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The Effect of Thiuram Variations When Used As Primary Accelerators in Sulfur-Cured EPDM Compounds
Thiurams are a family of organic accelerators known for their high rate of cure and ability to create high crosslink densities in sulfur-cured natural and synthetic elastomers. As sulfur donors, thiurams are used in cure systems where short cure times, low sulfur, and excellent heat resistant compounds are desired. They are commonly used to modify thiazole and sulfenamide cure systems to reduce scorch times, as well as improve overall state of cure. Today, there are many variations of thiurams which are commonly used in the rubber industry as primary and secondary accelerators, as well as activators for other cure systems when used in small amounts. Each variation contains slight differences in chemical structure. While maintaining the same thiuram functional group, which is responsible for the vulcanization characteristics, there are differences in other functional groups making up the other regions of the molecule. These other functional groups, while relatively inactive, influence the vulcanization in ways that can be utilized to obtain certain desired properties that cannot be done with other thiuram variations.
The focus of this paper is to observe the differences in rheology and physical properties of sulfur cured EPDM compounds when various thiurams are used as primary accelerators. Results will show how thiurams provide exceptional crosslink density, improving material performance and processability, while increasing the overall rate and state of cure. Each thiuram variation will affect each property differently, and these differences will be compared to provide insight into thiuram selection when compounding new material.