Thermomechanical Properties of Cross-Linked EVA: A Holistic Approach

Abstract

Cross-linked ethylene–vinyl acetate (EVA) is used in technically demanding applications ranging from solar cell encapsulants exposed to years of harsh environments to athletic shoes exposed to countless impact recovery cycles. The thermomechanical properties of this versatile material represent the combined responses of semicrystalline and elastomeric components. To fully describe structure–property relations of cross-linked EVA, it is necessary to explore the combined effects of vinyl acetate content, molecular weight, and chain topology on the thermomechanical properties. The interdependent effects of these factors influence both the amount of crystallinity and the size of the crystallites within the material. Subsequent cross-linking of EVA reduces crystallinity relative to the un-cross-linked starting materials. By controlling the properties of the un-cross-linked starting materials and the degree of cross-linking, it is possible to tune the performance properties of the cross-linked EVA. Understanding these effects enables material selection and property adjustment to meet the demands of existing and emerging applications.