Effect of different film preparation procedures on the thermal, morphological and mechanical properties of pure and calcite-filled HDPE films

摘要

The effect of different film preparation procedures on the thermal, morphological and mechanical properties of high density polyethylene (HDPE) films have been studied using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultimate tensile testing. Film preparation procedures included variation in cooling methods, including quenching, forces (fanning) and natural cooling and techniques such as extrusion followed by melt squeezing and compression molding. The heat of fusion (from DSC), the degree of crystallinity (from WAXRD) and the crystallite size (from WAXRD and AFM) were found to be highest for naturally cooled specimens, followed by fan-cooled and quenched ones. AFM images of surface topology exhibit stacked lamellar morphology for forcefully cooled (fan-cooled and quenched) samples and spherulitic 'lozenges' for naturally cooled ones. The Young's modulus and yield stress [from the universal testing machine (UTM)] were highest for naturally cooled samples, followed by fan-cooled and quenched ones. Among the calcite-filled composites, the 'base film,' which was prepared by extrusion followed by melt squeezing and natural cooling, exhibited the lowest heat of fusion and degree of crystallinity and a similar crystallite size relative to compression-molded films. Lower yield stress, tensile strength and Young's modulus and higher elongation at break were observed for the base film in comparison to the naturally cooled composite film. The low degree of crystallinity and crystallite size in the 'base film' explain all of its mechanical and morphological properties. (C) 2003 Wiley Periodicals, Inc. J Appl Polyrn Sci 91: 1427-1434, 2004. [References: 18]