聚脲
异氰酸酯
二胺
聚氨酯
缩二脲试验
六亚甲基二异氰酸酯
高分子化学
化学
异佛尔酮二异氰酸酯
化学结构
甲苯二异氰酸酯
傅里叶变换红外光谱
聚合物
材料科学
有机化学
尿素
化学工程
工程类
出处
期刊:Polymers
[MDPI AG]
日期:2023-08-24
卷期号:15 (17): 3524-3524
被引量:2
标识
DOI:10.3390/polym15173524
摘要
Industrial polyureas are typically synthesized using diisocyanates via two possible alternative pathways: the extremely quick and highly exothermal diamine–diisocyanate pathway and the relatively slow and mild water–diisocyanate pathway. Although polyurea synthesis via the water–diisocyanate pathway is known and has been industrially applied for many decades, there is surprisingly very little analytical information in the literature in relation to the type and extent of the occurring side reactions and the resulting chemical structures following this synthesis pathway. The synthesis of polyureas exhibiting very high concentrations of carbonyl-containing groups resulted in strong and accurate diagnostic analytical signals of combined FTIR and solid-state 13C NMR analysis. Despite the strictly linear theoretical chemical structure designed, the syntheses resulted in highly nonlinear and crosslinked polymers. It was analytically found that the water–diisocyanate pathway preferentially produced highly dominant and almost equal contents of both biuret structures and tertiary oligo-uret structures, with a very small occurrence of urea groups. This is in strong contrast with the chemical structures previously obtained via the diamine–diisocyanate polyurea synthesis pathway, which almost exclusively resulted in biuret structures. The much slower reaction and crosslinking rate of the water–diisocyanate synthesis pathway enabled the further access of isocyanate groups to the already-formed secondary nitrogens, thus facilitating the formation of complex hierarchical tertiary oligo-uret structures.
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