Laminating Creosote-Treated Hardwoods

A study was conducted to investigate the bondability of four selected hardwood species after being treated with creosote. A completely randomized block factorial design was employed. Experimental factors included five wood species (chestnut oak, red oak, red maple, yellow-poplar, and southern pine), five adhesive systems (elevated temperature cure phenol-resorcinol-formaldehyde, room temperature cure phenol-resorcinol-formaldehyde, resorcinol-formaldehyde, emulsion polymer isocyanate, and low-viscosity formulation emulsion polymer isocyanate) and two exposure levels (ambient room and vacuum/pressure/soak conditions). Exposure levels effects on the different wood species resulted in highly variable adhesive system performance. Exposure level effects were most evident for the higher density oaks. Shear strength and percent wood failure results for all wood species revealed a general trend towards a higher performance for the two phenol-resorcinol-formaldehyde systems. Res-orcinol-based adhesive systems had the highest shear strength values. Percent wood failure values were highest for the elevated temperature cure phenol-resorcinol-formaldehyde system for all species. Elevated temperature cure adhesive systems appeared to be required to successfully bond high-density creosote treated species. Successful bonding of medium-density species can be accomplished at room temperatures given proper adhesive system selection