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5.1 Viscosity—Viscosity values determined by this test method depend on molecular structure, molecular weight, and non-rubber constituents that may be present. Since rubber behaves as a non-Newtonian fluid, no simple relationship exists between the molecular weight and the viscosity. Therefore, caution must be exercised in interpreting viscosity values of rubber, particularly in cases where molecular weight is very high. For example, as the molecular weight increases, the viscosity values for IIR polymers (butyl rubbers) reach an upper limit of about 80, at 100°C (212°F) using a large rotor at a rotation speed of 2 r/min, and may then decrease to considerably lower values. For these higher molecular weight rubbers, better correlation between viscosity values and molecular weight is obtained if the test temperature is increased.5.2 Stress Relaxation—The stress relaxation behavior of rubber is a combination of both an elastic and a viscous response. Viscosity and stress relaxation behavior do not depend on such factors as molecular weight and non-rubber constituents in the same way. Thus both of these tests are important and complement each other. A slow rate of relaxation indicates a higher elastic component in the overall response, while a rapid rate of relaxation indicates a higher viscous component. The rate of stress relaxation has been found to correlate with rubber structure characteristics such as molecular weight distribution, chain branching, and gel content.5.3 Pre-Vulcanization Characteristics—The onset of vulcanization can be detected with the Mooney viscometer as evidenced by an increase in viscosity. Therefore, this test method can be used to measure incipient cure (scorch) time and the rate of cure during very early stages of vulcanization. This test method cannot be used to study complete vulcanization because the continuous rotation of the disk will result in slippage when the specimen reaches a stiff consistency.1.1 These test methods cover procedures for measuring a property called Mooney viscosity. Mooney viscosity is defined as the shearing torque resisting rotation of a cylindrical metal disk (or rotor) embedded in rubber within a cylindrical cavity. The dimensions of the shearing disk viscometer, test temperatures, and procedures for determining Mooney viscosity are defined in these test methods.1.2 When disk rotation is abruptly stopped, the torque or stress on the rotor decreases at some rate depending on the rubber being tested and the temperature of the test. This is called “stress relaxation” and these test methods describe a test method for measuring this relaxation.NOTE 1: Viscosity as used in these test methods is not a true viscosity and should be interpreted to mean Mooney viscosity, a measure of shearing torque averaged over a range of shearing rates. Stress relaxation is also a function of the test configuration and for these test methods the results are unique to the Mooney viscometer.1.3 When compounded rubber is placed in the Mooney viscometer at a temperature at which vulcanization may occur, the vulcanization reaction produces an increase in torque. These test methods include procedures for measuring the initial rate of rubber vulcanization.1.4 ISO 289 Parts 1 and 2 also describes the determination of Mooney viscosity and pre-vulcanization characteristics. In addition to a few insignificant differences there are major technical differences between ISO 289 and this test method in that ISO 289 does not provide for sample preparation on a mill, while this test method allows milling sample preparation in some cases prior to running a Mooney viscosity test. This can result in different viscosity values for some rubbers.1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 This test method is used to determine the vulcanization characteristics of (vulcanizable) rubber compounds.5.2 This test method may be used for quality control in rubber manufacturing processes, for research and development testing of raw-rubber compounded in an evaluation formulation, and for evaluating various raw materials used in preparing (vulcanizable) rubber compounds.1.1 This test method covers the use of the oscillating disk cure meter for determining selected vulcanization characteristics of vulcanizable rubber compounds.1.2 ISO 3417 is very similar to this test method. It has minor technical differences that are not considered to be significant.1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 This test method is used to determine the vulcanization characteristics of (vulcanizable) rubber compounds.5.2 This test method may be used for quality control in rubber manufacturing processes, for research and development testing of raw-rubber compounded in an evaluation formulation, and for evaluating various raw materials used in preparing (vulcanizable) rubber compounds.5.3 The test specimen in a rotorless cure meter approaches the test temperature in a shorter time and there is a better temperature distribution in the test specimen due to the elimination of the unheated rotor found in oscillating disk cure meters.5.4 Several manufacturers produce rotorless cure meters with design differences that may result in different torque responses and cure times for each design. Correlations of test results between cure meters of different designs should be established for each compound tested, and for each set of test conditions.1.1 This test method covers a method for the measurement of selected vulcanization characteristics of rubber compounds using unsealed and sealed torsion shear cure meters. The two types of instruments may not give the same results.NOTE 1: An alternative method for the measurement of vulcanization characteristics is given in Test Method D2084.1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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3.1 Class 1, Sulfenamides: 3.1.1 As a group, the 2-benzothiazyl sulfenamides are the principle sulfur vulcanization accelerators used in the rubber industry today. The role of these materials in vulcanization is dual. They provide scorch time (delay period) in the crosslinking or vulcanization operation at processing temperatures. The delay avoids premature crosslinking during the processing, for example, mixing, extrusion, etc. Once the mixed rubber is at the curing temperature, these materials promote a rapid rate of curing (crosslinking, vulcanization).3.1.2 The presence of certain impurities in this class of materials can affect their performance characteristics.3.1.3 The 2-benzothiazyl sulfenamides are subject to degradation on extended storage. Significance degradation can affect their performance characteristics. In particular, the quality of the material is a function of storage time, temperature, relative humidity, and the impurity profile of the material; for example, free amines, salts of 2-mercaptobenzothiazole, etc. Since sulfenamide degradation in storage is an autocatalytic process (degradation products accelerate further degradation), significant degradation may only occur after a long induction period.3.2 Class 2, Thiazoles—Thiazole derivatives are versatile vulcanization accelerators that are widely used in the rubber industry either alone or in combination with other accelerators.3.3 Class 3, Guanidines—The guanidines have little importance as primary vulcanization accelerators, except for thick-sectioned goods, because of a typically slow vulcanization rate. As secondary accelerators they are used with other accelerators of the thiazole class. These resulting combinations vulcanize faster and give higher levels of vulcanization than do their individual constituents when used separately. The thiazole-guanidine combinations are frequently used for technical rubber goods.3.4 Class 4, Dithiocarbamates—Vulcanization with dithiocarbamates is faster than with thiurams. Dithiocarbamates are used as ultra accelerators with normal sulfur levels. They are also employed as secondaries or activators for other accelerators.3.5 Class 5, Thiurams (disulfides)—Thiuram disulfide accelerators are used for vulcanization without elemental sulfur to produce rubber compounds that show essentially no reversion and that have low compression set and good aging characteristics. For low sulfur vulcanization, thiurams are normally used in combination with sulfenamides. With a normal amount of sulfur, thiurams act as ultra accelerators.3.6 Class 6, Thiurams (other than disulfides)—This class contains other thiuram types that are not disulfides. They are used as ultra accelerators with normal amounts of sulfur. Di, tetra, and hexasulfides can be employed without sulfur or with low sulfur levels to obtain rubber compounds with much reduced reversion tendencies.3.7 The chemical or physical characteristics, or both, of these materials may affect their use as vulcanization accelerators.1.1 This classification covers vulcanization accelerators and defines their important chemical and physical characteristics. The properties outlined herein are useful for quality control; they can frequently be directly or indirectly related to the performance characteristics in rubber compounds.1.2 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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