PVC-wood composite: Processing and compsition challenges for improving the environmental durability by nanoparticles

The objective in this study was to research the use and impact of newly developed nano-size additives on PVC-wood composites. The main focus was on environmental durability, mechanical properties were measured to ensure the quality of the samples. Properties like UV-resistance and resistance moisture are in many applications more important than maximized mechanical strength. The tested nano-additives in this study were ZnO and Mg(OH)2. ZnO was added to improve UV-resistance, purpose of Mg(OH)2 was to reduce smoke production in case of fire. Most of the work was concentrated on the use of nano-ZnO and other organic additives to improve durability in outdoor use. Nano-ZnO was incorporated as water dispersion, EVA-based masterbatch or external lubricant based masterbatch. Water dispersion was used because dispersed nanosize ZnO was easy to mix with wood and produced good dispersion in final compound. Different ways and equipment to process PVC-wood mixtures into extruded or extruded and moulded specimens were tested. Main challenge in processing was to simulate industrial processing by using only around 500 g material batches. The processing conditions had strong influence on the surface quality of the sample which had remarkable effect on environmental durability. As a result we finally had simultaneous compounding and profile extrusion process, which produced constant high-quality samples from less than 500 g raw material batches. From the results of tests we saw the effect of nanoparticles, lubricants and additives on behaviour of PVC-wood composites.