Mechanical properties of wood-fiber reinforced polypropylene composites: Effect of a novel compatibilizer with isocyanate functional group

Natural fibers are increasingly being used as reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. While the maleic anhydride modified polypropylene (MAPP) is most commonly used as compatibilizer to improve interfacial adhesion between hydrophilic wood fibers and hydrophobic polypropylene, in this study, a novel compatibilizer (M-TMI-gPP) with isocyanate functional group was synthesized by grafting m-isopropenyl-alpha,alpha-dimethylbenzyl-isocyanate (M-TMI) onto isotactic polypropylene (PP) in a twin screw extruder. The effect of filler concentration on the mechanical properties of wood-fiber filled composites, prepared by using m-TMI-g-PP as the compatibilizer, was investigated. The addition of the compatibilizer resulted in greater reinforcement of composites, as indicated by the improvement in mechanical properties. Tensile strength of composites so prepared increased by almost 45%, whereas 85% increase in flexural properties was observed. However the addition of wood-fibers resulted in a decrease in elongation at break and impact strength of the composites. (c) 2006 Elsevier Ltd. All rights reserved.