Influence of the irradiation dose in the cellular structure of natural rubber foams cross-linked by electron beam irradiation

Abstract

This work focused on the production of natural rubber foams by cross-linking the polymer matrix using high energy electron beam at different irradiation doses (from 50 to 150 kGy) and foaming it with a chemical blowing agent. The aim was to study how the irradiation dose influenced the cellular structure morphology of the produced foams. This was accomplished by quantifying the evolution of cellular structure parameters, such as cell size and cell density, with respect to foaming time and irradiation dose. The results showed that the foams irradiated at the lowest dose are more prone to suffer cellular structure degeneration, resulting in the formation of bimodal cellular structures, while foams irradiated with the highest dose, exhibited more uniform cellular structure. In the latter case, the nucleation density clearly increased resulting in the formation of foams with homogeneous cellular structures and smaller cell sizes (≈20 μm).