Influence of compatibilizers on the surface hardness, water uptake and themechanical properties of poly(propylene) wood flour composites prepared byreactive extrusion

Anisotropic wood flour (WF) particles, composed of fiber bundles, were melt compounded in a twin screw extruder at 200 degrees C together with poly(pr opylene) (PP) in the presence of maleic anhydride-grafted poly(propylene) ( PP-g-MA) and maleic anhydride-graftedpoly(styrene)-block-poly(ethene-co-1-b utene)-block-poly(styrene) (SEBS-g-MA). Mechanical properties, surface hard ness and water uptake were monitored as a function of compound composition and type of compatibilizer. PP/WF/SEBS-g-MA containing 30 vol.-% (40 wt.-%) WF and 3.5 vol.-% (3 wt.-%) SEBS-g-MA gave Shore hardness of 78 with respe ct to 70 for PP and increased simultaneously Young's modulus (100%), yield stress (20%) and notched Izod impact strength (24%). SEBS-g-MA compatibiliz er addition did not affect the surface hardness but accounted for substanti ally reduced water uptake and excellent interfacial adhesion. In comparison to talcum-filled PP,PP/WF/SEBS-g-MA composites exhibited lower density com bined with higher specific strength, specific Young's modulus, and higher s urface hardness. WF particle as well as composite morphologies were imaged by means of environmental scanning electron microscopy (ESEM).