Oxidatively stable thermosets derived from thermal copolymerization of acetylene-terminated imide monomer with an acetylenic monomer containing carborane

Abstract

One acetylenic monomer (APCB) containing carborane with extremely thermal and thermo-oxidative stability was synthesized and used as the thermal copolymerization component with acetylene-terminated imide monomer (m-EFDA) to improve the thermal and thermo-oxidative stability of the polyimide materials. The curing behavior of the blends of imide monomer and APCB was investigated by FT-IR and DSC. Rheometer study showed that the addition of APCB into m-EFDA reduced the minimum complex viscosity of m-EFDA and lowered the temperature of the minimum viscosity. The thermal and thermo-oxidative stability of the thermoset derived from m-EFDA was greatly improved by the addition of APCB based on thermogravimetric analysis. m-EFDA with an addition of APCB at a loading level of 50 wt% exhibited a high char yield of 91.5 % at 1000 o C in air and a weight retention of 95.6 % was obtained after aging in air at 400 and 500 o C for 5 h, respectively.

HighTgand Thermo‐Oxidatively Stable Thermosetting Polyimides Derived from a Carborane‐Containing Diamine

“…However, carborane‐free OBA‐BPDA‐2 thermoset showed a weight loss of 10% after aging 400 °C for 5 h. Even worse than that, due to the lack of passivation layer, OBA‐BPDA‐2 thermoset was observed to undergo catastrophic weight loss in 500 °C aging segment and burnt out quickly. A similar result was previously reported for other carborane‐free PI …”

“…Cheng et al. also reported a series of carborane‐containing copolymer PIs, which showed that the T g , thermal and thermo‐oxidative stability of the resulting PIs were improved by the addition of an acetylenic monomer containing carborane; and the thermoset derived from the pure carborane‐containing acetylenic monomer exhibited the highest T g value of 455 °C …”

“…In the field of advanced polymers, thermosetting polyimides (PIs) occupy a preponderant position due to their excellent chemical stability, thermal and mechanical properties . Thermosetting PIs are being designed for aerospace applications to meet the expectation of performance and durability in high temperature oxidative environments . It is well known that, the glass transition temperature ( T g ) is a fundamental characteristic of any thermoset, and polymers with higher T g are actively sought for a variety of high‐performance applications .…”

“…However, the conventional PIs, due to the influence of bond energy of C, H, O, and N, are susceptible to decomposition at elevated temperatures in oxidative environments, and have T g which are usually lower than 450 °C . In order to break through the limitations of conventional polymers, many studies have been carried out to improve the thermal stability by introducing organic heterocyclic groups into polymers’ chains …”

“…Since B 2 O 3 is one of the surface coatings to prevent carbon materials from oxidizing at high temperatures, the CBA‐BPDA‐2 exhibited only 2.1% decrease in weight after the temperature rising to 500 °C and aging at 500 °C for 5 h. Importantly, TGA trace of CBA‐BPDA‐2 thermoset showed the total weight retention of 99.9% after aging treatment. A similar trend was previously reported for the carborane‐containing thermoset derived from carborane‐containing acetylenic monomer, demonstrating that the introduction of carborane cage to thermosets resulted in excellent thermo‐oxidative stability.…”