Simple test method for determination of contribution level of crosslink density by crystalline structure of poly(ethylene-co-vinyl acetate) compound

Abstract

Poly(ethylene-co-vinyl acetate) (EVA) has crystalline structures of ethylene sequences and the crystalline regions influence on measurement of crosslink density by swelling method. A simple test method for determination of contribution level of crosslink density by crystalline structure of EVA was developed by employing swelling step at high temperature. Besides normal swelling method at room temperature (D_RT), two novel swelling systems were employed; one is containing high temperature swelling step after drying the free organic ingredients-extracted sample (D_HT) and the other is containing high temperature swelling step without the drying step (ND_HT) in order to dissolve the crystalline regions. Crosslink densities of cured EVA samples measured by the D_RT method were much higher than those by the D_HT and ND_HT ones. The ND_HT method was found to be more efficient for dissolution of the crystalline regions than the D_HT one. Contribution level of the crosslink density by the crystalline structure was obtained by difference in the crosslink densities measured by the D_RT and ND_HT methods, and it was found that the contribution level was about 90%. Influence of co-crosslinker (triallyl isocyanurate, TAC) on the contribution level was also examined.