Improvements of physical and mechanical properties of electron beam irradiation—crosslinked EVA foams

Abstract

In this work, ethylene–vinyl acetate (EVA) copolymer foams were prepared and crosslinked by using high‐energy electron beam (e‐beam) radiation (10 MeV). The effect of parameters such as irradiation dose, the contents of foaming agent, radiation activator, and radiation sensitizer on improvement of physical and mechanical properties of the EVA foamed samples were investigated. The foams were obtained through a four‐step process of melt mixing, forming, crosslinking, and foaming. During the melt mixing process EVA was compounded with different amounts of azodicarbonamide (ADCA) as a blowing agent, zinc oxide (ZnO) as a radiation activator, and trimethylol propane‐trimethacrylate (TMPTMA) as a radiation sensitizer. The samples were compression molded into flat sheets at low temperature (110°C) and were then radiation‐crosslinked by 20–80 kGy e‐beam. Finally, the crosslinked samples were converted to foams by a high temperature (210°C) compression molding process. The foamed samples were analyzed in terms of gel content, density, compression molding set, tensile properties, and micro‐structural features. It was found that an increase in absorbed radiation dosage increases crosslink density, elasticity, percentage recovery, tensile strength, and compression properties of the EVA foams. Due to the increased recovery the percentage of compression set was reduced. Similarly increasing the TMPTMA content in the formulation increased the crosslink density and the resulting mechanical properties. Contrary to these findings, addition of ADCA led to the formation of extra gases which in turn reduced the crosslink density, and resulted in the deterioration of the mechanical properties and hence an increase in the compression set. However, addition of ZnO and TMPTMA led to the formation of smaller and more uniform cell size with improved mechanical properties. Copyright © 2008 John Wiley & Sons, Ltd.

Study of the Foaming Kinetics in Epoxidized Natural Rubber Foams Crosslinked by Electron Beam Irradiation

“…For instance, the irradiation process is being used in the foam industry to produce flexible closed‐cell polyolefin foams . Several articles have been found in scientific literature which deal with the production of crosslinked polyolefin foams that have been previously irradiated to promote crosslinking and most of them are focused on studying how the absorbed dose influences their cellular structures. In general, when the absorbed dose increases the cell size decreases and the cell density increases.…”

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

“…It has been reported that the irradiation process is industrially used for the production of flexible closed-cell polyolefin foams (Rodríguez-Pérez, 2005). Moreover, a lot of scientific works have been published in the recent years dealing with the subject (Dias and Silva, 2007;I-Chun et al, 2004;Rezaeiana et al, 2009;Wang et al, 2013;Xing et al, 2008;Youssef et al, 2007) and most of them focused on studying the ID influence towards the obtained cellular structures. In the work of Wang et al several irradiation doses (25, 50, 75 and 100 kGy) were employed for the production of foams based on blends of LDPE/EVA by a physical foaming process where CO 2 was used as the blowing agent.…”

The role of nanofillers on (natural rubber)/(ethylene vinyl acetate)/clay nanocomposite in blending and foaming

“…Ethylene vinyl acetate copolymer (EVA), a copolymer of ethylene and vinyl acetate, is one of the polymers popularly used for the manufacturing of polymeric foam , because it has good property combination, such as resistance to chemicals, ozone, ultraviolet radiation, and flexibility. The EVA materials containing a medium content of VA (30%) have similar properties of rubber but can be processed like ordinary thermoplastics.…”