Alaskan timber resources for wood-plastic composites

Tony Ray Cameron

The goal of this study was to develop and demonstrate that commercially viable wood plastic composite products can be produced using two separate Alaskan low-value waste streams from secondary industry and woody biomass from urban wood waste lots (birch and woody biomass material (WBM)). Because of the harsh environmental exposures such products would experience in Alaska, further understanding of how environmental exposure influences mechanical properties, as well as their viscoelastic response, was also investigated. Particle size analysis of raw materials indicated a wider particle size distribution in birch and especially WBM samples relative to pine control specimens. Statistically lower diffusion coefficients associated with Alaskan material were also found during water soak testing. However, mechanical testing of specimens found no statistical difference in flexural strength, stiffness, creep recovery, or fastener withdrawal tests between any of the feedstock types. As a result, WPCs made with the two Alaskan low-value woody materials should be considered a viable option for the Alaskan forest products industry. Static flexure results indicated a significant influence of weathering with ultra violet light and freeze thaw cycling of specimens upon values of strength, stiffness, and strain to failure. It also appeared the coupled weathering created larger influences upon flexural properties than independent weathering. However, results suggest that freeze-thaw cycling had a significantly larger affect than UV exposure. Weathering of WPC caused significant increases in flexural creep strain as well, especially within the first minute of sustained loading. This is believed to occur as a result of the large influence weathering has upon static response of composites. Consequently, increases in creep strain after one minute and creep strain rates from weathering were not found to be statistically significant. Although not statistically significant, coupled weathering of specimens appeared to have a larger influence upon creep strains than independent weathering with freeze-thaw cycling and UV exposure.

Alaskan timber resources for wood-plastic composites

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