Preparation,Structure And Properties Of Wood Flour/Plastics Composites

Obtaining composites from compounding recycled plastics and waste wood or other solid waste is benefit for saving the limited nature resource and the environment protection. In this work, much efforts have been made on wood-flour (WF) /plastics composites (WPC). In which were investigated in detail the processing routes, technologies, properties, modification and reactive extrusion.Through exploring the processing technology and properties of high density polyethylene (HDPE)/WF composites, the processing parameters and the relationship between properties and WF content were obtained. The results indicated that the extrusion via twin-screw extruder in place of single screw extruder is a feasible routine, which provides better feeding ability, mixing and plastication effect, and prevents wood flour carrying when the content is relatively high. The tensile strength of WPC prepared in this way were almost unchanged. Especially when wood flour was lower than 40phr, the materials exhibited a good processing rheological properties,In WF/polypropylene composites, WF was well dispersed in composites as shown in scanning electron microscopy (SEM) photographs. Rather high tensile strength of the composites was achieved even when the WF content was high, but the impact strength decreased as WF content increased. The experimental data of different scanning caiorimetry (DSC) showed higher crystallization temperature and higher crystallinity with higher wood flour content, which indicated WF could has nucleation effect to PP matrix.The results of investigation on the compatibilization between WF and polyolefin resins showed that ethylene-acrylic acid copolymer (EAA) and maleated polypropylene (MA-PP) were effective compatibilizers in HDPE/WF composites and the MA-PP did the same work in PP/WF system. The two kinds of compatibilizers can improve the tensile strength greatly (30%) even with small content (5-8phr) for the two system, respectively.The morphology of the composites showed a good adhesion exists between the matrix and WF surface, even some wood particles were coated by matrix, which meant the load could be transferred from the matrix to the filler effectively.WF had little effect on tensile strength of recycled HDPE/PP/WF composites. The impact strength of composites decreased significantly when increasing WF content, whereas bending strength, modulus and heat resistance increased. MA-PP was a good compabilizer for the ternary composites. By adding ethylene/propylene/diene terpolymer (EPDM), styrene-ethylene/butylenes-styrene triblock copolymer (SEBS) and maleated polyolefin (POE) to toughen the composites , the results showed that all the elastomers could improve the impact strength of the composites but not as efficiently as prodiction. Tensile and bending tests showed that the impact modifiers decrease the tensile strength, bending strength and modulus.When melt reactive extruding PP/wood-flour composites, the rotating rate of main screw was maintained at 100rpm, which provided enough reactive time (about 160 sec) and avoided WF charring and the matrix degradation for long residence at such high processing temperature. The initiator dicumyl peroxide (DCP), maleic anhydride (MAH) monomers, PP and WF had better be added into extruder simultaneously, and the ratio of DCP and MAH needed to be proper to initiate enough PP chain radical and enough reactive rate for monomers. In our study , the suitable content of DCP was 0.01% and MAH 0.6%. Increasing the content of DCP and MAH could produce a negative effect to the composites.