State of Cure of Neoprene Vulcanizates. Measurement by the T-50 Test

Abstract

Abstract Generally the physical properties of elastomer vulcanizates are considered to depend on their states of cure. Although many tests for measuring the state of cure have been developed, none are completely satisfactory. Some of them fail to distinguish between the physical or chemical effects of compounding ingredients, others are too laborious to be of practical value. The T-50 test developed by Gibbons, Gerke, and Tingey for natural rubber vulcanizates eliminates some of these difficulties and further reduces the number of tests required for production control. The T-50 test is based on the retraction of a stretched and frozen specimen with an increase in temperature. The temperature at which the sample retracts to 50 per cent of its initial frozen elongation is termed the T-50 value. From a physical standpoint the test is sensitive, precise, and easily performed. From a chemical standpoint the original workers as well as Vila showed that, for any specific natural rubber composition, the T-50 value correlates with the amount of combined sulfur. Since the state of cure of a rubber vulcanizate is frequently discussed in terms of combined sulfur, the T-50 test offers a correlation of the state of cure with combined sulfur without the necessity for involved chemical analyses.