Prediction of high temperature performance of rubber products through simulation testing.Rubber compounds have a unique position and potential as being the only engineering material that simultaneously stores and dissipates energy (refs. 1-3). Due to its elastic elastic Of or relating to the demand for a good or service when the quantity purchased varies significantly in response to price changes in the good or service. nature, a high quality natural rubber (NR) can store over 150 times the energy stored per unit weight of a steel spring. During service, heat is being generated due to the viscoelastic Adj. 1. viscoelastic - having viscous as well as elastic properties natural philosophy, physics - the science of matter and energy and their interactions; "his favorite subject was physics" nature of rubber. Heat generated by this mechanism needs to be dissipated dis·si·pat·ed adj. 1. Intemperate in the pursuit of pleasure; dissolute. 2. Wasted or squandered. 3. Irreversibly lost. Used of energy. fast, otherwise it will degrade TO DEGRADE, DEGRADING. To, sink or lower a person in the estimation of the public. 2. As a man's character is of great importance to him, and it is his interest to retain the good opinion of all mankind, when he is a witness, he cannot be compelled to disclose the good properties of the product and hence result in premature failure of the rubber products. Since elastomers are poor conductors of heat, dissipation Dissipation See also Debauchery. Breitmann, Hans lax indulger. [Am. Lit.: Hans Breitmann’s Ballads] Burley, John wasteful ne’er-do-well. [Br. Lit. of the same becomes very difficult within the cycle of operation. The generated heat within the system leads to temperature rise, and the increase in temperature leads to gradual changes in properties of its constituent layers. Hence, the performance of the products under service conditions is always a function of temperature and time. Therefore, it is important to know how different properties change with temperature. Furthermore, there is a lack of correlation existing between the properties measured in a laboratory and those measured during service. Conditions experienced in service might not occur in the laboratory. For example, antiozonants are commonly added to rubber compounds to protect them from ozone attack. Protected compounds are tested at high ozone levels in the laboratory, whereas in service they might not face this much higher ozone concentration. The compounds are not exposed to acid rain in a laboratory test, whereas they might face this when exposed outdoors (ref. 4). Acid rain is a potentially important variable because it can leach leach v. leached, leach·ing, leach·es v.tr. 1. To remove soluble or other constituents from by the action of a percolating liquid. 2. antiozonants. Hence, a factor can reduce ozone resistance that is not included in a laboratory test. Another problem with determining rubber properties is hysteresis hysteresis (hĭs'tərē`sĭs), phenomenon in which the response of a physical system to an external influence depends not only on the present magnitude of that influence but also on the previous history of the system. , which causes an increase in temperature in rubber parts when flexed. Hence, the severity of the strain cycle must be limited in some tests to avoid excessive hysteresis (ref. 5). Some work has been reported on establishing the correlation of physical properties with temperature (refs. 6 and 7). However, a systematic study of this aspect for different general purpose rubbers and their blends is required. In this article, a mathematical correlation is established and reported for natural rubber (NR) and polybutadiene rubber (BR) along with their blends, and also for styrene sty·rene n. A colorless oily liquid from which polystyrenes, plastics, and synthetic rubber are produced. Also called vinylbenzene. butadiene butadiene (by  t'ədī`ēn), colorless, gaseous hydrocarbon. There are two structural isomers of butadiene; they differ in the location of the two carbon-carbon double bonds in the rubber (SBR SBR - Spectral Band Replication ). The mathematical correlation thus established
was further verified successfully against actual measurements.Experimental The compound formulations chosen to use in the experiment are given in table 1. Mixing Masterbatch mixing was done in a laboratory internal mixer mixer, either of two electronic devices in which two or more signals are combined. In the type of mixer used in radio receivers, radar receivers, and similar systems, a signal is translated upward or downward in frequency. keeping the temperature control unit (TCU (Transmission Control Unit) A communications control unit controlled by the computer that does not execute internally stored programs. Contrast with front end processor, which executes its own instructions. ) at 90[degrees]C and rotor rotor: see generator; motor, electric. speed at 60 rpm. The rubber (NR) was first masticated for about one minute, silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. (where applicable) was added then, which was allowed to mix for about one minute. The ingredients like carbon black, oil, antioxidant antioxidant, substance that prevents or slows the breakdown of another substance by oxygen. Synthetic and natural antioxidants are used to slow the deterioration of gasoline and rubber, and such antioxidants as vitamin C (ascorbic acid), butylated hydroxytoluene , antiozonant, zinc oxide zinc oxide, chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. , stearic acid stearic acid /ste·a·ric ac·id/ (ste-ar´ik) a saturated 18-carbon fatty acid occurring in most fats and oils, particularly of tropical plants and land animals; used pharmaceutically as a tablet and capsule lubricant and as an emulsifying and micro-crystalline wax were added at this time. At the elapse e·lapse intr.v. e·lapsed, e·laps·ing, e·laps·es To slip by; pass: Weeks elapsed before we could start renovating. n. of about three minutes "Three Minutes" is the 46th episode of Lost. It is the twenty-second episode of the second season. The episode was directed by Stephen Williams, and written by Edward Kitsis and Adam Horowitz. It first aired on May 17, 2006 on ABC. time, the ram was scraped. Batch dumping was done keeping the power integrator (1) In electronics, a device that combines an input with a variable, such as time, and provides an analog output; for example, a watt-hour meter. (2) See systems integrator. (PI) at 0.32 kwh. The dump temperature of the batches was found to be about 150-155[degrees]C. The masterbatches were sheeted off on a laboratory two roll mill. Remilling of the masterbatches was done after 24 hours maturation maturation /mat·u·ra·tion/ (mach-u-ra´shun) 1. the process of becoming mature. 2. attainment of emotional and intellectual maturity. 3. . The sheeted masterbatch was cut into small pieces to feed into the mixer chamber through the hopper A tray, or chute, that accepts input to a mechanical device, such as a disk duplicator or printer. In the days of punch cards, millions of cards were numerically or alphabetically organized by placing them into the hopper of a card sorter, taking them out of all the stackers and putting . The TCU was maintained at about 100[degrees]C and rotor speed at 30 rpm. The ram was scraped in between and the mix was dumped at a PI reading of about 0.20 kwh. The dump temperature of the batches was found to be approximately 135-145[degrees]C. The remilled batches were sheeted out on a two roll mill. Finally, the remilled batch sheet was cut into small pieces and was fed into the mixer chamber for making the final batch. The TCU was kept at 65[degrees]C and the rotor speed at 30 rpm. After nearly one minute, the curative curative /cur·a·tive/ (kur´ah-tiv) tending to overcome disease and promote recovery. cu·ra·tive adj. 1. Serving or tending to cure. 2. package (sulfur sulfur or sulphur (sŭl`fər), nonmetallic chemical element; symbol S; at. no. 16; at. wt. 32.06; m.p. 112.8°C; (rhombic), 119.0°C; (monoclinic), about 120°C; (amorphous); b.p. 444.674°C;; sp. gr. at 20°C;, 2. along with accelerator and pre-vulcanization inhibitor inhibitor /in·hib·i·tor/ (in-hib´i-tor) 1. any substance that interferes with a chemical reaction, growth, or other biologic activity. 2. ) was added. The whole material was dumped at about 2.5 minutes, at a PI reading of 0.12 kwh. The dump temperature of the batches was found to be approximately 95-105[degrees]C. The final batches were sheeted out on a two roll mill. Testing After a maturation of 24 hours at room temperature, the green rubber compounds were tested for determination of rheological rhe·ol·o·gy n. The study of the deformation and flow of matter. rhe  o·log properties. Mooney viscosity, ML (1+4) @ 100[degrees]C, was measured in
accordance Accordance is Bible Study Software for Macintosh developed by OakTree Software, Inc.[]As well as a standalone program, it is the base software packaged by Zondervan in their Bible Study suites for Macintosh. with ASTM ASTM abbr. American Society for Testing and Materials D 1646 (MV 2000E). The rheometric cure characteristics at 141[degrees]C were checked in accordance with ASTM D 5289 (0.5[degrees] arc, one hour, MDR MDR, n See multidrug resistance. MDR, n the abbreviation for minimum daily requirement, specifically the Minimum Daily Requirements for Specific Nutrients compiled by the United States Food and Drug Administration. 2000E). The compounded stock after maturation was cured in an electrically heated hydraulic press hydraulic press Machine consisting of a cylinder fitted with a piston (see piston and cylinder) that uses liquid under pressure to exert a compressive force upon a stationary anvil or baseplate. The liquid is forced into the cylinder by a pump. at 141[degrees]C temperature following compression molding Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, and heat techniques. The time required for curing of different compounds was different depending on the nature of the compound. The tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. and tear specimen was cured for 45 minutes. Additionally, curing was also done for optimum cure time (tc90), four times of optimum cure time (4tc90) and eight times of optimum cure time (8tc90) to see the effect of anaerobic anaerobic /an·aer·o·bic/ (an?ah-ro´bik) 1. lacking molecular oxygen. 2. growing, living, or occurring in the absence of molecular oxygen; pertaining to an anaerobe. aging. The tensile properties (including tear strength) were measured (using a Zwick UTM (Unified Threat Management) Refers to a stand-alone appliance or a software package that combines a firewall, antivirus, spam and content filtering as well as intrusion detection. See firewall, antivirus, antispam and IDS. 1445) as per ASTM D 412 and ASTM D 624. The hardness was measured with a dead load hardness tester in accordance with ASTM D 1415. Determination of the swelling swelling /swell·ing/ (swel´ing) 1. transient abnormal enlargement of a body part or area not due to cell proliferation. 2. an eminence, or elevation. index was done as per the following equation: Swelling index = swollen weight/original weight Approximately 0.2 - 0.3 grams of the vulcanized vul·ca·nize tr.v. vul·ca·nized, vul·ca·niz·ing, vul·ca·niz·es To improve the strength, resiliency, and freedom from stickiness and odor of (rubber, for example) by combining with sulfur or other additives in the presence of heat sample was kept in toluene toluene (tōl`y ēn') or methylbenzene (mĕth'əlbĕn`zēn), C7H8 for 45 hours in a
closed vessel. The swollen sample was taken out, the solvent solvent, constituent of a solution that acts as a dissolving agent. In solutions of solids or gases in a liquid, the liquid is the solvent. In all other solutions (i.e. was
absorbed with blotting blotting /blot·ting/ (blot´ing) soaking up with or transferring to absorbent material. blotting a technique used for the detection of DNA, RNA or protein. See northern blot, southern blot, western blot. Called also blot analysis. paper, and the sample was weighed immediately. For determination of accelerated aging Accelerated aging is a testing method used to estimate the useful lifespan of a product when actual lifespan data is unavailable. This occurs with products that have not existed long enough to have gone through their useful lifespan: for example, a new type of car engine or a new properties, tensile specimens were kept in a multi-cell aging oven at 70[degrees]C for two weeks and four weeks. The specimens were taken out from the oven after aging and kept for one day at room temperature for maturation. The aged tensile properties and hardness were then measured. For testing the samples at elevated temperature above 25[degrees]C, preheating of the specimen was carried out for 10 [+ or -] 2 minutes. Each specimen was placed in the test chamber for this interval ahead of testing so that all specimens of a series got the same environment for the same length of time. The preheating time at elevated temperature was limited to avoid additional vulcanization vulcanization (vŭl'kənəzā`shən), treatment of rubber to give it certain qualities, e.g., strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and cold. or thermal aging. Results and discussion The rheological properties and cure characteristics of the compounds are shown in table 2. From the data it was revealed, as expected, that the Mooney viscosity of the natural rubber com pounds was higher as compared to that of the synthetic rubber synthetic rubber: see rubber. . The high filler fill·er 1 n. One that fills, as: a. Something added to augment weight or size or fill space. b. A composition, especially a semisolid that hardens on drying, used to fill pores, cracks, or holes in wood, plaster, loading was also responsible for the higher Mooney viscosity for compound D. Both the optimum cure time and scorch time increased with the introduction of synthetic rubber. The room and high temperature physical properties of all compounds cured at 141[degrees]C for 45 minutes, including the retention of physical properties after air aging for two weeks and four weeks at 70[degrees]C, are shown in table 3. The room and high temperature physical properties of all compounds after curing at 141[degrees]C for the [tc.sub.90] time period are shown in table 4, including the retention of physical properties after anaerobic aging (in compression molding at 141[degrees]C for [4tc.sub.90] and [8tc.sub.90] time periods). The room temperature testing of durometer A hardness, angle tear and swelling index of all compounds cured at 141[degrees]C for 45 minutes, including the retention of physical properties after anaerobic aging (compression molding at 141[degrees]C for 4T[C.sub.90] and 8T[C.sub.90]0) are shown in tables 5a and 5b, respectively. The aim of the study was to develop equations to find the correlation of physical properties with temperature. Subsequently, the equations were developed and the correlation of properties with temperature was established. The correlation of physical properties (tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its and 300% modulus See modulo. ) with temperature of testing is expressed in table 6. Verification of the equation developed The equations were verified at a particular temperature (50[degrees]C). The predicted properties from the equation and the actual properties as obtained by testing at 50[degrees]C are presented in table 7. Conclusion The failure of rubber compounds does not follow the same mechanism at lower temperature and higher temperature. In every case, tensile strength and modulus decrease with an increase in test temperature. Hardness and modulus increase with time of air aging, while the tensile strength decreases with time of air aging. Swelling index does not change much with time and temperature. The equations developed in the study can be successfully used to measure the properties at any temperature for a particular compound. Reference 1. Grosch, K.A., Hardwood hardwood: see wood. hardwood Timber obtained from broad-leaved, flower-bearing trees. Hardwood trees are deciduous trees, except in the warmest regions. , J.A.C. and Payne, A.R.; Rubber Chemistry and Technology, vol. 41-5, p. 1,157 (1968). 2. Hardwood, J.A.c., and Payne, A.R.; Journal of Applied Polymer Science Polymer science or macromolecular science is the subfield of materials science concerned with polymers, primarily synthetic polymers such as plastics. The field of polymer science includes researchers in multiple disciplines including chemistry, physics, and engineering. , Polymer Symposium Part C, p. 171 (1974). 3. Payne, A.R., Journal of Applied Polymer Science; vol. 12, p. 889 (1968). 4. Nix, M.J., Plastics, Paints and RUbber, vol. 19, p. 22 (1975). 5. Clinard, R.L., Industrial Research and Development, vol. 24, p. 190 (1982). 6. Betty, J.R.; "Physical testing," paper presented at the tenth annual culture series of Akron Rubber Group, February 1973. 7. Derham, C.J., "Rubber in engineering," paper presented in the conference of Natural Rubber Producers Research Association (1973).
Table 1--compound formulations
Ingredients A B C D
Nat. rubber RMA-4 100 60 80 -
BR (Cisamer-1220) - 40 20 -
SBR 1502 - - - 50
SBR 1712 - - - 68.75
Peptizol7 0.10 0.10 0.10 -
Carbon black (N-220) 46 (N220) 48 (N-330) 45 (N-234) 70
Precipitated silica - 5 - -
Aromatic oil 8 14 8 14
Zinc oxide 5 3 5 3
Stearic acid 3 2 3 2
6PPD A.0. 2.3 2.0 2.3 1.5
TMQ A.O. 1.0 - 1.0 -
Microcrystalline wax 1.0 2.0 2.0 1.0
Soluble sulfur 2.5 1.9 1.6 2.1
NOBS Accelerator 0.5 1.3 0.7 1.5
PVI 100 0.3 0.2 0.3 0.1
Table 2. rheological properties and cure
characteristics
Compound id. A B C D
Test parameter
ML(1+4)@ 100[degrees]C 63 64 55 66
MDR at 141[degrees]C
Minimum torque (lb.-in.) 2.71 3.57 2.03 2.86
Maximum torque (lb.-n.) 14.77 16.37 11.12 14.95
Scorch safety time, [ts.sub.2] (min.) 7 18 16 12
Optimum cure time, [tc.sub.90], (min.) 21 31 27 29
Table 3--physical properties of compounds (A, B, C and D) molding
condition: 141 [degrees]C/45 minutes
Compound id. A
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 100% (MPa) 2.5 2.0 1.8
(160) (140) (128)
[212] [205] [183]
Modulus @ 3000% (MPa) 11.9 7.9 6.4
(136) (147) (122)
[-] [-] [-]
Tensile strength (MPa) 24.3 20.3 11.3
(86) (72) (87)
[64] [51] [58]
Elongation at break (%) 523 631 499
(75) (58) (72)
[48] [34] [37]
Compound id. B
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 100% (MPa) 2.2 1.8 1.6
(118) (128) (138)
[168] [156] [156]
Modulus @ 3000% (MPa) 8.1 6.1 5.2
(131) (144) (131)
[163] [177] [-]
Tensile strength (MPa) 19.8 15.2 10.5
(82) (82) (81)
[74] [72] [68]
Elongation at break (%) 593 599 543
(69) (67) (72)
[58] [51] [47]
Compound id. C
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 100% (MPa) 1.5 1.2 1.0
(133) (133) (130)
[173] [175] [160]
Modulus @ 3000% (MPa) 6.9 3.5 3.2
(125) (189) (144)
[148] [237] [167]
Tensile strength (MPa) 20.1 15.2 11.8
(80) (73) (61)
[72] [61] [54]
Elongation at break (%) 522 762 653
(91) (60) (66)
[78] [45] [52]
Compound id. D
Test temperature ([degrees]C) 25.0 75.0 125.0
Test parameter
Modulus @ 100% (MPa) 1.7 1.5 1.3
(118) (127) (123)
[141] [140] [138]
Modulus @ 3000% (MPa) 7.6 6.9 5.0
(125) (119) (126)
[158] [-] [-]
Tensile strength (MPa) 17.9 11.3 7.5
(85) (96) (93)
[75] [84] [71]
Elongation at break (%) 533 485 401
79 83 97
[59] [60] [60]
Values within ( ) indicate % retention of properties after aging at
70[degrees]C for two weeks, and values within [ indicate % retention
of properties after aging at 70[degrees]C for four weeks, respectively.
Table 4--physical properties of compounds (A, B, C and D) molding
condition: 141 [degrees]C for [tc.sub.90]
Compound id. A
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 1001% (MPa) 2.7 2.2 1.9
(70) (77) (79)
[67] [68] [58]
Modulus @ 300% (MPa) 12.7 7.7 6.1
(78) (88) (87)
[67] [73] [80]
Tensile strength (MPa) 25.7 19.6 10.9
(95) (103) (128)
[88] [88] [145]
Elongation at break (%) 531 607 448
(110) (108) (136)
[116] [146]
Compound id. B
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 1001% (MPa) 1.9 1.9 1.7
(105) (100) (94)
[84] [74] [71]
Modulus @ 300% (MPa) 8.7 6.3 5.7
(101) (108) (98)
[71] [68] [61]
Tensile strength (MPa) 19.9 14.2 9.9
(101) (85) (100)
[92] [93] [97]
Elongation at break (%) 545 562 490
(93) (105) (82)
[122] [124] [129]
Compound id. C
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 1001% (MPa) 1.3 1.2 1.1
(92) (67) (55)
[100] [83] [821
Modulus @ 300% (MPa) 6.1 3.8 3.4
(75) (76) (50)
[97] [113] [76]
Tensile strength (MPa) 21.0 16.3 11.8
(77) (76) (80)
[711 [74] [871
Elongation at break (%) 688 784 692
(98) (92) (89)
[83} [94] [93]
Compound id. D
Test temperature ([degrees]C) 25 75 125
Test parameter
Modulus @ 1001% (MPa) 1.5 1.4 1.3
(107) (107) (100)
[120] [114] [100]
Modulus @ 300% (MPa) 5.4 4.8 4.3
(148) (125) (135)
[144] [119] [130]
Tensile strength (MPa) 17.8 11.0 6.9
(107) (111) (112)
[116] [105] [112]
Elongation at break (%) 653.0 621.0 449.0
(86) (81) (84)
[84] [80] [85]
Values within ( ) indicate % retention of properties after anaerobic
aging at 141 [degrees] C for 4 [tc.sub.90], and values within []
Table 5a--room temperature testing of tear
strength, swelling index and hardness of
compounds (A, B, C and D)--molding
condition: 141 [degrees]C for 45 minutes
Compound id. A B C D
Test parameter
Hardness (durometer A) 62 60 52 60
(+6) (+6) (+8) (+2)
[+10] [+8] [+8] [+4]
Tear strength (N/mm) 97 97 89 47
(52) (53) (52) (89)
[41] [47] [47] [77]
Swelling index 2.38 2.62 3.13 2.83
(92) (92) (93) (95)
[91] [90] [91] [93]
Values within () indicate % retention of properties after aging at
70[degrees]C for two weeks, and values within [] indicate % retention
of properties after aging at 70 [degrees]C for four weeks,
respectively. In the case of hardness, + values indicate increase of
aged hardness over unaged hardness.
Table 5b--room temperature testing of
tear strength, swelling index and hardness
of compounds--molding condition: 141 [degrees]C
for [TC.sub.90] time
Compound id. A B C D
Test parameter
Hardness (durometer A) 62 58 52 56
(-4) (-1) (-2) (+2)
[-6] [-1] [-4] [+4]
Tear strength (N/mm) 106 84 84 48
(88) (93) (89) (100)
[77] [83] [81] [100]
Swelling index 2.47 2.65 3.14 2.89
(97) (96) (96) (94)
[96] [95] [92] [91]
Values within () indicate % retention of properties after anaerobic
aging at 141 [degrees]C for 4 [tc.sub.90], and values within []
indicate percent retention of properties after anaerobic aging at
141 [degrees]C for 8 [tc.sub.90] min., respectively. In case of
hardness, +/- values indicate increase/decrease of aged hardness over
unaged hardness.
Table 6--correlation of physical properties with temperature
Compound Equation
id. (x= test temperature)
A Y = -0.0006[chi square]-0.523x+26.18
Y = -0.0005[chi square]-0.126x+14.74
B Y = -0.0931 x+22.143
Y = -0.0001[chi square]-0.0499x+9.22
C Y = -0.0002[chi square]-0.1135x+22.76
Y = -0.0006[chi square]-0.1217x+9.56
D Y = -0.0003[chi square]-0.1497x+21.32
Y = -0.0002[chi square]-0.0026x+7.68
Compound Value Properties
id. of [R.sub.2] studied
A 0.9541 Tensile strength
0.9992 300% modulus
B 0.9999 Tensile strength
0.9697 300% modulus
C 0.9946 Tensile strength
0.9931 300% modulus
D 0.9756 Tensile strength
0.9869 3000% modulus
Table 7--verification of predicted property and actual property
Compound Test Predicted Experimental
id. parameter value in MPa value in MPa
A Tensile strength 22.1 22.7
300% modulus 9.7 8.8
B Tensile strength 17.5 17.6
300% modulus 7.0 6.5
C Tensile strength 17.6 18.1
300% modulus 5.0 4.8
D Tensile strength 14.6 15.5
300% modulus 7.3 7.3
The variation in predicted value and experimental values was
found to be within [+ or -] 10%.
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