Effects of wood fiber content on structure and properties of WF/PLA bio-composites

This study is devoted to investigate the effects of wood fiber content on structure and properties of wood fiber /poly(lactic acid) bio-composites (WF/PLA bio-composites). The WF/PLA bio-composites with WF from 30% to 60% and from 70% to 90% were prepared using melt extrusion and high-speed mixing methods respectively. The physical, mechanical, thermal, and macromolecular properties of WF/PLA bio-composites were evaluated. The results are as follows: Density of WF/PLA bio-composites increased when WF increased from 30% to 60%, and decreased when WF increased from 70% to 90%. Water resistance of bio-composite decreased with increasing WF content. The flexural strength of WF/PLA bio-composites were lowered when adding WF into PLA. The flexural strength decreased when WF increased from 30% to 50%, and then increased when WF increased from 60% to 80%. The flexural modulus of the bio-composite was higher than that of PLA without WF. Both (M) over bar (n) and (M) over bar (w) of PLA in WF/PLA bio-composite were decreased more than 70% with WF increased. The T-g, T-m values of PLA in the bio-composites were decreased with the WF increased. The cold crystal temperature (T-cc) was decreased with WF increased at low WF content. All the property changes were related to the decreasing of molecular weight of PLA in WF/PLA bio-composites.