脲醛树脂分子量分布与胶合性能关系的研究(续)——分次加尿素对脲醛树脂分子量分布与胶合性能的影响

Study on the Relationship of Molecular Weight Distribution of Urea-Formaldehyde (UF) Resins with Bonding Properties

主要探讨分次加尿素对脲醛树脂分子量分布及胶合性能的影响。研究结果表明 :在脲醛树脂合成过程中 ,分次加入尿素 ,不仅可起到降低胶中游离醛的作用 ,同时还可起到分子量的调解作用。尤其是加入第 2次尿素时 ,对胶中大分子部分可起到降解重排、减少胶中醚键含量的作用 ,从而达到低毒的目的。加入第 2次尿素时 ,可能会改变脲醛树脂的反应机理。

It had been investigated primarily that the effect of twice and thrice addition of urea on molecular weight distribution of UF resins and its shear strength during synthesizing UF resins in this paper.The experimental results show that multi-addition of urea can not only decrease free formaldehyde in resin,but also have a function of adjusting molecular weight of UF resin during synthesizing.Especially,when the second urea was added,it can have an effect of degradation and rearragnement for higher molecular weight part in UF resin,and decrease content of ether bond.It can change reaction mechanism of UF resin that the second urea was added.