Electron Beam Irradiation of Noncrosslinked LDPE–EVA Foam

Abstract

The conventional cross-linking method using an electron beam for polyolefin foams is highly efficient, but the drawbacks are: costly equipment, nonuniform crosslinking, uneven dispersion of chemical foaming agents and additives, and relatively low gel content, which affect physical properties of the foam. In this paper, low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) were blended in an 80/20 ratio, and this noncrosslinked foam was exposed to various doses of electron beam irradiation in air. The foam was made using isobutane as the blowing agent. It has been found that foam with uniform cell structure was not achieved in the case of precrosslinked foam with more than 40% gel fraction. On the other hand, noncrosslinked foams are easily crosslinked to a gel content of about 57% with an electron beam irradiation under optimum conditions. The gel content of the postcrosslinked foams increases with increase in the irradiation dose, beam intensity, irradiation temperature and with the crosslinking coagent content. As derived from experimental studies, beam intensity seems to be the most essential parameter in regard to gel content homogeneity. Noticeable changes in mechanical properties, e.g. tensile strength, tear strength, compressive strength and hardness, were also observed. This paper also presents an experimental study on the manufacture of low-density open-cell foam.

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

“…This means that the polymer chains after being cross-linked are less capable of being deformed under the pressure exerted by the gas molecules, which could make the cells to grow slower and give lower expansion rates as reported by several previous works in the literature (Kim and Kim, 2002;Klempner and Frisch, 1991;Sagane and Harayama, 1981;Wang et al, 2013;Youssef et al, 2007).…”

Microstructure, physical, and mechanical properties of LDPE/UHMWPE blend foams

“…[25][26][27][28][29][30][31][32][33] The results revealed that the control factor of gel content is mostly the foam cross-linking agent and the other parameters such as foaming temperature, foaming time, and foaming agent did not show significant influence on the gel content. 31,[34][35][36] The results suggested that increasing of cross-linking agent led to increase in the gel content. Based on the previous studies, increasing of the foaming agent slightly decrease the gel content.…”