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| Title: | Phenol-Urea-Formaldehyde (PUF) co-condensed wood adhesives |
|---|---|
| Author(s): | Tomita, Bunichiro; Hse, Chung-Yun. |
| Date: | 1998 |
| Source: | International Journal of Adhesion & Adhesives. 18: 69-79. |
| Description: |
The reaction of urea with methylolphenol under acidic conditions was investigated. The alternating copolymer of urea and phenol could be synthesized by the reaction of urea and 2,4,6-trimethylolphenol. The reactions of urea with polymethylolphenol mixtures also were investigated by changing the reaction conditions, such as the molar ratio and acidity. The co-condensates were analyzed by carbon-13 nuclear magnetic resonance spectroscopy to determine the ratios of co-condensation. Another synthetic method to obtain co-condensed resins was developed by reacting phenol with UF concentrate, which is a type of urea-formaldehyde resin prepared with a high molar ratio of formaldehyde to urea (F/U) such as greater than 2.5. Further, it was found that resol-type co-condensed resins can be synthesized by alkaline treatment of the co-condensed resins that were once prepared under acidic conditions. The curing process and thermal properties of resol-type co-condensed resins were investigated by torsional braid analysis. The co-condensed resins displayed almost the same curing behavior and heat resistance as a commercial resol. Their adhesive performance against plywood was evaluated by conducting a cyclic 4 h boil test and a 72 h boil test. The plywood test results passed the requirements for JAS special-grade structural plywood. |
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