Abstract:

Wood flour/polypropylene composites were prepared by the special designed twin screw/single screw extruder system. The effect of EPDM-MA on water absorption, static and dynamic mechanical properties of wood flour (WF)/polypropylene (PP) composites were studied by static test, dynamic mechanical thermal analysis and scan electron microscope. The static mechanical properties of polypropylene/wood flour composites showed that the tensile strength and flexural strength were improved with the maleic anhydride modified ethylene propylene diene rubber (EPDM-MA), especially the impact strength of the composites was improved remarkably but decreased the composites' stiffness. The dynamic mechanical spectra of the composites showed that the storage modulus and tanδ peak values were decreased with increasing EPDM-MA loading. The reduction of the tanδ peak values revealed an improved interfacial adhesion between wood flour and polypropylene matrix. An increase in the main transition temperature implied the effect of EPDM-MA on thermal properties of composites. The second transition peak was also found from the spectra of DMTA about -50℃, which was especially in favor of improving impact properties. The scanning electron microscope study verifies an improved interfacial adhesion between wood flour and polypropylene matrix with EPDM-MA. EPDM-MA rubber domains were dispersed in the PP matrix, and the diameter of domains is between 0.1～1 μm. The water absorption of the composites was also decreased by EPDM-MA. EPDM-MA played a dual role, not only as a toughening agent but also as compatibilizer between wood and the polypropylene matrix.

Key words: wood flour, polypropylene, composites, maleic anhydride modified ethylene propylene diene rubber(EPDM-MA), dynamic mechanical properties