Hot pressing veneer-based products: the interaction of physical processes

Internal vapor pressure, internal temperature, and compaction are quantified during the laboratory pressing of five-layered Douglas-fir plywood panels. The techniques used to collect these data are described. Some interactions among the variables, and their effect on the attainment of product integrity, are considered. Most attention is given to the accumulation and dissipation of water vapor pressure within panels. Interestingly, such pressures were found to be greatest within the core plane of panels at all but the early stages of the pressing cycle. It is suggested that the gas permeability of gluelines changes as pressing proceeds and that this may play an important role in affecting vapor entrapment and therefore the efficiency of veneer-based systems’ manufacture.

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