Plasma Modified and Unmodified Polyethylene as Filler in Natural Rubber Compounds: Morphology, Cure Behavior and Vulcanization Kinetics

Abstract

The present paper investigates the influence of polyethylene (PE) and plasma modified polyethylene (PPE) as fillers in natural rubber (NR) compound. The NR/PE and NR/PPE compounds were prepared through mechanical mixing using two roll mill by varying their compositions. The morphology of the compounds was analyzed in detail using field emission scanning electron microscopy (FESEM) to understand the dispersion of PE and PPE in the NR matrix as well as its interfacial adhesion. Morphological analysis revealed that unmodified polyethylene was nicely dispersed in the NR matrix whereas plasma modified polyethylene showed agglomerated structure due to the polar functional groups on the PPE surface. The vulcanization kinetics and cure characteristics of natural rubber compounds containing PE and PPE were examined using an oscillating disc rheometer. The cure behavior of the composites were studied at different temperatures (140, 160, and 180 °C) using conventional sulphur vulcanization system. The addition of polyethylene influenced the cure properties to a great extent. Theoretical modeling was done to follow the mechanism of the cure reaction. The cure reaction was kinetically controlled at the beginning followed by the diffusion mechanism. The curing reaction was found to be autocatalytic and extent of reaction increased with increasing temperature.