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The tear resistance of elastomeric vulcanizates at elevated temperatures

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The tear resistance of elastomeric vulcanizates at elevated temperatures

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Content THE TEAR RESISTANCE OF ELASTOMERIC VULCANIZATES < i AT ELEVATED TEMPERATURES A Thesis Presented to The Faculty of the School of Engineering The University of Southern California In Partial Fulfillment of the Requirements for the Degree Master of Science in Chemical Engineering By Norman David Lewis v»‘ August 1965 UMI Number: EP41786 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. IMI' Dissertation Publishing UMI EP41786 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Proj^yesf ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 -1 3 4 6 A. C h ! 6> ( o l * s This dissertation, w ritte n by . under the guidance of h .l& ..F a c u lty Committee and approved by a ll its members, has been presented to and accepted by the School of Engineering in p a rtia l fu lfillm e n t of the re quirements fo r the degree of Master of ..Science..in ........ Chemical Engineering Da/e...A^ust..l96j>....... F a c u lty C om m ittee L..... ACKNOWLEDGMENTS ! The author wishes to express his appreciation to j ithe TLARGI Rubber Technology. Foundation for awarding him a I |TLARGI Fellowship which made available to him its labora- i | tory facilities and materials used for the experimental work* I Appreciation is also expressed to Mr. James R. jScott whose assistance in the design, construction, and [maintenance of the equipment was most helpful. In addi- jtion, the support, helpful suggestions and general teehni- jcal direction of Dr. E. G. Partridge throughout the course of this study is gratefully acknowledged. I i ii ABSTRACT Recently, a new method was developed by workers at the B. F. Goodrich Company Research Center for measuring the tear resistance of rubber compounds. The new test uses a modified trousers specimen called the CRT test piece. In this study, tear resistance as defined by the CRT test piece, as well as the ASTM B test piece and the ASTM C test piece was measured. Emphasis was placed on measuring tear resistance at elevated temperatures. The variables mea sured were the effect of elevated temperatures on tear re sistance, the effect of rate of testing on tear resistance at elevated temperatures, the effect of prolonged exposure to elevated temperatures on tear resistance, and the ef fect of aging on tear resistance. Although values of tear resistance obtained by the CRT test method are less reproducible than those obtained using the two ASTM test pieces, they give a more accurate representation of the true tear resistance of a rubber com pound. Also, the CRT tear test method allows a quantita tive measurement of the ^knottiness” of the tearing process to be calculated. It was found, In this study, that the tear resist ance measured with the modified trousers test piece is less iii dependent upon temperature and more dependent upon the rate of testing than is the tear resistance measured with either the nicked crescent test pieGe, or the right angle test piece, fhis can present a serious problem when using the GrRT test piece to measure the tear strength of a rubber compound which is to be used under conditions of high temperature. TABLE OP CONTENTS X. XI. m . rv. v. VI. INTRODUCTION ........... .......... 1 EXPERIMENTAL PROCEDURES AND EQUIPMENT .... 1$ A. Sample Preparation .......... 1$ 1. Compounding ............. 1$ 2. Curing ........ ........... 15 3* Special Preparation 16 B. Physical Testing 1? 1. Room Temperature Tests ........ 17 2. Elevated Temperature Tests .......... 21 RESULTS AND DISCUSSION..................22 A. Reproducibility of Tear Tests ...... 22 B. Effect of Test Temperature on Tear Resistance ........ ........ 27 C. Effect of Rate of Jaw Separation and Temperature on Tear Resistance ...... 32 D. Effect of Aging at Elevated Temperatures on Tear Resistance ..••••...••. l j . 2 E. Effect of Prolonged Exposure to Elevated Temperatures on Tear Resistance ..... $1 CONCLUSIONS . ......... 58 BIBLIOGRAPHY ........... 6l APPENDIX ............63 A. Recipes and Physical Properties of Compounds ................ 6lj. B. Raw Data .............. 68 v n LIST OP FIGURES : Figure Page 1* Dies for Tear Test Specimens ASTM<D624~48- • • * 3 2. Configuration of ASTM Die C Specimen During Testing • ........... . . . . ............. 5 3* Simple Extension or ^Trousers” Test Specimen . 8 4» Modified Trousers Specimen. • . . 13 f>. GRT Tear Curve .......... 18 6. Effect of Temperature on Tear of Compound N - l ............................ 7* Effect of Temperature on Tear of Compound S-l ........ ........ 29 8. Effect of Temperature on Tear of Compound #-1 . 29 9# Effect of Temperature on Tear of Compound B-l .............. . 30 10. Effect of Rate on Tear of Compound,S-l.at Room Temperature ............... 34 11. Effect of. Rate on Tear of Compound S-l at 70°G .............. 3£ 12. Effect of Rate on Tear of Compound S-l at 100°C......... 36 13. Effect of Rate on Tear of Compound S-l at 125>°C . . . . » . . . . . . 37 l i j . . Effect of Rate on Tear of Compound N-l at Room Temperature.......... . 38 15. Effect of Rate on Tear of Compound N-l at 70°C 39 16. Effect of Rate on Tear of Compound H-l at 100°€ . . . . . . . . . . . . . . . . . . . . 40 vi Figure Page 17* Effect of Rate on Tear of Compound N-l at 125°C . . ....................... 41 18. Tear Resistance of Compound S-l After Aging at 70°C...................................... 19. Tear Resistance of Compound S-l After Aging at IOOOO . h$ 20. Tear Resistance of Compound S-l After Aging at 125gG ................. i|£ 21. Tear Resistance of Compound N-l After Aging at 70°C . ........................... 1 ^ . 7 22. Tear Resistance of Compound N-l After Aging at 100°C ..................... . . 48 23. Tear Resistance of Compound N-l After Aging at 125° C ........... 49 Tear Resistance of Compound S-l .at 7G°G ... 52 25* Tear Resistance of Compound N-l at 70°C ... 53 28* Tear Resistance of Compound S-l at 100°C ... 5 t y - 27. Tear-Resistance of Compound N-l at 100°C . . . 5 i j - 28* Tear Resistance of Compound S-l at 125°C ... 5£ 29. Tear Resistance of Compound N-l at 125°C . . . 5£ 30. Exposure of Tear Test Specimens to Heat ... 57 X. INTRODUCTION Tear resistance may be described (!) as the resist ance- to the growth of a cut when tension is applied to the i cut specimen. It is a property of rubber that is very im- Iportant In applications sueh as tires,* tubes, footwear, I clothing, and mechanical goods. When a rubber product !fails due to excessive forces, it usually fails through a tear or tearing mechanism. The failure of - a rubber dumb bell in a tensile test is a tear failure where the rate of tearing is extremely high... Flex-cracking is a tearing of rubber at a very slow rate* The tear test is a rough per formance test useful in observing the reinforced effects of various compounding ingredients. Many methods are used to test for this property and most of them express tear i ■ resistance as the force necessary to tear a specimen.one inch thick. ! ' One of the oldest methods of judging the resistance to tear of a rubber compound was by snipping the edges and gauging the resistance to tear by a hand separation. A modification of this, the old "scissors test," frequently applied to inner tubes, consisted of cutting a half-inch section of a tube, stretching it over a 12-ineh board, and snipping the edge with a pair of shears. If the tube did 1 z not "let go” or the tear did not grow, the tube was con- l sidered to be a very good tube. This test is still in use, but of course, has the disadvantage that the results cannot be expressed quantitatively so that objective comparisons • are not possible* s Through the years, a large number of machine tear i ‘ tests have been devised, the most popular of which are the tear tests described in ASTM (6)* The samples used for these tests are illustrated in Figure 1* Dies A and B are similar except for the tab ends and both require that a nick 0.02 inches deep be cut in the crescent shaped portion* The samples are pulled in a tensile testing ma- i chine and the tear is supposed to progress from the nick across the narrow section* The load required to do this is recorded and the tear resistance is calculated on the basis of the load that would be required to tear a speci- jmen one inch thick* The tear value measured, however, is | very sensitive to the depth of the nick (3) which makes it necessary to control this depth accurately* However, this I is extremely difficult because the specimen is died from a tensile sheet and the cut edge of the specimen is not always perpendicular to the face* Thu3, the depth of the cut will vary from one specimen to the other. 1 3 i DIE A I DIE B i DIE C 1 Figure 1* Dies for Tear Test Specimens ASTM D62lj.-L|.8 i k I To avoid this difficulty, di© € was designed with a right-angle ”nick, r which does not require cutting. This greatly improves the reproducibility of the test. However, the values obtained are generally lower than those obtainedJ j with the nicked, crescent-shaped specimen* This is due to j the higher stress gradient developed in the right angle j ■ test piece* j The fact that the angle die specimen gives differ- ; ent tear values from the crescent specimen and that these ivalues are not a constant fraction of values obtained with the crescent shaped specimen is evidence that the property, or combination of properties being measured is different for the two specimens. Graves (if) reasoned that the load reported as the measurement of tear strength for a parti cular material is made up of stresses at the apex of the !tear and of other stresses not involved in the process of |a tearing*. An ideal test would exclude the latter, and a test piece designed to be an improvement over the crescent j | would minimize the unwanted stresses. This was aceom- i plished in the angle specimen, according to Graves, by effecting a higher stress concentration at the point of .tearing than can be accomplished with the nicked crescent i : I test piece* | i I Figure 2 shows an ASM die € specimen in three j i configurations which all such specimens assume during any 5 | fc) i F F i I i Figure 2 Configuration of AS® Die C Specimen During Testing [tear test* Configuration (a) shows the unstrained posi- !tion, prior to testing, configuration (b) is one of inter- i ■ I [mediate strain early, or midway in the test, and configura- | \ ' ! I |tion (c) is just short of tear or rupture. Prom looking ! |at these diagrams it can clearly be seen that the load re- | corded by the stress measuring device during a tear test I 1 | is going to be some function of the modulus of the stock. j i [Before rupture occurs, the test has many features of a i "modulus” test with an ill-shaped test piece. Stresses are, however, concentrated in the region of the apex and j tear eventually does occur there, so that the resistance to tear is also being measured. The tear strength as mea- j sured by this specimen is thus a function of two proper- ! I ties, the inherent tear resistance and the modulus of the |stock. However, these two properties contribute to the ; i ! I total load in unknown proportions. This may be visualized j by thinking of the test specimen as being made up of two i zones, the arms shown as (I) in Figure 2(c) and the apex region shown as (II). The stresses built up in the apex j region are transmitted to it by the arms and the mechani- j 1 . f jcal properties of these arms (modulus and stiffness), j ! ! therefore, play a dominant role in governing the actual j j load recorded on the test machine. I It should be pointed out that what is being said is [ [not that the mechanical properties of the rubber should not[ 7 influence tear strength. Obviously, they do. They do so, however, in a very direct manner — their influence being i from it as with the ASTM die C specimen. , , i The angle specimen is not, therefore, ideally suited! i jfor measuring tear strength. An ideal test piece must be mum or eliminated completely, if possible. Ideally, this stress should be transmitted to the tearing zone in a .direct manner and be as free of interfering effects as possible. results obtained, with the angle specimen, measure the force necessary to initiate a tear, while th© nicked crescent specimen gives a measure of the force required for propa gating an initiated tear. He also criticizes the angle |specimen on the grounds that the stress concentrations are ;too high, and tear occurs too soon, so that for non-black A simplified version of the theoretical work done on the rupture or tear of rubber by workers of th© National Rubber Producers1 Research Association (7,8,9,10,11,12) is given by Veith (13) and is further simplified below. Al- felt only In the immediate zone of tearing and not removed ' one in which the modulus effect is reduced to a bare mini- In addition to this, Buist (5) maintains that the jfilled compounds the test fails to distinguish between materials. though they used several tear specimens in their work, the 8 most useful test piece is called the simple extension or the "trousers” tear specimen*. This type of specimen is very similar to the hand tear test .specimen which was used in the rubber industry for many years* A simplified ver sion of this test piece is shown in Figure 3* U J UMJEFORMED DEFOBMED Figure 3* Simple Extension or "Trousers” Test Specimen The specimen is shown in its unstrained or unde formed shape aswell as its deformed state as it is tested* The piece can be cut from a slab with a cut length, e, placed as shown; both legs are gripped and pulled in oppo- 9 site directions• The thickness of the rubber sheet is re presented by h. When equal loads, P, are applied to both ends of s the sample, it will assume a shape similar to the one shown! I in Pigure 3. There are essentially three zones of strain j ;in the test piece* Zone A is in simple extension at some j j extension ratio, X » where X = l/lg; 1 = extended length, lg = * unextended length* Zone B is under no strain; it is an undeformed area* Zone C is a region of complex strain varying from a maximum strain in the region near the apex to a minimum strain in the areas near zone A. Suppose forces, P, cause a tear to take place such that the cut, c, is increased by Ac. When this occurs the forces will move through some distance, Al« In moving ; through this distance, Al, work has been done on the test piece; energy has been added to it. The test piece, how- I |ever, looks almost the same as it did before the tearing ! took place* Zone C is the same size with this same complex i - i ; strain distribution, zone A has increased in size although the extension ratio, X, is unchanged (It only depends ©n F), and zone B has decreased in size by an amount, Ac. The length of b after tear is (b - Ac). In other words, an element of length, Ac, has been transferred from zone | I B to zone A and a certain amount of work has been done to effect this change.. 10 Sine© the cut length, c, increases by Ac, and the forces, P, move through a distance, A 1* it might be as- j sumed that A 1 = Ac. However, A c is referred to the un- | ; strained state and when a piece of length, A e, disappears ! t | ! j from zone 1 and turns up in zone A, it is in a different j : state of strain* In zone A it is at some strain, |Therefore, do is transformed to a new length, )\jAc and (1) A 1 * XxAc | Also, the total work done on the sample due to an increase in the tom length of c is (2) W * 2P AXAC The factor 2 is introduced because the forces, P, act on both ends of the sample. j i This work is the result of two separate actions. It I j is a combination of the work that has been used to produce !- ■ tear and the work that has been stored elastically in zone | a . i (3) w « WT * WE = 2F Xxdc where = energy of tearing 1 I WE energy stored in legs, elastically. ; If we assume that the legs do not stretch on the application of the forces, P, Wg * 0 and Xi = 1. Then I ( I j . ) ¥ = ¥t = 2FAc i i | It has already been shown in the literature (7>8,9* t l |10,11,12), however, that i W j (5) — = Th jwhere T is the characteristic tearing energy of a material, j I the energy necessary to form one square centimeter of new i !surface by a tearing process, and h is the thickness of l the specimen. By equating ¥ in equations (if) and (£>), and solving for the tearing energy (6) T = -gIL h Thus, if the magnitude of the force, F, applied in tearing a specimen and its thickness, h, are known, the tearing energy of the material may be calculated. It will |be remembered, however, that in developing equation (6) it was assumed that the arms of the sample did not stretch on pulling; that is, Wg =* 0. Also, it was implied in the development that It is necessary that the tear propagate along the central axis of the test specimen* If such a test piece could be developed, it would be close to the ideal tear test sought in the rubber industry for years. Recently, a method of measuring tear along these I lines was developed by the B. F. Goodrich Company Research 12 Center. The new test specimen is called the GET test i piece. It consists of a molded flat strip one inch wide and five inches long and 0.210 inches thick. A groove of ! I a specific cross sectional geometry is molded down the ’ ! central axis of the specimen. The geometry is smch that ! idle tear will propagate down the groove. The specimen is i • icut with shears for a distance of approximately 2% inches j down this groove and both of the cut ends are placed in the jaws of a testing machine and the load to tear the re maining 2|r inches is recorded. To prevent unwanted effects due to energy absorption by elongation of the legs during testing, a piece of square woven rayon fabric is used to reinforce the legs* The initials., G - , E, T, describe the modifications made on the original "trousers** tear test; id * grooved, E - reinforced with fabric, and T = trousers. |See Figure I j . . i In developing the new modified trousers test piece, j workers at the B. F. Goodrich Besearch Center did most of f jtheir testing and measuring at room temperature. Many rub ber products, however, perform in service at temperatures considerably higher than room temperature. A knowledge of j the tear resistance of rubber over a range of temperatures, j therefore. Is valuable in judging the high'temperature ser- j ( vice characteristics of a compound. j This .study was undertaken to .measure the tear j 5 1 - ; I < 0 1 TOP VIEW Nominal Thickness of Torn Section 0.070" Puncture Pin OO OQ O CO O O O O O O O O O O 0.030 Fabric at Mid Plane CROSS SECTION Figure i j . * Modified Trousers Specimen 14 ! resistance of elastomers over a range of temperatures using the nicked crescent-shaped specimen, the right-angle shaped specimen, and the GET test., piece* In, addition to measuring i the three kinds of tear as a function of temperature the i jeffect of the rate of jaw separation in testing was mea- f |sured over the range of temperatures involved* In order :to better judge the ability of each type of tear test to measure the high temperature service characteristics of the compounds tested, the effect of prolonged exposure to ele vated temperatures and the effect of aging of the rubber compounds on the tear resistance were also measured* 1 ♦ II. EXPERIMENTAL PROCEDURES AND EQUIPMENT A. Sample Preparation i 1. Compounding ' i All the mixing was done on a 6 x 12-inch labora- ! | 1 , tory roll mill..*. In almost all of the batches mixed 600 j \ ! j grams of polymer was used as a basis for the compound. j ' ■ i i Compounds of natural rubber, SBR, and butyl rubber were mixed according to the procedures outlined in ASTM 3>15>- ! 62T (6). The EPT compound was mixed according to the pro cedure outlined in the du Pont technical report on Nor del (04) • The compounds used were chosen on the basis of their simplicity and because they were thought to be typi cal of the recipes used with these elastomers in industry. i i 2. Curing The mixed batches were cured with a steam press 1 using 2,100 pounds platen pressure, and the desired tempera- i ture to give tensile sheets for the preparation of the ■ crescent-shaped samples and the right angle shaped samples.j The CRT test pieces were molded separately in electrie 1 Preco presses using 35,000 pounds pressure and the desired temperature. j The tensile sheets were molded in the conventional manner described in ASTM D15-62T (6). The GET specimens I were built prior to cure bj forming sandwiches of rubber 1 i over woven rayon fabric. The pieces of rubber used were f ■approximately five inches long, inch wide and 0.085 inch , i I thick. The reinforcing fabric was five inches long and i 3/8 inch wide and was treated with a natural rubber latex- santoeure mixture to avoid slippage. Two of these sand wiches were made and one was placed on each side of the groove insert. The fabric is placed at the mid-plane of the piece to avoid any appreciable bending moment and to facilitate its reinforcing action during testing. The bottom section of the GRT mold contains two puncture pins. These pins puncture and hold the fabric as the mold is closed and prevents a lateral fabric shift. Slippage of i the fabric into the groove area might interfere with the ;tear test. : i 3* Special Preparation ' The crescent-shaped test piece and the right-angl© shaped test piece were stamped out of the tensile sheets using ASTM dies of the proper proportions. A nick 0.02 j l inches deep was placed in the crescent portion of the ASM B die. The nick was made using a razor blade clamped in a holder as described in ASTM D 6 2 ! { . - 5 i j . (6). The GRT test ' 17 piece was cut approximately half way down the groove with shears to form the ntrousers, # shape used in. the test. The thickness of the samples was measured and the samples were tested. I i I i 3 t ( I B. Physical Testing j i I 5 1. Room Temperature Tests Testing at room temperature was conducted accord ing to ASTM Dip.2-62T (6), inside a constant temperature room kept at 72° ± 2°P using a table model Instron Tester. The optimum cure times of the compounds were selected on the basis of the stress-strain properties of the elas tomers rather than tear resistance. After an optimum cure time was selected, tear resistance using each of the three types of tear tests was measured. For the ASTM tests the force was measured in pounds; pull required to break the sample. This value was divided by the specimen^ thickness in inches giving the resulting tear value in pounds required to tear a sample one inch thick. When the G-RT specimens were torn using the table ! I model Instron Tester, the tear curves produced were similar[ to the one 3 shown in Figure 5>. ! 18 Q < O J a w S e p a r a t i o n , IN C H E S Figure 5* G-RT Tear Curve As the specimen is strained and the jaws are sepa rated the load builds up at a rapid rate until the stress at the apex of the cut exceeds some critical value. At this point a catastrophic rupture takes place that propa gates itself at a rapid rate until it races ahead of the stress field that existed in the apex area prior to tear. During this rapid propagation the jaws continue to sepa rate and shortly, a new stress field is built up around a new apex. As the jaws continue to separate the stress I again builds up to a high value, a catastrophic rupture 19 again occurs and the process repeats* Each peak produced on the curve represents the tearing load for catastrophic tear and several estimates of this tear strength are ob tained from a single specimen. The best measure of this tear strength Is given by the median upper peakload* Therefore ! (7) T = n o where T - tear strength ~ median upper peakload h = thickness of the rubber torn. When a strengthening structure or a strain energy dissipation process in the immediate zone of tearing takes place, the result is a "knotty" type of tear* The mecha nism consists of a great buildup of stress in the tearing zone as the load is applied with a concurrent strengthen- | ing structure formation (crystallization in the direction of the applied load in natural rubber compounds) or energy dissipation process. In other words, if the elastomer crystallizes on stretching, as does natural rubber, the crystalline structure will tend to align itself in the direction of stretching and act as a barrier to tear propa-j i gation* The process of tearing becomes like tearing a j bunch of fibers one by one until the entire bunch is ruptured. This knotty tearing manifests itself in the_ ( 20 I j ASTM tear tests as a change in the direction of tear from j i one perpendicular to the direction of stretching to a tear i i i along the direction of stretching* In the GRT test method ! the knottiness of the tear can be seen in the relative ! peakiness of the tear curve* A method is given for mea- jsuring this relative peakiness of the curve by calculating | a “knotty tear index” which is defined as where Lu = median upper peakload « median lower peakload h = thickness of the rubber torn. The thickness of the torn surfaces can be measured i in one of two ways . The most accurate way is by measuring ■the torn surface width using a hand magnifier with a grad- ; I juated recticle. Another way is to measure the total j thickness of the specimen and from this subtract the com- ! bined height of both mold insert pieces (0.070 inches ; each - see Figure if). For convenience the latter method I was adopted; that is, h was taken as j (9) h = total thickness - O.llfO This method of measuring h is said (13) to introduce an j error of about 5$ to the GRT tear values * J 2. Elevated Temperature Tests ( The methods described above for calculating the j results at room temperature were used for evaluating the |results obtained at elevated temperatures* ; j , Modifications of the table model Instron Tester i were made to adapt the machine for measuring tear at ele- i i vated temperatures. An insulated enclosure was built a- round the machine to keep the heat from escaping* In order : to keep the atmosphere inside the chamber uniform, air was blown in the bottom of the enclosure and exhausted out of i the top. Heat was provided by controlled heating elements iplaced below, behind, and In front of the sample being l | tested* The heat in the chamber was controlled such that at no time during the testing did the temperature sur rounding the sample vary more than ± 2*J>°C from the de- i sired temperature* ! The aging and prolonged exposure tests were carried out using an insulated aluminum block as the constant temp- |erature medium* At no time during the entire series of tests did the temperature of the aluminum block vary more than ± 1°P from the desired temperature. The samples were aged and exposed to the elevated temperature In the alumi num block in test tubes according to the method described in ASTM ©665-62 (6). ’ ’ j III. RESULTS AND DISCUSS 101 I A. Reproducibility of Tear Teats j In order to get an indication of the reproducibility j i lof the tear resistance values obtained, a study was under- taken to evaluate each test method using simple statistical 'concepts. Tests were run on compound S-l, the SBR com- | pound, and on compound H-l, the natural rubber compound. All data were taken at room temperature and at a testing rate of 20 inches/minute jaw separation. The data collect ed are summarized in Table I. In evaluating the series of data taken, the follow ing concepts and definitions were used: MEDIAN - the middle value in a series of data | points, X I . . | MEAN - the arithmetic average value, x « i ; where N = number of values in a series of data points i x^ = any one value RANGE, R = - x^ where - uppermos t value j X£ = lowest value j VARIANCE, s2 g N X Compound S-l- MEDIAN, I mean, x NUMBER, N RANGE, R VARIANCE, s2 STD. DEV., s GOEF. VAR. Compound N-X MEDIAN, X MEAN, x NUMBER, N RANGE, R VARIANCE, s2 STD. DEV., a COEP. VAR. TABLE I REPRODUCIBILITY OP TEAR DATA . ASTM ! < Bt f TEAR ASTM ”0” TEAR GRT TEAR 373 lb/in. 371 lb/in. 21 345 lb/in. 1,355 lb2/in2 36.8 lb/in. 9.92$ ASTM, t T Bn TEAR 851 lb/in. 8 i | . 2 lb/in. 21 302 lb/in. 6,983 lb2/in2 83.5 lb/in. 9.92$ 360 lb/in. 359 lb/in. 21 J j . 8 lb/in. l l }i }. . l lb2/in2 12,0 lb/in. 3.3^ ASTM HC” TEAR 965 lb/in. J 4 . 8 6 lb/in. 21 278 lb/in. 6,599 lb2/in2 81.2 lb/in. 16.70$ 66.7 lb/in, 67.5 lb/in. 15 20.0 lb/in. 39.93 lb2/in2 6.32 lb/in. 9.37$ GRT TEAR 187 lb/in. 129 lb/in. 15 111 lb/in. 1,323 lb2/in2 36.i j . lb/in. 20.3$ GRT KTI 5.97 lb/in. 5.78 lb/in. 15 5.76 lb/in. 2,36 lb2/ln2 1.51+- lb/in. 25.56$ GRT KTI 122 lb/in. 115 lb/in. 15 89 lb/in. 836 lb2/in2 28,9 lb/in. 25.13$ STANDARD DEVIATION, s * i , 100 x STD. DEV, COEFFICIENT VARIATION, $ « ~ — ----- I , It can readily be seen from Table I that for the j most part, the reliability of the values of tear resist- ; - * 1 jance obtained depends not only on the test method used, butj also on the elastomer tested. In the case of the smooth i ■ tearing compound, the SBR compound, the GRT tear values are as reliable as the erescent tear valuesj each has a coeffi cient variation of approximately 10$. The right angle tear on this compound, however, is much more reproducible i with a coefficient variation of approximately yfo. The re lative reliability of the ASTM tear test methods, angle tear more reliable than erescent tear, is what was expected i * and was a major reason for the elimination ©f the razor cut in tear testing. In the ease of the knotty tearing com- !pound, the natural rubber compound, an entirely different i j picture was obtained. For this case the most reproducible ' value of tear resistance was gotten using the erescent shaped die, with a coefficient variation of approximately 10$, the same as with the SBR compound. This time, con- I trary to expectation, the ASTM B tear resistance surpassed ' the ASTM G tear resistance in reliability, the latter i having a coefficient variation of approximately 17$. In /(X - Xj)2 V I - 1 25 addition, the tear strength as measured with the GRT test piece was found to have a coefficient variation of about 20$. The trousers tear was relatively not very reprodu cible* The knotty tear index as measured by the GRT speci men was found to be accurate to within approximately ± 25$ for both compounds. As far as the reliability of the data is concerned, when testing the tear resistance of a smooth tearing com pound, any one of the three test methods will give a good degree of reproducibility, with the right angle test piece being exceptionally good* When testing a knotty tearing compound, however, the values obtained with the nicked crescent test piece are the most reproducible. In both cases the GRT tear values are the least reproducible. It should be emphasized,, however, that there is a difference between being reproducible and being accurate. Although the data obtained using the GRT test piece was shown to have a relatively higher variance than the data obtained with the other two test pieces, it still might yield a more accurate value of the true tear resistance of a rubber compound. If tear resistance is the variable to be measured, then a less reproducible value of true tear resistance might be more valuable than a more reproducible value of a combination of tear resistance and other proper ties. In addition, although the knotty tear index does 36 i not yield a very reproducible number, it is still better ( ' than no number at all. To date, the only method for get- | ' ting an indication of the kno.ttine.ss' of a tear is to watch j • i the rubber test piece while it is being pulled and t© re- | | port the tear as being either knotty or smooth. With the j i i |GRT test has come the only method of getting a quantitative! ! ! ;value of the relative knottiness with which a compound 5 i 'tears. Although the date clearly show that the GRT tear values are less reproducible than the ASTM tear values, physical limitations in the equipment and limitations in the time available for this study made it impractical to test more than one GRT tear specimen per data point. The data presented on the tearing of the ASTM specimens, how ever, represent the median tear resistance obtained from ! testing three specimens. Throughout this study, when the ! ;tear resistance of the angle or erescent specimens was mea- I sured, three samples were pulled and the median value re ported, and when the tear resistance of the GRT test piece was measured, only one sample was pulled. This applies to the natural rubber and the SBR compounds only, however. When the tear resistance of the butyl or the EPT compounds was measured, five samples of eaeh specimen were pulled and the median value was reported. ! 27 B. Effect of Test-Temperature on Tear Resistance The tear resistance of compounds of natural rubber, SBR, EPT rubber, and butyl rubber was measured over a range of temperatures using all three tear test methods. The re sults of these measurements are shown in Figures 6, 7* 8, and 9, respectively. In general, It can be said that tear resistance as defined by each tear test decreases with in creasing temperature. A notable exception to this general ization is compound B-l, the butyl rubber compound. It can clearly be seen from looking at the figures that the greatest effect of temperature on tear resistance was felt by the ASTM B die specimens. For each compound the crescent tear has the steepest slope and, therefore, the greatest rate of change of tear resistance with temp erature of the three test methods used. The GRT tear, on the other hand, seems to be the least affected by tempera ture. For each elastomer, the curve representing the trousers* tear has the shallowest slope. This small effect of temperature on GRT tear will be discussed in greater detail in a later section. The effect of temperature on right angle tear seems to be greatly dependent upon the elastomer tested. For the natural rubber compound and the SBR compound the angle tear seems to slowly decrease as temperature is increased and then to decrease rapidly; 28 1 V, Figure 6, Effect of Temperature on Tear of Compound U-l •H \ © © § 43 © •H © © 20; © E4 Figure 7, Effect of Temperature on Tear of Compound S-l .T;emperatu t x Lx . 1 - i . j - T r r ; . . i i t nr&tTn •Figure 8, Effect of Temperature on Tear of Compound E-l Ttartr -f-t irHin m Figure 9* Effect of Temperature on Tear of Compound B-l whereas, the crescent tear seems to decrease rapidly with increasing temperature and then to level off. The tear resistance of compound E-l, the EFT compound, has the same i i behavior pattern for each of the three test methods; tear i I first decreases sharply and then slowly as the test temper-j ! ature is raised. The butyl rubber compound, compound B-l, shows a different shaped curve for each tear test method used. The crescent tear for the butyl compound has the same shape curve as it did for all the other elastomers tested. The GET tear eurve is essentially a straight line, with the possibility that this trousers tear may hit a maximum as indicated in Figure 9. The angle tear, however, seems to hit a minimum after decreasing as the temperature is raised, after which the tear resistance increases. It is fairly obvious from the curves shown that the GET tear is considerably lower than both the ASTM B tear r and the ASTM C tear. This comes as no surprise; the GRT I test was devised so as to remove as much of the extraneous : modulus effect from tear resistance as possible. Also, de pending on the temperature of test and the elastomer tested i the tear resistance measured with the nicked crescent spe- i cimen will be higher than the angle specimen. This is | i largely the fault of the unwanted modulus effect. The cre-j I scent specimen is longer than the angle specimen and when placed in the jaws of a testing machine, it has longer arms and therefore, more rubber in which to store elastic energy than does the angle specimen. In other words, be cause It has longer arms, the crescent specimen is more stretchable than the angle specimen. As far as the nick is ; concerned, It becomes apparent quite soon, from watching I specimens tear, that the nick in the crescent specimen i i serves no purpose other than that of concentrating the stresses at the apex of the crescent shaped portion of the sample. It does not start a cut which increases in length ; as the specimen is pulled. The right angle nick, however, is much more efficient in concentrating stresses at a ,point and, therefore, right angle specimens will rupture !at that point sooner than nicked crescent-shaped specimens will. Angle specimens, therefore, will require a smaller 'load to rupture than crescent specimens. It can also be seen from looking at the figures that the variations in tear resistance as temperature is I ! increased from room temperature depend not only on the ! j test method used, but also on the elastomer and the com pound being tested. C. Effect of Hate of Jaw Separation and Temperature on Tear Resistance It has been reported in the literature (15>,l6) that l j for filled vulcanizates there exist temperatures and rates 33 of extension during tear testing for which, the nature of tear is knotty* Since it is said in the rubber industry that a knotty tear is a good tear, a study was undertaken to measure the effect of the rate of jaw separation on the > !tear resistance of compound N-l and compound S-l over a j • - ! range of temperatures from room temperature up to 12$°G. | | The rate of jaw separation was varied from 0.2 in./min. j 1 to 50 in./min. Tear resistance was measured using the j nicked crescent-shaped sample, the right angle shaped | sample, and the modified trousers specimen. The data eol- 1lected are presented in Figures 10, 11, 12, 13, lh* V?> 16, and 1?* The kind of tear, knotty or smooth, was noted and is presented along with the data in the appendix. The knottiness of the tear, however, was thought to have little significance except as reflected in the tear resistance values, and so will not be discussed further. I At least two important observations can be made ! from studying the accompanying figures* Once again it is > jquite clear that tear resistance as measured using the J ; GRT test piece is much lower than tear resistance as mea- j sured by the ASTM specimens. Also, it can be seen that the ASTM tear v alues are relatively unaffected by varia tions in the rate of jaw separation; whereas, the GRT tear ! values vary significantly as the rate is changed. In j every case, for both the SBR compound and the natural | Figure 10. Effect of Rate on Tear of ' Compound S-l at Room Temperature 35 $ S h Figure 11* Effect of Rate on Tear of Compound S-l at 70°C» Figure 12. Effect of Rate on Tear of Compound S-l at 100°C. Figure 13* Effect of Bate on Tear of Compound S-l at 125°G. Figure lk* Effect of Rat© on Tear of Compound N-l at Room Temperature Figure 15* Effect of Rate on Tear of Compound N-l at 70°C. | ji;{ j8 is s ;s :s ;s s g » g :i 8 8 S g 5 s s s 5 « 8 a B a a a w u . j y , Figure 16. Effect of Rate on Tear of Compound N-l at 100°C. H* f f i H —J aw O H M * 0 o 0*0 1 ! a j Hp ct P O c+ O HEi ru U\t-3 OCD PB o -P“ H rubber compound, at every temperature tested, the GET tear Obits a maximum at some testing rate* The rate at which this maximum is reached is always a loxtf testing rate, lower than the standard 20 in*/min. Since the tear resistance as measured by the GRT test piece varies with the rate of testing, care must be used, when measuring GET tear, in selecting a rate of jaw separation which will give an accurate indication of the tear resistance of the compound* This problem does not arise when measuring angle tear or crescent tear, since these are relatively independent of the testing rate* B* Effect of Aging at Elevated Temperatures on Tear Resistance Konkle et al.(17) point out that in order to get an indication of the high temperature service characteristics of a rubber compound, aging tests, in addition to physical tests at elevated temperatures, must be carried out on the compound* For this reason, the effect of aging at elevated temperatures on tear resistance was included in this study. Samples of compound S-l and compound N-l were aged in test tubes according to ASTM D865-57 (6). The samples were al lowed to age for specific periods of time after which they were cooled down to room temperature and then tested* Specimens of all three tear tests were aged in this manner j and the data collected are presented in Figures 18, 19, 20, i 21, 22, and 23, i ■ From looking at the figures, once again it can be ' seen that the GRT tear values are lower than the ASTM tear j values* The significance of this has already been dis- ; ! * ,cussed in the preceding sections* | ' In compound S-l, the ASTM B tear showed the usual decay pattern with increasing aging time; a large initial decrease in tear strength followed by a leveling off as the time. .the. sample were aged increased* As the test tempera ture was raised, the initial decay in tear resistance be fore the leveling off also increased; that is, at 7Q°C the tear resistance of compound S-l after a short period of aging dropped from 350 lb./in. to about 225 lb./in., and at 125°C the drop was from 350 lb./in. to about 100 lb./in. As the periods of aging were lengthened, the ASTM O ! 1 Itear for compound S-l rose to a maximum value and then de- j I creased again. This pattern can be seen in the data pre- i ,sented for aging at both 70°C and 100°C, but not for aging I at 125°0 • It seems that as the aging temperature is In- j creased, this maximum angle tear value is pusher further j and further towards the left in the figures until at 125°C j It cannot be seen at all. This rise, which presents itself only in the aged and cooled ASTM G samples of compound S-l, 'is probably due to a stiffening of the outer surface of the Figure 18. Tear Resistance of Compound S-l After Aging at 70°C. TiJMfi. m nur.SaAged • T-I-! ;|l Figure 19* Tear Resistance of Compound S-l After Aging at 100°C. Figure 20. Tear Resistan.ee of Gompound S-l After Aging at' 125>°C. k7 Figure 21. Tear Resistance of Compound U-l After Aging at 70°C. i 00 m. Figure 22. Tear Resistance of Compound M-l After Aging at 100°G. 2*9 00 200 ' t i i ? Figure 23* Tear Resistance of Compound N«1 After Aging at 125>°C. jrubber sample. This toughening process takes place on the entire surface of the rubber and probably affects the sur face in such a way as to make tear initiation at the apex iof the test piece more difficult. As the periods of aging jbecome longer, however, or the temperature of aging is raised, the outer surface layer becomes affected to such an extent that it becomes stiff and brittle and cracks when pulled. Thus,under these circumstances it hastens rather I than hinders quick tear and a reduction in the recorded i I value of tear resistance. This brittle cracking phenomenon I became quite apparent when compound N-l was aged at the high temperature. The outer stir face of the samples became j"toasted” like slices ©f bread and had a hard, brittle I I outer layer surrounding a soft inner layer of material. The outer layer of rubber was so brittle that upon the ap- | plication of just a slight pulling force several cracks j ! 1 i ; were immediately formed. Rupture occurred at the most ! i ; : severe crack in the surface. The sample did not neces- < • sarily tear at the nick when the crescent sample was be- j ing tested or at the apex when the right angle sample was I ' being tested. This "toasting" effect was observed only on the ASTM: samples of compound N-l after aging at 12$°G. j It was not observed on GST specimens of compound N-l or on specimens of compound S-l at any temperature or period of aging. 51 GET tear resistance was relatively unaffected by prolonged periods of aging at elevated temperatures. The reason for this will be discussed in the next section. E. Effect of Prolonged Exposure to Elevated Temperatures on Tear Resistance When a rubber vulcanizate is heated to an elevated temperature the physical properties of the rubber undergo several changes. Some of these changes are reversible, being due to the greater mobility conferred upon the rub ber molecules by the elevated temperature; others are ir reversible and are due to the thermal and oxidative break down of the rubber. The extent to which these changes in the rubber take place depends on the temperature and the duration of exposure to that temperature which the rubber faces. The term used to describe the irreversible thermal' and oxidative degradation of rubber is aging. The effect of aging on tear resistance has already been discussed. The reversible changes, the effect of prolonged exposure to elevated temperatures on tear resistance was also stud ied and the data collected are presented in Figures 2lj., 25, 26, 27, 28, and 29. The data clearly show the relatively low GET tear resistance compared to the ASTM tear resistances as well I as the insignificant effect prolonged exposure to elevated liS: e m Figure 2ij.« fear Resistance of Compound S-l at 70°C. 53 I S Hours m m Figure 25>. Tear Resistance of Compound H-l at 70°C. Figure 26* Tear Resistance of Compound S-l at 10O°C Figure 27* Tear Resistance of Compound N-l at 100°C m K Time r t ours Figure 28. Tear Resistance of Compound S-l at 12£°C. O M i Figure 29* Tear Resistance of Compound N-l at 125°C, 56 |temperatures has on GRT tear resistance. In addition, an i indication of the extent to which. the change in tear re- i sistance with temperature is reversible can be obtained by j comparing Figures 21}., 25, 26, 27, 28, and 29, the , r hotw Jtear curves, with Figures 18, 19, 20, 21, 22, and 23, the i |aged tear curves. | A reason for the relatively insignificant effect of | ] i temperature on GET tear resistance when compared with the i ASTM tear resistance can be found by studying the geometry of the tear test specimens. The two ASTM test pieces, the i |angle and the nicked crescent, are both thin, flat, sheet- like specimens. Because of their shape, when they are ex posed to heat, their entire surface area is also exposed to heat. Ho part of them is unexposed or insulated. The (SIT test piece, however, is a molded, relatively thick, grooved specimen. The design of the groove is such that the apex of the groove, the region where tear takes place, ; comes in contact with the rubber at a 0° angle. (See Fig ure 30.) It is very difficult, therefore, for heat in the form of circulating hot air to come into contact with the irubber at its point of tearing. The rubber at this point | is insulated from the elevated temperature and GET tear resistance is relatively unaffected by temperature and j | aging. 9lr J t 3 t t OOOOOOf OOOOO 0° Angle ASTM TEAR TEST SPECIMENS GRT TEST PIECE Figure 30. Exposure of Tear Test Specimens to Heat IV. CONCLUSIONS The results of this study have shown that the GRT | tear test measurements are not as reproducible as either i the nicked crescent tear test measurements or the angle tear test measurements. However, GRT tear resistance is ‘ a closer measurement of true tear resistance than either , of the two ASTM tear test performed. To avoid this prob- • lem of reproducibility, it is recommended that for each 1 value of tear resistance measured using the GRT tear test method, five specimens be pulled and the median value taken as the true value. The ASM recommends that three specimens of tear test pieces be measured for each value i I of tear resistance. It has also been shown that GRT tear resistance is lower than tear resistance measured using the ASTM speci mens. This is an indication that GRT tear test piece eli minates at least a part of the undesirable modulus effect encountered in tear testing. I ASTM tear resistance is relatively unaffected by variations in the speed of jaw separation during testing; whereas, GRT tear resistance is affected. This can pre- 1 sent a problem In that, in order to get an Indication of the tear resistance commensurate with service conditions, 58 _ : an indication..of the rate ,of jaw separation applicable to conditions must be known. Otherwise, erroneous and mis leading values of GRT tear resistance can be obtained. GRT tear resistance is relatively unaffected by ex posure to elevated temperatures; whereas, the ASTM tear resistances are decreased by exposure to elevated tempera tures. Therefore* in order to get an indication of how the physical property of rubber called tear resistance decays with exposure to elevated temperature, the GRT tear test specimen cannot be used. The data collected showed that, in general, the knottier the tear the higher was the measured tear resist ance. This was found to be the case whether using the ASTM tear tests or the GRT test method. It was found that tear resistance measured with the ASTM B test piece had a great er tendency to be knotty than tear resistance measured with the ASTM G test piece. Also, it can be said that for the elastomers tested there exists a range of temperatures and rates of testing for which the nature of tear is knotty. Knotty tear index values calculated from the GRT tear data are not very reproducible* They were shown to be jreliable only to within ± 2%%. However, even though they are not reproducible numbers they are the only available quantitative measurement of the degree of knottiness with which a rubber, specimen tears* The knotty tear index is, i therefore, valuable in that it ±& a rough measurement of a heretofore immeasurable property of rubber. It can be concluded that GRT tear test measurements should be made only at room temperature and only at one standard rate of testing. In addition, if the GRT tear test piece were modified in such a way as to increase the reproducibility of the measurements .made.,, at least to the level of reproducibility obtained with measurements made using the ASTM tear test specimen, it would be very close to the ideal tear test piece sought in the rubber industry for many years* BIBLIOGRAPHY I 1* Winspear, G. G., ed. Vanderbilt Rubber Handbook, R. T. ; j Vanderbilt Company, Inc., Hew York, 195^7 i 2. Drogin, I,, Physical Testing - Classification of | Physical Tests and Their Slgnificancet Compounding , | for Specific Effects. Lecture delivered on October 28,1 I 195>7 before the Mew York Rubber Group basic elastomer ; ! technology course, United Carbon Company, Inc., : j Charleston, West Virginia. j I 3. Juve, A. E., “Physical Test Methods and Polymer Eva- | luation,** Chapter 12, Synthetic Rubber, Whitby, G. S., j ed. John Wiley and Sons, Inc., Mew York, 1954* ! 4* Graves^ F. L., India Rubber World, 111, 305 (1944)5 ! . Rubber Chem, Tech., 18, 4^4 (1945)* | 5* Buist, J. M., India Rubber World, 120, 328 (1949). : 6* ASTM Standards on Rubber Products, 20th edition, j October, 1961. 7. Rxvlin, R. S., and Thomas, A. G., J. Pol. Sci«, 10, 291(1953)* 8. Thomas, A. G., J. Pol. Sci., 18, 177 (1955). 9. Greensmith, H. W., and Thomas, A. G., J. Pol. Sci., j 18, 189 (1955). | ;10. Greensmith, H. W., J. Pol. Sci., 21, 175 (1956). ' | 11. Thomas, A. G., J. Pol. Sci., Jl,. 467 (1958). j 12. Mullins, L., Trans. I. R. I., 213 (1959). 13* Veith, A. G., Tearing of Rubber - In Search of an ; Ideal Test, B. P. Goodrich Go. Research Center, Brecksville, Ohio (unpublished). 14. Mordel Hydrocarbon Rubber, E. I. du Pont de Wemours and Company, Elastomer Chemicals Department, April, 1965. 61 62: jl5. Lukomskaya, A. I., Rubber Chem. Tech.., 57 (1961). 16. Thomas, A. G., Rubber Chem. Tech., 3k-> 66 (1961). i 117. Konkle, G. M., McIntyre, J. T., and Fenner, J. V., ; Rubber Age, j[9, 1&5 (1956). !l8. Van Raamsdonk, G. W., Rev* Gen. Caoutchouc, 32, 806 j (1955). jl9. Blanchard, A. F., ’ ’Theoretical and Basic Principles of! Reinforcement,” Chapter VIX, The Applied Science of | ! Rubber, Naunton, ¥. J* S., ed. Edward Arnold~Publish- j j ers, Ltd., London, England, 1961. j I20. Buist, J. M., “Physical Testing of Rubber,” Chapter ! The Applied Science of Rubber, .Naunton, W. J. S., ed. Edward Arnold Publishers, ktd., London, England, ! 1961. i ^21. Veith, A. G., A Few Tear Test for Rubber, B. F. Good- j rich Company Research Center, Brecksville, Ohio. ' Paper presented before A.C.S. Rubber Division meeting, Miami, Florida, May i|.-7, 1965. i22. Veith, A. G., Tearing of Rubber, B. F. Goodrich Company Research Center, Brecksville, Ohio. Talk i given at the symposium on ’ ’ Analytical Methods in the ; Study of Stress-Strain Behavior,” Boston, Massachu setts, October 28, I960. ;23. Schoch, M. G., Jr., and Juve, A. E., “The Effect of Temperature on the Air Aging of Rubber Vulcanizates,” I American Society for Testing and Materials, Special i ! Technical Publication No. 89, Symposium on Aging of j Rubbers, Chicago Spring meeting, March 2, 1949, Philadelphia, Pennsylvania (19ij.9). ' I \ I APfBIfSIX 63 VI. APPENDIX A. RECIPES AND PHYSICAL PROPERTIES OF COMPOUNDS COMPOUND N-l Ingredients Natural Rubber (RSS Ho. 1) Zinc Oxide Sulfur Stearic Acid MBTS (Benzothiazyl Disulfide) PBNA (Phenyl Naphthylamine) EPC Black Total phr 100,0 5.0 3.0 3.0 1.0 1.0 5o,o 163.0 Curing Time Min. at 2%°F. Physical Properties Modulus psi 300# Modulus psi Tensile Strength psi Ultimate Elongation 10 200 1210 2020 420 20 330 IT 00 3730 550 40 460 2200 4200 500 60 540 2370 4150 480 80 5£o 2450 3850 440 Optimum Cure Time - 4° minutes 65 COMPOUND S-l Ingredients SBR (S-1500) Zinc Oxide Sulfur Stearic Acid MBPS (Benzothiazyl Disulfide) HAF Black Total 100.0 5.0 2.0 1.5 3.0 IiQ.0 151.5 Physical Properties Curing Time Min* at Modulus Modulus psi Tensile Strength Mi. Ultimate Elongation 1000 Optimum Cure Time - J 4 .O minutes COMPOUND E-l Ingredients EPT Rubber (Nordel 107©) Zinc Oxide Stearic Acid Process Oil (Circosol NS - Napththenie Type Oil) MET (Mereaptobenzothiazole) Thionex (Tetrame thyl thiur am Monosulfide) Sulfur EFC Black Total Physical Properties Curing Time 100^ 300$ 5©0$ Tensile Ultimate j Min. at Modulus Modulus Modulus Strength Elongation' 320°F.____psi psi psi psi % ' 10 160 p o 1100 3090 800 15 180 630 1550 3410 720 20 190 790 1800 3180 650 30 200 900 2190 2810 560 k$ 200 1020 21f00 2900 5P 100.0 £.0 1.0 20.0 0.5 1*5 1.5 55*0 I8p5 Optimum Cure Time - 25 minutes 67 COMPOUND B-l : Ingredients Phr | Butyl Rubber (Enjay Butyl 325) 100,0 ( Zinc Oxide 5*0 i Sulfur 2*0 I | Stearic Acid 3*0 | MBTS 0.5 TMTD (Tetramethylthiuram Disulfide) 1,0 EPC Black 50*0 i Total 161.5 Physical Properties Curing Time 100$ 300$ 500$ Tensile Ultimate Min. at Modulus Modulus Modulus Strength Elongation 31Q°F. psi psi psi psi $ 10 160 H70 1030 2690 930 20 200 730 1520 2890 780 30 220 910 1800 2860 700 kS 2I|D 1080 2150 2790 620 60 270 1200 2280 2720 580 Optimum Cure Time - 30 minutes I i L. 68 !B* RAW DATA 1. Tear Resistance as a Punetion or Temperature Tear Resistance lb./in. 8£l 545 31$ COMPORHD N-l Type Tear In© tty Knotty Knotty Temperature Qq_____ 23.4 70 12$ Tear Test ASTM B ASTM 1 ASTM B ASTM B 4*>5 k03 Knotty Smooth Smooth Smooth 23.4 70 125 ASTM C ASTM C ASTM G ASTM G 18? 75.7 50.8 KTI = 122 KTI * 47.1 KTI = 38.1 23.4 70 100 G-RT GST OUT 69 COMPOUND S-l ; T©ar Resistance lb./in. Type Tear Temperature °c Tear Test l 373 Smooth 23.il- ASTM B 182 Smooth 70 ASTM B 1 J | ) | Smooth 100 ASTM B 129 Smooth 125 ASTM B 360 Smooth 23*i|. ASTM G i 338 Smooth 70 ASTM C 257 Smooth 100 1 ASTM C 190 Smooth 125 ASTM C 66.7 KTI =6.0 23.il- CRT | 21.2 KTI = l.£ 70 grt ; 15.0 KTI = 1.7 100 GST j 19.0 KTI = 15.2 125 GRT I I I f Tear Resista&e© lb,/in. 235 119 88.6 72.6 290 189 162 134 43.1 23.1 21.6 13.8 70 COMPOUND E-l Type Tear Smooth. Smooth Smooth Smooth Temperature og_____ 23.4 70 125 Tear Test ASTM B ASTM B ASTM B ASTM B Smooth Smooth Slaooth Smooth 23*4 100 125 ASTM C ASTM C ASTM C ASTM C KTI KTI KTI KTI 3.2 1.6 1.7 1.6 23*4 70 100 125 GET GRT GRT GRT 71 tesi stance >•/in. G0MP0UHD Type Tear B-l Temperature °c Tear Test 369 Knotty 23.% ASTM B 281*. Knotty 70 ASTM B 233 Knotty 100 ASTM B 229 Knotty 125 ASTM B 286 Shoo th 23.% ASTM C 223 Smooth 70 ASTM C ■ 20£ Smooth 100 ASTM C 261*. Smooth 125 ASTM C 86*6 KTI - 1.5 23.% GET . 92.6 KTI « 30.5 70 • GET 110 ITT a 68.6 100 GET 89.7 KTI a i|.2.2 125 GET 72 2. Effect of Kate of Jaw Separation and Temperature on Tear Resistance Rate in./min. 0.2 0.5 1.0 2.0 5.0 10 12 COMPOUND N-l at 23 .lj.°C Type Tear Knotty Knotty Knotty Knotty Knotty Knotty Knotty Tear Resistance lb./in. 795 50 7 % 871 776 801 851 701 Tear Test ASTM B ASTM 1 ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B 0.2 0.5, 1.0 2.0 5.0 10 12 5o Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty 635 657 lj.86 i*.8l 606 M>5 ASTM C ASTM C ASTM G ASTM C ASTM G ASTM C ASTM G ASTM G ASTM G ! COMPOUND N-l at 23 .^°C (con't.) Tear Resistance Rate in./min. Type Tear lb./in* 0.2 KTI w kS.B 80.I f . j 0.5 KTI = 89.9 133 ; 1.0 KTI * 103 172 J . I 2.0 KTI = 82.8 13*1- | 5.0 KTI « 69.7 115 1 10 KTI = Q9.k 130 12 KTI = 71.2 112 20 KTI = 122 187 KTI ■ 58.0 COMPOUND N-l at 70°C Tear Resistance Rate in./min. Type. Tear lb./in. 0.2 Knotty 553 0.5 Knotty 1.0 Knotty 2.0 Knotty 5^1 5.0 Knotty 591 10 Knotty 555 12 Knotty 5lU 20 Knotty $i\$ 50 Knotty 578 Tear Test GRT GRT GRT GRT GRT GRT GRT GRT GRT Tear Test | i ASTM B j ASTM B | I ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B 74 COMPOUND N-l at 70°C (eon't.) Bate in./min. 0.2 0.5 1.0 2.0 5.0 10 12 20 50 Type Tear Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Tear Resistance lb./in. 455 445 5o6 419 Tear Test ASTM C ASTM 0 ASTM € ASTM C ASTM C AS TM C ASTM C ASTM S ASTM C 0.2 0.5 1.0 2.0 5.0 10 KTI KTI KTI KTI KTI KTI KTI 171 50 KTI 108 16? 83.8 34.9 48.5 47.1 24.7 142 223 66.6 76.6 75.7 76.8 GRT GRT GRT GRT GRT GRT GRT 75 Hate In./min* COMPOUND Type Tear N-l at 100°C Tear Resistance lb./in. Tear Test 0.2 Knotty 3i*o ASTM B 0*5 Knotty 1*00 ASTM B 1.0 Knotty 383 ASTM B 2.0 Knotty 109 ASTM B 5*0 Knotty 528 ASTM B 10. Knotty 105 ASTM B 12 Knotty 1*57 ASTM B 20 Knotty 382 ASTM B 50 Knotty 1*99 ASTM B 0.2 Knotty 316 ASTM C o.5 Knotty 353 ASTM C 1.0 Knotty 358 ASTM 0 2.0 Knotty 388 ASTM 0 5.0 Knotty 1*32: ASTM 0 10 Knotty 1*33 ASTM C 12 Knotty 1*32 ASTM € 20 Knotty 1*03 ASTM C 5o Knotty 1*01 ASTM C COMPOUND N-l at 100°G (eon't.) Bate in./mlru I ! 0.2 ! 0.5 ; 1.0 2.0 I 5.0 10 12 ! 20 ! 50 Type Tear KTI = 196 KTI = i{.5.3 KTI = 71.6 KTI = 78.1}- KTI « 79.0 KTI = 79.0 KTI = 55.5 KTI = 38.1 KTI * 19.1* Tear Resistance lb./in. 62.5 97.0 120 1*4-5 76.1 50.8 .2 Tear Test GIT GRT GRT GRT GRT GRT GRT GRT COMPOUND N-l at 125°C Rate in./min. 0.2 0.5 1.0 2.0 5.0 10 12 20 50 Type Tear Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Tear Resistance lb./in.____ 276 280 377 1*21 1*23 375 1*35 Tear Test ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B 77 COMPOTJHD H-l at 125°C (con’t.) Rate in./min. 0,2 0.5 1.0 2.0 5.0 10 12 50 Type Tear Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Knotty Tear Resistance lb./in. 2ijX 256 296 351 398 391 Tear Test ASTM 0 ASTM 0 ASTM G ASTM G ASTM 0 ASTM G ASTM C ASTM 0 ASTM G 0.2 0.5 1*0 2.0 5.0 10 12 50 KTI KTI KTI KTI KTI KTI KTI 71*6 63.7 95.2! 62.7 60.6 51.5 68.3 25.8 102 103 10i{. 75.8 78.8 87.il- 51.6 GRT GRT GRT GRT GRT GRT GRT GRT 78 COMKTCJHD S-l at 23*ij.0C Bate in./min. 0.2 0.5 1*0 2.0 5.0 10 Type Tear Siaooth Smooth Smooth Smooth Smooth Smooth 3 Smooth Smooth Smooth Tear Beslstanc© ,1b./in. 3 $ k 3 k l 383 318 337 362 373 315 Tear Test ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B ASTM B 0.2 0.5 1.0 2.0 5.0 10 12 20 50 Smooth Smooth Smooth Smooth Smooth Smooth Smooth Smooth Smooth 3 5 k 358 358 362 3 1 k 3k9- 370 360, 378 ASTM C ASTM C ASTM C ASTM C ASTM 0 ASTM C ASTM 0 ASTM C ASTM 0 79 ; COMPOUND S-l at 23.1{.0C- (eon’t.) "Rate in./min. Type Tear Tear Resistance lb•/in. Tear Test 0.2 KTI = 9.5 81.0 GRT . 1 0.5 j KTI * I t .5 77.3 GET ; 1.0 KTI = I 4..8 72.6 GRT t j 2.0 KTI - 6.1 75.8 GRT ! 5*0 KTI =3-0 57.6 GET : 10 KTI =8.1 59.6 GRT 12 I KTI = 3.2 52. k GRT ! 20 KTI = 6.0 66.7 GRT 50 KTI = 3-0 56.1 GET ■ ■ COMPOUND S-l at 70°C Rat© in./min. Type Tear Tear Resistance lb./in. Tear Test 0.2 Knotty 201 ASTM B 0.5 Knotty 173 ASTM B | ? 1.0 Knotty 196 ASTM B | 2.0 Knotty 190 ASTM B 5.o Knotty 200 ASTM B 10 Smooth 192 ASTM B i 12 Smooth 206 ASTM B j 20 Smooth 182 ASTM B 5o Smooth 193 ASTM B 80 COMPOUND S-l at 70°C (eon*t.) Hate in./min* 0*2 0.5 1.0 2 l ; 0 5.0 10 12 SO Type Tear Knotty Smooth Smooth Smooth Smooth Smooth Smooth Smooth Smooth Tear Resistance lb./in. 256 304 390 299 312 338 32*1 Tear Test ASTM C ASTM C ASTM G ASTM C ASTM C ASTM G ASTM C ASTM G ASTM G 0.2 0.5 1.0 2*0 5.0 10 12 50 KTI KTI KTI KTI KTI KTI KTI KTI KTI 105 3.4 3.1 12*5 4.9 3.2 3.2 1.5 1*£ 131 23.7 25.0 34.4 26*2 21.0 22.6 21.2 24.2 GHT GRT GRT GRT GRT GRT GRT GRT GRT 81 COMPOUND S-l at 100°G Tear Resistance 0.2 Knotty 138 ASTM B 0.^ Knotty m ASTM B 1.0 Knotty 169 ASTM B 2.0 Knotty 150 ASTM B 5.0 Knotty 135 ASTM B 10 Knotty 160 ASTM B 12 Knotty 152 ASTM B 20 Smooth 1 1 ASTM B 50 Smooth 155 ASTM B 0.2 Smooth 169 ASTM G 0.5 Smooth 175 ASTM 0 1.0 Smooth 185 ASTM G 2.0 Smooth 197 ASTM C 5.0 Smooth 223 ASTM G 10 Smooth 26i|. ASTM C 12: Smooth 2?8 ASTM G 20 Smooth 257 ASTM 0 50 Smooth 309 ASTM G COMPOUND S-l at 100 °G (con't.) Rat© in./min. Type Tear Tear Resistance lb./in. Tear Test 0.2 KTI = 9.1 27.3 GRT 0.5 KTI = 67.1 80.6 GRT 1.0 KTI = 45.1}- 5^.7 GRT 2.0 KTI - 6.5 19.1}. GRT 5.0 KTI = 33.9 i}5.1 GRT 10 KTI * 1.6 11*5 GRT 12 KTI =1.6 12.5 GRT 20 KTI = 1.7 i5.o GRT 50 KTI = 1.6 COMPOUND S-l 12.7 at 125°C GRT Rate in. /rain. Type Tear Tear Resistance lb./in. Tear Test 0.2 Knotty 177 ASTM B ? • 0.5 Knotty 135 ASTM B 1.0 Knotty 9i|..5 ASTM B 2.0 Knotty 116 ASTM B 5.0 Knotty 127 ASTM B 10 Knotty 118 ASTM B 20 Smooth 116 ASTM B 50 Smooth 12.5 ASTM B 83 COMPOUND S-l at 12$°G (con’t.) Rate in,/min. Q.2 0*5 1.0 2.0 5.0 10 20 50 Type Tear Knotty Knotty Knotty Smooth. Smooth Smooth Smooth Tear Resistance lb*/in. 114 151 138 151 166 176 197 190, Tear Test ASTM C ASTM C ASTM 0 ASTM 0 ASTM 0 ASTM 0 ASTM 0 ASTM 0 0.2 o,5 1.0 2.0 5.0 KTI KTI KTI KTI KTI 16.9 36*4 36.6 48*5 71.5 50 KTI - 15.2 KTI *1.6 29.2 44*Q 55.6 57.6 79.4 ill 25.8 12*9 GRT GRT GRT GRT GRT GRT GRT |3. Effect of Prolonged Exposure and Aging at Elevated Temperatures on Tear Resistance COMPOUND N-l at 70°C | Time Exposed Hot Tear Time Aged Aged Tear I Tear Test to 70°C, hr s.— lb ./in* at 70°C, hrs. lb./in. * j ' " r '"t ■ - n , -T - ' - ..... r ASTM B 0.2 545 0 851 ASTM R 15.3 579 12*0 834 ASTM B 37.9 609 36.0 861 ASTM B 61.6 551 60.0 856 ASTM B 73.2 71.5 865 ASTM B 86.6 m SI4..0 814 ASTM B 108.5 511 108.3 841 ASTM B 133.0 585 132.8 722 ASTM B 113.0 I 4 -O7 llj.2.8 719 ASTM B 189.6 lt-55 189.2 759 ASTM B 2i}.0.5 460 21).0.0 525 ASTM B 336.9 1*18 336.7 555 ASTM G 0.3 390 0 465 ASTM G 15*4 428 12.0 503 ASTM 0 37.9 399 36.0 482 ASTM 0 61.6 419 60.0 504 ASTM 0 73.2 392 71.5 430 ASTM C 86.6 396 84..O 453 85 § O S 3 N-l at 70°0 (eon’t.) Pear Test Time Exposed to 70°C, hrs Hot Tear . lb./in. Time Aged at 70°0, hrs. Aged Tea] lb ./in. ASTM C 108*5 384 108.3 440 ASTM C 133.1 388 132.8 480 ASTM G 12|3.0 440 142.8 512 ASTM C 169.0 436 168.0 435 ASTM C 189.6 436 168.0 435 ASTM e 240.6 361 240.0 452 ASTM C 336.9 371 336.7 419 GRT 0.3 75.7 0 187 GRT 15.7 70.0 12.0 122: GRT 35.3 139.0 36.0 156 GRT 61.7 95.4 60.0 155 GRT 73.2 40.3 71.5 68.2 GRT 86.7 42.6 84.O 132 GRT 108.6 78.0 108.3 77.1 GRT 133*2 37.9 132.8 75.4 GRT 143.0 50.0 142.8 51.5 GRT 169.0 32.9 168.0 56.5 GRT 189.7 39.7 189.2 71.4 GRT 240.6 49.3 240.0 54.5 GRT 336.9 29.0 336.7 61.2 86 j COMPOUND S-l at 70°C Time Exposed Hot Tear Time Aged Aged Tear Tear Test to 70°Cj hrs. lb./in. at 70°0» hrs. lb./in. ASTM B 0,2 182 0 373 j ASTM B P . 5 l6£ 48*2 242 j ASTM B 245.0 12£ 144.7 216 j ASTM B 242.2 127 242*0 223 ASTM B i 312.7 113 312.0 197 | ASTM B 431.8 121 431.0 189 ASTM B 575.5 115 575.3 157 ASTM C G.2 336 0 360 | ASTM G 48.6 289 48.2 432 | j ASTM C 145.0 274 244.7 414 ASTM G 242.2 257 242.0 P 9 ASTM G 312.7 241 312.0 398 : ASTM G 432..8 245 431.0 421 : ASTM C 575.5 254 575.3 400 i t GRT 0.3 21.2 0 66.7 1 GRT P .6 14*3 48.2 33.3 i GRT 145.1 13.7 244.7 55*5 GRT 242.3 13.7 242.0. 30.3 GRT 312.7 21.0 312,0 22.6 GRT 431.8 13.7 431.0 22.7 GRT 575*6 11.3 COMPOUND N-l at 100°G Time Exposed Hot Tear Time Aged Aged Tear Tear Test to 100°C. hrs. lb./in. at 100°C, hrs* lb./in. ASTM B 0.2 382, 0 ASTM B 12.5 378 12.0 746 ASTM B 2^.5 33£ 2ij..2 591 ASTM B • 36.ii. 270 36.0 ASTM B 43.4 270 48.2 ASTM B 60.3 250 60.1 ASTM B 72.4 135 72.0 380 ASTM 0 0.2 i|.03 0 465 ASTM C 12^6 391 12.0 1 ASTM 0 24^5 343 24.2 414 ASTM 0 364|. 298 36.0 392 ASTM C 48. 2 1 0 48.2 361 ASTM C 60.3 192 60.1 332 ASTM C 72.4 100 72.0 288 GET 0.2 50.8 0 187 GET 12.6 3 i l - . i l - 12.0 50.8 GET 24.5 25.i|. 2I 4. . 2 53*2 GET 36.4 19 *4 36.0 57*4- GET 4. 8.4. 25.0 48.2 37*3 GET 60.3 17.9 60.1 17.5 GET 72.5 17.^ 72.0 15.6 88 Tear Test ASTM B j ASTM B j ASTM B ! | ASTM B ASTM B ASTM B ASTM B ASTM C ASTM 0 ASTM G ASTM 0 ASTM C ASTM C ! ASTM C i i GET GET GET GET GET GET GET COMPOUND S-l at 100°C Time; Exposed Hot Tear Tims Aged Aged Tear to 100eC, brs. lb./in. at 10Q°C, hrs. lb./in. 373 0.2 12,1 36.0 1*9.1 72.0 96,3 132.2 0.2 12. 2 36.1 .1*9.1 72,0 96 .1* 132,2 0.2 12.2 36.1 1*9.2 72.0 96,1* 132.2 Ujlj 97.2 71.5 61*. 0' 56.2 1*8. 1* 1*3.7 257 26^ 181* 180 11*6 139 163 15-0 ll.l 6.5 10.8 7.8 6.6 6.6 0 12.0 36.0 1*8.5 72.0 96.2 132.0 0 12.0 36.0 1*8.5 72.0 96.2 132.0 0 12.0 36.0 1*8.5 72.0 96.2 132.0 220 159 1 1* 1 * 121* 105 91.1* 360 1 * 1 * 1 1*32 382 322 289 291* 66.7 32.3 21*.2 33.9 U*.7 21*. 2 15.6 89 COMPOUND ¥-1 at 12£°C Tim© Exposed Hot Tear Time _ Aged , hrs. Aged Tear lb,/in# 1 ASTM B 0.4 372 0 821 | ASTM B 2*0 320 2.0 297 I 1 ASTM B i 6,1 138, 6.0 182 i ASTM B 10,0 deteriorated 10.0 246 ASTM B { 14.0 120 j ASTM B 19.0 105 ASTM B * 23.0 108 ASTM C 0*4 282 0 462 ! ASTM C 2.1 253 2.0 342 ! ASTM G 6,2 87.4 6.0 212 ASTM C 10.2 73.3 10.0 146 ASTM C 14.0 deteriorated 14.0 103 ASTM G 19*0 94.4 ASTM C 23.0 72.4 i GRT 2.1 23.8 0 I 187 GRT 6.1 24.2 2.0 0 H GRT 10.1 21*4 6.0 62.7 GRT 14.1 22 . 7 10.0 47.6 GRT 19.1 19.0 14*0 32.3 1 < GRT 23.0 20.2 19.0 24.2 i 90 COMPOUND S-l at 125°C Time Exposed Hot Tear Time Aged Aged Tear Tear Test to 125°C, hrs* lb./in. at 125>°C, hrs. lb ♦/in* ASTM B 0.4 142 0 373 ASTM B 4* 1 ^6.2 4.0 169 ASTM B 12.1 39.3 12.0 107 ASTM B £0.1 34-4 20.0 ASTM B 28.1 34*7 28.0 89.4 ASTM B 36.1 39.6 36.0 88.0 ASTM B l|4.4 41.3 lf4‘0 98.6 ASTM G 0*5 182 0 360 ASTM G 4.1 120 4.0 313 ASTM G 12*2 94*4 12.0 191 ASTM C 20.2 73.0 20.0 196 ASTM 0 28.0 72.0 28.0 169 ASTM G 36.1 84.0 36.0 197 ASTM G 1*4.4 7£.3 44*0 154 GET 0*4 12.3 0 66.7 GET 4.1 8.1 20,0 30.9 GET 12.0 8.6 28.0 62.5 GET 20.1 6.6 36.0 51.6 GET 36.1 6.0 44.0 50.0 GET 44.3 9.21

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Asset Metadata

Creator Lewis, Norman David (author)

Core Title The tear resistance of elastomeric vulcanizates at elevated temperatures

Contributor Digitized by ProQuest (provenance)

Degree Master of Science

Degree Program Chemical Engineering

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag engineering, chemical,OAI-PMH Harvest

Language English

Advisor Partridge, Edward G. (committee chair), Lockhart, Frank J. (committee member), Rebert, Charles J. (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c20-311683

Unique identifier UC11259014

Identifier EP41786.pdf (filename),usctheses-c20-311683 (legacy record id)

Legacy Identifier EP41786.pdf

Dmrecord 311683

Document Type Thesis

Rights Lewis, Norman David

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA