A combination of poly(diphenylmethane diisocyanate) and stearic anhydride as a novel compatibilizer for wood-polyethylene composites

A combination of poly(diphenylmethane diisocyanate) (PMDI) and stearic anhydride was investigated as a new compatibilizer system for improving the interfacial adhesion between wood and polyethylene (PE). The treatment of wood flour with PMDl increased both the modulus-of-rupture (MOR) and the modulus-of-elasticity (MOE) of the resulting wood-PE composites. The combination of stearic anhydride and PMDl further increased both MOR and MOE of the resulting composites. Compared with the commercially used compatibilizer maleic-anhydride-grafted polyethylene (MAPE), the PMDI-stearic anhydride compatibilizer system resulted in significantly higher MOR and MOE. The moisture content of wood flour affected the compatibilization of both the PMDI-stearic anhydride compatibilizer system and MAPE. The compatibilization mechanisms of PMDI-stearic anhydride system were investigated in detail. Water-resistance tests indicated that the composites with the PMDI-stearic anhydride system were statistically more water-resistant than those with MAPE.