PEER-REVIEWED ARTICLE bioresources.com Shang et al. (2012). “Pressure-treated fibers in WPC,” BioResources 7(4), 5181-5189. 5181 HIGH-DENSITY POLYETHYLENE-BASED COMPOSITES WITH PRESSURE-TREATED WOOD FIBERS Lu Shang, a Guangping Han, a, * Fangzheng Zhu, b Jiansheng Ding, b Todd Shupe, c Qingwen Wang, a and Qinglin Wu c, * High-Density Polyethylene (HDPE)-based composites with alkaline copper quaternary (ACQ)- and micronized copper quaternary (MCQ)- treated wood fibers were manufactured through injection molding. The mechanical properties, water absorption, and biological resistance properties of the fabricated composites with different coupling treatments were investigated. Composites with ACQ- and MCQ-treated wood had mechanical properties comparable with those made of untreated wood. The different coupling agents worked well for the treated wood materials. Similar water absorption behaviors were observed for the HDPE composites containing treated wood and those containing untreated wood. The results of the termite test showed that the composites containing untreated wood had slightly more weight loss. The decay test revealed that the composites containing treated wood had less decay fungal growth on the surfaces, compared with samples from untreated wood, indicating enhanced decay resistance for the composites from the treated material. The stable mechanical properties and improved biological performances of the composites containing treated wood demonstrated the feasibility of making wood-plastic composites with pressure-treated wood materials, and thus offered a practical way to recycle treated wood into value-added composites. Keywords: Pressure-treated wood; HDPE; Mechanical property; Termite; Decay Contact information: a: Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), Northeast Forestry University, Harbin 150040, China; b: Nanjing Jufeng Advanced Materials Co., Ltd, Nanjing 210061, China; c: School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA; * Corresponding authors: a, guangpingh@hotmail.com; c, wuqing@lsu.edu INTRODUCTION Over the past two decades, extensive effort has been devoted to wood-plastic composites (WPCs) due to their many emerging applications as building materials, automobile components, and materials for infrastructure and decking/fencing (Clemons and Caulfield 2005). As new generation composite products, WPCs presents many advantages for both structural and non-structural uses, including availability in a variety of colors, shapes, and surface textures, ease of maintenance, lack of need for painting or other finishes, and little tendency to warp compared with wood materials. The outdoor application of structural WPCs has led to increased exposure of the materials to wetting. WPCs are susceptible to bio-deterioration under prolonged exposure to high humidity or liquid water, which can severely affect the economic value and usefulness of the product. This is due to the fact that the wood component in WPCs can be attacked by decay fungi, termites, and mold fungi (Laks et al. 2000 and Verhey et al. 2001). Like other wood materials, WPCs need to be treated with the appropriate chemicals to prevent biological