot switch. , 1‘B. W. Pocock, C. C. Rhodes, Reflective Haterials, Lansing, Michigan 38 The receptor photocell is clamped firmly against the rear end of the metal tube. The cell is a weston Photronic Cell Model 59hRR, equipped with a Teston Viscor filter, and is thus chromat— ically corrected to have a special response comparable to that of the average human eye. The cell is connected to a measuring circuit containing a mic- roammeter with an original sensitivity of approximately 0.03 of a microampere per millimeter division. A suitable shunt system is in- cluded to increase the range of the instrument by steps of approxi- mately 10 to l and 50 to l. The incident light on the specimen is measured with a Weston Foot-Candle Meter, Model 61h, containing a duplicate of the recep- tor photocell, also visually corrected. n. waDOE , Ce 520.3338 53.6.: 393.543; : 3....ch kzu2h¢4310_I mhdkm 240.10.! mZOhbDD COhouncmm 02:.me mo... thm>m oEkaOhOIQ I (as: soon; It) inveroxcé n20.15- c0533.. ~2u1>n33< ‘14... 450459 02.5313 so; 55192009 5530.35.39 02:3 :3. 34¢: 93 02 u 06 no. 25an 312.36 .343 4(39>.oz.@ . z . .._-..~.flfl\uv Page ho PANELS IQ? FEFIECTIVITY TESTS Three panels, each containing a paint stripe exactly four inch— es wide and eighteen inches long, were painted on metal rlates which later were attached to the goniometer. Three stripes h x 18 inches gives a total painted area of 216 square inches or 1.5 square feet. It was found that an area of 1.5 square feet would return enough light to the photocell to produce sufficient sensitivity of the gal- vanometer to make accurate readings possible. An under coat of .007 inches was first applied, (using a doctor blade), to each panel and allowed to thoroughly dry before the final coat of .011 inches was applied. This final coat was allowed to be- come slightly tacky before the beads were applied. Even distribu- tion of the beads was obtained by using a salt shaker held six inches above the paint stripe. The glass beads were applied at the rate of 6#/gal., the Plexi- glas beads at the rate of 2.h9#/gal. and Polystyrene beads at the rate of 2.20#/gal. As has previously been stated, the value of 6#/ga1. was found by the Prismo Glass Corporation, after extensive research, to be the most economical rate of application. An in- crease in the application of the beads above éfi/gal. increases the reflectivity but not sufficiently to justify the increase in cost. The values of 2.h9 and 2.20f/gal. were obtained as shown below. a 1.19 sp gr Plexiglas ._ , 6ffi( 2. ‘ Sp gr glass ) "' 20h97/galo '1 0. ‘~ t ' 6# $.95 92,8? Polys_yrene) : 2.20#/g31. 2.07 SD gr elaob The distance between the goniometer upon which the test pan— els are fastened and the photocell receptor was arbitrarily set at 50 feet. The 50 foot distance was measured exactly. A black drop cloth was lowered behind the goniometer. All x- traneous light was kept at a minimum, although the light in a dim i? corridor has very little effect upon the accuracy of the tests. The 1 window shades on all windows leading into the corridor were drawn to i keep the extraneous light at a minimum. Next, the three test panels (total area equal to 1.5 square feet) were fastened on the goniometer with "C" clamps in such a vay that the center of the middle panel was opposite the center of the goniometer face. The lamps were now turned on, individually, and adjusted so that the sample was uniformly illuminated. Each lamp threw an oval shaped pattern on the test specimen. The object was to adjust each lamp individually until a uniform illumination was obtained. Uni- formity of illumination is considered satisfactory only when the incident light, as measured at five points (four corners and the middle) by a foot-candle meter, varies by no more than plus or minus 5% the average value. The average illumination in foot-candles was recorded as the total incident light. Next the ambient incident light, which is the illumination from the hall falling on the sample is measured with a foot-candle meter and is subtracted from the total incident liflrt. The difference be- tween the total incident light and ambient incident light is known as the incident light. Page h2 The total reflected light returned to the receptor photocell is now measured by'xeans of a galvanometer. The test specimens are now covered with a black sheet nd the reflected light (using all four lamps) again recorded. This value, which includes all stray light entering the tube from other sources, is know as the basic reflected light. The actual reflected light from the four lanps shining on the test specimen is then equal to the total re- flected 1i ht minus the basic reflected light. The reason the author used an area equal to one and one-half square feet of beaded surface was to provide sufficient reflecting surface area for adequate galvanometer response. Page hB he soecific intensity test results are recorded in Tables V to XIX. The actual galvanometer readings (Column L) must first be con- )1. I\ verted to equivalent illumination in foot-candles (Column 5). The reflected lifht in foot—candles is now converted to apparent candle- power of the reflector (Column 6) by multiplying by the square of the distance (50 feet) or ?500. This is simply an anplication of the inverse wouare law. The specific intensity (Column 7) is found by dividing the apparent candle-power by the incident lieht and_a- gain by the area of the reflecting surface. Figures Lh—-18 show a graphical renresentation of the specific intensity test results. % With the shunt used by the author, h0.27 scale divisions on the galvanometer are equal to one foot—candle. Therefore to change galvanometer readings to foot—candle merely divide by hO.27. TABLE V Plexiglas Reads Rate of Application : 2.h9#/Gal. II H Area: 3 (gan2138 ): 216 sq. in.: 1.5 sq. ft. Entrance Scale Divisions .Ibid.. APP. Angle Basic Total Actual F.C. E;§:_ C.P./1erT2 3.8 o l.t 3.7 2.35 .oSGh 1&6 1.1 10L 3.7 2.30 .0571 lh3 1.1 R 3.7 20L 3.7 2.30 .0571 1&3 1.1 R 3.7 30L 3.5 2.20 .05h6 137 1.1 R 3.7 Shunt Box Setting: no.27 Scale Divisions/F.C. 89 80 FC : 90 102 86 "" 3.5 = 85.9 AI‘Ca. = 105 Sq. ft. F.C. (Area) = 85.9(1.S) ::128.9 Page he TABLE VII Plexiglas Beads Passing A #70 And Retained On A #80 Sieve Rate of Apblication': 2.h9#/Gal. b" X 18" Area: 3 (Panels ): 216 sq. in. = 1.5’ sq. ft. Entrance Scale Divisions lbido. APP. Angle Basic lbinl Actual F.C. .ELE; C.P./FCXFT2 0 1.3 2.9 1.6 .03973 99.3 0.75 2.9 10L 2.9 1.6 .03973 99.3 0.75 R 2.9 20L 2.8 1.5 .03725 93.3 0.71 R 2.8 30L 2.8 1.5 .03725 93.3 0.71 R 2.7 Shunt Box Setting: h0.27 Scale Divisions/F.C. 88 88 Area =-" 1.5 sq. ft. F.C. (Area) = 87.8(1.5) = 131.7 Page b8 TAB LE. IX Plexiglas Beads After Five Day Nanhtha Bath Rate of Application‘: 2.h9#/Gal. Area: 3 (ggn:1:8")‘: 216 sq. in. = 1.5 sq. ft. Entrance Scale Divisions .Ibid.. APP. 2 Angle Basic Total Actual F.C.__ C.P. C.P./stFT 1.2 2.7 1.5 .0372 93.00 0.77 0 2.7 10L 2.7 1.5‘ .0372 93.0 0.77 R 2.7 20L 2.8 1.2 .0298 78.5 0.61 R 2.h 30L 2.3 1.1 .0273 68.3 0.56 R 2.3 Shunt Box Setting: h0.27 Scale Divisions/F.C. 8 133:8? 93 88‘3=81°O Area = 1.5 sq. ft. F.C. (Area) 1' 81.0(1.5) : 121.5 Page 19 TABLE X Plexiglas Reads After Five Day Gasoline Bath Rate of Application = 2.h9#/Ga1. h" X 18" Area: 3 (Panels ) = 216 sq. in. : 1.5 sq. ft. Entrance Scale Divisions Ibid., APP. 9 Angle Panic Total Actfial f.0. C.P. C.F./FCYFTb 0 1.7 3.2 1.5 .0372 93.0 0.8 3.2 101. 3.2 1.5 .0372 93.0 0.8 R 3... 20L 3.0 1.3 .0323 80.8 0.7 R 3.0 30L ' 3.0 1.3 .0323 80.8 0.7 R 3.0 Shunt Box Setting: 80.27 Scale Divisions/F.C. _ 8h 80 FC—72100 Bil—2:82 Area = 1.5 Sq. ft. F.C. (Area) : 82(1.5) = 123 Page 50 TABLE. XI Plexiylas After Five Day Calcium Chloride Path Rate of Application.= 2.h9#/Gal. . Area: 3 ggnglian) : 216 sq. in. = 1.5 sq. ft. Entrance Scale Divisions Ibid. . APP. 2 Angle Basic Total Actual 17.0. 1.3:; C.F./FC:(‘;‘T 0 1.7 3.3 1.6 .0397 99.3 0.8 3.3 10L 3.3 1.5 .0372 93.0 0.7 R 3.1 ' 20L 3.1 1.11 .03h8 87.0 0.6 R 3.1 30L 3.0 1.3 .0323 80.1 0.6 R 3.0 Shunt Box Setting: b0.27 Scale Divisions/F.C. 82 80 area 2 105 Sq. ft. F.C. (Area) = 83.3(1.5) = 121.35 TABLE XII Red Polystyrene Beads Rate of Application = 2.2#/Cal. Area: 3 (“EMS Entrance Scale Divisions Angle Basic Total Actual 2.0 0 1.0 1.9 0.95 10L 1.8 0.90 R 2.0 20L 1.8 0.85 R 1.9 50L 1.7 0.75 R 1.8 Ibid. F.C. .0208 .0197 .0186 .0165 ) 3 216 sq. in. B 105 sq. ft. Page 51 APP. C.P. C.P./FCXFT2 52.00 0.5 £9.25 0.14 L650 0.4 h1.25 o.h Shunt Box Setting: no.2? Scale Divisions/F.C. 8 FC: 71881779 — 2 875.14. Area-c: 1.5 sq. ft. F.C. (Area) - 75.h(1.5) : 113.1 Page 51 TABLE XII Red Polystyrene Beads Rate of Application = 2.2#/0a1. n H Area: 3 (hPafieIE ) = 216 sq. in. = 1.5 sq. ft. Entrance Scale Divisions Ibid. APP. Angle Basic ToteI' Actual F.C. .913; c.P./'F0xFT2 . 2.0 0 1.0 1.9 0.95 .0208 52.00 0.5 10L 1.8 0.90 .0197 h9.25 0.h R 2.0 20L 1.8 0.85 .0186 h6.5o 0.4‘ R 1.9 50L 1.7 0.75 .0165 h1.25 0.h R 1.8 Shunt Box Setting: h0.27 Scale Divisions/F.C. 8 FC: $381439 — 2 375.1}. Area‘z 1.5 sq. ft. F.C. (Area) - 75.h(1.5) : 115.1 Page 52 TABLE XII-A Orange Polystyrene Beads Rate of Application ; 2.e#/ca1. Area: 5 (hga:e%§" : 216 sq. in. = 1.5 sq. ft. Entrance Scale Divisions Ibid. APP. Angle Basic Total Actual F.C. C.P. C.P./PCxFT2 5.0 ' 0 1.0 5.2, 2.1 .0A61 115.5 1.1 10L 5.2 2.1 .0h61 115.5 1.1 R 5.0 20L 5.0 1.9 .0b17 10h.5 1.0 R 2.8 50L 2.9 1.8 .0595 98.8 0.9 R 2.7 Shunt Box Setting: 110.27 Scale Divisions/F.C. 70 78 FC = 80 'l' = 2.2 70 78 3 7 Area. : 105 sq. ft. F.C. (Area) : 72.2(1.5) = 108.5 Page 53 TABLE XIII Polystyrene Rate of Application = 2.20#/Ga1. Area: 3 (8:81:85 : 216 sq. in. : 1.5 sq. ft. Eiiiiice Rasggalgogiiisigtial 38818:" gig; C.P./FCXFT2 0 1.3 3.9 2.7 .06705 167.8 1.28 8.0 10L 3.9 2.6 .06856 161.5 1.23 R 3.9 20L 3.8 2.5 .06208 155.3 1.18 R 3.8 30L 3.6 2.2 .05A63 136.5 1.0a R 3.0 Shunt Box Setting: h0.27 Scale Divisions/F.C. 88 8 FC :3 8L1 106 925 — 3 : 87014 Area = 1.5 sq. ft. F.C. (Area) = 87.h(1.5) : 131.1 Page 5h TABLE XIII-A Polystyrene Rate of Application :.6#/Ga1. (approx. saturated) ll 1d" Area: 3 (ll-tanxls ) z: 216 Sq. in. : 103 Sq. ft. Entrance Scale Divisions Ibido. APP. _ 2 Angle Ragic Total .Actual P.3. C.P. C.P./PCxPT 5.0 0 1.2 5.1 3.85 0.096 2t0.0 1.90 10L 5.1 3.85 0.096 2t0.0 1.90 R 5.0 20L 5.0 3.8 0.095 237.5 1.88 R 5.0 30L 5.0 3.75 ' 0.09h 235.0 1.86 R u.9 bOL 5.0 3.7 0.093 232.5 1.8b R h.8 50L 8.7 3.3 0.083 207.5 1.68 R 8.3 60L 3.5 2.2 0.055 137.5 1.09 R 3.3 75L 1.2 0.3 0.008 20.0 0.16 R 1.8 Shunt Box Setting: h0.27 Scale Divisions/F.C. F" 77 78 Area : 1.5 sq. ft. F.C.(Area) : 8h.2(l.5) - 126.30 Page 55 TfiBIE XIV Polystyrene Beads After Five Day Nanhtha Bath Rate of Application = 2.20#/Gal. I." X 18" Area: 3 ($811818 ) = 216 sq. in. : 1.5 SQ. ft. Entrance Scale Divisions .Ibid.. APP. Angle Basic Total Actual F.C. C.P. C.P./FCXPT2 1.2 3.0 1.8 .ohh7 111.75 0.9b O 3.0 10L 2.9 1.7 .0h22 105.50 0.89 R 2.9 20L 2.8 1.6 .0397 99.25 0.83 R 2.8 30L 2.8 1.55 .0385 96.25 0.81 R 2.7 Shunt Box Setting: h0.27 Scale Divisions/F.C. F0233 92 ;g_3=79.h Area.= 1.5 sq. ft. F.C. (Area) = 79.1.(1..5).= 119.1 Page 56 TABLE XV Polystyrene After Five Day Gasoline Bath Rate of Application»: 2.20#/Ga1. ,n X 18" Entrance Scale Divisions .'lbid.. APP. 2 Angle Basic Total Actual 3.0. C.P. F.P./RCvRT o 1.7 h.3 2.6 .06R6 161.5 1.2 b.3 lOL h.3 2.6 .06h6 161.5 1.2 R h.3 20L 1.1 2.1 .0596 1L9.0 1.1 R h.1 30L 3.9 2.2 .05h6 136.5 1.1 R 3.9 Shunt Box Setting: hO.27 Scale Divisions/F.C. 8 FC : 812‘ 103 23 ._ 1.5 = 85.5 Area : 1.5 sq. ft. F.C. (Area) = 86.5(1.5) = 129.75 Page 57 0 TABLE XVI Polystyrene After Five Day Calcium Chloride 13'3le Rate of Aonlication .-.: 2.20#/Gal. )4" X 18" Area: 3 (Panels ) = 216 sq. in. : 1.5 sq. ft. Entrance Scale Divisi ons lbid. . A}? . Angle Basic Total Actual F.C. 0.?. C.P./FCXFT 0 1.7 3.7 2.0 .0897 128.3 1.0 3.7 10L 3.6 1.9 .Oh72 118.0 0.9 R 3.6 201 3.8 1.7 .0122 105.5 0.8 R 3.h 30L 3.3 1.6 .0397 99.3 0.8 R 3.3 Shunt Box Setting: no.27 Scale Divisions/F.C. ‘0 FC 56315100 35)" 2 = 83.8 Area = 1.5 sq. ft. F.C. (Area) : 83,8(1,5) : 125.7 Page 57 - TYLEIJS 3571 Polystyrene After Five Day Calcium Chloride Beth Rate of Annlication = 2.20#/Gal. )4" x 18:: Area: 3 (Panels ) = 216 SQ. in. = 105 Sq. ft. Entrance Scale Divisions lbid.. APP. 2 Angle Basic Total Actual F.C. 9:3: C.P./PCXFT 0 1.7 3.7 2.0 .0897 128.3 1.0 3.7 10L 3.6 1.9 .0872 118.0 0.9 R 3.6 20L 3.8 1.7 .0822 105.5 0.8 R 3.8 30L 3.3 1.6 .0397 99.3 0.8 R 3.3 Shunt Box Setting: 80.27 Scale Divisions/F.C. .n ' 88 80 Area = 1.5 sq. ft. F.C. (Area) : 83.8(1.5) = 12507 Page 58 TABLE XVII Cataphote Type I Glass Beads Rate of Application : éflybal. Area: 5 (h;a§e%§") I 216 sq. in. s 1.5 sq. ft. Entrance Scale Divisions Ibid .APP. Angle Basic ifotel Actual F.C. .ggg; C.P./PCXFT2 8.2 0 1-3 8.3 2.95 .0733 183-3 1.8 10L 8.2 2.85 .0708 177.0 1.3 R 8.1 20L 8.0 2.7 .0670 167.5 1.3 R 8.0 30L 8.0 2.7 .0670 167.5 1.3 R 8.0 Shunt Box Setting: 80.27 Scale Divisions/F.C. 4 '86 81- : PC - 89 101 89 1 89.2 Area : 1.5 sq ft. F.C. (Area) = 89.2(1.5) : 153.8 Page 59 TABLE XVIII Cataphote Type I Glass Beads (90 Hour Reflux) Rate of Application 3 6}/Cal. n '1" Area: 3 (14139391: ) : 216 sq. in. = 1.5 sq. ft. Shunt Box Setting: 80.27 Scale Divisions/F.C. Entrance Scale Divisions Ibid APP. Angle Basic Total Actual F.C. C.P. can/Mn":2 8.1 0 1.5 8. 2.85 .0708 177.0 1.5 10L 8.2 2.80 .0695 175.8 1.5 R 8.0 20L 8.1 2.65 .0658 168.5 1.2 R 3.8 50L 8.2 2.65 .0658 168.5 1.2 R 5.7 FC = 33 106 g: - 3 = 88.8 Area : 1.5 sq. ft. F.C. (Area) : 88.8(1.5) : 153.2 Area: 3 ( Entrance Angle 10L 20L 30L )4" X 18" Panels TABLE XIX White 1951 Highway Paint Scale Divisions Basic ‘Total Actual 2.5 1.2 2.3 1.15 2.3 1.15 2.3 2.2 1.05 2.2 2.0 0.85 2.0 ) = 216 sq. in. I 1.5 sq. Ibid F.C. .0286 .0286 .0261 .0211 APP. Page 60 0.2. C.P./FC>:FT2 71.5 0.6 71.5 0.6 65.5 0.5 52.8 0.8 Shunt Box Setting: 80.27 Scale Divisions/P.C. FC : 8 79 - - 8; 99 82 1 - 85.8 £1.99": 105 sq. ft. F.C. (Area) : 85.8(1.5) : 128.7 Page 61 4 .-- . i . T . t ; 1 . i . M~Pfi '” i . l .——H»4 I. . J v I 11',’ u ,.,.,-'.-._... l . | . 1...-._.7L..._.,._.... . . . I F0. 1-. P ADS I r- p 77,5:L : I O I "E .4 0. n I , ‘ i I l f D l l 4 .. O .. [01»le I'QL‘uq 5 Tav134¥88834$ UREtmfltanb? a I V I -r- -. 1 I L i 5775887 t*"*”r" I ....l‘,, 951 8:45 '1’“ 77%. Ii ..IIJIItdlolIO .l. sucumexn. -4>--—. WPL. t v u . _.....,-... ..-- c- - o . - W’f-f—"-T I 1IJ‘I. o . y . fi . 1w . L . I. 1 o v ‘1 r ”x Toluoillloolllox v.7 . . a .- .. v .c .. — . o > Cc. T ’$ 4 . LI 1704+4vlrl+l T #944? O A T 7‘i M H—i , if, } ! :8 l l swuidéfki I 2' l --: :7 7‘. ,11111 We 1 7" 1. K V 1-- y. j ; 77 o fin. -0—4 . ..- l 155: 1 H 4 _.A 7+ .v.|.l.ll+oc.;.'LI nxu.irhxmxsmpcc\ usucumsmfiq N». «*— Page 62‘. II'II'c'Id' |vvl I- ' Yflllllili . E *II- .‘ JAN “Er-4 ."l. I t I J 1.. 1L 1 l 'b I I . | i I t I I .220 _ C v .—¢--1 72m * I are I A T W fir r“? _ 9 1.7-RA I I Y ..I .-.L._. i I we _ .7 . It . I . I. I .9. I . . I . . . _ _ _ . m- t 1 I« e O I. If I. I ‘14... JI'L r ..-.-. 4 I. . o I. . . o . t . _ _ . a _ _ . I ..l a . . . I . o 1 I. I . . . AI . I t I. I . 'lc - . - 7. o ' ' _. w! v '1 a. i. r. . I I 6 l i >0. 6 ..I. . . . v d . . _ a 1 . _ . . m .r 7 71!! “ II . 1 L. I [III I_ IIIIIILIII _ . 1. _ _ — t ... 1.. IoI . c. . J I" . T .4 ur% I . *.I. ‘4. . V . . It . 040 s . a, * I. a . r . OI '76 .o 5.. _ _ . . _ . . IA 7 w 1" 4 7..- . IfL' _|'Y I cl .Ill 7 I .11 vol . .7. .v I . A IAr . . . i . _ fl. IT. ~ 4 . II+I . _ . _ . . v o < o .0 T a .- ... V . I «ILI_ . .._- .Ilv . fl; + H .- .- .--+I . .1 c _ . u r . 7 . . 4 . _ 1 N _ . 1 II “I . Ill o . .I . . .1. R F... o .I . Iv . _ -9 -VIIa. L. .-I. .I’? .I I. . I ..... IL II .- 7 . . c 1 II II p | . _ _ _ . . T 'I. A“ 4'1 Alla-ll! III... I It! i 14 :III.’ 101.4!“ lit-la .91. I. III! III»! » I 1 I. {4.0 IILYI‘IIIFSI. '4’. Ir * I fill I 3 I {I 7.9 I . _ . _ . . . AI— . ... . . .If ..IT.+I+ « . .1 . I. «.7Iw. . ¢ . |~I « w .7 0 I. . O . . I w . » .IIA ' AI . lo .. . - r . .II. ...“I *“ _.I_r. .IL . . ,£.|V T.v . l o- a p a . 4 ,. .Iq . . O . no. u . s 4' 0. “ “II? n (.4 u . H rifi 1 f. ..7 rlt It .I ..qul I. * .1 III. I: 4 H Y IO. . . t W . c . .. '3 . L . l . 0. "I t 9 I. - c _ “ II- » ~ 9.1411 . . _. 7 o u -I - III . II. I -. .. a. * .v t. o . _ 1 r . I r _ . 4 . 4 1 . . J T c . . J . 1 .8 7 . 7 , I 7. L -I II - - 1 . 1 I 1 «s'w , . ..4 *7 I T I f 1 {fr v 57 wt" I I I I I :73 . as 1.41»! t I .Ii: . WWI ' 774158 .;If'i 7 , I -l I O y ‘ -~-——+—-— H-gk-‘q—0 --.- —--o'-‘-* . . ' . [— I I I 7’ HH+I ’ " I I ‘l:' 4.; | 40 ...J.._L. . . . . . 7b EIN . IIIIIIIfiIIIII FIII IL A . Y resume 1. “ 4'00" E'L. lr‘l t I . 9 ‘ ¢ _ 'l. I. I. a . . c _ e. . . . .0 . . 1 v . ‘l 00.0I «1:101... S'Ir O l '0 v . Y Page 63 I I I .II .I I ...—J“. I I I I - J 5.8 I I -1. «I I .17 .44 . ; A757 8 » . j ..r- ‘—I I . 7 . . ... .. I7. . . . I8 1 117 u I .I . c.0777. Q . . I4 -9- . L . . .I F. . . c u -. I. J I I. e L ~ F! . .7IILII' I007- WIIFIIII II... IYII II .IIIIIQ. QIbiT-L.. . . . I. I I: ‘3'. fl: 2'! 81:. q I . I J8 Y 6.9IN OI - It I. O . ET I has; R; I f MED. 1*. file, I. ...‘I— —.-—-o—o_— .. . I I I I7. 8 r- r . .I. ..... v . III” 8 ‘ I 4 ' 9 4 . . c 1 . 7 7 III .8871 a 7 7 7. . . 8 8 .. o . 1,. .8 v-7 .. I . . cII+ - 8. G 8; . I I 8 m.._..;VLCE 8.. . .. h ...WL/P M . I . o 8 S ... .L ~ _“ . 7- i. 81 I I . . c . . . 0 I.. ..I II. 5-!I . W4 - M- - I. 7 I I -I 8 - - --. ... I- - .8 -- .. - .I . . .8 .8 I c . . .. w . . . _. 7| III? .+_. L o g H . . n . 5 . . . 8. _.I V V... I I 8 I . IN “.A I 8 . 8 - . T . . ,7 . . .7 II. . .8 1 -. . I. . . . . , .. ..7 . .. .. «H I \II 5 . 7 . . A II 4| .I. .I > 8I..AI. D . S a .I . . .. . .7 ...I ... .. .I . . . . .8. . . . I+ . . ... .. . . . - . - . I." . . 8. . o .- . . . .L . M 7- . .0. . .8 8. . 4 . .1. .8. .01; h_ a . w--- .874. ...- $8.? H.... 7. .. ..- .7“..I. a H.....8.. . - 08v .II 7-77. 7-..-” 17.8-1 gin; ...I..7I-. 78-- 1.75..-. I I7... «87......77 .. .77..-.7? 8 7 .I .-....8... .. 8 . .-7- . 7 - 8.. . 8 7-. l o . . . .7 .. .. I .8 X I L c . . I.. . . . 8 . I .. . axkxukbh. 8843.:th Uibmkw . . f . .nhxbethG 78.59ch3 9 8.68.00 . 7 . T. II ... ... . .. . 8 ” ¢ .—-I. -74 .I .-. . fl . . “7. . _. u.. u h v 9. . .0.” . ..4 . .-. .. 8 ... . .+ . c .. . . I . 8. . . . . 7. . . 8 . . . . . . I .7 .. _. . I . _ . . . . o n . n . . . I .4 t . . . .8 8 -w . _ . ... TI.I ITIII - IIHIIIIIIII-I . II+I III- IIIIIII . III IJtII. _ I71! _ TLII'II . > I. II.I I ..III I-.-I IIIt- IIIILIIIIJ 8 .8. -.8 .11.. 8.7. 8. ... - n .. 8 .. .4II.I.II.IIJ 8. 8 1 .8 . 8 r .4 J M 8 . .78IL. 8- 8.. .r. .-.. .. .8. . .8 8.8!.-. .. ... 887... 8... 8 .8.. 8. 5-87......-..87.7.58..g.8.;9.7.1.8., _..i..87nn...8;...7.7.tf M .8 .88. w.... OI I III 7 +6 I “III. .0 I“. I a 8 . 9.. . ~ . .77. .I4 . . I81 I . u . . In“. I. I 8 .lo._1.8r.I_MIIT ..I+IIIU + - I-IIII ...+ I + IHLIT . 8. . 8 . 8 . 8 .. ..f... ..-1. . 8. 1...: q o I I _ 7 4 8 w I .I‘ . a 4 _ r .88 . . |. IL .. 8 e .. a .v .c e . L . -- . I . .. e m I. . I .w . . m . 8 . 8 8 8 8.88 . 8 .-I . h . I . 8 +I I III I”: o .3 WI“ 4 . . I o . . o _. v _ . . . . g . . 1 o 4 8 .rI*.. . "I. .7 . . J . h . ~. .... L I II I .— III .. mIIIIIIIIIIIIfII III.I.I. . bIL. . Ir I I 8 . I . L L 8 I. III . I III L .L 8.0-448* . H ‘r—V "L85 "I fT ‘8 .L. 8 , - I 8'87: [Arm I ’8 . "T' ...I .— 84-... . ' r I 8 18.1.. . .- I 8-. I-u-o—u? ”...-0-.“ ...}.1- /CI. 773513 f ['5 ‘ 51 } I IIIIO|IOI| OIIII ’Uv‘3$ 2:; Page 65. Page 66 CHAPTER IV STREWGTH PROFRRTIES CRUSHIHG STRENGTH The average crushing strength of the beaded material was de- termined by placing one bead between two highly polished steel planed surfaces and loading at the rate of 250 grams per second until failure. Twenty—five beads were crushed in this manner and the aver- age of these values was taken as the value to be used in determin- ing the average crushing strength. A diagramatic sketch of the apparatus used in fliis test is shown in Figure 19. l A single Plexiglas bead (passing 60 sieve and retained on 100 sieve) is placed on a movable anvil "0" directly under the station- ery highly polished surface "D". With the bead directly under "D" and resting on "0", small shot is poured from can "A" into can "B" until the bead is crushed. Arm "E" drops down slightly when the bead is crushed. The weight of the shot used to crush the bead is carefully noted and recorded. This process is repeated twenty-five times, recording the weight of shot used each time. The average crushing strength in kilograms is determined by taking the average weight of shot used to crush the 25 beads and multiply by the factor 10.9 and divide by 1,000 grams. The factor 10.9 is obtained by dividing the dimension b(17.875) by the dimension a(l.6h). By taking the weight of shot used and . . . .8 multiplying by'thls factor, (1%:5£§:: 10.9), the actual force that is applied between the two highly polished surfaces "0" and "D" is Page 68 obtained. The results of the average crushing strength of Plexiglas beads which have been subjected to (1) room temperature, (2) lthF temperature, and (3) negative 20F are shown in Table XX. The author was interested in determining what effect temperature would have on the crushing strength of Plexiglas beads. The results of Polystyrene Type II beads, crushed at room temp- erature, are shown in Table XXI. Table XXII shows the results of Cataphote Type I beads, crushed at room temperature. The plastic beads were screened to pass a #60 sieve and be re- tained on a #100 sieve. The glass Cataphote beads were screened to pass a #30 sieve and to be retained on a #hO sieve. The Michigan State Highway Department Specifications require that Type I bead must have an average crushing strength of 7.5 kilo- grams and that Type II must have 2.5 kilograms. The reason that the Type II bead crushing strength is lower than Type I is that there are many more beads to withstand.the pressure caused by the vehicles and also the paint binder gives the Type II bead the extra needed support. As shown in Tables XX and XXI, the Type II Polystyrene Plexi- glas beads meet the Michigan State Highway Department Specifications for the Type I bead. Obviously, as far as crushing strength is con- cerned, Plexiglas beads are very practicable for highway marking material. The author believes that it is just coincidence that both same ples subjected to temperature changes showed a higher average crushing Page 69 strength than those which were subjected to only room temperature. Page 70 TABLE XX Average Crushing Strength 0f Plexiglas Reads Room Temperature lhhoF -2OF Trial 1 728 grms 707 arms 716 grms 2 658 728 702 3 671 673 703 h 669 669 701 S 668 658 7&0 6 680 669 759 7 696 651 685 8 670 666 700 9 676 676 729 10 652 693 LE2; 11 665 691 Total 7,138 grms 12 653 707 13 661 732 Average Crushing Strength = 1h 6h6 68b 15 6b? 688 Vagfiifggg? = 7.8 Kg. 16 6h7 702 17 6&2 692 18 6h8 ‘ 71:0 19 651 688 20 653 701 (Continued on next page) Page 71 TABLE XX (chT.) Average Crushing Strength of Plexiglas Beads Room Temperature 1thF Trial 21 663 717 22 6M9 ' 707 23 660 . 736 2b 660 737 25 as 9:”; 26 665 Total 17,377 grms Total 17,123 grms Average Crushing Average Crushing Strength = Strength = 17,123(1o.9) _ .2 Kg. _1_7 377(10.9) : 7,6 Kg 26(1,eooj ‘ 7 “ fiSKIfiGU) {\3 0\ W L“ b0 TA ELF, XXI ng72 Average Crushing Strength of Polystyrene Beads grms 10 11 12 13 11, 15 16 17 Trials 700 7h1 703 695 710 719 716 703 grms Average Crushing Strength = 17,763(10.9) _ 2571,0003 - 7.8 Kg. Trials 18 639 19 731 20 708 21 696 22 718 23 726 2b 727 25 .622 TOtal 17, 763 0\ U1 5" to K] Trials 502 750 Ste 627 695 616 682 706 I 1.37:: vv 7' {IDLJLLIJ ILLI.‘ Page 75 Average Crushing Strength 0f Cataphote Beads {$13115 Tri 10 ll 12 13 15 16 Average Crushi S trength = 16,800(10.9) _ 25(1,0007 - als 526 grms 660 519 526 615 70h 709 ng 7.h Kg. 17 713 grms 18 693 19 713 20 72b 21 967 22 69b 23 735 2b S90 25 967 Total 16,800 gnns 0\ VI 11‘" w «1 Trials 502 750 5&2 627 695 616 682 706 mar-Tm AIL 2.1—”J XXII Page 75 Average Crushing Strensth 0f Cataphote Beads grms Tri 10 11 12 13 15 16 Average Crushi Strength :- 16,800(10.9) _ 25(1JXXD' ‘ als S26 grms ng 7.h K3. 17 713 firms 18 693 19 713 20 726 21 967 22 69b 23 735 2h S90 25 967 Total 16,800 firms Page 7h ‘FER'EBT The object of this test is to determine the durability of four paint stripes, one containing no beads, another containing glass beads, a third Polystyrene beads and a fourth Plexi; as beads. A four wheeled rubber-tired dolly was pulled over the four stripes until 100% failure was noted. The total failure uas consid— ered to be that point at which the paint over which the wheel travel- ed was completely worn through. The number of trips required by each wheel to produce this failure was carefully noted and recorded. The average number of trips by the four casters to produce 100% failure was taken as the final result. The results of the test are charted in Figure 20. Page 75 H’LJC’eDURflE‘. ‘.-— Panels Four stripes, each four inches by eighteen inches, were paint- ed on one long continuous panel of plywood using a do tor blade to insure a uniform thickness of .015 inches. To one of these stripes the author applied 11.6 grass of Type I glass beads which was at the rate of six pounds of glass beads oer gallon of paint. To another stripe was added h.3 grams of Polysty— rene beads which is equivalent to 2.20 hounds of Polystyrene beads per gallon of haint. t should be remembered that there is in 2.20 pounds of Polystyrene beads, approximately the same number as in 6.00 1" pounds 01 glass beads. To the third stripe was added h.8 grams of Plexiglas beads which is eqaivalent to 2.L9 pounds per gallon of Plexiglas beads or 6 pounds per gallon of glass beads. The fourth panel was left without the annlication of any beads to be used as a control for the other stripes. The paint was allowed to dry for five days at room temperature and humidity before the actual wear testing was started. Dolly The dolly used by the author consisted of four rubber-tired casters, one—half inch wide by one and three—quarters inches in die- meter, fastened to a small wooden platform twelve by seven by three- ouarters inches. The four rubber—tired castors were staggered in such a way that no two of them would travel in the same path. In this way the author Page 76 was able to perform four tests at one time. On top of the small wooden platform was placed a seventeen pound weight which made the total dolly weigh approximately eiehteen pounds. This meant that theorectically each wheel of the dolly was carrying four and one—half pounds. The four wheels of the dolly were placed at an angle of twenty degrees with the direction of travel in order to create a slight skid- ding effect as well as a rolling effect. Testing A very thin layer of sand was applied to each panel before the start of the test. This sand was used to act as an abrasive and thereby greatly reduce the time required to complete the test. After each fifty trips across the stripes the sand was redistributed and the test continued. Ropes were fastened on both the front and back end of the plat- form. The dolly was propelled by pulling these ropes, first in one direction and then in the other. Guides for the dolly were placed a- long the two edges of the panel to insure proper alignment. It was pulled at an angle of thirty degrees with the four stripes which means that each caster actually travelled a distance of b.62 in- ches along each of the stripes. P e 77 * 1.11 .11 . 1111.11 . 1 . 1. 111] 11.1 ...... I 1 _ . 1 . - . .. . 1 1.? 1 11 11 1 .1 . e . . 1 . 1 .. + . . 1 1J1 -111-- 1 1 _ 1 _. 1 H 1 a . 41.1 11 ‘11 . . . . . -. _ 1|11111 1 11 w h. a v l— 1114. a . 1 91 *_ .7 W . 1&1. m 1 v . 4 s .1111 111111111 . . 1 - . . . . 1 . _ 1 -- -. 1 1 -1 - 1 1 a . - F — q o e m .0 h o . . o . . 1 _ . n . 1 «l . A... Q o 4.1 a .1 l n * _ _ 1 . 1 . . 1 . a . + . 4 . . . T1111 1 . . 1 _ 1 . - 1. 1. . 1 H . . . ..lf 11de 1.0.11 11‘! 1. r _ 1 . _ A 1 .rv 1 I. a . 1| 1 .111- . 1 . 1 ill-5+1 _ . . . . . 1 . . o . . . . i1 .1 1-1 . ., . . _ W . -1 11 1111.111 1 1.. 1.11 . 1 . - 1 1 . 1 I . _ . 111 1|.1i-1.11 1. u. 11 . ... . . 1 11 1. _ . - .1 . - - . 1 11111111111 1 . 1 . -1 1 1. 1 . 1 1.1 . . 1. _ 1 n a . . _ . 111 _ . I 11 1|1 . _. o 11 .. w r . .1 . A . . . iJOVIt-i . 1 1 . . 1 w . 1.111 _ _ . .. T1 . 1 11101111011611 _ _ .. 1 1a . 1 r 11.0111. V 1‘ .v Q 1 k . Tlvlftllu’ :1 I11" _ . ...1 -. . - 1.1.11-1.1 - M . . V q . 1 v 9 w \ so. 1 . v . . a 1 fl '11 111r ‘Lvllflu‘ilu 1 . . . 1. .. .11 t 1. -1. .. 1 . 1 . o . . \ x I . \.. ll 1 11.1“ rlrb ~ .e H 5\. . ....x. 1. .. .1.. 1N 11 . .1 1 1 ..1 . e . . .... x .. .1 \1 _ 1 ‘1. f ‘ 141.111.111-117}! d \\ . L.‘.. l 1.6 .. k 1 .- h 1 s. 10.... .. 11 INT-WWW ..QN 1.1.x . . 1 1 1 1 . .. 1 . -. ..\.\ .. w a 1 . 1- 1 1 11 . K n - 11 . . w 6 M11 1 .. FL I1|Lb\llh. rt}.W\u‘\ L1\NIU It . . 11.1 . - .- .- .11.- . 1. 1.- 41.17 0. I Y w 1‘01 14- 1. 4 o 1 <1 .. .. . u 0. '11.“ 1 > 6 fl -1 . 1 1 1 111 11111-1 . .. 11 . 1 - -1- .111 1 ..rl‘ . . 011 r 1&1 1 11.1 . . 1 - _. 1.1-1-1.3-.. . . - . - 1- 1w .1.--- 111111111111 . . . . .- .. . 1111 . .. q . -l 1 _ . . 111 .- . _ _ 1,101. ’llp 1. v1.0. * .- 1‘. \. {NW \I*u. \.\ s‘.\ . o _ 1 1-‘1‘ . .A 1 ... . \1\V\\ \ \\.-....1... , -- fl-.. . 1 . . F1. - a 0K: . . . . . . - 1 , , . . . \.: ...-$.6va v . .- _ . . 1 . . . 1 . . .1.-... -1 .1. . 1 1L111 * . 104! . 1. 1.1 M 11.1.11FL\\N..1F. L1 K\\ .\ .\.\X \.Av\.\. u .L . \vhhfixfi f1 1 1|?l-011 , .1 . a . . Lhflhk 1. 111-1M.-.1.1\A,L \x111 . V a it); ~. . 11-.. .1 . v 11 . 1 _ L. Rk‘k \v.\. k 1 1 . t l1 . 1. 111 v1 . . ”- 1 1 o 1 ._ «J K 1 KN . . \ 1 \~ N. . .. . 1 ¢11 .. .01 . .1.. IL ‘ O 9.1 o _ 1 1.: 1. 1“ . A. d L I» h o . ..‘\‘ ‘ x I 1 _ Y o 1 1111101111111 I01 . v. . a1 . . 14 _ .0 u .1 . . ll Ls .. L . 1‘ 1 .. \F . . ... H . . I V 1 117.16. . 9 v ‘ . A o . 4 v“ LI 1 . L - 1‘ . ... . . ..1. . 1 - ...1 114- . ... .1 . _ 1110 . v .I’ . 01 01 m . U 11 1O s. . 7 a I v11.v b. t 1' ‘1 1“ V . . _ O 1< Iflll. . . . 7 t _ 1 .14 \ 1 l4 t 5 . r 1 . g ‘11.. A . .Al 1 * 1’ ~ TII¢1 . .. . . \n ,1. .\ . 1114 11 I? 4117 o 1111 . . 1 a It. . 1 . IA 1.11--11 .. IJ _ a _ 1.. . .w- - O 1 1.121211.- .1 -. \«\\. «11.x..x11.\ l1 \ «Q11 .. - - . . . 1 . 1 + . . . 1 1 J . .11 . . \ \. .. . . w‘.‘ K \.\ N lie-1H ’1), t o .I _ . I o 1 1 1 . 4 fl 5 X . 1 X. \ 04V \ 1‘ . \ 1,.\.\. LV \ x q . . . - 1 11. 1 1. . a a l . .. .. Y .1 .\ \ 1 + . . x .. w-\ 1.11. . 1 V1 LI _ 11» . . 11 1. an; 1.. . .-.. . Ni. . -..-.....1..-. .1 1- . - . H . - . . . g ..i» 1 . 1 h h. .11.1\ .... ...\.\.\ a 1 . .. . n‘ ..N . th Vite ..‘N. K .. .. -. .... - ...1. ..1 xiaLid -111 - .1 76.11 1 . _ - . . _ - .. . - . . .1. 1 1 «1 k p . «R 1.1.1.-. x x... . . 1.1.... 1.; ...-F. “5%. ... A... a k 1 x 1111. .. . 1 . . . . I . fl 9 . a u. . 4 11 1L1! L L1|h1 . x . K1.\ . .. 1. L ...\ .\ . . . . Q .~ 1 .3 T \. \ .¢ . y 4‘! 1 I a . . . 1 1 I. s . a 1. .1..1L k .. . . . . . .1 x x .1 J I -1111 .wl 1 . 1. V . . .1 . T 7 f 1 . +1. L11 11 N111 1?, .~ K K. a 1 . 1 v 4 L L .. 1 1 11. ,k l ... a . 1‘ . . . 01 g 5 11111- 1 . o v u 1 u . 1 L \ 0‘ ’1‘. .. 5. ‘.~ . . . .9. ... 1 ... _ I u . T. 1111111 1. 1 . a . w —1 . 1 . .1. . .. +1+ W1 a , 1 F L ~ i ...m ..k L 1.‘ L V n . F _ . . . 1 _ . . :1. . 1. . . 1 1 . . . + . 4 ...1. .1111 . n 1..W .10. ._ . .4 .. . . o 7 fl 1 1 r . ~ . i ll! 1. - . . .. 9 1 .. 1 . 111' _ . .. L . ’1 1.1.1 1 . 1 .1 1 _ . . 1 . _ i111 F . é . _ 1.1... 1 ¢ 1 5|»; ‘ o V1111 “ L h .. o . *1. 41.10 1 u g n H u . - v .1 1 to v _ _ \ 1+ 1 l 1 _ 9: o O _ 1 11 1 a I l 611. i I. 1 1 .- .. fl - .. 11 . * 1 .1. h \ .1l.l . o v k . F .. 1111 .1111 -.r- - 1 ...1. . 1 1 . ., .5 . .. .. \1. 1 1 . - 1 .1 .111. 1 . 1-1 - .1111 a - . 1 .a.. .. . - . - - . 1 1 . . 31.111-111-111 . ., 1.. -_ .1.-x -. .1, x 1 1 1- -..; . 1 1 ..fi. . .D 111. 11?..1 111-11- 1 - H .8. \111-11 ...-......K 1.. ..1 . r11 1-1 . 1 . r .1. . 1 . a i _ . 1 1 .... x . .\.. 1 . .. - A . o t” . o 1 \\ . fl. 0. .1: , . . . 4 o 1 . ,. o1 1 ‘ . 1 I 1 * _ . v1H7* . _ F _ 1 . _ . k \. .1 . * . ' 1 t! +1.? cl . h.» 3 o D . & r I ‘1 \\ \ . b 11. O ,. . 1.1-11.1. . E s _ .1 1 111 1. - 1 H . _ . _ . 1 11 - 1 1. - L . . 1 - - 1 . 1 . . 1 - - - . B . , . 1 . 11111 11 . * .1 .. . 1 1 a * - _. - 1.. .. L. .. 1 + 0 . . 1 11 1 . . . _ . ’ . ..1._. .91 11011111 . e . i .. 1 '41111Inl+1 01.111 1? «1. m o 1. o. 1 JOL 1. ~ . n . . 11 . .. _ 111111 1.9111- . . J _ o -1 .1.- . ....-.111111111 1... :31 .3 23K . . -- - 1. . 4.. . H 1 .11- 11111l1100.\.muu..ou.v1 1 Tl- ~ 1 _ ‘1 +1 . 11.1 1. . . . ‘11111lrl'1m . 1.. + . p . . . ... 1 o . .. . . . . . 1.11 Tolls 1'1 . .1 .1 11.1-1.- 1 ....1. _ -_ 1 . . .4 . . 1 ”1 41.1.L1141111TJ .1 . 1 . 1 . y ._ 1 ,. . * T . 11 . .. r, . «1‘11 w . 1 1 .v . r . a H .1 17.. 1... . 1. 11 1. u .1. 1.13.1” . . ._ . . .9 1 41.; o.r1 141.111....1111 '- . w . 1 _ 1 1 . v 10.. 3.1. . I1 1 ..r fl I; 4 1 p .o . |1r . q . 1. 1 e * ~ ”1411.. 13.111. v 1.11 . fl 0 . 1 . . . H 1.1 . 1 -. 1 r 1. . T .1 . 1 ..~ .1 “L ~ . 1 ... .4 . .. . .1 ...,1111. 1 1 a lip 1111 111. .. . . 1 1 1 a o.- . p 1. . . . 1 .. . F 1. . v . A 1 .. a . . .1. . 1 ,1 - .4 u . . 1 a 1 . ~ . . 1 a ti}! . . . 1 v. o . . . .. elk. . 1|11lirL .. . 11 . . . +1. 1 . 4 p . H . ‘ .. 1111111111 1 ..111. 1 .1.. . 1. ..1... . \ III '~1.r'rll“tl . . o » o . . . Q . .5 «1. .vv. . o .-. o .1 11r11.|11.1 . . .. T . + _ . 1 1. 1 } llrlkl'l . . _ . . . IJ- 1 1Lr111'l1 . 4 a . ... . . _ A 1 . ‘ {Lille . 1 . .- lolitbl . 1 1 . .1.- 1 111117.1111. . 1 1 Vail q o . 1111 1‘111L1I 1. 11 .71 Page 78 PT1'1RT'1‘F5’S {YT} 51-7-37 S‘1"--‘-ICN 1he hardness of glass beads lies between the range of 5.5 and 6.5 on the Kohs scale of hardness. The hardness of both Poly— styrene and Plexiglas beads is aoproxinately 3 or L on the Vnhs scale. Polys yrcne is slightly harder than Plexiglas.l For convenience Mohs scale of hardness is shown below: .9 l. Talc 6. Feldspar 2. Gypsum 7. Quartz 3. Calcite 8. Topaz h. Fluorite 9. Corundum S. Apatite 10. Diamond Although the surface hardness of Plexiglas is not as great as glass, Plexiglas is a resilient material and was found to withstand abrasion nearly as well as did glass. The ability of the Polystyrene .beads, on the other hand, to resist abrasion is very Door. 1 . 1 . . . Handbook of Chemistry and rhySics, 31 edition Chemical Rubber Etblishing Company Page 79 CHAPTER v ceNcLU3Ieps SUT T RY As has previously been stated, the use of plastic (Nethyl Methacrylate and Polystyrene) beads for pavement center-line and lane marking materials can not be economically justified at today's prices, since the plastic beads cost approximately three times as much as do glass beads. The crushing strength of Polystyrene beads is fairly high, 7.8 Kg. The crushing strength of Plexiglas was found to be 7.2 Kg. Polystyrene beads, which tested slightly higher than Plexiglas beads in nearly all the tests run by the author, were found to be very susceptible to abrasion. The ability to withstand abrasion of the white paint stripes containing Plexiglas, Polystyrene, and glass beads, placed in order of decreasing efficiency, is glass, Plexielas, and Polystyrene beads. The surface of the Polystyrene beads was found to be badly marred by abrasion. Faced with this fact, it is doubtful that Polystyrene beads could ever be used for this purpose. The Polystyrene beads were found to have a much better grada- tion for center—line marking material than did the Plexiglas beads; the Plexiglas beads being too uniform in size. The color of the plastic beads, while transparent, was not as transparent as the glass beads. The plastic beads showed a marked decrease over the glass beads in the number of imperfect beads (ex— cess air, out-of—rounds, surface mars, pits and so forth). As was stated before, the specific intensity of glass beads is l.h, of Polystyrene beads is 1.3, and of Plexiglas beads is 1.1. The specific intensity of the plain 1951 Michigan State Highway white Page 80 paint was found to be O.6_CP/FC/3Q.FT. Naphtha was found to lower slightly, the specific intensity of both the plastic beads tested. It was further found that gasoline had practically no effect on the reflectivity of Polystyrene and very little effect on Plexiglas beads. A saturated solution of calcium chloride was found to have a slight reducing effect on the reflectiv- ity of both plastic beads. Confronted with the data collected by the auflaor, he reconvends that the use of glass beads be continued until a better and more suit- able material is found. In order to decrease the number of night time accidents, which take the lives of hundreds each year, a constant effort to improve the present glass bead or find a more effective material must never end 0 BIBLIOGRAPHY American Hi ghway, July 19M». Prismo Technical Bulletin #hh}, Prismo Glass Corporation. Handbook of Chemistry and Physics, 31 Edition, Chemical Rubber Publishing Company. Photometric Tests for Reflective Materials, B.V. Pocock, C.C. Rhodes, December 10, 19h9. The Condensed Chemical Dictionary, 3 Edition, Reinhold Publishing Corporation. Physical and Chemical Examination, Paints - Varnishes . Lacquers - Colors, Henry A. Gardnerfilaboratory,ilU Edition T9715- "'TI'I'I'I‘flLIIHIL I71! Ml I! liflflllflflfliflfflflu‘mm