A low-cost and liquid oxygen-compatible epoxy matrix of composites by introducing aryl phosphinate diglycidyl ether

Abstract

Replacing traditional metal tanks with composite liquid oxygen (LOX) tanks would make significant contribution to the weight reduction of rockets. However, the epoxy resins (EP) matrix of composites is incompatible with LOX, which limits the application of composite LOX tanks. In this study, an aryl phosphinate diglycidyl ether (PDGEP) was synthesized using 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) and epichlorohydrin via a single step. The structure of PDGEP was confirmed by FTIR spectra, NMR and LC-MS analysis. Meanwhile, PDGEP was introduced into biphenol A (E51) resin at different weight ratios by physical blending. When the content of PDGEP exceeded 10 phr, E51 matrix exhibited compatibility with LOX. The LOX-compatible mechanism was investigated by TGA, UL-94, TG-FTIR-MS analysis and XPS analysis. The results showed that the enhanced thermal stability under high temperatures, the quenching effects from the phosphorus-containing free radicals, the decrease of the combustible volatiles, and the shielding and protective char layer with highly carbonized aromatic networks were all responsible for the compatibility of E51 matrix with LOX. Furthermore, the flexural strength (883.31 MPa) and flexural modulus (14.83 GPa) of the carbon fiber reinforced EP10 (CF/EP10) composites at 90 K increased by 2.3 % and 12.9 % than those of the CF/EP0 composites. The LOX-compatible resin matrix and composites exhibit good potential for developing light-weight LOX composite cryotanks.