Synthesis and characterization of carborane-containing polyester with excellent thermal and ultrahigh char yield

A series of wholly carborane-containing polyesters with high thermostability were successfully synthesized by the catalytic polycondensation of carborane diol monomers with carborane diacid chlorides. They can be used for the preparation of materials of high temperature resistant coatings and adhesive. The influence of solvent, reaction temperature, and reaction time on the molecular weight and yield of the polymers were studied. In comparison with the carborane-free polyester, the carborane-containing polyesters showed higher degradation temperature and char yield and lower degradation rate. The thermal gravimetric analyzer (TGA) curves indicate that the carborane group could effectively reduce the degradation rate of carborane-containing polyesters, which give a char yield of exceeding 64% under air (47% under N2) at 700 °C. Such data are superior to the carborane-free polyester, which showed a low char yield of around 0.3% under air (5% under N2) at the same condition. Moreover, the thermal transition mechanism of carborane-containing polyesters was also studied. The FTIR spectra and TG-FTIR analysis indicate that the carborane cage could react with oxygen to form BOB and BC linkages at elevated temperatures, which postpones the thermal decomposition of polyester and accounts for the high char yield. The newly prepared kind of high temperature polyesters have enormous technical and economic value, especially in the high temperature fields. They can be widely used as raw materials to prepare the high temperature resistant coatings or adhesives for automotive engine, aircraft and other equipments worked in high-temperature environments. Under high environmental temperature, the good thermal stability is capable of keeping polyesters stable and expanding their service lives. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44202.