Structure-Property Analysis of Unfilled Polyisoprene (IR) Vulcanizates Characterized by Mechanical and Rheological Measurements

Rubber vulcanization systems have inherent advantages and disadvantages that are directly related to their structure-property relationships.  The balance of static and dynamic physical properties and heat resistance is quite different for rubber articles cured by sulfur or peroxide systems.

In this study, the use of mechanical and analytical tests were be used to characterize the crosslink network differences that are unique to each vulcanization system. Understanding of the fundamental differences between networks of these disparate systems help to better understand the effect of networks on physical properties. Unfilled NR was cured to a constant crosslink density using either semi-efficient sulfur vulcanization system or dicumyl peroxide in combination with several different monomeric coagent species. Variations in the resulting network structures were characterized using tensile properties (modulus, tear strength, elongation, etc.) and the structure-property relationships were further probed using complex rheological tests and analytical measurements (time domain NMR, DMA, FTIR, etc.). The results will provide a direct comparative analysis of the two vulcanization systems, establishing structure-property relationships for each.