Mechanical properties of HDPE/bark flour composites

Tensile and impact properties of Neem bark flour (BF) containing high density polyethylene (HDPE) composites were studied at 0-0.26 volume fraction of filler. Tensile modulus and strength and breaking elongation decreased with increase in BF concentration. The decrease in tensile modulus and strength was attributed to the decrease in crystallinity of the polymer compared to the imposed mechanical restraint by the BE Analysis of tensile strength data indicated formation of stress concentration in the interphase. Because of this stress concentration and the mechanical restraint, the elongation-at-break and Izod impact strength decreased. Use of a coupling agent, HDPE-g-MAH, brings about enhanced phase adhesion, increasing the tensile modulus and strength. Enhanced adhesion marginally lowers composite ductility at higher filler contents and aids stress transfer increasing the Izod impact strength inappreciably. Scanning electron microscopic studies indicated better dispersion of BF particles and enhanced interphase adhesion in presence of the coupling agent. (c) 2007 Wiley Periodicals, Inc.