The Effect of Stoichiometric Ratio on Viscoelastic Properties of Polyurea

摘要

Polyurea is a commonly utilized elastomer due to its excellent thermo-mechanical properties. In this study, the polyurea is synthesized using Versalink P-1000 (Air Products) and Isonate 143 L (Dow Chemicals). The diisocynate blocks generally assemble into hard domains embedded in the soft matrix, creating a lightly cross-linked heterogenous nanostructure. We seek to evaluate the effect of the stoichiometric ratio of the two components on the viscoelastic properties of the resultant polyurea. By altering the ratio, polyurea samples with different stoichiometric variations are made. In order to approximate the mechanical properties of polyurea for a wide frequency range, master curves of storage and loss moduli are developed. This is achieved by time-temperature superposition of the dynamic mechanical analysis (DMA) data, which is conducted at low frequencies and at temperatures as low as the glass transition. Furthermore, in order to access the effect of the stoichiometric ratio on the relaxation mechanisms in the polyurea copolymer system, continuous relaxation spectra of all the stoichiometric variations are calculated and compared.