Effect of damp‐heat aging on the structures and properties of ethylene‐vinyl acetate copolymers with different vinyl acetate contents

Abstract We reported herein the damp‐heat aging of ethylene‐vinyl acetate copolymers (EVA) with different vinyl acetate (VAc) contents simultaneously for weeks. The aging was carried out under temperature of 40°C and relative humidity of 93% in air atmosphere. The changes of copolymers' structures and properties were investigated by means of FTIR, wide angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) and mechanical tests. CI values derived from ATR‐FTIR spectra have a decrease when aging time is 1 week and then increase during damp‐heat aging process which suggests the first loss then incorporation of OC group. WAXD infer that the narrowing trend of FWHM and increase of crystal sizes may attribute to the melting and re‐crystallization of secondary crystallization, which is also confirmed by DSC results. Mechanical tests including Shore A and Shore D hardness, modulus at 100%, tensile strength and elongation at break, are all depending on the primary crystallization and influenced little by damp‐heat aging. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009