Evaluation of wood-thermoplastic-interphase shear strengths

A macroscopic pull-out technique has been developed to determine the interphase properties in wood /low-molecular-weight-thermoplastic systems. Experimental variables affecting the shear properties of these types of composites were first identified so that the test could be used to compare the effect of different surface treatments on the interfacial properties. The relationship between the debonded force, F, and embedded length, L, was not linear, suggesting a failure mechanism that was different from interfacial yielding. Low embedded lengths provide useful comparative data on the maximum interfacial-shear strength of the system. The test is also useful for evaluating the quality of the fiber-matrix bond after exposure to water, since dimensional stability is an important consideration for wood-fibre-based composites. The test can be used to screen the effects of modifications on the lignocellulosic and/or the thermoplastic matrix on adhesive bonding for the development of composites. The use of lignocellulosic fibers (recycled wood fibres and natural fibers such as jute) in combination with recycled plastics could find applications in the automotive, furniture and building-materials industry. Matrix materials tested were low molecular weight polyethylene and a copolymer of ethylene and acrylic acid.