Study On The Green Synthesis Of Polycarbonate Urethane

The green process to synthesize polycarbonate urethane (PCU) was studied in this paper. PCU was prepared from 1,6-hexamethylene dicarbamate (HDC) and polycarbonate diols (PCDL) via transesterification and polycondensation. The whole synthetic route was environmental friendly using low-toxic HDC instead of high-toxic 1,6-hexamethylene diisocyanate (HDI) which was widely used in the traditional production of polyurethane. HDC was prepared from the green chemical dimethyl carbonate (DMC) synthesized from carbon dioxide, which meant the whole process was beneficial to reduce carbon dioxide emission.The influence of catalyst categories, polycondensation temperature, the amount of catalyst, polycondensation time, the composition ratio of raw materials, rotation rate, prepolymerization temperature and time on transesterification and polycondensation of HDC and PCDL was investigated respectively. The optimal conditions were confirmed as follows: using titanium tetraisopropanolate as catalyst, the molar ratio of HDC to PCDL being 1:1, the amount of catalyst being 0.20wt%, the rotation rate being 40r-min-1, at atmospheric pressure and 110℃, prepolymerizing for 1.25h, then in vacuum condition, at 180℃, polymerizing for 5h. The intrinsic viscosity of the PCU product was 51.92ml·g-1 and Shore hardness was 36D.Gel permeation chromatography (GPC) and thermogravimetric analyzer (TGA) were used to characterize the PCU product synthesized under the optimal conditions. The results showed that the molecular weight of PCU was up to 49,381 with narrow molecular weight distribution, and the extensional-thermal decomposition temperature was 328℃.