Improve The Weathering Resistance Of Wood Plastic Composites By PMMA Co-extrusion And Adding Pigments

Wood plastic composites, which are widely used in outdoor conditions, are more likely to suffer from aging phenomenon, including porosity appearing, cracking, color turning to yellow or fading. Furthermore, the composites decrease its mechanical performance in weathering condition. In order to make it available to use as doors and windows, this paper explore the method to improve the anti-aging properties of wood flour (WF)/high density polyethylene (HDPE) composite by co-extrusion technology and nano-oxide masterbatch process. The main results of the research are summarized as follows:1. The co-extruded WF/HDPE composites had been prepared by the shell consists of Polymethyl methacrylate (PMMA, added in a level of 30%,50% and 70%) and HDPE, and the core layer composed of WF/HDPE. The results showed that with the using of PMMA, thickness swelling rate after absorbing water and mass change of co-extruded composite had been decreased; when the content of PMMA in the shell is 70%, before and after aging, the bending strength of the composite material are higher than that of other contents; and color difference is minimal when the content of PMMA in the shell is 30%.2. The modified WF/HDPE was prepared by adding different levels (1%,2%,3%,4%) of nano titanium oxide, nano silica, iron oxide nano-particles. UV accelerated aging was tested, and the effect of the oxide type, content and ageing time on the properties of the composites was discussed. The results show that the content of 1% and 2% of nano titanium oxide, nano ferric oxide provides better mechanical properties and small color change after aging.3. The different masterbatch had been prepared by HDPE and Titanium oxide or iron oxide, and then blended with the wood flour, by extrusion to prepare the WPC. Before and after aging, the masterbatch WF/HDPE composites with 1% and 2% nano titanium oxide have the same bending strength. For the masterbatch composites with 1% nano titanium oxide is higher in bending strength than 2% of nano titanium oxide masterbatch. For the Same oxide sample, the color difference for the content of 2% is greater than the content of 1%.4. After experiencing UV accelerated aging, the color change of adding nano titanium oxide masterbatch is less than that of ordinary WF/HDPE process composite technology, but color change of adding nanometer iron oxide masterbatch is greater than the ordinary wood plastic composite material technology. The bending strength for masterbatch process WF/HDPE composite is greater than the ordinary process.