Abstract: Poly(styrene-random-acrylic-random-methyl methacrylate)［P(St-r-AA-r-MMA)］was prepared by free-radical polymerization and then used to modify the surface of high-density polyethylene (PE-HD)/wheat-straw fiber (WF) composites through a solution method. As a result, a superhydrophobic surface with a water contact angle (WCA) > 150 ° was obtained. The preparation parameters of superhydrophobic surface, mechanical properties and water absorption of these wood-plastic composites were investigated. The optimum preparation parameters were determined as follows: the ratio of polymer monomer was nSt∶nMMA∶nAA=2∶1∶1, the WF content was 40 wt%, the polymer concentration was 3 %, the drying time was 15 h, and the drying temperature was 70 ℃. The results indicated that the surface of the composites prepared under the optimal modification conditions achieved a WCA of （156±2.9） ° , which increased by 84 ° compared to that of unmodified composites. Moreover, their tensile and flexural strength increased by 6.1 % and 6.9 %, respectively, and however their water absorption decreased by 1.70 %. After placed for 5 months, a WCA of （142±5.7） ° was gained for the modified PE-HD/WF composites but only a WCA of （54 ± 6.2） ° was obtained for the unmodified ones.

Key words: high-densitypolyethylenewheat-straw fiber, wood plastic composites, free-radical poly merization, superhydrophobic, water absorption