尿素用量对苯酚-尿素-甲醛共缩聚树脂的影响

Influence of urea addition on phenol-urea-formaldehyde resin.

该文以13C-核磁共振分析和热机械性能分析为手段,研究了一定范围内尿素用量变化对苯酚-尿素-甲醛(PUF)共缩聚树脂结构和性能的影响,并通过压制胶合板,进一步评估了该影响。13C-核磁共振结构分析结果显示:改变尿素用量对PUF共缩聚树脂的结构构成无显著影响。热机械性能分析结果表明:在相同甲醛/苯酚摩尔比条件下,适量增加尿素用量对PUF树脂凝胶化或固化反应的影响并不显著;而相同甲醛/(苯酚+尿素)摩尔比条件下,随着尿素用量的增加,树脂凝胶化或固化反应呈逐渐提前的趋势,但速度呈下降趋势。胶合性能研究结果表明:尿素用量不超过苯酚质量25%左右时,PUF树脂性能优于酚醛(PF)树脂,增加尿素用量对PUF树脂胶合性能没有显著影响;超出该范围后,PUF树脂性能随尿素用量的增加而逐渐下降。

The influence of urea addition level on the structure and curing performance of phenol-urea-formaldehyde co-condensate resin was studied by carbon 13 nuclear magnetic resonance（^13C-NMR） spectroscopy and thermo mechanical analysis（TMA）.This influence was further evaluated by preparing PUF-bonded plywood panels.^13C-NMR spectroscopy indicated that the structures of PUF were similar at different urea addition levels.The results of TMA showed that there were no significant changes on cure performance when the molar ratio of F/P was kept as a constant.The cure performance,however,was observed to become earlier and the cure rate decreased with the increase in urea addition at constant molar ratio of F/（P＋U）.Evaluation of laboratorial plywood showed that when the amount of urea added was less than 25% of phenol amount,the performance of PUF resins would not be affected by the urea addition levels and the performance of PUF bonded plywood was better than PF bonded plywood as well.Over use of urea,however,would lead to a dramatic decreased performance of PUF.