Considering factors for analysis of crosslink density of poly(ethylene-co-vinyl acetate) compounds

Relationship between crosslink densities of peroxide cured poly(ethylene-co-vinyl acetate) (EVA) and delta torques of EVA compounds in cure curves was examined, and considering factors for analysis of crosslink densities of EVA articles were investigated. The relationship between crosslink densities and delta torques of EVA samples was not found to be correlated when EVAs with different VA contents and co-crosslinker (triallyl isocyanurate, TAC) were used. Though the delta torques of EVA compounds with the different VA contents were nearly the same, crosslink density of the EVA sample with the low VA content was greater than that with the high one. And the delta torques of EVA compounds containing the co-crosslinker were much larger than those without the co-crosslinker though crosslink densities of the EVA samples were nearly the same irrespective of the co-crosslinker. From the experimental results, considering factors for analysis of crosslink densities of EVA articles were found to be formation of semi-crosslink points by crystalline structure of the ethylene sequences of EVA and long crosslink points formed by the co-crosslinker and VA moiety. Increase of the crystalline structure increased the crosslink density, whereas formation of long crosslink points led to higher swelling ratio.