Exploring the influence of electron beam irradiation on the morphology, physico-mechanical, thermal behaviour and performance properties of EVA and TPU blends

Abstract

The effects of electron beam radiation (EBR) on the blends of ethylene vinyl acetate/thermoplastic polyurethane (EVA/TPU) at two different blend ratios prepared via melt blending technique were investigated. All the samples were irradiated by using a 2.5 MeV electron beam accelerating energy over a dose range from 25 to 200 kGy. The blends exhibit drastic improvement in the mechanical properties with increasing radiation dose upto an optimum dosage, beyond which the properties began to deteriorate. Modification of the blends via EBR enhances the elastic recovery of the blends resulting significant improvement in tension set behaviour. DSC study shows that electron beam irradiation causes a marginal change in melting temperature (T_m), glass transition temperature (T_g) and crystallization peak temperature (T_c) of EVA/TPU blends. Dynamic mechanical analysis (DMA) was conducted to investigate the change of loss tangent and storage modulus with varying radiation dose. Thermogravimetric analysis (TGA) suggests that irradiation induced crosslinks also help to improve the thermal stability of the blends to some extent. Scanning electron microscopy (SEM) study was performed to explore the changes in morphology before and after irradiation. All the irradiated blends have higher electrical resistivity than the blends without irradiation and the volume resistivity increases upto 150 kGy. The samples were found to exhibit remarkable improvement in oil resistance property after irradiation which is more prominent in EVA/TPU 70/30 blends.