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In this paper the foamed polystyrene (PS) based wood plastic composites, which using azodicarbonamide (AC) as blowing agent, wood flour and PS as main materials, were prepared by free foaming method. The effects of wood flour particle size and nucleating agent on cell morphology, cell distribution and mechanical properties of the composites; effects of coupling agent on the interface compatibility; the relationship between temperature of mold and melt; effects of elastomer SBS on notched impact strength of the composites; effects of content of polyethylene on the mechanical properties of the polyethylene/polystyrene/wood composites were studiedThe results showed that when the wood flour particle size is 80-120 mesh, the composites have better cell morphology, higher cell density, smaller cell size, much more uniform cell distribution, and the flexural strength and tensile strength were increased by 21.9% and 47% compared to the composites containing 40-80 mesh wood flour. The 1200 mesh talc was a promising nucleating agent, which could effectively increase the cell density and decrease the apparent density of composites. For the foamed composites with PS-g-MAH, the mechanical properties were improved, and the average diameter of the cell became much smaller, and for that with the silane coupling agent, the average diameter of the cell was bigger, and the mechanical properties behaved poorly, but the apparent density was lower. As the die temperature increased, the viscosity of the polymer melt decreased, and the free volume increased, thus result in the increasing of cell dimension and cell density of the composites, which finally decreased the apparent density of the composites; SBS can enhance the notched impact strength of the composites (when SBS content was 10%,the notched impact strength of composites was best), but it will decrease the flexural strength and tensile strength at the same time; with increasing the amount of the polyethylene, the flexural strength and tensile strength of the composites both enhanced, and the morphology of the cell also improved, when polyethylene content was more than 30%, all the performances of the composites decreased
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