Journal of Applied Polymer Science, Vol.67, No.9, 1503-1513, 1998
Mechanical properties and morphology of impact modified polypropylene - Wood flour composites
The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene-ethylene/butylene-styrene triblock copolymer (SEES-MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEES gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEES had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM-MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1-1 mu m.
Keywords:MALEATED POLYPROPYLENE;COMMON THERMOPLASTICS;FILLED POLYPROPYLENE;CELLULOSIC FILLERS;SYNTHETIC-POLYMERS;PROCESSING AIDS;COUPLING AGENTS;BLENDS;POLYETHYLENE;EFFICIENCY