Effect of Foaming Temperature and Blowing Agent Content on Cure Characteristics, Mechanical and Morphological Properties of Natural Rubber Foams

Abstract

Influences of foaming temperature (i.e. 150 and 160OC) and blowing agent content on cure characteristics, mechanical and morphological properties of natural rubber (NR) foams were investigated. The blowing agent used in this study was oxybis (benzene sulfonyl) hydrazide (OBSH). The expandable rubber samples were prepared using a conventional compression molding technique via a heat transfer foaming process and an air-circulating oven. For cure behavior, it was found that maximum torque and torque difference tended to decrease with increasing the OBSH content for both processing temperatures. Decreasing of cure time was observed at 3 phr of the OBSH content and then it tended to increase. Moreover, cure time and scorch time decreased with increasing foaming temperature. As a result, the NR foam with large cell size and non-uniform foam cell distribution was observed. Mechanical properties of the NR foam in a term of hardness gradually decreased upon increasing the OBSH content. Whilst compression set increased with increasing the OBSH content up to 6 phr after that it decreased.