Effects of Accelerator Type and Curing Temperature on Crosslink Distributions and Tensile Properties of Natural-Acrylic Rubber Blends

Abstract

Abstract Effects of curing temperature and accelerator type on tensile properties of natural-acrylic rubber blends (NR:ACM) were investigated. Three different types of accelerators namely, MBT, ZDEC and DPG, were separately compounded with the rubber blends (50/50, % w/w) along with stearic acid, ZnO, sodium stearate, and sulfur (S) on a two-roll mill. The compounded blends were vulcanized to their optimum cure time in a hydraulic press at 150 and 170 °C. Morphology and tensile properties of the rubber blends were determined by using a scanning electron microscope and a universal testing machine, respectively. Crosslinking characteristics of both NR and ACM phases in the rubber blends were investigated by using a swollen state 1H-NMR and a differential swelling technique. From the tensile test, it was found that strength and strain of the blend vulcanized with the S/ZDEC curing system were remarkably lower than those of the blends vulcanized with the S/MBT and S/DPG systems. The superior tensile properties of the two latter blending systems were accompanied by greater chain mobility of both of the NR and ACM molecules, along with a lower volume fraction of rubber in swollen gel (Vr) of the both NR and ACM phases. These changes were discussed in the light of various possibilities including curative distribution, which were affected by the accelerator type. In term of the effects of curing temperature, it was found that Vr and tensile properties of the blends did not significantly change with the temperature.