Improvement of interfacial adhesion between wood and polypropylene in wood-polypropylene composites

摘要

N-vinylformamide-grafted polypropylene(VFPP)was successfully synthesized through a free radical grafting reaction.Both polymeric methylene diphenyl diisocyanate(PMDI)and VFPP were effective compatibilizers for increasing both the strength and stiffness of the resulting wood-PP(polypropylene)composites.Both the modulus of rupture(MOR)and the modulus of elasticity(MOE)of the resulting wood-PP composites were further increased when PMDI and VFPP were used together as an integrated compatibilizer system.This new PMDI-VFPP compatibilizer system was comparable to maleic-anhydride-grafted polypropylene in terms of enhancing the strength and stiffness of the wood-PP composites.Study of the fractured surfaces of the wood-PP composites with scanning electron microscopy revealed that this new PMDI-VFPP compatibilizer system greatly improved the interfacial adhesion between wood and PP.This PMDI-VFPP compatibilizer system also greatly reduced the water absorption of the resulting wood-PP composites.In this PMDI-VFPP compatibilizer system,PMDI is proposed to function as a wood-binding domain and VFPP to function as a PP-binding domain.PMDI reacted with the amide group in VFPP,thus forming covalent linkages between PMDI and VFPP.