Influence of Acetylating Bi-amine Chain Extenders on the Properties of Polyurea

In this paper, hexamethylene-diamine(HAD) and m-phenylene diamine (m-PDA) were acetified to decrease the reaction activity of synthesizing polyureas and improve their properties. Novel sterically hindered chain extenders, diacetyl hexamethylene-diamine(MHAD) and diacetyl m-phenylenediamine (Mm-PDA) were synthesized with HAD, m-PDA and glacial acetic acid in the presence of phosphoric acid. Their chemical structures were confirmed through FTIR, Kjeldahl Nitrogen Determination method, High resolution ESI-FTICR mass spectrometry and 1H-NMR analysis. The results of measuring their melting stages showed that the purity of products was better. Polyureas were synthesized by two-step solution process of 4,4'-diphenyl diisocyanate(MDI) and amine terminated polyether(Jeffamine D-2000) with different chain extenders. The influence of modified diamine chain extenders on the gel time of the polyurea was investigated. The gel time was prolonged, that is, the reaction activity was decreased when MHAD and Mm-PDA were used as chain extenders instead of HAD and m-PDA. Thermal stability of polyureas was not affected, and their mechanical properties were heightened remarkably.