Effect of adding wood flour to the physical properties of a biodegradable polymer

Wood flour/polymer composites (WPC) gained a significant interest during the last decades, due to several advantages related to the use of a natural-organic filler rather than an inorganic-mineral one. However, most of the studies have been performed on composites based on polyolefin matrices. A further step is the use of biodegradable polymers instead of traditional ones. In this work, wood flour (WF), under the form of short fibers, with two different sizes (coarse and fine) was added to a corn starch based biodegradable polymer of the Mater-Bi family. The effect of WF size, WF content, thermal treatment on the mechanical properties was investigated. The tensile mechanical tests showed an increase of rigidity of the composites upon increasing the WF content, together with a sharp decrease of the elongation at break. With regard to the tensile strength, no remarkable differences were observed upon changing wood flour size or type. In both cases, on average, there were often slightly better results with the samples which had underwent a drying pre-treatment. The increased rigidity was confirmed also by the impact tests, even though it decreased upon increasing the WF content. The heat deflection temperature followed the same trend as the elastic modulus. The immersion tests suggested that these materials are not suitable to prolonged contact with water. Humidity absorption tests revealed that the matrix plays a fundamental role in humidity absorption. 2007 Elsevier Ltd. All rights reserved