Abstract:

The present study has shown that the composite of high quality could be successfully prepared using straw and recycled low density polyethene(LDPE)as main raw materials with isocyanates and hydroxyl acrylates copolymer emulsions(PA) synthesized as coupling agents,through the process of high temperature moulding.Influencing factors on properties of the composites were studied based on orthogonal experiments.The results showed that:1)Isocyanate of high free isocyanate groups content(PAPI), PA containing higher hydroxy content and lower glass transition temperature(T_g),could significantly improve the properties of composites,such as internal bonding strength(IB),IB of boiling water for 2 h later ( 2 hWIB),modulus of rupture(MOR),modulus of elasticity(MOE) and thickness expansion rate of water adsorbing for 24 h(24 hTS); 2)There were not significant effect on the properties of composites with 30/70 and 70/30 mass ratios of isocyanate to PA; 3)When 4.5% coupling agents were added,IB,2 hWIB,MOR,MOE and 24 hTS of corresponding conposites were better than others; 4)Increasing LDPE proportions in raw materials,IB,2 hWIB and water resistance of the composites inceased significantly; 5)IB,2 hWIB,MOR and MOE of composites improved with densities change form 0.85 to 1.0 g·cm^-3 ,moreover water resistance decreases a little; 6)When 4.5% coupling agents(1.35% PAPI and 3.65% PA4) were added,the properties of the composite satisfied the standard GB/T 4897.7-2003 for heavy duty load bearing boards for use in humid conditions.

Key words: wood-plastic composite, coupling agent, isocyanate, acrylate, wheat straw, recycled LDPE