English Abstract

Qualitative Analysis of Cross-linked Ethylene Vinyl Acetate/Polyethylene Blended Foam

Kenichi HARANO
Asics Corp., Kobe, Hyogo, Japan
Nippon Gomu Kyokaishi,(2017),90(8),375-381 Original Paper in Japanese

Ethylene vinyl acetate (EVA) foams with good cushioning and durability have been widely applied as packing materials and sport equipments. Recently, EVA blended with polyethylene (PE) has been studied in order to improve the lightness and cushioning property. Because of cross-linkage of the blended foam, it is difficult to distinguish them by the conventional analysis techniques. In this study, a new analytical method with acetic acid elimination treatment technique is investigated. The crystallization temperature (Tc) of original and treated EVA/PE blended foam was both analyzed by using differential scanning calorimetry (DSC). As a result, after the treatment, Tc of EVA became higher while Tc of PE did not change. Therefore it was confirmed that the cross-linked EVA/PE blended foam can be analyzed. However, this method was not applicable to the specific foams consisting mainly of linear low density polyethylene (LLDPE) and of small amount of EVA. In these foams, Tc of PE also became higher after the treatment. In the above foams, a trace amount of non-cross-linked components was focused. They were extracted with tetrahydrofuran, fractionated with gel permeation chromatography (GPC) and analyzed with fourier transform infrared spectroscopy (FT-IR). The content of vinyl acetate in EVA and the blended ratio of EVA and PE can be analyzed by this method.

Keywords: Ethylene vinyl acetate, Polyethylene, Cross-linked, Foam, Acetic acid elimination, DSC, GPC, FT-IR