Improvement of the liquid oxygen compatibility of epoxy via the addition of surface‐modified boehmite

Abstract

To improve the liquid oxygen compatibility and cryogenic mechanical properties of epoxy resin, we synthesized and characterized a hybrid compound (functionalized boehmite) containing boehmite, phosphorus, and silicon element. The thermal properties and liquid oxygen compatibility of the composites were investigated in detail. The results show that the addition of functionalized boehmite increased the char residue obviously but had little effect on the thermal decomposition temperature and glass-transition temperature of the composites. The liquid oxygen compatibility of the composites was significantly improved. Composites with 4 wt % boehmite, 0.99 wt % Si, and 1.1 wt % P passed the impact test. Surface element analyses before and after the drop tests suggested that the functionalized boehmite in epoxy might have prevented the impact reaction in liquid oxygen through two steps. First, the compound decomposed into phosphoric oxyacid and Al 2 O 3 under the impact energy and captured the H• and •OH radicals produced from the decomposition of the resin. Then, the decomposition covered the surface, forming a protective layer to isolate the oxygen. The mechanism of the liquid oxygen compatibility of the epoxy composites was subsequently analyzed. In addition, the cryogenic tensile properties of the epoxy composites containing functionalized boehmite showed that the composites had potential applications under cryogenic liquid oxygen environments.

A Review of the Polymer for Cryogenic Application: Methods, Mechanisms and Perspectives

“…The functioned nanomaterial could improve the flame retardancy, thermal stability and cryogenic mechanical properties of the resin system. Mixing a certain amount of the DOPO modified nanofiller (boehmite) into pure epoxy could also improve the liquid oxygen compatibility of the resin system [157]. Peng et al synthesized a phosphorous-containing benzoxazine monomer (PBA), and treated PBA as harder to cure EP [158].…”

“…Due to the flame-retardant ability of phosphorous and the thermal stability of benzoxazine [159,160], the modified polymer mentioned above showed great potential manufacturing the LOX composites tank for its comprehensive performance (mechanical properties and LOX compatibility). Therefore, it has been proven that improving the flame retardancy, thermal stability of polymer is an effective way to enhance its LOX compatibility [150][151][152][153][154][155][156][157][158].…”

Siloxane-decorated MXene nanosheet-reinforced EP composites with outstanding flame retardancy and liquid-oxygen compatibility for ultra-low-temperature applications

“…When the KH550–MXene content was increased to 3%, one burning phenomenon occurred out of 20 experiments, indicating that the liquid-oxygen compatibility of EP nanocomposites decreased. 45 IRS was computed according to formula (1) below:…”

Liquid Oxygen Compatibility and Ultra-Low-Temperature Mechanical Properties of Modified epoxy Resin Containing Phosphorus and Nitrogen

“…Li et al [ 35 ] synthesized EP modified by 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) and EP-A, and the enhanced flame retardancy and thermal stability were proven to improve the LOC of EP, but the mechanism of ODOPB affecting the LOC has not been analyzed in depth. Wang et al [ 36 ] introduced a hyperbranched compound containing phosphorus, silicon elements and boehmite into EP; the results showed that the modified EP could achieve LOC, but the tensile properties of the modified EP at 90 K were decreased and the fracture toughness has not been studied. Li et al [ 27 ] utilized DOPO-PGE to modify EP, and the results indicated that DOPO-PGE was a promising additive in the field of enhancing the LOC of the EP matrix and CFRP, but the mechanical properties of DOPO-PGE-modified EP need further research.…”