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E11“; 2“ 2.1111} 222‘ W [-I I2! 25‘1“. 121 I .222st IIIII‘ .22» I22” I .. I... make-II 432' I‘IIr 1' J: 2 b LIBRARY Michigan State University This is to certify that the thesis entitled INVESTIGATION INTO THE TEST VARIABLES FOUND IN INCLINED PLANE ASTM 3334 AND TAPPI 503 TEST METHODS APPLIED TO WOVEN POLYPROPYLENE FABRIC presented by SU-ER JOE has been accepted towards fulfillment of the requirements for M.S. degree in PACKAGING a). James W. Goff, P . _* Major professor Date July 17, 1987 0-7639 MS U i: an Affirmative Action/Equal Opportunity Institution ' MSU LIBRARIES _—:—. RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. INVESTIGATION INTO HE TEST VARIABLES FOUND IN INCLINED PLANE ASTN 3334 AND TAPPI 503 TEST METHODS APPLIED T0 WOVEN POLYPROPYLENE FABRIC BY Su-Br Joe A THESIS Suhnitted to IIGIGAN STATE UNIVERSITY in partial fulfillment of the require-eats for the degree of NASTER OF SCI-(3 School of Packaging 1987 ABSTRACT INVESTIGATION INTO THE TEST VARIABLES FOUND IN INCLINED PLANE ASTN 333‘ AND TAPPI 503 TEST METHODS APPLIED TO WOVEN POLYPROPYLENE FABRIC BY SU-ER JOE This paper investigates the test factors involved in friction measurements on woven polypropylene (PP) bag fabrics. The test factors studied include the inclination rate, contact pressure, dwell time, and the usage of foam padding underneath the sled. This study proposed that the lack of acceptable tolerances in test factors associated with the testing method cause the measurement discrepancies. Single and multiple factor models were utilized. 4A nonparametric statistical technique, the Kruskal-Hallis H Test, was chosen for analyzing the experimental data. The results obtained showed that, among the four factors tested, only the usage of foam padding had independent effect on the resultant variations. There was little or no effect on friction measurements caused by individually varying the inclination rate, contact pressure, (n: the dwell time. The interaction of inclination rate and contact pressure had a significant influence on the measurements 0 ACKNWLENEHENTS I am greatly indebted to Dr. James W. Goff for his sincere help to the completion of this study. My thanks are also conveyed to Ms. Diana Twede who always offers enthusiasm and encouragement to me. I am grateful to Dr. Julian Lee and Dr. George Wagenheim for their counsel on this paper; Ms. Beth Waggoner, who proofread the draft for me. Finally, I want to thank Mr. Tom A. Hgbee for his help to build up the tester made this research possible. 1‘0 my beloved husband. parents and sisters. TABLE OF (DNTENTS LIST OF TABLES 000......0......OOOOOOOOOOOOOOOOOOO LIST OF FIGURES O0.0...OOOOOOOOOOOOOOOOOOOOOOOOOOO INTRowaION OOOOOOOOOOOOOOOOOOOOOOOOOOOOOCCOOOOOO LITERATURE RWIW OOOOOOOOOOOOOOOOOOOOOOOC00...... “TERIMIS AND “mans OOOOOOOOOOOOOOOO0.00.0000... (1) Materials and Sample Preparation ......... (2)Te8t1ng Apparatus oooooooooooooooooooooooo (3) Testing Procedures OIOOOOOOOOOOOOOOOOOOOO. (4)P110t8tudy 0.0.0.000...OOOOOOOOOOOOOOOOOO (5) Experimental nethOda OOOOOOOOOOOOOOOOOOOOO (6) Statistical Analysis Technique ........... RESULTS AND DIstSIONS O0.00.00.00.000.0.0.000... A. Single Factor Analysis .................... (1) (2) (3) (4) Inclined Plane Speed .................. Contact Pressure OOOOOOOOOOOOOOOOOOOOOO well Time OOOOOOOOOOOO0.00000000000000 Foam Padding .0.000000000000000000000CO Page iii iv 21 21 23 28 29 32 34 37 37 37 40 44 47 B. Multiple Factors Analysis ................. CONGJDSIONS 0.000000000000000000000000.0.0.0000... APPENDICES ...................................... Appendix As Woven Sack Manufacturing ......... Appendix B. Nonparametric Statistical Analysis: KurskaléWallis H Test ............ ENDNOTBS OOOOOOOOOOOOOOOOOOOOOOO0.00...00.0.0.0... BIBLImRAmY 0......0.0.0.000...OOOOOOOOOOOOOOOOOO ii 50 61 63 63 65 68 70 Table 1. 10. LIST OF TABLES Comparison of test variables of horizontal plane method in ASTM 1894, ASTM 2534, and IPC friction testing procedures. Comparison of test variables of inclined plane method in TAPPI 503, TAPPI 815, ASTM 3248, and ASTM 3334 friction testing procedures. Design of experimental treatments for single factor model. Design of experimental treatments for multiple factors model. Friction measurements of PP woven fabrics at test variables: 1 /sec and 2 /sec. Friction measurements of PP woven fabrics at test variables: 0.16 psi and 0.24 psi. Friction measurements of PP woven fabrics at test variables: 25 sec. and 35 sec. Friction measurements of PP woven fabrics at test variables: with foam and no foam padding on sled. Friction measurements of PP woven fabrics by using multiple test variables. The selective pairwise comparisons of friction measurements for PP woven fabrics at multiple test variables. iii Page 12 19 33 35 38 41 45 48 51 52 LIST OF FIGURES Figure 1. The cutting patterns of tubular PP woven sacks. 2. Assembly of the inclined plane device and the MTS T 5000 tensile tester. 3. Schematic of incline plane device. 4. Distributions of friction measurements at 1 /sec and 2 /sec inclined speed. 5. Distributions of friction measurements at 0.16 psi and 0.24 psi contact pressure. 6. Distributions of friction measurements at 25 sec and 35 sec dwell time. 7. Distributions of friction measurements with foam and without foam padding. 8. Distributions of friction measurements at 1 /sec, 0.16 psi and 1 /sec, 0.24 psi. 9. Distributions of friction measurements at 2 /sec, 0.16 psi and 2 /sec, 0.24 psi. 10. Distributions of friction measurements at 0.16 psi, 1 /sec and 0.16 psi, 2 /sec. 11. Distributions of friction measurements at 0.24 psi, 1 /sec and 0.24 psi, 2 /sec. 12. Distributions of friction measurements at 0.24 psi, 2 /sec and 0.16 psi, 1 /sec. 13. Distributions of friction measurements at 0.16 psi, 2 /sec and 0.24 psi, 1 /sec. iv Page 22 25 27 39 42 46 49 54 55 56 57 58 59 INTROIIIQION In distribution packaging,sacks are the oldest and most important containers for transporting grain and other small piece solids. With the advent of palletization for filled sack handling, most shipping sacks are stacked on pallets without the benefit of load-locking methods or restraining straps. It has been recognized that the slippage of sacks during shipment and handling causes most troubles.l These problems result in breakage, wasting time, and extra.handling expenses, as well as safety concerns for human life. The problems encountered were not in the strength of the sacks, but in their surface anti-skid characteristics. As a result, considerable interest has been generated in the friction measurement of sacks as a routine control to insure adequate skid-resistant performance.2 In the sack industry, paper, textile and plastic sacks are the three major categories.:3 The dominant form of paper sack is the multiwall paper sack. Most plastic sacks are low density polyethylene (LDPE) film bags and l 2 polyproplene (PP) woven sacks. Up to 1979, paper and textile sack manufacturers encountered both cost competition from the plastic sacks, and the strength requirements needed for effective bulk handling performance. The market for paper and textile sacks declined considerably as a result of the increased substitution of plastic sacks.4 According to a 1979 to 1983 UK sack market study, the sales of paper and textile sacks were reduced by 22.91 percent and 52.93 percent respectively. The usage of LDPE heavy duty sacks was also reduced by 18.42 percent. In contrast, the total consumption of PP woven sacks had increased by 25 percent over the same time period. With the decline of paper and textile sacks, many manufacturers in the sack industry have diversified and entered into the production of plastic woven sacks. It is said that the one-trip plastic woven sack is going to be a predominant item in the sack industry.5 The typical method for assessing the friction preperties of two contacting surfaces is to measure the friction coefficient. Early studies of slip-resistant performance involved the friction measurement of paper and board used in boxes by utilizing the horizontal plane method. But this kind of conventional procedure failed to adequately predict field performance of multiwall paper 3 sacks.6 Designers voiced the necessity of a more accurate and easily Operated friction testing method for sacks.7 The inclined plane method was then develoPed from a simulated bag slide angle test to measure the static coefficient of friction for shipping sacks. In 1967, the inclined plane method was first adopted by the Technical Association of Pulp and Paper Industry as an official standard for testing the friction properties for shipping sack paper.8 In 1972 and 1973, the inclined plane method was developed for determining the coefficient of friction of corrugated and solid fiberboard. These specifications included TAPPI 815 and ASTM 3248 for measuring the static coefficient of corrugated and solid fiberboard. With the increasing usage of PP woven sacks, it was assumed by the sack industry that the inclined method for measuring the friction coefficient of paper or fiberboard could be.ad0pted.for determining the slip-resistance of plastic woven fabrics. Thus, the TAPPI 503 "Coefficient of Static Friction of Shipping Sack Papers (Inclined Plane Method)" was generally accepted as a standard method for measuring the friction coefficient of plastic woven sacks by the industries and government.9rlo In the inclined plane method, when an object is 4 slowly lifted at a constant speed, it is subject to a constant net force,which increases with respect to the friction force. While the friction force exceeds the net force, the object will rest on the original position. Once the net force is greater than the friction force at a certain angle of the incline, the object starts to slide.11 In all real cases where sliding between surfaces occurs, the friction forces result in a loss of energy which is dissipated in the form of heat. Thus, friction measuring depends greatly on the angular velocity, mass of the object, and the nature of contacting surfaces among other things.12 Few studies have been done on measuring friction for plastic woven fabrics by using the inclined plane method. The adequacy of the generally accepted test for measuring the static coefficient of friction of plastic woven bags is still unknown. According to the preliminary experiments which have been done by the School of Packaging at Michigan State University, there is a high level of variation between laboratories for measuring the friction coefficient of PP woven fabrics. This occurred even when each test was conducted using the same TAPPI 503 testing procedure, but by different testers and Operators. In view of the resultant discrepancies and the 5 importance of slide resistant performance for PP woven sacks, it is imperative to investigate the adequacy of the adopted friction test. Therefore, the purpose of this study is to test for factors in ASTM 3334 and TAPPI 503 which cause variations among laboratory results. Based on a literature review and preliminary experience, this paper proposes that the lack of acceptable tolerances in factors associated with the testing method causes the resulting variations. The major testing factors which will be studied are; (1) The Inclination Rate. (2) The Contact Pressure. (3) Dwell Time For The Contacting Surfaces. (4) Foam Padding Underneath The Sled. In addition, this paper evaluates the existing testing procedures to determine their adequacy in determining the frictional pr0perties of plastic woven fabrics. LITERATURE REVIEW According to results of sack tests done by the School of Packaging at Michigan State University for Agriculture Stabilization and Conservation Service (ASCS) commodity sacks, sl ip-resistance is a basic concern for shipping sacks. The parameter which defines the friction properties of shipping sacks is the friction coefficient for the two contact surfaces. A sack with a high coefficient of friction is expected to resist sliding. A low coefficient indicates potential problems with the sacks slipping off the load. First, a few words about friction. Consider a block of weight (W) placed on a horizontal surface. In order to move the block, a certain force (F8) will be required to start the block in motion. Once the block is in motion, a smaller force (Fk) will be needed to maintain an unaccelerated motion. They are expressed mathematically as: F = USW cases... (1) 311d Fk = Uk W 0000...... (2) 7 U8 is called the coefficient of static friction, which is the ratio of the force that resists initial motion of the block. Uk is called the coefficient of kinetic friction, which is the ratio of the force once the motion is in progress to the block. Therefore, the problem of determining either the static or the kinetic coefficient of friction involves measuring the weight of the block and the forces required to start and continue motion. In this paper, the static coefficient of friction is of chief interest in measuring the anti-skid performance of PP woven fabrics. Both static and kinetic friction coefficients can be obtained by either the inclined plane method or the horizontal plane method. The horizOntal plane method gives the coefficient of static friction as the force required to overcome friction divided by the weight. Horizontal plane testers are usually large and hard to operate. A more common friction tester uses the inclined plane method, which measures the angle at which slippage begins. The coefficient of static friction is equal to the tangent of this angle. The first investigations of friction properties for packaging materials were done for paperboard, combined board, and boxes by using the horizontal plane method. When sliding took place, it was observed that there was a 8 series of sticks and slips at certain points on the two contact surfaces. Bowdbn (1939) interpreted this as being a fundamental property of friction.13 Others, such as Block (1940) suggested that the problem was due to the nature of the apparatus.14 In the beginning of the 19503, work at The Institute of Paper Chemistry (IPC) was sponsored by several bag companies to study the smoothness properties of paper and paperboard with different friction testers. The friction testers evaluated by IPC were all of the horizontal plane type. It was found that some instrumentation design factors would affect the static and kinetic coefficients of friction for paper and paperboard. These factors included contact pressure, contact area, and the relative velocity between the surfaces. After the smoothness testing, the Institute of Paper Chemistry presented five progress reports. In the No. 1 IPC report, dated.July 1955, it was revealed that the coefficient of friction is slightly greater for small pressures on large areas than for large pressures on small areas. The kinetic coefficient of friction decreases as the relative velocity increases. It was also proposed that the time of contact between the two surfaces affects the measur ements.15 9 Inl955,Walter Egan studied the frictional characteristics of plastic films and laminates. In his studies, the inclined plane method and the horizontal plane method were both used to investigate some factors which would affect measurements of the coefficient of friction. Those factors that Egan studied included temperature and humidity as well as contact pressure.16 First, Egan compared the friction measurements for various films on both the horizontal and inclined plane methods. The results showed that both methods appeared to have general applicability. Under specified testing procedures, similar results could be obtained. Secondly, Egan tested various polyethylene films to study the effect of variable factors on friction measurements. In the study of the effect of temperature and humidity, he performed the test at different atmospheric conditions over a temperature range of 70° F. to 94° F. at a constant relative humidity (SR-55%), and over a humidity range of 24% to 81% at a constant temperature (84° Fn-89° FJ. These temperatures and humidities cover a substantial part of the range which might be encountered in normal testing situations. Results of tests at these various conditions showed that the coefficient of friction of polyethylene films should not be affected under changing atmospheric conditions. 10 In the study of the effect of contact pressure, Egan used a sled block with a bottom surface of 2 inches width by 4.5 inches length. Contact pressures from 0.04 psi to 0.51 psi were applied. The results showed that no appreciable change in the coefficient of friction of plastic films occurred with the changes of contact pressure.17 In 1958, W. W. Appleton studied the friction measurements for multiwall papers by using the horizontal plane method. He found that the relation between the coefficient of friction and the distance traversed changed in an oscillatory manner and in magnitude. The relation of the former part of the test was irregular and fluctuated. The relation of the latter part of the test tended to be more stable. Appleton also proposed that the smoother-finished papers are more subject to irregular behavior in the test. He interpreted this phenomenon as to the increased effect of slight imperfections in the surface of the sample. In Appleton's studies, the coefficient of static friction for most uncoated papers ranged from 0.55 to 0.85, and their kinetic coefficients are usually within 0.40 to 0.60. Generally, the kinetic friction was from 70% to 80% of the static friction.18 In many cases, the static friction was used.as the 11 most important criteria to determine the 31 ip-resistant performance of multiwall bags. While measuring the friction coefficient of coated multiwall papers, Appleton found that a relatively light treatment will provide substantial increases for static friction coefficient. When the amount of coating was increased, the static coefficient decreased and the kinetic friction coefficient became greater. Therefore, Appleton pr0posed that in the development of anti-slip multiwall sacks, the high kinetic friction was primarily responsible for good performance in handling and stacking of filled units. Up to 1961, the determination of the friction coefficient was still restricted to utilizing the horizontal plane method. Most horizontal plane methods were standardized for determining the friction properties of plastic film,and wax coatings for paper substances. These specifications include the ASTM 1894 “Static and Kinetic Coefficient of Friction of Plastic Film and Sheeting“ and ASTM 2534 ' Coefficient of Kinetic Friction For Wax Coating". The testing variables specified in the ASTM 1894, ASTM 2534 and the horizontal plane method used by Appleton for testing multiwall paper are shown in Table 1. From Table 1, one can easily recognize the variances between each technique for testing different materials. In these 12 Table 1. Comparison of test variables of horizontal plane method in ASTM 1894, ASTM 2534, and IPC friction testing procedures. ASTM 1894 ASTM 2534 Test Static and Kinetic 'Coefficient Coefficient of of Kinetic Factor Friction of Plastic Friction of Film and Sheeting Wax Coating (1961) (1966) Sliding 0.1 -_I-_ 0.02 0.983; 0.02 Velocity in/sec in/sec Contact Pressure 12.5 i 2.5 psi 0.13 psi Dwell --— --- Time Foam 12.5 i 2.5 psi Padding compress 25 % --- Sliding Distance 5 in. 6 in. Test Specimens 5 3 Result lst 1 st Recording slide slide IPC Friction Test-Static and Kinetic Coefficient of Friction for Board 1.56 in/sec 0.53 psi Just 81 ide lst slide 13 specifications utilizing the horizontal plane method, each specimen is tested once. Only the first slide will be recorded. From 1961 to 1963, joint efforts were carried out in studying the friction pr0perties of paper sacks to improve the natural slip-resistance of certain multiwall paper grades. When this development work first began, it was found that the horizontal procedures and techniques for measuring surface friction of paper resulted in poor reproducibility. The conventional procedures of conducting single slides failed to adequately predict the field slip—resistant performance of multiwall paper sacks. A testing program was carried out by R. W. Bolling (1963) to improve testing methods and techniques for the friction measurement of multiwall paper, and to obtain better correlation of controlled frictionmeasuring with actual field performance.19 This testing program involved studies of the effects of repeated slides, dust on the test material, and relative orientation of the contact surfaces to the paper being tested. He also compared the horizontal plane method with two other simulated bag tests to develop a better testing procedure. Bolling found that for very rough or embossed surfaces, changes in orientation of the specimens relative 14 to machine direction axis causes variations in the results. For smooth paper surfaces, the orientation changes will not result in significant variation. Sliding two rough surfaces with cross direction to cross direction obtains the highest skid resistance in all orientation arrangements. In the study of repeated slides, the static coefficient measurements drapped off quite drastically after the first slide, and leveled off at the fourth or fifth slide to a gradual sloPe. The kinetic coefficient of friction was less variable than the static coefficient of friction, with very little difference in variability between the first and subsequent slides. Bolling evaluated the effect of handling by using pressure and hand contact. The results showed that the pressure exertion, scuffing, and hand contact will cause false test results. When these influences occurred, the slip-resistance of shipping sack paper was drastically decreased. The results obtained from the study of the effect of print and dust revealed that print will drastically reduce the skid resistance of bags. On the contrary, the addition of cement dust acted as a very effective nonskid additive in returning the skid resistance to a level almost equal 15 to the unprinted cement dusted level. The cement dust on the bag surfaces improved the slip resistance of the coarse, rough finish grades of paper. The cement dust had little or no effect on the regular finish grades, and drastically lowered the slip resistance of the smooth, hard finish grades of paper. Acknowledging that the conventional single slide method failed to predict field anti-skid performance, Bolling compared the horizontal plane method with two simulated bag skid tests to determine how well the horizontal plane method would correlate with actual bag skid performance. One of the simulated methods was a homemade bag slide angle device for measuring the static coefficient of friction. The other device was a pendulum impact tester normally used for measuring the impact resistance of corrugated boxes. In order to simulate field conditions, the filled test sacks and test specimens were dusted with cement prior to testing. The paper surfaces in contact were oriented machine direction to cross direction. The orientation of the machine and cross directions was intended to simulate the crossing pattern of bags during palletizing. Only unprinted sacks and paper were tested. Tests were conducted on several grades of papers. The results showed that only the bag 16 slideangle test was directly comparable with the horizontal plane method. The static coefficient of friction obtained from the slide angle tester was considerably lower than those obtained from the horizontal plane method but follow generally the same rate of deterioration with repeated slides. In the impact test, the distance the bag slides after impact included a measure of the ccmbined resistance of static and kinetic friction forces. The results obtained from the bag impact test can not be directly related to static or kinetic friction independently. In 1963, a round-robin test was carried out under the direction of the Shipping Sack Testing Committee and the Technical Association of the Pulp and Paper Industry, to correlate the data collected by three different groups of testers in ten laboratories. The three groups of testers included 9 homemade and 2 different commercially available devices. The homemade devices were the inclined plane testers and horizontal testers. The results of the round robin test showed that there exists significant result variations between laboratory-to-laboratory and tester-to-tester. H. C. Martin (1963) pr0posed that the measurement discrepancy was from instrument variance as well as operator variance 17 within the friction testers. He also proposed that the contact pressure was not a major factor contributing to the high level of variance. Based on the studies done by Bolling, Martin and The Institute of Paper Chemistry, the TAPPI 503 'Coefficient of Static Friction of Shipping Sack Paper" was prepared by the Paper Shipping Sack Testing Committee in 1967. This method was written specifically for an inclined plane apparatus. Later studies have indicated significant variability in the slide angles obtained from the first to subsequent slides. The TAPPI 503 considered the first slide as a preconditioning slide, and the third slide was recorded. In the inclined friction test, the orientation of machine to cross direction was chosen to simulate the cross- 1ocking of bags during palletizing. Other factors such as inclined speed, contact pressure, and dwell time were specified in the TAPPI 503 method. There are some inclined plane methods derived from TAPPI 503, and used for measuring the coefficient of static friction of corrugated and solid fiberboard by using the inclined plane method. These specifications include TAPPI 815 (1972) and ASTM D-3248 (1973). In 1974, the American Society For Testing And 18 Materials published ASTM D—3334, “Standard Method of Testing Fabrics Woven From Polyolefin Monofilment’. In ASTM D 3334, the testing method for measuring the coefficient of static friction on woven polyolefin fabric is directly derived from the TAPPI 503. Therefore, the inclined plane method, which was first developed for measuring the friction preperties of shipping sacks paper, was standardized for determining the slip-resistant performance of plastic woven bags. The testing variables consisting of TAPPI 503, TAPPI 815, ASTM 3248 and ASTM 3334 are compared in Table 2. In TAPPI 503 testing procedures, there are three test variables which have wide tolerances. One test variable concerns the inclination rate. The inclination rate is 1.5 i 0.5 degree/second. This indicates that the friction measurements will not be changed significantly when changing the inclination rate from 1 degree/second to 2 degree/second. The difference between the maximum and minimum, inclination rate is 100 percent of the slowest inclined speed. The second testing variable which has a wide tolerance is the weight of the sled. In the TAPPI 503 standard, the contact pressure will be varied from 0.24 psi to»0.16 psi with a bottom area of 14 square inches. Therefore, the weight of the sled varied from 2424 pounds 19 Table 2. Comparison of test variables of inclined plane method in TAPPI 503, Tappi 815, ASTM 3248, and ASTM 3334 friction testing procedures. Test TAPPI 503 TAPPI 815 ASTM 3248 ASTM 3334 Coefficient Coefficient Coefficient Coefficient Factor of Static of Static of Static of Static Friction of Friction of Friction of Friction of Shipping Corrugated Corrugated Woven Sack and Solid and Solid Polyolefin Paper Fiberboard Fiberboard Fabric (1967) (1972) (1973) (1974) Inclina- 1.5 i_0.5 1.5 i 0.5 1.5 i 0.5 1.5 1_0.5 tion degree/sec degree/sec degree/sec degree/sec rate Contact Pre- 0.2 i 0.04 0.2 + 0.1 0.2 i 0.1 0.2 psi ssure psi psi psi Dwell Time 30 i 5 sec --- --- 3013 see Foam 12.5 i 2.5 psi Padding compress --- --- -—- 25 % Test Speci- mens 5 5 5 3 Result 3rd 3rd 3rd 3rd Record slide slide slide slide 20 to 3.36 pounds. The difference between the heaviest and lightest weight of the sled will be 50 percent of the lightest sled weight. The third testing variable which has large tolerance is dwell time. In the standard procedure, the dwell time can be changed from 25 seconds to 35 seconds. The fourth testing variable concerned is the application of foam padding. As an alternative to clamping, the bottom surface of the sled may be covered with foam padding of the same dimensions as the sled. In the TAPPI 503, the foam should have a smooth surface, and require 12.5 + 2.5 psi pressure to compress it 25%. Foam padding on the sled is believed to more closely simulate the non-rigid contact normally found between shipping sacks. In addition, it compensates for any small deviations in flatness of the plane or sled, and reduces the likelihood of the hard edge of the sled from influencing the results.20 NEHHUILSIMEINEHHEB (1) lflflflRLMfliANDEMflRmBIEBPNMHHON All the materials are supplied by the Poly Sac annfiouston, Texas: uncoated, unprinted, and 23' wide PP circular woven fabrics packed as a bale of tubular unsewn sacks. These tubular sack fabrics consist of 9 picks/inch in both warp and weft direction. Upon arrival at the School of Packaging, the bale of circular woven fabrics were immediately placed in a laboratory with TAPPI standard condition of 73.0 i 3.5 0 F. and so i 2% 12.3. Because the quality variability of this roll of woven fabrics is unknown, it is doubtful whether the samples taken from the outer part of a roll of tubular woven fabrics will represent also the inner part of the roll. In order to eliminate the quality variability, all specimens were cut before the test began and then distributed to each group of test units on a statistical random basis. Specimens were taken from the belly of the tubular woven sacks. The cutting pattern is shown in Figure l. 21 22 Figure 1 Cutting pattern of tubular woven PP fabrics 23 Only the outside surfaces of the woven fabric was tested. Each specimen consisted of two sheets. One of the two sheets was cut as 5' by 8' to be affixed to the sled and will extend beyond the side edge of the sled. The other test sheet was cut 6" by 10" to be affixed to the surface of the inclined plane and to be large enough to cover the working surface of the plane. In order to simulate the cross—lockingjpatterns x3 with (k-l) degrees of freedom. To determine how large B must be before we reject the null hypothesis, we have to consult the critical values 01‘- X2 (chi square), such that P ( x2 > X: ) = a . This means that when the H value is larger than XE I we conclude that at least two pOpulations are different. The significance level is a . In the x2 distribution, when degrees of freedom is equal to 1, x20.100 is 2.70554, 1:20.050 is 3.84146, and 1:20.025 is 5.02389. is ENDNOEBS 1. Bolling, R. W. "Measuring Frictional Properties of Multiwall Bag Papers', m1, Vol. 47, No. 7, July 1964, p.439. 2. Textile Bag Manufacturer's Association, 1986 Fall Meeting in Washington D. C., Northbrook, Ill: TBMA, 1986. 3.8w1nbank. c. Packaging of Ehemicals and Other Industrial Liquids and Sends (England: c. Tinling 8 Co Ltd., 1973),pp.66-101. 4. Guise, Bill "Paper, Plastic and Composite Sacks,“ WI November, 1981, p.14. 5. Anon, "An Analysis of The Market for Paper, Plastic and Textile Sack 1979-85", 231221 .6 W Bulletin, No. 118, August, 1984, p. 10. 6. Bolling, R. W. “Measuring Frictional Properties of Multiwall Bag Papers,‘ TAPPI, July 1964, p.439. 7. Martin, H. C. "Friction Testing of Shipping Sack Paper: A Round Robin," TAPPI, September, 1964, p. 162A. 8. Technical Association of the Pulp and Paper Industry. Proposed suggested Method T 503, 1967, ”Coefficient of Static Friction of Shipping Sack Papers (Inclined Plane Method),' (Atlanta: TAPPI, 1967). 9. Technical Association of the Pulp and Paper Industry. T 503 0111-84, "Coefficient of Static Friction of Shipping Sack Papers (Inclined Plane Method),' (Atlanta: TAPPI, 1984). 10. United States Department of Agriculture. Agriculture StabLLnuudam and ikumdce Handbddkz .91 min Pmdmts (Washington. DIC- : United States Department of Agriculture). 68 69 11.Blatt, Frank J. Prindiplss df Physids 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. (Massachusetts: Allyn and Bacon, 1983), pp. 57-61. Meriam, J. L. Engineering Mechanics-Statistics (New York: Wiley & Sons, 1984) pp. 267-308. Bowden, F. P. and Leben, L. "The Nature of Sliding and The Analysis of Friction“, Exggggdlng of mammary, Vol. 169, 1939, p. 371. Block, H.£L “Fundamental Mechanical Aspects of Boundary Lubrication,” 59.91.2113: df Autdmdtixs WW. Vol. 46, February. 1940. p- 54. The Institute of Paper Chemistry. Subject: “Testing Smoothness,‘ Subtitle: ' A Study of Frictional PrOperties of Paperboard Surfaces, Part I: Investigation of Methods.", July, 1955. Egan, Walter "The Frictional Characteristics of Plastic Films and Laminates,“ Proceedings of the 17th Annual Forum of the Packaging Institute, Paper No. 48, 1955, p. 4. Walter Egan, “The Frictional Characteristics of Plastic Films and Laminates,“ Proceeding of the 17th Annual Forum of the Packaging Institute, Paper No. 48, 1955, p. 5. Appleton, W. W. “IPC Friction Meter,“ TAPPI, May 1958, p. 152A. Bolling, R.VL “Measuring Frictional Properties of Multiwall Bag Paper',.IARRI, July 1964, pp. 439-444. American Society for Testing and Materials, D 1894, "Standard Test Method for Static and Kinetic Coefficient of Friction of Plastic Film and Sheeting,‘ Philadelphia: ASTM, 1978. Scheaffer, Richard L. and McClave, James T. Statistics mBnQinssrs (BostonzPrindle, Weber & Schmidt, 1982): pp. 134-135. , BIBLIOGRAPHY BIBLIOGRAPHY American Society for Testing and Materials, D 1894 , Coefficient of Friction of Plastic Film and Sheeting, 'Philadel phia: ASTM 1 978. American Society for Testing and Materials, D1776, “Standard Method of Conditioning Textiles and Textile Products for Testing,” 1967. American Society for Testing and Materials, D 3248, “Standard Test Method for Coefficient of Static Friction of Corrugated and Solid Fiberboard (Inclined Plane Method)," 1973. Ameriacn Society for Testing and Materials, D 3334, “Standard Methods of Testing Fabrics Woven From Polyolefin Monof ilaments,‘ 1980. Appleton, w.w. 'IPC Friction Meter," mm, Vol. 41, No. 5, May 1958, pp. 151A-152A. Blatt, Frank J. Principles of Physics Massachusetts: Allyn and Bacon, 1983. Block, H. J. I'Fundamental Mechanical Aspects of Boundary Lubrication. " Society of Adrenal-.123 Engineers W, Vol. 46, February 1940, pp. 54-68. Bolling, R.W. ”Measuring Frictional PrOperties of Multiwall Bag Papers,‘I TAPPI, Vol. 47, No. 7, July,1964, pp. 439-444. Bowden, F.P. and Leben, L. "The Nature of Sliding and the Analysis of Friction,“ Proceeding of 113; ml Society, Vol. 169, 1939, pp. 371-391. Dorsteen, Ing. J.W. and Mot. Dr.Ir.E., "Measuring the Coefficient of Friction of F1exib1es,' Modern musing, July 1974. pp- 43-45- 70 71 Egan Walter, “The Frictional Characteristics of Plastic Films and Laminates," Preeeeding ef the 11th Annual ileum ef the 21915331119 Institute. Paper NO- 48: pp- 1-20. Guise, Bill. "Paper, Plastic and Composite Sacks," .anyettet,‘Vol. 18, No. 11, November 1981, pp. 14-17. Martin, H.C. "Friction Testing of Shipping Sack Paper: A Round Robin," TAPPI, Vol. 47, No. 9, September, 1964, pp. 162Arl65A. Meriam, J.L. Engineering Meehanieszfitatisties, New York: Wiley & Sons, 1984. Scheaffer, Richard L., and McClave, James T. W £91 Engineets. Boston: Prindle, Weber & Schmidt, 1982. Swinbank, c. Raekdging dffihemieelsandfltherlnddstrial .Lidnids.end.£elids. England: C. Tinling & Co Ltd., 1973. Technical Association of the Pulp and Paper Industry. PrOposed New Suggested Method T 815, 1972, “Coefficient of Static Friction of Corrugated and Solid Fiberboard.” Technical Association of the Pulp and Paper Industry. T 402, 1949, “Conditioning Paper and Paperboard for Testing.“ Technical Association of the Pulp and Paper Industry. T 503 su-67, 1967 "Coefficient of Static Friction of Shipping Sack Papers (Inclined Plane Methode Technical .Association of the Pulp‘and Paper Industry; T 503 om-84, 1984, “Coefficient of Static Friction of Shipping Sack Papers (Inclined Plane Method)J' The Institute of Paper Chemistry. IPC Report No. 1, dated July 29, 1955, Subject:' A Study of Frictional PrOperties of Paperboard Surfaces, Part I: Investigation of Me thod.‘ Turk, John G. and Maxson Richard, "The G.C.M.I. Friction Tester-An Instrument for Measuring Coefficient of Friction of Paperboard," 13221, Vol. 38, No. 5, May 1955. 72 UK Study, No.14 'An Analysis of The Market for Paper, Plastic and Textile Sack 1979-8S,"£§pg;‘§,£§§k§ging Bulletin, No. 118, August 1984, pp. 1-11. United States Department of Agriculture. Astignltnte Stabilizetienendsdnseryetienfiemieesdendmm Peekegins ef Grain Prednets. Washington D.C.,November 19, 1979. S "'Minimum)(Minimum?)Es