Interrelationship of Bond Performance and Some Physical Properties of Elastomeric Construction Adhesives

Performance properties of wood laminates bonded with elastomeric construction adhesives and the physical and mechanical properties of the adhesives themselves were compared. The adhesives examined were polyvinyl acetates (PVAc), styrene-butadiene-rubber (SBR), and polyurethanes. Possible on-site construction environments were approximated by bonding the laminates under dry, wet, and frozen conditions. To simulate the effects of different indoor and outdoor exposures, laminate shear strengths were measured after dry (i.e., 5 percent MC), wet (i.e., water saturated), and elevated temperature (i.e., roof type exposure) conditions. The absolute shear strength value depended on adhesive type, exposure condition, and glueline thickness, with PVAc showing the greatest sensitivity to heat and moisture. Percentage wood failure found in most tested samples was low. Laboratory physical-mechanical tests were also conducted on the adhesive alone to give both a rapid indication of creep properties and results that could be compared to laminated bond strength values. Tensile stress-strain measurements on cured elastomeric adhesives films showed PVA’s water sensitivity and the high elongation but good recovery properties of polyurethane. Thermal softening determinations showed the higher superior thermal stability characteristics of polyurethane compared to PVA and SBR.

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