TOUGHENED THERMOPLASTIC COMPOSITE .1. CROSS-LINKABLE PHENOL FORMALDEHYDE AND EPOXY RESINS-COATED CELLULOSIC-FILLED POLYPROPYLENE COMPOSITES

Composites of polypropylene (PP) or maleic-anhydride-modified polypropylene (MAH-PP) with uncoated or thermosetting resin-coated sawdust or explosion pulp (V-pulp) were prepared by dynamic cross-linking and their properties were compared to those of unmodified and uncross-linked composites. The effects of modification and dynamic cross-linking on the interfacial adhesion between polymer and filler have also been investigated by a solvent extraction study and microscopic analysis. The new method of dynamic cross-linking in combination with the additional effect of compatibilization suggests a practical route to obtain high-strength, toughened thermoplastic composites. Dynamically cross-linked epoxy-or phenolic resin-coated sawdust or V-pulp that can be grafted or can have affinity to MAH-PP was found to improve tensile strength as well as elongation at yield point. The tensile toughness of the dynamically cross-linked-compatibilized composites is better than that of an uncross-linked composite of MAH-PP and sawdust. The improved toughness of the dynamically cured composites appears to be that further chemical bonds form between coated filler and MAH-PP in addition to grafting of MAH-PP onto cellulose chain.