Swelling and its Rate in Wood Plastic Composites made with Polypropylene and Acetylated Wood Fibers

Influence of the acetylation and the compatibilizer MAPP on the long term swelling rate of polypropylene/ acetylated wood fiber composites (WPCs) was the main concern of the current research. Wood fibers were reacted with acetic anhydride without a catalyst to achieve weight percent gains (WPGs) of 4. 5، 7. 5 and 17. 68%. The acetylated fibers were mixed with MAPP (0 and 2%) as well as the polypropylene as the matrix polymer and molded at 180°C in a hot press. Test specimens were cut from the samples and soaked in water for 1512 hours at room temperature to determine the thickness swelling as well as the rate of the swelling in the WPCs. Results revealed that the thickness swelling of the acetylated composites was significantly reduced in comparison with the non-acetylated one. Application of the MAPP decreased the swelling as well. However، there were no significant differences between the acetylated WPCs containing the compatibilizer with the composites without MAPP. The Shi and Gardner (2006) model was adopted to evaluate swelling in the acetylated composites.