Shear Strength Development Of The Phenol-formaldehyde Adhesive Bond During Cure

摘要

The development of the shear strength of the phenol-formaldehyde (PF) adhesive bond during curing was investigated. Five different PF adhesive mixtures and 1.1 mm thick peeled beech (Fagus sylvatica L.) veneer were used to produce lap-shear specimens, which were cured at a pressing temperature of 160℃. Dielectric analysis (DEA) and modified ABES (automated bonding evaluation system) were used to evaluate the physical-chemical and mechanical aspects of PF adhesive cure in a miniature hot-press. The degree of cure, which was calculated from conductivity data, was dependent on pressing time and the composition of the PF adhesive. An addition of rye flour to the PF adhesive significantly postponed the curing process as determined by DEA. It was found that the adhesive bond started to develop in the last stage of the curing (vitrification), by which time most of the physical-chemical conversion of the adhesive had been completed.