Thermal degradation behaviors of phosphorus-containing liquid oxygen-compatible epoxy resin
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摘要:
环氧树脂在液氧环境中受到机械冲击时,局部温度上升,导致树脂分解产生可燃物质,易引发环氧树脂与液氧之间发生不相容反应。因此,研究液氧相容树脂的热降解行为有助于理解其液氧相容机制。本文采用10-(2, 5-二羟基苯基)-10-氢-9-氧杂-10-磷杂菲-10-氧化物(ODOPB)化学改性双酚A环氧树脂,制备了ODOPB改性液氧相容环氧树脂(ODOPB-EP),通过对其热降解行为进行研究,为理解其液氧相容机制提供理论基础。ODOPB-EP的热降解活化能为154.96kJ/mol,降解机制为相边界反应。在热降解过程中,改性树脂先从C—N和C—O弱键处断裂,随温度升高树脂骨架逐渐断裂生成苯酚及其衍生物等芳香类物质,同时ODOPB会分解生成联苯等物质,过程中伴随着含磷自由基的释放,能淬灭高活性的·H和·OH自由基,从而阻断自由基与液氧的氧化反应,提高树脂的液氧相容性。 ODOPB-EP树脂的降解路径 -
关键词:
- 环氧树脂 /
- 液氧相容性 /
- 热降解 /
- 热重-红外-气质联用
Abstract: The liquid oxygen tanks that made of carbon fiber/epoxy resin composites are vital for weight reduction in new generation spacecraft such as heavy rockets and space shuttles. However, the incompatibility of epoxy resin with liquid oxygen limits their application. Thermogravimetric analyser, the Kissinger method, the Coasts-Redfern method and thermogravimetric-Infrared-gas chromatography/mass spectrometry were used to investigate the thermal degradation behaviors and mechanism of 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphafi-10-oxide (ODOPB)-modified liquid oxygen-compatible epoxy resin (ODOPB-EP). The results show that the thermal degradation mechanism of ODOPB-EP is a phase boundary reaction, corresponding to the degradation mechanism function g(α)=1−(1−α)1/3. During the thermal degradation process, the resin breaks from the weak bonds of C—N and C—O. With the increase of temperature, aromatic substances such as phenol and its derivatives are released. Besides, ODOPB part in resin produces biphenyl and other substances, accompanied by the release of phosphorus-containing radicals. The phosphorus-containing radicals could exert quenching effects, which is conducive to improving the compatibility of the resin with liquid oxygen. This study provides a theoretic basis for verifying the compatible mechanism of polymers with liquid oxygen.-
Key words:
- Epoxy resin /
- Liquid oxygen compatibility /
- Thermal degradation /
- TG-FTIR-GC/MS
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表 1 ODOPB-EP在氮气和空气下的热重数据
Table 1. TG and DTG data of ODOPB-EP under N2 and air atmosphere
Atmosphere Heating rate /(℃·min−1) T5%/℃ Tmax/℃ Residue at 800℃/% Tmax1 Tmax2 N2 5 371.1 389.4 — 18.7 10 376.1 400.6 — 17.8 15 388.3 405.8 — 16.8 20 397.6 421.3 — 16.6 Air 5 319.4 382.7 581.7 0.70 10 335.6 394.6 599.7 0.72 15 353.3 405.3 618.2 0.88 20 358.1 415.6 627.3 1.52 Note: T5%—Temperature corresponding to mass loss 5% of material; Tmax—Temperature corresponding to maximum thermal degradation rate. 表 2 Coasts-Redfern方法计算不同机制模型的活化能及相关系数[22, 23]
Table 2. Activation energy and correlation coefficient calculated by Coasts-Redfern method [22, 23]
Kinetic mechanism models g(α) 5℃/min 10℃/min 15℃/min 20℃/min E/(kJ·mol−1) r E/(kJ·mol−1) r E/(kJ·mol−1) r E/(kJ·mol−1) r F1 −ln(1−α) 158.71 0.875 157.11 0.915 180.91 0.911 186.19 0.906 F2 1/(1-α) 58.89 0.986 56.94 0.974 65.85 0.978 68.02 0.980 F3 1/(1−α)2 129.07 0.988 124.82 0.976 144.33 0.980 149.08 0.983 A2 [−ln(1−α)]1/2 73.72 0.856 73.08 0.900 84.13 0.896 86.58 0.891 A3 [−ln(1−α)]1/3 45.39 0.835 45.07 0.882 51.88 0.878 53.37 0.873 A4 [−ln(1−α)]1/4 31.22 0.808 31.07 0.860 35.75 0.855 36.77 0.849 R2 1−(1−α)1/2 142.04 0.843 140.97 0.889 162.24 0.885 166.93 0.879 R3 1−(1−α)1/3 147.40 0.854 146.17 0.872 168.25 0.894 173.13 0.889 D1 α2 265.41 0.822 263.87 0.872 303.57 0.867 312.26 0.862 D2 (1−α)ln(1-α)+α 284.33 0.842 282.23 0.888 324.80 0.884 334.17 0.879 D3 [1−(1−α)1/3]2 306.08 0.864 303.28 0.906 349.14 0.902 359.31 0.897 D4 (1−2α/3)−(1−α)2/3 291.55 0.849 289.22 0.895 332.88 0.890 342.51 0.885 Note: g(α)—Degradation mechanism function; E—Activation energy; r—Degree of fit. 表 3 不同温度下ODOPB-EP的热分解气相产物
Table 3. Pyrolytic compounds of ODOPB-EP under different temperatures
Peak Compounds m/z Peak Compounds m/z 1 92 9 121 2 106 10 136 3 94 11 160 4 108 12 134 5 107 13 158 6 121 14 174 7 122 15 154 8 122 16 172 -
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