ASTM-D6746 › Standard Test Method for Determination of Green Strength and Stress Relaxation of Raw Rubber or Unvulcanized Compounds
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1.1 This test method covers methods to evaluate a characteristic of raw rubber or unvulcanized rubber compounds that is designated as green strength. This special strength property for uncured rubbers is an important processing performance attribute in rubber product manufacturing.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 and health practices and determine the applicability of regulatory limitations prior to use.
Significance and Use
5.1 The stress-strain properties of unvulcanized rubber (either in a compound or in the raw state) are important to certain processing operations in the rubber industry. These unvulcanized rubber properties are frequently referred to as “green strength.”
5.2 Green strength is determined primarily by the physical and chemical characteristics of polymers, such as molecular weight, tendency to crystallize, degree of branching, and so forth. It is also related to the compound formulation, particularly filler and plasticizer content, and the presence of peptizers. Green strength can be a good indication of processing behavior. It is a particularly important characteristic for all processing operations in which elongation predominates.
5.3 Green strength is dependent on the test piece preparation, rate of extension, and test temperature. Therefore, a single-point method cannot be expected to give correlation between green strength and processing behavior over the whole range of processing conditions.
green; green stress relaxation; raw rubber; rubber; stress relaxation; tensile green modulus; tensile green strength; unvulcanized compounds; yield stress;; ICS Number Code 83.040.20 (Rubber compounding ingredients)
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Jan. 1, 2016