Electron beam irradiation for enhancing the properties of natural rubber latex

Abstract

Raw rubber must be vulcanized to produce a useful rubber product. Vulcanization is a chemical process that creates crosslinking points between rubber molecules, transforming it into a thermosetting material. This study aimed to prepare vulcanized natural rubber latex containing a sulfur curing package by irradiating it with electron beams at doses of 1–30 kGy. The crosslink density increased with increasing electron doses. Additionally, electron beam irradiation increased the entanglement of rubber molecules, resulting in superior mechanical properties such as modulus, tensile strength, elongation at break, and tear strength in the natural rubber latex. However, when high electron doses (>10 kGy) were applied, the crosslink density reduced owing to polymer degradation or chain scission, leading to inferior mechanical properties. To evaluate the potential of using irradiation as a replacement for conventional vulcanization processes, the properties of natural rubber latex containing a sulfur curing package vulcanized by electron beam irradiation were compared with those vulcanized by heat (conventional process). The mechanical properties of the natural rubber latex vulcanized by electron beam irradiation were superior to those of the rubber vulcanized by heat, with a 40% increase in modulus, 80% increase in tensile strength, 14% increase in elongation at break, and 36% increase in tear strength. According to these findings, electron beam irradiation, which offers high productivity and shorter processing time, is a suitable vulcanization process for natural rubber latex containing a sulfur curing package, with electron doses of 5 and 10 kGy providing superior overall balanced properties.