Abstract: PPg(MAH/St) and PPgMAH were prepared by melt grafting polypropylene(PP) resin with maleic anhydride(MAH) and styrene(St) in a torque rheometer, and were used as compatiblizers in polypropylene/wood flour composites. The structures of PPg(MAH/St) and PPgMAH were confirmed by FTIR analysis. The effect of these two compatiblizers on the microstructure and crystal properties of PP/wood flour composites was examined by SEM and DSC to interpret and explain the difference of processing and mechanical properties of PP/wood flour composites. SEM analysis indicates that wood flour modified by PPg(MAH/St) has better dispersion in the PP matrix with a blurrier interface and better compatibility than that modified by PPgMAH. DSC results show that the heterogeneous nucleation of wood flour to PP in PPg(MAH/St) modified system is stronger and their crystallization temperature and crystallinity increase. The processing and mechanical properties of PP/wood flour composites reveal that PPg(MAH/St) has better performance than PPgMAH. The meltmess flow rate of the two kinds of composites shows a steady downward trend with the increase of compatiblizer contents, while the tensile and flexural strength of PPg(MAH/St) modified system show a steady upward trend, and reach a maximum at 4.8 g PPg(MAH/St)/100 g PP. The tensile strength reachs to 40.62 MPa which is 1.29 and 1.17 times of the unmodified system and PPgMAH system, respectively, and at the meantime the flexural strength rises to 45.72 MPa which is 1.23 and 1.59 times as high as those of the unmodified system and PPgMAH system. At 3.6 g PPg(MAH/St)/100 g PP, the unnotched impact strength of PPg(MAH/St) system is 13.35 kJ/m2 which is 1.62 and 1.42 times as high as that of unmodified and PPgMAH system, respectively.

Key words: polypropylene, wood flour, polypropylene melt grafted with maleic anhydride/styrene monomer, compatibility, properties