Wood plastic composites manufactured from hot water extracted wood . Part I : Mechanical evaluation

The University of Maine, through its Forest Bioproducts Research Initiative (FBRI) project has developed a patent pending hot water hemicellulose extraction process for wood to produce a feedstock for chemicals and/or fuels. Depending on the form of the wood feedstock (chips, strands, particles), the remaining extracted wood can be utilized in traditional product forms such as paper, oriented strand board and particle board. In the present study, the utility of using extracted wood flour for producing extruded wood plastic composites has been investigated. Polypropylene was used as the thermoplastic resin and a lubricant was added to produce extruded WPC boards based on un-extracted and extracted wood material. Mechanical characterization was performed according to ASTM standards and consisted of tensile, flexure and impact measurements. In addition, flame, specific gravity, and thermal expansion analyses were also performed. The results indicated that the mechanical properties were not adversely affected by the extraction process and, indeed in several cases the properties increased significantly. Flame, specific gravity and thermal expansion did not present significant differences. Based on the results and considering that the aspect ratio did not suffer a significant change, it is expected that the increase in mechanical properties due to increase in the stress transfer from wood particles to the resin was mainly because of changes in the surface chemistry of the extracted material. Continuing work consists of the evaluation of the microscopic, chemical and surface energy of the extracted material and, adhesion and microscopic characterization of the final composites.