Properties Of Composites Made Of High-Density Polyethylene And Pressure-treated Wood Removed From Service

Wood plastic composite is a new environmental friendly and widespread material made of plastic and wood fiber. In recent years, wood plastic composite is widely used outside. Its biological resistance properties attract the public attention due to the sun and rain erosion. The value and durability of wood will be improved after treating with preservatives. However, once the pressure-treated wood exceed its durable years, the recycle of pressure-treated wood and the pollution of oilborne preservative will become an issue. In this study, pressure-treated wood removed from service were used to prepare pressure-treated wood/high-density polyethylene composites, and then explore the feasibility of preparing wood plastic composites using pressure-treated wood through the characterization of physical and mechanical properties, biological resistance properties. Furthermore, core-shell structure wood plastic composite with high performance were prepared using pressure-treated wood to provide a new effective way to recycling pressure-treated wood.High-Density Polyethylene (HDPE)-based composites with alkaline copper quaternary (ACQ)-and micronized copper quaternary (MCQ)-treated wood fibers were manufactured through injection molding. Using scanning electron microscopy, differential scanning calorimetry, thermal gravimetric and other analysis methods, the mechanical properties, water absorption and biological resistance properties, thermal stability of the fabricated composites with different coupling treatments were investigated. The results showed that:Composites with pressure-treated wood fiber had good mechanical properties, ACQ-HDPE、MCQ-HDPE and SYP-HDPE composites had similar mechanical properties. The different coupling agents used worked well for the treated wood materials. Similar water absorption behaviors were observed in composites with pressure-treated wood fiber and composites with untreated wood fiber. Moisture content increased with the increasing of the water absorption time. The composites with EGMA showed the lowest moisture absorption values. The thermal stability of composites with pressure-treated wood fiber and untreated wood fiber were basically consistent in general, the characteristic data of DSC and TG curves were very close. The results of the termite test showed that all the wood plastic composites performed very well, while untreated SYP controls had large weight losses (37%) and low sample damage ratings. Among two composites with treated wood, the samples with ACQ-HDPE composites had less weight loss than those with MCQ-HDPE composites. The ACQ-HDPE and MCQ-HDPE composites had lower weight losses than the untreated wood-HDPE in the decay test, indicating the enhanced decay resistant performances of polymer composites with pressure-treated wood materials. In addition, coextruded MCQ treated wood and high density polyethylene or recycled high density polyethylene composites with core-shell structure were manufactured using a pilot-scale coextruded line in the study. The mechanical properties, water absorption and leaching resistance properties were investigated. The results showed that:the bending strength and bending modulus of pure core layer composites compared well with the co-extruded composites, while the impact strength were lower than co-extruded composites. By using a shell layer, water absorption and thickness swelling of the co-extruded composites were reduced significantly in comparison with pure core layer. The solid shell layer with less wood loading will also have potential to prevent chemicals within treated wood in the core layer from leaching-leading to long term protection.The results of this study demonstrated the feasibility of wood-plastic composites containing pressure-treated wood materials, recycling treated wood fiber into wood plastic composite manufacture offers advantages in recovering valuable wood resources and in helping to create wood plastic composite products that are less biological properties, and therefore offers a new and practical approach to recycling treated wood into value-added composites. And also offer a reference basis for the further research of core-shell structure wood plastic composite.