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A thermoplastic adhesive bonding process with a high-density polyethylene (HDPE)-based adhesive has been developed for galvanized steel to polypropylene (PP) composite. The processing temperature significantly affects the strength of the adhesively bonded lap joints. Melting of the surface of the PP composite prior to bonding was found helpful for interdiffusion between adhesive and PP composite during the bonding process. Cataplasma aging tests showed that use of a polyester–melamine-based primer on the galvanized steel before preparation of the PP composite/galvanized steel joints reduced durability. However, the primer did not cause significant adhesion loss under cyclic moisture/temperature condition. It was established that the loss in adhesion of joints made from galvanized steel treated with primer was due to the blistering of the primer in Cataplasma environment. [Copyright &y& Elsevier]

Rate effects in the failure behavior are investigated for adhesive bonds in which the source of time- dependence is the rate of the material separation in the fracture process zone. A rate-dependent cohesive zone model (CZM) is described and used to analyze rate effects during debonding. The model consists of a rate-independent CZM in parallel to a Maxwell element. General implications derived for the model with respect to rate effects in the failure behavior of adhesives are presented. The application of the model to the analysis of crack growth is described in a companion paper. [Copyright &y& Elsevier]

Results of a combined experimental and numerical study of the rate-dependent fracture behavior of thermoplastic bonded joints are presented. Double cantilever beam joints bonded with a high-density polyethylene based adhesive were investigated, and a rate-dependent crack growth behavior was found in tests under constant loading rates. In tests with variable loading rate, stress relaxation effects had considerable influence on the crack growth behavior. A rate-dependent cohesive zone model is applied to the analysis of these rate effects during crack growth. [Copyright &y& Elsevier]

The mechanical interlocking of a thermoplastic adhesive and wood substrate is studied with scanning electron microscopy. A thermoplastic/glass composite is bonded to oak (Quercus) using a polypropylene based adhesive. The wood is etched away using a combination of chromic, nitric, and sulfuric acids, leaving the morphology of the adhesive interface intact. The revealed surface is examined with environmental scanning electron microscopy. We have shown for the first time that a thermoplastic adhesive conforms to features of the wood as small as 1 μm across. The adhesive penetrates the vascular tissues of the wood for more than 150 μm through openings 15 μm across, and invades hundreds of microns through larger channels. [Copyright &y& Elsevier]