Zhi Wang

The liquid oxygen compatible epoxy resin was obtained by the polycondensation between tetrabromobisphenol A and neat epoxy resins. The results of liquid oxygen impact test indicated that the synthetic epoxy resins were compatible with liquid oxygen. The relationship between impact reaction sensitivity (IRS) and flame retardancy were studied by liquid oxygen impact test and limiting oxygen index test. The results showed that the flame‐retardant modification of epoxy resin was valuable to reduce the IRS. The thermal gravimetric analysis results indicated that the Br · radical was quickly released in relatively low temperature (approximately 370°C) for compatible epoxy resin. The Br · radical was a key factor to promote the epoxy resin compatible with the liquid oxygen. The X‐ray photoelectron spectroscopy was used to survey the distribution of functional groups on the surface of samples before and after impact. The results showed that the oxidation reaction and carbonization process may occur on the surface of samples after impact. The liquid oxygen compatibility mechanism is proposed in this paper. The bromine‐containing epoxy resin has the potential to be the material used in liquid oxygen tank. Copyright © 2015 John Wiley & Sons, Ltd.

Liquid oxygen compatibility mechanism of bromine-modified epoxy resin.

Bisphenol A and bisphenol F epoxy resins (BA and BF) were chemically modified by 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide to improve their liquid oxygen compatibility. The structures of the modified epoxy resins were confirmed by Fourier transform infrared spectroscopy. Significant enhancement of liquid oxygen compatibility for the modified resins was detected according to the liquid oxygen mechanical impact test. Thermogravimetric analysis showed that during the degradation in oxygen atmosphere, the modified resins exhibited much lower weight loss rate and possessed much higher char residues than the control ones. Based on limited oxygen index test, better flame retardancy was also observed for the modified resins. In addition, the modified BA system was more excellent than the modified BF system in liquid oxygen compatibility, thermal stability, and flame retardancy. X‐ray photoelectron spectroscopy analysis showed that after the liquid oxygen impact, the modified resins was still in oxidation stage and the control ones already begun to decompose and char. It could be attributed to formation of the phosphoric oxyacid on the surface of the modified resins, which prevented decomposition and inhibited the reaction between the specimen and liquid oxygen. Copyright © 2014 John Wiley & Sons, Ltd.

The mechanical and thermal properties of epoxy nanocomposites filled with 7–40 nm spherical silica particles were investigated as a function of silica loadings. Due to the ultrasonic dispersion and modification of the coupling agent, the silicon dioxide (SiO₂) nanoparticles were readily dispersed in the epoxy resin with light aggregation for the loading of up to 5 wt% as determined using a scanning electron microscope (SEM). The tensile test indicated that the tensile strength and elongation at break of the nanocomposites increased by up to 23% and 31%, respectively, compared with the neat epoxy resin. The glass transition temperatures of all the epoxy nanocomposites were higher than that of the neat epoxy resin for about 35–45°C, but did not show significant changes with an increase in the silica loading. The fracture surfaces were also observed using SEM, which showed evidence of the SiO₂ nanoparticle debonding.

The bromine element was introduced into an epoxy resin to improve the liquid oxygen compatibility of the epoxy resin. After curing using 4,4′-diamino diphenylmethane, the liquid oxygen compatibility of all specimens was measured by the liquid oxygen mechanical impact test (ASTM D2512-95). The results suggested that the bromine-modified epoxy resin (BEP) was compatible with liquid oxygen, whereas the bisphenol F epoxy resin (EP) had poor liquid oxygen compatibility. The results of thermogravimetric analysis indicated that the incorporation of tetrabromobisphenol A into EP could accelerate the second-stage thermal degradation of BEP, leading to improvement of the liquid oxygen compatibility. X-ray photoelectron spectroscopy analysis indicated that the C–C/H groups on the surface of specimens could be oxidized to C–O–H/C and C=O groups during the impact process. The mechanism of bromine enhancement on the liquid oxygen compatibility of epoxy resin is proposed.

A phosphorus‐containing epoxy resin was synthesized successfully by 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and bisphenol F epoxy resin (DGEBF) and its molecular structure was confirmed by FTIR spectra. The results of the liquid oxygen mechanical impact test indicated that the cured phosphorus‐containing epoxy resin did not show any reactions during the 20 times of mechanical impact, which revealed that it was compatible with liquid oxygen. Thermal properties of the cured epoxy resins were evaluated by differential scanning calorimetry and thermal gravimetric analysis. It was found that the cured phosphorus‐containing epoxy resin had a better thermal stability than DGEBF. The enhancement of thermal stability for the epoxy resin was favorable to improve liquid oxygen compatibility. The X‐ray photoelectron spectroscopy analysis confirmed that the mechanical impact resulted in phosphorus‐containing groups on the surface of the cured phosphorus‐containing epoxy resin thermally decomposed to form phosphoric oxyacid which was in accordance with the mechanism that organo‐phosphorus compounds could work in the condensed phase to inhibit the combustion. These results suggest that the phosphorus‐containing epoxy resin has the potential as the matrix of the liquid oxygen composite tank. POLYM. ENG. SCI., 55:651–656, 2015. © 2014 Society of Plastics Engineers

In this study, bisphenol A epoxy resin (DGEBA) was chemically modified by 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and the molecular structure of the modified epoxy resin was characterized by Fourier transform infrared spectra. The effects of DOPO on liquid oxygen compatibility of DGEBA were calculated using mechanical impact method. The results indicated that epoxy resin (EP‐P1)/4,4‐diaminobisphenol sulfone (DDS) was compatible with liquid oxygen. When compared with EP/DDS, differential scanning calorimetry and thermogravimetry analyses showed that EP‐P1/DDS and EP‐P2/DDS had much higher glass transition temperatures and char yield. X‐ray photoelectron spectroscopic analysis suggested that phosphorus atoms on the surface of EP‐P1/DDS and EP‐P2/DDS could act in the solid phase to restrain the incompatible reaction, which was in accordance with the flame‐retardant mechanism of phosphorus‐containing compounds. The compatibility mechanism of EP‐P1/DDS was further proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 40848.