Application of Flame Treatment to Promote Structural Adhesive Bonds in Wood-Plastic Composite Laminates

摘要

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 epox-ies. In this study, flame treatment is explored as a means to modify and enhance the WPC surface toward adhesive bonding with epoxy adhesives. HDPE, PP, and polystyrene (PS) WPC composite lumber was manufactured on a Davis Standard Woodtruder at a 60 percent wood/40 percent 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 lami-nate 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.