EFFECTS OF THE CHARACTERISTICS OF WOOD FLOUR ON THE PHYSICO-MECHANICAL AND THERMAL PROPERTIES OF RECYCLED POLYPROPYLENE

Recycled polypropylene (rPP) from synthetic raffia big bags was reinforced with 50 and 60% of Pinus radiata wood flour of two particle size (60 and 100 mesh) through a blending process with and without maleated polypropylene (MAPP), used as a coupling agent. The processability of the pure rPP and wood-rPP composites was studied in terms of the mixing process torque and also the physico-mechanical properties and then compared with a commercial virgin polypropylene (PP). The results showed that the tensile and flexural strength (MOR), tensile and flexural modulus (MOE) and impact strength of the pure and reinforced rPP, did not decrease in comparison with the virgin PP, and in terms of the elasticity modulus (MOE) and impact strength, the rPP composites were superior to the virgin plastic. The mechanical properties were slightly enhanced by the MAPP, but the particle size and the filler content (50 and 60%) had no clear influence on the mechanical properties. Differential scanning calorimetry (DSC) was used to study the crystallization and melting behaviour of the rPP and rPP-wood composites and the results were compared with the virgin PP. The DSC analysis indicated that the wood flour particles acted as a nucleating agent, increasing crystallization rate and decreasing the crystallinity degree, and consequently, decreasing slightly the melting temperature of the rPP/wood composites. Thermogravimetric analysis (TGA) revealed that the thermal stability of the rPP and rPP/wood composites were slightly greater than that of the virgin PP. In general, the results of this study showed that it is feasible to obtain composite materials with good thermal and mechanical properties with recycled PP from postconsumer synthetic raffia reinforced with 50 or 60% wood flour.