A growing demand in low thermal expansion and water uptake for structural wood plastic composites (WPCs) have recently appeared in applications such as curved structure design, where minimum dimension movement and water absorption are required. Thus, thermal expansion and water absorption caused by external environment variations have to be taken into account in the design of WPCs for final application. The values of linear coefficient of thermal expansion (LCTE) for wood (or grain) and mineral (e.g., calcium carbonate) fillers are about 20 times lower than those of plastics and about 10 times lower than those of WPCs. We have studied thermal and mechanical properties of wood flour (WF) and talc filled high density polyethylene (HDPE) composites1,2. The addition of WF and WF-talc mixture into neat HDPE resulted in some decreases in the glass transition and crystallization temperatures of the composites. Hybrid bio-composites from talc, WF, and polyhydroxybutyrate-co-valerate (PHBV) were analyzed by Singha et al 3. A 36% decrease of LCTE and an improvement in heat deflection temperature of the hybrid composite were also observed. To enhance the properties of WPCs, Hisashi et al4 improved water-repellent property of wood. The results suggest that the addition of SiO2 into wood-inorganic composites had a positive effect on water-repellent property.
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