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Reference Details
Gardner DJ, Peterson M, Robinson J 2005. "The application of flame surface pre-treatment to promote structural adhesive bonds in wood-plastic composite laminates", 8th International Conference on Woodfiber-Plastic Composites (and other natural fibers).

The formation of waterproof, structural adhesive bonds in wood plastic composite (WPC) materials is extremely challenging because of the poor adhesion properties of polyolefinic polymers such as high density polyethylene (HDPE) and polypropylene (PP) in their natural state. Both HDPE and PP exhibit low surface energy, non polar surfaces that are poorly wetted by most polymeric adhesive systems such as epoxies. In this study, flame treatment is explored as a means to modify and enhance the WPC surface towards adhesive bonding with epoxy adhesives. HDPE, PP and polystyrene (PS) WPC composite lumber was manufactured on a Davis Standard Woodtruder at a 60% wood/40% polymer ratio. The resulting lumber was planed, sanded or left in the natural state prior to flame treatment using a handheld propane torch. Flame treated and control WPC laminates were manufactured using epoxy adhesive, and the resulting adhesive bonds were tested for shear strength and material failure following ASTM D 905. Additional laminate samples were manufactured and evaluated for delamination following ASTM D 2559. The application of the flame-treatment significantly increased the bonding properties of the WPC laminates as evidenced by the improved shear strength, material failure, and absence of delamination when exposed to the cyclic testing of ASTM D 2559. Scale-up of WPC flame treatment to the pilot scale is also discussed.
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