Composition-dependent properties of polyethylene/kaolin composites part IV- Thermophysical characterization of the deformation behavior of polyethylene/kaolin composites

The deformation behavior at room temperature of injection-molded and blow-m olded samples of high-density polyethylene (HDPE) differing in orientation (with respect to the melt flow direction) and in filler content (untreated and surface,treated kaolin, respectively) were characterized by the stretch ing calorimetry technique. Samples with longitudinal and transversal orient ations were examined. Strain-softening and strain-hardening phenomena were observed, respectively, in the range of inelastic strains above the yield p oint. The depression of yield stresses for the filled composites compared t o those for the corresponding neat polymers is associated with the onset of debonding of the matrix polymer from the filler surface. The analysis of t he energy balance of the debonding process suggests that the fraction of a debonded interface is smaller in samples containing a coupling agent and la rger filler particles.