Effects of Foaming Temperature and Carbon Black Content on the Cure Characteristics and Mechanical Properties of Natural Rubber Foams

Abstract

The influences of the foaming temperature and carbon black content on the cure behavior and me- chanical properties of the NR (natural rubber) foams were investigated at various temperatures and different feeding ratios of the carbon black. The physical properties of the foamed NRs were then measured as a func- tion of the foaming temperature and carbon black content. The optimal temperature for vulcanization and foaming of NRs in this study was 155 o C; where the density of the foamed NRs was lower than those at 145 and 150 o C. The cure rate index of the NRs foamed at 145 o C was smaller than those at 150 and 155 o C. The results of the expansion ratio and micrographs of the foamed NRs supported the density characteristics. The tensile properties of the foamed NRs, such as tensile strength, tear strength, and modulus, gradually increased upon increasing the carbon black content, while the elongation at break decreased. The increase of the foaming temperature led to different results relative to those from the increase of the carbon black content.