Laboratory simulated aging and the effect on the oxygen content in rubber.Aging of rubber in internal tire components is typically associated with oxidation oxidation /ox·i·da·tion/ (ok?si-da´shun) the act of oxidizing or state of being oxidized.ox·idative ox·i·da·tion n. 1. The combination of a substance with oxygen. 2. . With exposure in the field, oxygen levels in rubber components can significantly change with time. Laboratory simulated aging of rubber samples, using accelerated exposure conditions, may also produce significant changes in oxygen content. Recently, there has been significant interest in expanding the understanding of the aging process of tire belt skim compounds. This program has been designed to study the impact of laboratory aging conditions upon the oxygen content of belt skim compounds and related physical mechanical properties. Many recent aging studies involving radial radial /ra·di·al/ (ra´de-al) 1. pertaining to the radius of the arm or to the radial (lateral) aspect of the arm as opposed to the ulnar (medial) aspect; pertaining to a radius. 2. tires have focused upon the belt edge area, which is a high strain energy density location in the product. This type of work may be conducted for a variety of purposes, for example: To attempt to correlate laboratory tests with actual tire performance: to develop improvements in compounds or raw materials for overall product improvements; or to develop or improve laboratory simulations of the behavior of tire composites. Regardless of the objective of the research, such basic properties of the belt coat recipes as tensile strengths 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 , ultimate elongations, moduli In theoretical physics, moduli are scalar fields whose different values are equally good (each one such scalar field is called a modulus). The reason is that the potential energy for moduli is constant, which can be guaranteed, for example, by supersymmetry (with and crosslink densities are routinely investigated. These properties may then be used to conduct correlation studies with some measure(s) of tire performance, or to ascertain rubber property degradation rates as a function of laboratory aging exposure times, temperatures and/or exposure media. Efficiencies are frequently required for developing materials for rubber products in the laboratory, and thus 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 at elevated temperature is usually employed (ref. 1). In these circumstances CIRCUMSTANCES, evidence. The particulars which accompany a fact. 2. The facts proved are either possible or impossible, ordinary and probable, or extraordinary and improbable, recent or ancient; they may have happened near us, or afar off; they are public or , heat may become interpreted as the overriding (programming) overriding - Redefining in a child class a method or function member defined in a parent class. Not to be confused with "overloading". cause of degradation, without offering proper consideration of oxygen attack as a true major factor of damage at the molecular level. Although it is true that 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. heat may indeed 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 polymers, work investigating tire belt composites has suggested that aerobic aerobic /aer·o·bic/ (ar-o´bik) 1. having molecular oxygen present. 2. growing, living, or occurring in the presence of molecular oxygen. 3. requiring oxygen for respiration. 4. aging, and thus oxygen degradation, are prevalent reactions occurring in actual tire belt composites (ref. 2). Three general purpose base elastomers with unsaturation un·sat·u·rat·ed adj. 1. Of or relating to an organic compound, especially a fatty acid, containing one or more double or triple bonds between the carbon atoms. 2. Capable of dissolving more of a solute at a given temperature. in the polymer backbone and lower resistance to oxidation compared to elastomers having predominantly pre·dom·i·nant adj. 1. Having greatest ascendancy, importance, influence, authority, or force. See Synonyms at dominant. 2. saturated saturated /sat·u·rat·ed/ (sach´ah-rat?ed) 1. denoting a chemical compound that has only single bonds and no double or triple bonds between atoms. 2. unable to hold in solution any more of a given substance. backbone structures are natural rubber, 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 and polybutadiene (ref. 3).
These same elastomers are the primary three polymers used for tire
manufacturing applications. Thus, attempts to improve the quality of
laboratory simulations of tire belt compound aging behaviors should
benefit from attaining the ability to quantify Quantify - A performance analysis tool from Pure Software. the oxygen present in the
belt coat as a means of monitoring an important process in the overall
degradation phenomenon.In general, the reaction of oxygen with elastomers causes both chain scission scis·sion n. 1. A separation, division, or splitting, as in fission. 2. See cleavage. and crosslinking. Chain scission tends to be responsible for losses in tensile strength and elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth. . Modulus changes, particularly modulus increases, are probably due to radical-induced oxygen crosslinking (ref. 4). The altered network contains increased chain-end defects, and strength and elongation are reduced (ref. 5). Gent studied the chemistry of flex cracking cracking - cracker and concluded that the behavior was due to oxidative ox·i·da·tive adj. Of, relating to, or characterized by oxidation. oxidative, adj having the ability or property to oxidize. oxidative pertaining to or emanating from oxidation. chain scission of the elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber. at mechanically induced cracks (ref. 6). Other work indicated that anaerobic aging alone reduced crack growth rates Growth Rates The compounded annualized rate of growth of a company's revenues, earnings, dividends, or other figures. Notes: Remember, historically high growth rates don't always mean a high rate of growth looking into the future. to only 25% of the aerobic levels measured using one atmosphere of air (ref. 7). Ono et al. conducted studies with cis-1,4-polyisoprene vulcanizates which indicated that the diffusion diffusion, in chemistry, the spontaneous migration of substances from regions where their concentration is high to regions where their concentration is low. Diffusion is important in many life processes. of oxygen was coupled with first-order oxygen consumption, and that the rate of chain scission was proportional to the rate of oxygen consumption (ref. 8). Gillen et. al found that for modulus studies in thermal-aging conditions, diffusion-limited oxidation effects are important (ref. 9). Work conducted to investigate the impacts of aerobic aging upon dynamic mechanical properties of natural rubber vulcanizates indicated that dynamic modulus Dynamic modulus is the ratio of stress to strain under vibratory conditions (calculated from data obtained from either free or forced vibration tests, in shear, compression, or elongation). It is a property of viscoelasticity materials. increased, but depending upon the recipe, could pass through a maximum, and damping damping In physics, the restraint of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipating energy. Unless a child keeps pumping a swing, the back-and-forth motion decreases; damping by the air's friction opposes the decreased (ref. 10). The availability of laboratory equipment to measure total oxygen has offered an important step in permitting focus upon the important oxygen content link in the degradation process. This type of equipment routinely measures total oxygen content, and thus does not focus upon either solely the oxygen content directly available for degrading 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 reactions, or solely the oxygen content of degradation products. Nevertheless, with proper measurements of controlled, unaged compounds, the researcher can generate oxygen content data for purposes of creating correlations with tire performance criteria, or alternatively, correlations with any of a range of common laboratory measurements of properties ranging from simple static tensile strength, modulus and strain ratio, to more complex behaviors such as crack-propagation or dynamic mechanical responses. The benefits of achieving quantitative information about oxygen contents are greater than merely "filling a missing link" in rubber degradation correlation studies. Endeavors to study the impacts of innerliner permeabilities, gaseous gas·e·ous adj. 1. Of, relating to, or existing as a gas. 2. Full of or containing gas; gassy. solubilities in rubber tire components and intracasing pressurization Pressurization generally refers to the application of pressure in a given situation or environment; and more specifically refers to the process by which atmospheric pressure is maintained in an isolated or semi-isolated atmospheric environment (for instance, in an aircraft, or can also benefit from quantifications of rubber oxygen content levels. The study described in this article was directed at examining the behavior of a single simulated belt compound in a laboratory simulation of aging using thermal exposures The total normal component of thermal radiation striking a given surface throughout the course of a detonation; expressed in calories per square centimeter or megajoules per square meter. . The tests employed specimens that were aerobically heat-aged at various temperatures, in various oxygen concentration levels, and over a range of exposure times. The objective of the work was to identify the magnitudes and rates of degradation by monitoring symptoms of degradation impacts upon basic tensile strength, modulus and ultimate strain levels. Correlations with time were studied, and of key interest, correlations with measured oxygen contents were developed. The interpretation of the data was oriented o·ri·ent n. 1. Orient The countries of Asia, especially of eastern Asia. 2. a. The luster characteristic of a pearl of high quality. b. A pearl having exceptional luster. 3. toward offering direction to a few basic questions: * Can the oxygen concentration in a laboratory exposure medium be used as a tool to control oxygen content in specimens? * Can oxygen concentration in a laboratory exposure medium be used as a tool to accelerate rubber degradation studies? * Heat applied to an adequate threshold level Noun 1. threshold level - the intensity level that is just barely perceptible intensity, intensity level, strength - the amount of energy transmitted (as by acoustic or electromagnetic radiation); "he adjusted the intensity of the sound"; "they measured the of severity is expected to accelerate oxygen-induced degradation reactions in a rubber tire component. Can this be simulated in simple laboratory aging studies? * For a given model compound, what quantitative oxygen content corresponds with significant degradation of overall properties? * Does oxygen content affect the basic physical properties at the same rate? Experimental Overview The objective of this study was to design and conduct a laboratory study to evaluate the effects of accelerated degradation of rubber compounds. Mechanical properties testing and measurement of oxygen content using a pyrolysis py·rol·y·sis n. Decomposition or transformation of a chemical compound caused by heat. pyrolysis (pīrol´isis), n method were performed after the compound was exposed to various aging cycles. Regression analyses were conducted on the resulting measurements. Compounding and mixing A single compound was mixed in a laboratory BR size 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. . This compound, designated as "M1," was used as a model belt skim compound. The formulation formulation /for·mu·la·tion/ (for?mu-la´shun) the act or product of formulating. American Law Institute Formulation for this compound is shown in table 1. A two-pass process was used for mixing this compound. A masterbatch was mixed using a controlled mixing profile consisting of approximately 1,200 grams. and dumped at 160[degrees]C. The masterbatch was cooled for 24 hours Adv. 1. for 24 hours - without stopping; "she worked around the clock" around the clock, round the clock before the final pass was completed in the mixer. This pass was dumped at 95[degrees]C. The finished compound was conditioned in the laboratory environment for 24 hours before samples were prepared and cured. Sample preparation Optimum cure conditions were determined by using a moving die curemeter at 150[degrees]C, 0.5[degrees] arc at tin oscillation frequency The Oscillation frequency (fundamental period): to give an example you can think of a grandfather clock. The pole swings beating the second; the time it takes to start from a point and then go back to that point is the oscillation period (as you can see, the grandfather clock has of 1.7 Hz. Samples were cured based on these data. A total of 20 standard tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. sheets (150 x 150 x 2 mm) and 10 sheets (100 x 100 x 1 mm) were cured in a laboratory press at 150[pounds sterling]C. All test sheets were conditioned trader laboratory conditions for 16 hours before the aging cycles were started. Six die C dumbbells were cut from each tensile sheet in the grain direction as described in ASTM ASTM abbr. American Society for Testing and Materials D412. Samples were later removed from these 1 mm sheets, after aging and prior to dynamic mechanical testing. Aging conditions A test matrix was designed to include the aging conditions as shown in table 2. The oven aging method was followed as described in ASTM D573, and the pressure chamber method was used per ASTM D572. The following conditions were used to simulate simulate - simulation accelerated oxidation: * Countertop aged lit standard laboratory conditions: * circulating cir·cu·late v. cir·cu·lat·ed, cir·cu·lat·ing, cir·cu·lates v.intr. 1. To move in or flow through a circle or circuit: blood circulating through the body. 2. air oven at 70[degrees]C; * compressed air compressed air, air whose volume has been decreased by the application of pressure. Air is compressed by various devices, including the simple hand pump and the reciprocating, rotary, centrifugal, and axial-flow compressors. in pressure vessel Pressure vessel A cylindrical or spherical metal container capable of withstanding pressures exerted by the material enclosed. Pressure vessels are important because many liquids and gases must be stored under high pressure. at 2,068 kPa, 70[degrees]C: * blend of 50% [N.sub.2]/50% [O.sub.2] in pressure vessel at 2,068 kPa, 70[degrees]C; and * oxygen in pressure vessel at 2,068 kPa, 70[degrees]C. All dumbbells to be aged were wrapped in cheesecloth cheese·cloth n. A coarse, loosely woven cotton gauze, originally used for wrapping cheese. cheesecloth Noun a light, loosely woven cotton cloth Noun 1. prior to placing in the oven or the pressure vessels to provide separation of surfaces while aging. Upon the completion of each aging cycle, test pieces were vacuum-sealed in plastic film to prevent additional oxidation before testing. Testing All test pieces were allowed to condition at standard laboratory conditions, after aging, for 24 hours sealed in the vacuum bag. At the end of each aging cycle, the following testing was performed: * Tensile properties per ASTM D412, the median value Noun 1. median value - the value below which 50% of the cases fall median statistics - a branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population of five tests is reported; * hardness per ASTM D2240, the median value of five tests is reported; * dynamic testing dynamic testing Lab medicine A testing format in which 2+ samples of Pt blood or urine are obtained at a specified time interval. See Glucose tolerance test, Timed specimen, Xylose absorption test. per ASTM D5992, test results of a single sample are reported: and * oxygen content, after eliminating the low and high value, the mean value of the middle three of five tests is reported. Tensile testing was performed on an Instron 4465. Hardness was measured using a durometer A Durotronic digital durometer. Dynamic properties were determined using a Rheometrics Solid Analyzer analyzer /ana·ly·zer/ (an´ah-li?zer) 1. a Nicol prism attached to a polarizing apparatus which extinguishes the ray of light polarized by the polarizer. 2. , RSA (1) (Rural Service Area) See MSA. (2) (Rivest-Shamir-Adleman) A highly secure cryptography method by RSA Security, Inc., Bedford, MA (www.rsa.com), a division of EMC Corporation since 2006. It uses a two-part key. II. Dynamic testing was performed in tension, at a frequency of 10 Hz, a 1% strain, and using a temperature sweep from -30[degrees] to 60[degrees]C. Oxygen content analysis was performed on a Leco CHNS-932 with a VTF-900 furnace furnace, enclosed space for the burning of fuel. There are many kinds of furnaces, the type depending upon the fuel and the use to which the heat produced within it is put. Most familiar are the furnaces used in the heating of buildings. . For this method, samples were placed into a high-carbon environment inside the high temperature (1,300[degrees]C) pyrolysis furnace of the instrument. The oxygen released during pyrolysis of the rubber sample combines with the carbon-rich environment to form CO. The CO is swept from the furnace and converted to C[O.sub.2] before being measured. A highly selective infrared An invisible band of radiation at the lower end of the visible light spectrum. With wavelengths from 750 nm to 1 mm, infrared starts at the end of the microwave spectrum and ends at the beginning of visible light. detection system measures oxygen levels to a precision level of 0.01%. The sample size for the test pieces is 0.002 grams. These test pieces used for oxygen analysis were removed from tested dumbbells. All testing was performed under standard laboratory conditions. Results and discussion Tables 2-6 contain the test data from the study. Table 2 shows the results of the oxygen content tests, as well as the physical/mechanical test results for tensile strength, modulus, ultimate elongation and hardness. To summarize sum·ma·rize intr. & tr.v. sum·ma·rized, sum·ma·riz·ing, sum·ma·riz·es To make a summary or make a summary of. sum the data for oxygen content, the low and high value was dropped, and the mean value of the remaining three tests was used. The median value of the five tensile tests results was used. A series of 3D column graphs, figures 1-5, display the property results versus aging time and aging condition. [FIGURES 1-5 OMITTED] In figure 1, the graph shows: * The oxygen content of the cured rubber stock, after aging on the countertop under ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. conditions, did not change significantly over time. The oxygen percentage stayed at just over 2% during the 168-hour aging period. * Aging of specimens in a forced air oven at 70[degrees]C resulted in a minimal increase in the oxygen content. * Elevating the oxygen percentage in the aging gas mixture, at the selected pressure test condition, significantly increased the oxygen content in the test samples. * The length of the aging time and the percentage of oxygen in the aging gas had a synergistic effect Synergistic effect A violation of value-additivity in that the value of a combination is greater than the sum of the individual values. . The test condition having the longest exposure (168 hrs.) and the highest oxygen percent in the aging gas (100% [O.sub.2]) yielded a significantly higher oxygen content result (8%) than any other condition. As expected, when using a natural rubber compound, the thermo-oxidative aging process drove initial increases in hardness and modulus (figures 2 and 3). For both properties, aging time had more of an impact than aging condition (either [O.sub.2] percentage or pressure). The longest duration/ highest [O.sub.2] percentage boundary aging condition produced the most significant changes. This condition yielded the highest hardness value and caused enough degradation to result in an ultimate elongation to drop to 51%, and thus not allow for reporting of a 100% modulus value. The correlation of oxygen content to either hardness or modulus was not strong. The results for tensile strength and ultimate elongation show a more direct correlation Noun 1. direct correlation - a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1 positive correlation with not only aging time, but also aging condition. In figures 4 and 5, the order of the aging conditions on the axis has been reversed to more clearly show the decrease in both properties with increased aging time and increased pressure or oxygen percentage in the aging gas. Again, the boundary aging condition with the longest duration/highest [O.sub.2] percentage had a very deleterious deleterious adj. harmful. impact on both tensile strength and ultimate elongation. To determine if there was a correlation between increasing oxygen content and decreasing tensile strength and/or ultimate elongation, the plots in figures 6 and 7 were created. The plot (log fit) of tensile versus oxygen generated an R squared value of 0.97. Ultimate elongation also yielded a good correlation with an R squared value of 0.89. Lastly, a plot of the log of the strain ratio versus time for each aging condition is shown in figure 8. The plots, with the exception of the counter top aging condition, all show very good correlations. [FIGURES 6-8 OMITTED] Tables 3-6 show the results of the dynamic property testing for elastic modulus elastic modulus or elastic constant In materials science and physical metallurgy, any of various numbers that quantify the response of a material to elastic or springy deflection. , viscous viscous /vis·cous/ (vis´kus) sticky or gummy; having a high degree of viscosity. vis·cous adj. 1. Having relatively high resistance to flow. 2. Viscid. modulus, complex modulus and tangent tangent, in mathematics. 1 In geometry, the tangent to a circle or sphere is a straight line that intersects the circle or sphere in one and only one point. delta. Data were gathered for the full temperature range, but -25[degrees], 0[degrees], 25[degrees] and 60[degrees]C were selected for purposes of investigating correlations. Similar to the modulus results from the tensile testing, overall there was the expected increase in dynamic modulus with thermo-oxidative aging. This trend, however, was much more apparent in the lower ranges of the temperature sweep. Figure 9 shows the results for complex modulus, [E.sup.*] at -25[degrees]C versus aging time and aging condition. The correlation to oxygen content is shown in figure 10. The 0.90 R-squared value for the log-fit plot is similar to that found at the -25[degrees]C lest lest conj. For fear that: tiptoed lest the guard should hear her; anxious lest he become ill. [Middle English, from Old English temperature for elastic modulus ([R.sup.2] = 0.91) and viscous modulus ([R.sup.2] = 0.86), figures 11 and 12. Tangent delta at the lower temperatures showed no obvious trends for either aging time or aging condition, and a good correlation with oxygen content was not found. [FIGURES 9-12 OMITTED] At the higher temperature ranges of the dynamic testing, the findings in terms of trends and correlation were almost reversed from that found at the lower temperatures. The good correlation of the modulus components to oxygen content was not found. However, tangent delta yielded a good correlation with oxygen content. Figure 13 shows an R-squared value of 0.88 for a linear plot of tangent delta at 60[degrees]C versus oxygen content. In figure 14, all of the tangent delta data for 60[degrees]C are displayed. [FIGURE 13 OMITTED] Conclusions In many rubber applications, the degradation of mechanical properties over time is significantly influenced by both temperature and the presence of oxygen. Simulating aging in the laboratory often involves exposing test specimens to elevated temperatures. Occasionally, the degradation is further accelerated by introducing a gas mix with a higher percentage of oxygen at elevated pressures. Typically, the degree of degradation is measured by studying the change in mechanical properties such as tensile, modulus, elongation and hardness. Unfortunately, correlating the changes in these properties to changes in properties observed in field-aged samples is very difficult. Field samples potentially have a much broader exposure environment, and these other factors can influence the mechanical properties. Finding additional measurements that correlate with aging and other mechanical properties can be an important step in connecting accelerated laboratory aging and field aging. In this study is was determined that: * Oxygen concentration in the aging gas directly impacted the oxygen content in the test specimens. * Oxygen concentration in the aging gas lead to accelerated rubber degradation. * Within the realm of these experiments, increasing the temperature did not directly relate to an increase in the oxygen content of the test specimens. For the specific model compound studied, the oxygen content of the test specimens correlated cor·re·late v. cor·re·lat·ed, cor·re·lat·ing, cor·re·lates v.tr. 1. To put or bring into causal, complementary, parallel, or reciprocal relation. 2. strongly with degradation of selected mechanical properties. Typically, the best curve fit for this degradation was a log plot. The unaged compound started with the oxygen content level at just over 2%. At the boundary aging condition with the highest temperature/highest % [O.sub.2] aging gas, the oxygen concentration in the aged stock was almost 8%, and a very severe change in properties was noted.
Table 1--model compound
Model belt coat formulation
M1 Master Phr %
Natural rubber SIR 10 100 57.54
Carbon black N326 60 34.52
Plasticizer Aromatic process oil 2 1.15
Activator Stearic acid 2 1.15
Activator Tire grade zinc oxide 7 4.03
Antidegradant 6PPD 1 0.58
Adhesion activator 10% cobalt 1.8 1.04
naphthenate
173.8 100.00
M1 Finish
M1 Master 173.8 96.45
Accelerator DCBS 1.4 0.78
Sulfur 20% OE insoluble 5 2.77
sulfur
180.2 100.00
Table 2--test matrix and testing results
Temp. Time Gas Pressure Oxygen
([degrees]C) (hrs.) mix (kPa) content *
(%[O.sub.2]) (%[O.sub.2])
21 0 21 101.3 2.031
21 24 21 101.3 2.083
21 72 21 101.3 2.065
21 168 21 101.3 2.017
70 24 21 101.3 2.097
70 72 21 101.3 2.065
70 168 21 101.3 2.195
70 24 21 2,068 2.398
70 72 21 2,068 2.713
70 168 21 2,068 3.026
70 24 50 2,068 2.473
70 72 50 2,068 3.052
70 168 50 2,068 3.675
70 24 100 2,068 2.508
70 72 100 2,068 3.228
70 168 100 2,068 7.999
Temp. Hardness Stress Tensile Ultimate
([degrees]C) durom. A at 100% (stress at elongation
** strain break) (%) **
(MPa) ** (MPa) **
21 67 5.3 24.6 383
21 73 5.3 24.6 382
21 74 4.9 24.5 395
21 74 5.2 24.8 388
70 74 5.8 23.0 355
70 76 5.9 22.8 318
70 77 7.0 21.2 265
70 74 5.7 21.6 317
70 77 6.1 21.1 300
70 77 7.1 18.8 244
70 73 5.9 22.2 328
70 75 6.1 19.1 279
70 78 6.3 14.7 214
70 75 5.9 20.7 308
70 78 6.2 18.4 272
70 85 n/a 6.1 47
* Oxygen content = mean value of 5 test specimen results after dropping
high and low.
** Median of 5 tests.
Table 3--elastic modulus
Dynamic testing results--elastic modulus, E' (MPa)
Aging condition Selected data
from tempera-
Temp. Time Gas Pressure ture sweep
([degrees]C) (hours) mix (kPa)
(%[O.sub.2]) -25[degrees]C
21 0 21 101.3 28.2
70 24 21 101.3 33.5
70 72 21 101.3 32.7
70 168 21 101.3 34.7
70 24 21 2,068 28.6
70 72 21 2,068 37.1
70 168 21 2,068 39.9
70 24 50 2,068 34.5
70 72 50 2,068 36.7
70 168 50 2,068 55.2
70 24 100 2,068 35.4
70 72 100 2,068 44.2
70 168 100 2,068 75.8
Selected data from
temperature sweep
Temp.
([degrees]C) 0[degrees]C 25[degrees]C 60[degrees]C
21 16.3 13.1 11.0
70 19.6 16.1 13.7
70 19.7 16.0 13.5
70 20.3 16.7 14.4
70 16.9 14.0 11.9
70 21.2 16.7 13.6
70 22.4 17.0 13.5
70 20.0 15.8 12.7
70 20.6 15.8 12.6
70 25.5 17.2 12.5
70 19.9 15.7 12.7
70 23.6 17.8 14.0
70 29.9 18.1 11.6
Table 4--viscous modulus
Dynamic testing results--viscous modulus, E" (MPa)
Aging condition Selected data
from tempera-
Temp. Time Gas Pressure ture sweep
([degrees]C) (hours) mix (kPa)
(%[O.sub.2]) -25[degrees]C
21 0 21 101.3 12.2
70 24 21 101.3 16.1
70 72 21 101.3 14.0
70 168 21 101.3 15.6
70 24 21 2,068 14.2
70 72 21 2,068 16.2
70 168 21 2,068 15.9
70 24 50 2,068 14.5
70 72 50 2,068 15.1
70 168 50 2,068 22.6
70 24 100 2,068 15.4
70 72 100 2,068 18.7
70 168 100 2,068 32.6
Selected data from
temperature sweep
Temp.
([degrees]C) 0[degrees]C 25[degrees]C 60[degrees]C
21 3.4 2.0 1.3
70 4.3 2.5 1.7
70 3.8 2.3 1.5
70 4.2 2.5 1.7
70 3.7 2.3 1.6
70 4.5 2.8 1.8
70 4.6 2.8 1.8
70 4.0 2.4 1.6
70 4.2 2.6 1.6
70 6.0 3.2 1.9
70 3.9 2.4 1.6
70 5.2 3.1 2.0
70 7.9 4.0 2.3
Table 5--complex modulus
Dynamic testing results--complex modulus, E*(MPa)
Aging condition Selected data
from tempera-
Temp. Time Gas Pressure ture sweep
([degrees]C) (hours) mix (kPa)
(%[O.sub.2]) -25[degrees]C
21 0 21 101.3 30.7
70 24 21 101.3 37.2
70 72 21 101.3 35.6
70 168 21 101.3 38.0
70 24 21 2,068 31.9
70 72 21 2,068 40.5
70 168 21 2,068 43.0
70 24 50 2,068 37.4
70 72 50 2,068 39.7
70 168 50 2,068 59.6
70 24 100 2,068 38.6
70 72 100 2,068 48.0
70 168 100 2,068 82.5
Selected data from
temperature sweep
Temp.
([degrees]C) 0[degrees]C 25[degrees]C 60[degrees]C
21 16.7 13.3 11.1
70 20.1 16.3 13.8
70 20.0 16.2 13.6
70 20.7 16.9 14.5
70 17.3 14.2 12.0
70 21.7 16.9 13.8
70 22.8 17.3 13.6
70 20.3 15.9 12.8
70 21.1 16.0 12.7
70 26.2 17.5 12.7
70 20.3 15.9 12.8
70 24.2 18.1 14.1
70 31.0 18.5 11.9
Table 6-tangent delta
Dynamic testing results--tangent delta
Aging condition Selected data
from tempera-
Temp. Time Gas Pressure ture sweep
([degrees]C) (hours) mix (kPa)
(%[O.sub.2]) -25[degrees]C
21 0 21 101.3 0.432
70 24 21 101.3 0.480
70 72 21 101.3 0.428
70 168 21 101.3 0.449
70 24 21 2,068 0.498
70 72 21 2,068 0.436
70 168 21 2,068 0.398
70 24 50 2,068 0.420
70 72 50 2,068 0.413
70 168 50 2,068 0.409
70 24 100 2,068 0.436
70 72 100 2,068 0.422
70 168 100 2,068 0.430
Selected data from
temperature sweep
Temp.
([degrees]C) 0[degrees]C 25[degrees]C 60[degrees]C
21 0.210 0.156 0.122
70 0.219 0.158 0.121
70 0.196 0.142 0.112
70 0.207 0.151 0.118
70 0.221 0.167 0.131
70 0.211 0.165 0.132
70 0.207 0.165 0.133
70 0.198 0.153 0.123
70 0.206 0.162 0.130
70 0.236 0.189 0.151
70 0.198 0.154 0.124
70 0.219 0.176 0.142
70 0.265 0.221 0.194
References (1.) A. Ahagon. M. Kida and H. Kaidou. "Aging of tire parts during service--I: Types of aging in heavy-duty tires," Rubber Chem. Technol., 63, 683 (1990). (2.) S. Govindjee, Firestone fire·stone n. 1. A flint or pyrite used to strike a fire. 2. A fire-resistant stone, such as certain sandstones. Noun 1. Tire Failure Analysis, http://www.bridgestone-firestone.com/news/media_center_fr.html, Jan-uary 30, 2001. pp. 1-73. (3.) R. W. Keller, "Oxidation and ozonation of rubber," Rubber Chem. Technol., 58, 637 (1985). (4.) B. Stenberg, L. Peterson, P. Flink and F. Bjork, "Effect of butyl rubber butyl rubber: see rubber. coating on accelerated aging of natural rubber," Rubber Chem. Technol., 59, 70 (1986). (5.) G.R. Hamed, "Engineering with rubber: How to design rubber components," Gent, A.N., ed., Hanser, chapter 2. (6.) A.N. Gent, "Some chemical effects in fatigue cracking of vulcanized rubbers India rubber, vulcanized. - Knight. See also: Vulcanize ," 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. , vol. 6, Issue 23, September/October 1962, pp. 497-502. (7.) A.N. Gent, G.L. Liu and T. Sueyasu, "Effect temperature and oxygen on the strength of elastomers," Rubber Chem. Technol., 64, 96 (1991). (8.) K. Ono, A. Kaeriyama and K. Murakami, "Effects of diffusion in the oxidative degradation of 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 rubbers--I: Rate of chain scission in the steady state," Journal Polymer Science: Polymer Chemistry Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules. , ed. 13, 2,615-2,620 (1975), pp. 43-48. (9.) K.T. Gillen, R.L. Clough n. 1. A cleft in a hill; a ravine; a narrow valley. 2. A sluice used in returning water to a channel after depositing its sediment on the flooded land. 1. (Com.) An allowance in weighing. See Cloff. and J. Wise, "Prediction of elastomer lifetimes from accelerated thermal aging experiments," American Chemical Society The American Chemical Society (ACS) is a learned society (professional association) based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has over 160,000 members at all degree-levels and in , 1996, pp. 557-575. (10.) I.R. Goodchild and T.J. Pond. "Effect of aerobic aging at elevated temperatures on dynamic mechanical properties of certain natural rubber vulcanizates," Journal of Natural Rubber Research, vol. 12 (1), 1997, pp. 1-10. |
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