The Effect of Wood Species on the Mechanical and Thermal Properties of Wood-LLDPE Composites

Different wood species can be expected to affect the properties of wood-polymer composites (WPCs) differently, as they have different chemical compositions. The chemical composition (cellulose, lignin, hot water, and ethanol/cyclohexane extractive contents) of acacia, eucalyptus, pine, and oak and the morphological properties such as wood fiber length distribution were determined in order to investigate this effect. Composites of linear low-density polyethylene and 10 wt% of each of the wood species were prepared, using polyvinyl alcohol co-ethylene as a compatibilizer. Significant differences were found between the wood species in terms of both chemical composition and wood fiber length distribution. These affected the properties of the WPCs in different ways. Use of acacia resulted in a WPC with superior mechanical properties and thermal stability compared with the other species, due to its higher cellulose and lignin contents and a favorable wood fiber length distribution; however, acacia composites also showed a higher water absorption rate due to the higher cellulose content. We also found that WPCs containing wood species with a high lignin and extractive content, such as acacia and oak, had a higher resistance to UV degradation.