Abstract:
This research related resin synthesis variables of phenolformaldehyde resins to their chemical content and reactivity. The study was part of a larger project correlating resin properties to their performance as plywood adhesives. Formaldehyde-to-phenol and Na0H-to-phenol mole ratios were examined within the ranges used commercially. I also examined various proportions of caustic added in each of three steps and the effect of an initially low reaction temperature. Samples were collected at intervals during each reaction to determine formaldehyde, phenol, and orthomethylol contents and to qualitatively measure molecular size distribution via gel permeation chromatography (GPC). Reactivity was measured with a gel timer. The greater the proportion of formaldehyde, the faster a resin cooked and the more reactive it was. More caustic in the initial stages of cook produced a faster cooking resin with less reactivity. The UV absorbance at 254 nm of resin fractions from GPC were shown to increase with cook progression as did resin viscosity. No beneficial effect was seen for the low initial temperature.
