Reprocessing of Extruded Wood-Plastic Composites; Mechanical Properties

This paper presents an experimental study on the reprocessing of wood-plastic composites (WPCs) with an emphasize on the multistage reprocessing and its effect on their mechanical properties. WPCs present numerous benefits in various aspects such as mechanical-physical properties and processing. These, also categorized as, green composites have a remarkable environmental advantages including recycle ability. This study attempted to explore the effects of polymeric matrix and wood content on their final properties when reprocessed in several stages. In order to investigate the properties of virgin and reprocessed composites, three different polymeric matrices of various melt flow indexes (MFIs) and three levels of wood contents were selected. Utilizing a counter-rotating twin-screw extruder and a rod-shaped die, thus, nine compositions of WPCs were produced. For reprocessing, WPC profiles were then ground using a grinding machine and dried to feed into the extruder with no additional materials. Three stages of reprocessing were performed to yield 36 specimens with different characteristic. Production rate and processing conditions such as die pressure and temperature were recorded. Properties such as density, flexural strength, ultimate strain, modulus of elasticity and impact resistance of the specimens were measured. Interestingly, properties of some composites improved significantly via reprocessing.