Thermal and dynamic mechanical characterization of polypropylene-woodflour composites

The performance of wood particle/polypropylene (PP) composites with modified compatibilities was compared. Woodflour modification was performed by esterification with maleic anhydride (MAN) and a non-commercial maleic anhydride-polypropylene copolymer (PPMAN) was selected as compatibilizing agent. The thermogravimetric analysis indicates that the onset of thermal degradation of treated woodflour occurs at lower temperature than that of the untreated one, and the same behavior was found in the corresponding composites. Differential scanning calorimetry indicated that both woodflours acted as nucleating agents for PP, while only treated woodflour induced PP crystallization in beta-phase in the composites. X-ray diffractometry demonstrated that the crystallization in beta-phase was a shear-induced phenomenon favored by the chemical modification of the woodflour surface. Dynamic mechanical studies suggested that composite properties decreased at concentrations higher than 40 wt% of woodflour and that the overall performance of MAN-treated woodflour composites was lower than that of the composites where a compatibilizing agent was added.