Effect of chemical pre-treatment of wood furnish on resin consumption and panel dimensional stability. Part III. Chemical pre-treatment of wood strands for OSB manufacture
Experimental work was carried out to investigate the effect of chemical pre-treatment of wood strands for the manufacture of OSB. The chemicals used for the pre-treatment included low molecular weight liquid PF, low molecular weight poly(ethylene glycol) and hydrogen peroxide. These chemicals were tested at two dosage levels. The untreated strands and chemically pre-treated strands were characterized for their pH, acid buffer capacity, base buffer capacity and PF resin gel time. Eighteen OSB panels were made with different chemically pre-treated wood strands and compared with the untreated OSB panels as a control using PF or MDI resins. A total of 27 OSB panels were made in this study.
The results suggested that the moisture resistance and dimensional stability of the OSB made from chemically pre-treated wood strands were generally better than the control panels made from untreated wood strands and 3.5% PF resin (C1). However, no obvious improvement was made when comparing to the control OSB panels using untreated wood strands bonded with 7% PF resin (C2) or 3.5% MDI resin (C3). The three different chemicals studied performed differently. The low molecular weight liquid PF performed better than hydrogen peroxide, followed by the low molecular weight poly(ethylene glycol). It was found that the wood pH and acid and base buffer capacities were changed after the chemical treatments. However, there was no obvious correlation between these changes and the corresponding PF gel times.