采用酰基化方法对扩链剂间苯二胺进行了改性,以减缓聚脲的高反应活性来研究合成反应的动力学方程.以间苯二胺、冰乙酸为原料,磷酸为催化剂合成了新型位阻型扩链剂二乙酰间苯二胺,并用红外光谱、高分辨质谱、凯氏定氮法和核磁共振氢谱分析确定了合成产物的化学结构.将它和端氨基聚醚、4,4'-二苯甲烷二异氰酸酯(MDI)通过两步溶液法合成了新型聚脲,考察了改性二胺扩链剂对聚脲性能的影响,并用傅里叶变换红外光谱仪(FTIR)跟踪该固化反应过程,得到了不同温度下的反应速度常数.实验结果表明,当用改性扩链剂代替原扩链剂合成聚脲时,凝胶时间大大延长.该反应体系表现为良好的一级动力学关系,并得出该反应的活化能.
Diacetyl m-phenylenediamine, a new hindered chain extender of polyurea, was prepared by acylation of m-phenylenediamine with glacial acetic acid at the presence of phosphoric acid as catalyst. This extender can decelerate the rate of polymerization between amines and isocyanates, easing to study the kinetics of curing of polyurea reaction. FTIR, HRMS (ESI), Micro-kjeldahl method and ~1H-NMR were used to determine the chemical structure of the extender. Polyureas were synthesized using methylene diphenyl-4,4'-diisocyanate and amine terminated poly (oxypropylene) by a two-step solution process. The influence of modified diamine extender on polyurea was investigated. And the curing prescess was followed with FTIR to obtain the reaction constant at various temperatures. It was found that the gel time was prolonged, i.e, the reaction activity was decreased when diacetyl m-phenylenediamine was used as chain extender instead of m-phenylenediamine. The results of kinetics experiments showed that the reaction belongs to a first-order reaction and give the value of Ea.
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