Wood fiber/high density polyethylene composites: Ability of additives to enhance mechanical properties

Improvement of mechanical properties, for a composite of Aspen Hardwood fibers and recycled High Density Polyethylene (HDPE), can be achieved by the inclusion of additives. The four additives investigated in this study were: Ionomer Modified Polyethylene (Surlyn), Maleic Anhydride Modified Polypropylene (MAPP), and two Low Molecular Weight Polypropylenes (Proflow 1000 and Proflow 3000). Each additive was combined with recycled HDPE and Aspen Hardwood fibers in a twin-screw extruder to form the composite, and then compression molded. Creep, water sorption, tensile properties and impact strength were evaluated following ASTM standard procedures. All composites were approximately 40% by weight Aspen hardwood fibers. The effects of Surlyn and MAPP were studied at 1%, 3%, and 5% weight ratios. The effects of Proflow 1000 and Proflow 3000 were studied utilizing 5% additive. The inclusion of MAPP in the composite improved its mechanical properties overall. Addition of Surlyn produced some positive effects but not at a statistically significant level. The inclusion of Proflow 1000 and Proflow 3000 generally decreased the mechanical properties of the composites.