Crystalline property change of poly(ethylene‐co‐vinyl acetate) by compounding and curing procedures

Influence of manufacturing processes of poly(ethylene‐co‐vinyl acetate) (EVA) on the crystalline properties was investigated using various EVAs with different VA contents. Four compounds with different compositions for each EVA were prepared to examine the influence of the ingredients. Stearic acid, dicumyl peroxide (DCP, crosslinking agent), triallyl cyanurate (TAC, co‐crosslinker), and azodicarbonamide (JTR, blowing agent) were employed as principal ingredients. By compounding, percentage crystallinities (Xcs) increased irrespective of kinds of the EVAs and their compound formulations. It was found that stearic acid, TAC, and JTR improved crystallinities of the EVA compounds. And milling process could accelerate crystal formation of EVA chains by strain‐induced crystallization. The Xcs of the EVA compounds were notably decreased through curing process, but some EVA vulcanizates showed greater Xcs than their raw EVAs. Especially, the EVA foam samples had higher Xcs than their raw EVAs and it could be explained with compression of EVA chains by blowing. Xc changes of the two crystals of [110] and [200] by the ingredients and manufacturing procedures were also examined. The Xc ratios of [110]/[200] of the foam samples were greater than those of the unfoamed ones.