Development of An X-Ray, KBR Embedding Method for Determination of Resin Cure

An X-ray, KBr embedding method was developed to measure the degree of cure of urea-formaldehyde (UF), urea-melamine formaldehyde (UMF) and phenol-resorcinol formaldehyde (PRF) resin. In this method, KBr was mixed thoroughly with the resin before cure. After curing, the resin was extracted with water and the trapped KBr in the resin matrix was determined using X-ray spectrophotometry. Good correlations between percent KBr retention and bond quality or cure time of adhesives were found. Because the PRF in plywood panels had much lower KBr retention values than the UF or UMF resins, the uncertainty in determining degree of cure by this method is much higher for this resin. As an application study, this described method was used to study the effect of bleached and unbleached wheat flour on the curing of UF resin. The results showed that UF resin with bleached wheat flour required more energy to cure. The method has been proven for various adhesive formulations and applications and can be a relatively fast and accurate technique for examining the degree of cure of adhesives in wood-glue composite products under different curing conditions. The method also has the advantage of having no interference by wood and moisture.

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