The effect of 10-(2,5-dihydroxyphenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide on liquid oxygen compatibility and cryogenic mechanical properties of epoxy resins

In the present study, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) was chemically incorporated into bisphenol A epoxy resin (EP) to improve liquid oxygen compatibility of the EP. Fourier transform infrared (FTIR) spectroscopy verified that ODOPB was successfully introduced into the molecular chain of bisphenol A EP. Thermogravimetric analysis confirmed that the ODOPB-modified EPs exhibited much better thermal stability than the pristine ones during the whole decomposition process under oxygen atmosphere. The 4,4-diaminodiphenyl sulfone (DDS)-cured resins showed higher initial degradation temperature, and the 4,4-diaminodiphenyl methane (DDM)-cured resins demonstrated better thermal stability at high temperature. The results of limited oxygen index measurements indicated that the modified EPs also possessed much improved flame retardancy. Furthermore, the enhanced liquid oxygen compatibility of the modified EPs characterized by the liquid oxygen impact test implied that improving thermal stability and flame retardancy of EPs was beneficial to enhance their liquid oxygen compatibility. X-ray photoelectron spectroscopy results demonstrated that the DDS-cured modified EPs had much higher reactivity with liquid oxygen compared to the DDM-cured ones. Mechanical performance tests indicated that the introduction of ODOPB could simultaneously improve the tensile properties and fracture toughness of the EPs at cryogenic temperature. Summarily, it can be considered that the ODOPB-modified EPs have the application prospect in the fabrication of the composite liquid oxygen tanks.