M-TMI Grafting Polypropylene And Application In Wood-plastics Composites

Polyolefin belongs to nonpolar polymer, which is incompatible with wood flour. In order to realize the compatible blending between wood flour and polyolefin, it is necessary to modified polyolefin. Then the functionalized polyolefin as the compatibilizer is added to the composite system which is based on polyolefin. In this paper, a kind of polar monomer with a special functional group was adopted to graft polyolefin by melt reactive extrusion technology, a new type of reactive compatibilizer was prepared, and was applied in the wood-plastics composites (WPC) system with high wood flour content, in the meantime, the compatibilizing effect and capacity of the compatibilizer were discussed.A new kind of polar monomer, m-iso-propenyl-a, a-dimethyl benzyl-isocyanate (m-TMI) which has unsaturated bonds and isocyanate group was used to modify the polypropylene(PP) by the melt-grafting method, the effect of influencing factors included monomer m-TMI concentration, initiator DCP concentration, comonomer St concentration, reaction time, reaction temperature and screw speed on the grafting degree was studied. The result showed that m-TMI was successfully grafted onto PP; St could greatly improve the grafting degree of m-TMI.The thermal properties of poly-propylene (PP), m-TMI grafted PP (m-TMI-g-PP), and styrene(St), as comonomer, together with m-TMI grafted PP (m-TMI-St-g-PP) was investigated by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), Three methods, namely, the Avrami, the Ozawa, and the Mo were used to describe the crystallization process of the three samples under non-isothermal conditions, The Mo method can successfully describe the overall non-isothermal crystallization process of ail the samples. The activation energy (△E) for non-isothermal crystallization of all samples was determined by using the Kissinger method, the result confirmed the nucleating effect of St and m-TMI on crystallization of PP. the result of TGA indicated that St effectively inhibit the degradation of PP in the grafting process and improve the thermal stability of grafted products.m-TMI-St-g-PP was applied in the WPC as reactive compatibilizer. The effects of m-TMI-St-g-PP content (0-14%) and wood flour content (60-80%) on the properties of WPC were investigated by means of mechanical properties, thermal analysis(HDT, VST, TG, DSC), dynamic rheological analysis(G', G" andη*), water absorption and SEM. The results demonstrated that:10% m-TMI-St-g-PP was the best in WPC. As the same time, the comprehensive consideration of the cost and environmental issues, wood flour content of 70% was chosen at last.The effect of wood flour content on the thermal stability and combustion behavior of WPC was investigated using thermal gravimetric analysis (TGA) and cone calorimeter (CONE). The TGA showed that, as the wood flour content increased, the thermal stability of WPC decreased, but the amount of char forming significantly enhanced; The experiment of CONE displayed that the values of HRR, SEA and SPR were all lower than that of PP, and as the increasing of wood flour content, the reduction was more significantly, which indicated that wood flour restrained the combustion and smoke release of WPC in some extent, delaying the decompose combustion process of composite.