Two types of polypropylene(PP) and Korean pine sawdust wood flour were used as matrix and filler materials for wood/plastic composites. These composites were prepared by melt-blending process in a single screw extruder. Maleic anhydride modified polypropylene(MAPP) was used as coupling agent. The WF(wood flour) was added up to maximum 50 wt% and the coupling agent was added up to 15 wt%. Without the coupling agent, the tensile modulus was improved with increasing amount of WF, but the tensile strength and the impact strength were decreased. The tensile strength could be improved by adding the coupling agent, but the impact strength was not affected. The reduced properties were caused by some defects formed from decomposition of the WF at the high processing temperature. For solving this problem, the processing conditions such as temperature setting, compounding route and pretreatment of WF were checked with two kinds of polyproplene which have different level of melt index. To evaluate the properties, tensile, impact and flexural properties were measured and the fracture surfaces of the composites were investigated by SEM. Also, the effect of water absorption on the properties was evaluated.

두 종류의 폴리프로필렌 수지와 잣나무 목분을 단축압출기를 사용한 용융블렌딩으로 복합재를 제조하였다. 목분은 최대 50wt%까지 투입하였으며, 결합제로서 maleic anhydride polypropylene(MAPP)을 15wt%까지 첨가하였다. 결합제를 사용하지 않은 경우에는 목분의 투입량이 증가할수록 인장탄성율은 증가하나 인장강도와 충격강도는 감소하였다. 결합제가 투입되면 인장강도는 향상시킬 수 있었으나 충격강도의 저하는 큰 변화가 없었다. 이러한 물성 저하는 수지가공을 위한 고온에서 목질이 분해되며 발생하는 기포들의 결함이 원인이 되는데, 특히 용융지수가 낮아 높은 가공온도를 필요로 하는 수지를 사용하였을 때 더욱 현저하게 나타났다. 이러한 문제를 해결하기 위해 수지의 종류, 가공방식 및 가공온도 조건을 바꾸고, 목분을 전처리하여 가용성 물질을 제거하는 실험을 하였다. 물성평가를 위해 인장, 충격, 굴곡물성을 측정하였으며, SEM을 이용하여 파단면을 관찰하였고, 수분흡수에 따른 물성변화를 측정하였다.

Keywords: composite; polypropylene; wood flour; korean pine; sawdust; MAPP