Effect of isocyanate content on thermal and mechanical properties of polyurea

Novel polyureas with soft segments based on a difunctional amine, Versalink P-1000, and hard segments based on Isonate 143L, which is a mixture of difunctional and trifunctional isocyanates, were synthesized. The stoichiometric ratio of Isonate 143L to Versalink P-1000 in the polyurea material system was incrementally varied. The properties of the resultant polyurea formulations were characterized using dynamic mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). The dynamic mechanical properties measured as storage and loss moduli were significantly altered through the variation of the stoichiometric ratio; however, the glass transition temperatures exhibited in all variations were quite consistent. The experimental results indicate that judicious selection of hard segment content can have a marked effect on the ultimate properties and performance of the polyurea material system.