Accelerated cure of phenol-formaldehyde by the addition of cure accelerators : studies with model compounds

Abstract

Fast curing phenol-formaldehyde (PF) resins could potentially allow wood to be bonded at higher moisture contents and at lower press temperatures than those currently used commercially. Recent reports in the literature have shown that the addition of esters, lactones, or organic carbonates increased the curing rate of PF resins. Several mechanisms have been proposed to ex-plain the accelerated cure. The PF model compounds 2-and 4- hydroxymethyl phenol (2-HMP and 4-HMP) were reacted in alkaline conditions at 20°C, with and without cure accelerators, such as ethyl formate, propylene carbonate, g-butyrolactone, and triacetin. The disappearance of 2-HMP (or 4-HMP) and the appearance of reaction products with time were determined by high-pressure liquid chromatography (HPLC). The addition of cure accelerators significantly increased the rate of product formation from reactions that are similar to those that occur during the cure of PF resins. A dimeric and a trimeric reaction product were isolated by preparative thin-layer chromatography, and their structures were determined by 13C-NMR spectroscopy. These results are consistent with a mechanism in which the hydroxymethylated phenol is esterified by the cure accelerator, facilitating its conversion to a reactive quinone methide intermediate.

Citation

Lorenz, Linda F.; Conner, Anthony C. 2000. Accelerated cure of phenol-formaldehyde by the addition of cure accelerators : studies with model compounds. Wood adhesives 2000 : June 22-23, 2000 ... South Lake Tahoe, Nevada. Madison, WI : Forest Products Society, 2000: Pages 391-395