【作者】 胡娟；

【导师】 蔡浩鹏；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2020， 硕士

【摘要】 传统的航天飞行器液氧贮箱通常采用合金材料制造,而具有高比强度、高比模量优点的碳纤维增强树脂基复合材料（CFRP）制备液氧贮箱时因为可进一步减重、提高飞行器的载荷成为研究的热点。由于液氧具有低温性和强氧化性,所以CFRP在液氧环境中应用,需要具备优异的低温韧性并且与液氧相容,而其中树脂基体性能是主要决定因素之一。一方面,树脂与液氧不相容的本质是材料的热氧老化,提高其阻燃性和热稳定性可以提高材料的液氧相容性;另一方面,改善树脂的低温韧性可以通过添加柔性增韧剂实现。基于以上机理,合成了含有大量柔性硅氧键的超支化聚合物,将这种具有增韧作用且含有阻燃元素的聚合物加入双酚F环氧树脂/二乙基甲苯二胺（DETDA）和异佛尔酮二胺（IPDA）混合胺体系中,改善了环氧树脂体系的低温韧性和液氧相容性;进一步在超支化聚合物中引入磷元素,合成具有硅磷协同阻燃作用的超支化聚硅氧烷,使得改性树脂体系与液氧的相容性更好,得到了兼具韧性与液氧相容性的树脂体系。主要研究内容如下:1、首先将乙烯基三乙氧基硅烷（VTES）与一缩二丙二醇（DPG）反应得到含有大量Si-O键的超支化聚硅氧烷（HBPSi）,然后HBPSi作为增韧剂加入双酚F环氧树脂中。采用红外、核磁表征HBPSi的分子结构;K_IC、拉伸、冲击、SEM、TGA以及液氧冲击测试等对树脂体系固化物的韧性、热稳定性以及液氧相容性等进行研究。结果表明:（1）HBPSi的¹H NMR光谱相比于VTES中（Si-O-CH₂）（3.77ppm）和（Si-O-CH₂-CH₃）（1.16ppm）的峰明显减弱以及相比于DPG中的羟基的峰（4.50ppm）的峰也明显减弱,表明VTES中的-CH₂-CH₃与DPG中的-OH发生反应产生乙醇排出,证明HBPSi成功合成;（2）室温条件下,随着HBPSi的加入改性树脂的断裂延伸率和断裂韧性K_IC呈现先增加后减少的趋势。其中纯环氧树脂的断裂延伸率为3.29%、断裂韧性K_IC为1.98 MPa·m^1/2、冲击强度为7.65KJ/m²,当HBPSi的含量为3%时的韧性最优,断裂延伸率、K_IC和冲击强度分别为6.07%、3.61 MPa·m^1/2和32.9 KJ/m²,分别增加了84.5%、330.1%和82.3%;（3）77K温度环境下,随着HBPSi的加入改性树脂的断裂延伸率呈现先增加后减少的趋势。HBPSi的含量为3%时,断裂延伸率为1.54%相比于纯环氧树脂提高了23.2%,低温韧性提高;（4）随着HBPSi的增加,改性体系的残炭率从15.4%提高到21.7%,热稳定性能提高;改性树脂的液氧冲击敏感性（IRS）不断降低,当含量超过10%时,IRS=0,树脂与液氧完全相容。2、进一步将9,10-二氢-9氧杂-10-磷杂菲-10-氧化物（DOPO）与VTES反生加成反应合成含磷的硅烷（DTES）,然后DTES与DPG反应得到含有硅、磷两种基团的超支化聚合物（P-HBPSi）。结果表明:（1）通过红外、核磁等对其进行表征,DOPO中P-H键和VTES中C=C键特征峰消失,证明P-HBPSi的成功合成;（2）随着P-HBPSi的增加,改性体系的残炭率从15.4%提高到21.8%,极限氧指数LOI值从24.0%提高为31.8%,改性树脂的热稳定性和阻燃性能显著提高;（3）随着P-HBPSi的增加,改性体系的液氧冲击敏感性不断降低。当P-HBPSi的含量超过5%时,IRS=0,树脂与液氧完全相容,对比加入5%的HBPSi的树脂体系,IRS仅为3%,树脂与液氧不相容,表明硅、磷协同作用可以显著改善环氧树脂的液氧相容性且符合热氧老化的机理。含磷、硅官能团在降解过程中产生聚偏磷酸和二氧化硅,同时抑制材料的热分解以及与液氧的反应,提高树脂的液氧相容性。（4）随着P-HBPSi的增加,改性体系的断裂延伸率和冲击强度先增加后降低。并且当P-HBPSi的含量为5%时,断裂延伸率和冲击强度分别从3.29%、7.65 KJ/m²增加到5.27%、19.9 KJ/m²,改性树脂的韧性提高,得到兼具液氧相容性和韧性的环氧树脂体系。更多还原

【Abstract】 Conventional spacecraft liquid oxygen tanks are usually made of alloy materials,and carbon fiber reinforced resin matrix composites（CFRP）with high specific strength and high specific modulus have advantages in the preparation of liquid oxygen tanks because they can further reduce weight and improve the aircraft’s load has become a research hotspot.Due to the low temperature and strong oxidizability of liquid oxygen,the application of CFRP in a liquid oxygen environment requires excellent low temperature toughness and compatibility with liquid oxygen,which mainly depends on the properties of resin matrix.On the one hand,the nature of the incompatibility of the resin with liquid oxygen is the thermal oxygen aging of the material.Reinforcing the flame retardancy and thermal stability of resin matrix can improve the liquid oxygen compatibility of the material;on the other hand,the low temperature toughness of the resin can be optimized by adding flexible toughening agent.Based on the above mechanism,hyperbranched polymer containing a large amount of flexible silicon-oxygen bonds and flame retardant elements was synthesized.Subsequently,the obtained toughening polymer was added into bisphenol F epoxy resin/diethyltoluene diamine（DETDA）and isophorone diamine（IPDA）mixed amine system.Leading to the improvement of the low temperature toughness and liquid oxygen compatibility of the epoxy resin system.In addition,phosphorus was also introduced into the hyperbranched polymer to synthesized the Phosphorus-containing hyperbranched polysiloxane.The silicon-phosphorus synergistic flame retardant effect improves the compatibility of modified resin system and liquid oxygen.Thus,the resin system with good toughness and liquid oxygen compatibility was obtained.The main research contents are shown as follows:1.First,vinyl triethoxysilane（VTES）and dipropylene glycol（DPG）were used to synthesize hyperbranched polysiloxane（HBPSi）containing a large amount of Si-O bonds.Then,the HBPSi,as a toughening agent,was dispersed in bisphenol F epoxy resin.The FTIR,NMR were used to characterize the molecular structure of HBPSi.The K_IC,tensile and impact test,SEM,TGA,and liquid oxygen impact tests were used to study the toughness,thermal stability,and liquid oxygen compatibility of the cured resin system,respectively.The results can be summarized as four points:（1）For HBPSi,the peak intensity of ¹H NMR spectrum of HBPSi is significantly weaker than those of（Si-O-CH₂）（3.77ppm）and（Si-O-CH₂-CH₃）（1.16ppm）in VTES.And compared with DPG,the peak intensity of the hydroxyl group（4.50 ppm）weakens significantly,indicating the reaction between-CH₂-CH₃ in VTES and-OH in DPG,and the production of ethanol,which can the successful synthesis of HBPSi.（2）At room temperature,with the addition of HBPSi,the fracture elongation and fracture toughness K_IC of the modified resin show a trend of increasing first and then decreasing.The pure epoxy resin exhibits an elongation at break of 3.29%,a fracture toughness K_IC of 1.98MPa·m^1/2,and an impact strength of 7.65KJ/m².When the HBPSi content is 3%,the toughness is the best,the elongation at break,K_IC,and impact strength are 6.07%,3.61MPa·m^1/2and 32.9 KJ/m²,which increase by 84.5%,330.1%and 82.3%respectively.（3）Under the environment of 77K temperature,with the addition of HBPSi,the fracture elongation of the modified resin shows a trend of increasing first and then decreasing.When the content of HBPSi achieves 3%,the elongation at break is 1.54%,which is23.2%higher than that of pure epoxy resin,and the low temperature toughness is improved.（4）With the increase of HBPSi,the char yield of the modified system increases from 15.4%to 21.7%and the thermal stability is improved as well.The modified resin’s liquid oxygen impact sensitivity（IRS）decrease constantly.When the content exceeds 10%,IRS=0,the resin was fully compatible with liquid oxygen.2.Further,9,10-dihydro-9oxa-10-phosphaphenanthrene-10-oxide（DOPO）and VTES were used to prepare a phosphorus-containing silane（DTES）.Then,the reaction of DTES and DPG was applied to obtain hyperbranched polymer（P-HBPSi）containing both silicon and phosphorus groups.The results showed that:（1）It was characterized by infrared,nuclear magnetic,etc.The characteristic peaks of P-H bond in DOPO and C=C bond in VTES disappear,proving the successful synthesis of P-HBPSi.（2）With the increase of P-HBPSi the char yield of the modified system increases from 15.4%to21.8%,the limiting oxygen index LOI value increases from 24.0%to 31.8%,indicating the significant improvement in the thermal stability and flame retardancy of the modified.（3）With the increase of P-HBPSi,the modified system’s sensitivity to liquid oxygen shocks continues to decrease.When the content of P-HBPSi exceeds 5%,IRS=0,the resin is completely compatible with liquid oxygen.Compared with the resin system with 5%HBPSi,the IRS is only 3%.This shows that the synergistic effect of silicon and phosphorus can significantly improve the liquid oxygen compatibility of epoxy resin and conform to the mechanism of thermal oxygen aging.During the process of degradation,phosphorus and silicon functional groups produce polymetaphosphoric acid and silica.Which inhibiting the thermal decomposition of the material and the reaction with liquid oxygen to improve the liquid oxygen compatibility of the resin.（4）With the increase of P-HBPSi,the fracture elongation and impact strength of the modified system increase first and then decrease.When the content of P-HBPSi achieves 5%,the elongation at break and impact strength are increase from 3.29%and7.65 KJ/m² to 5.27%and 19.9 KJ/m²,respectively.Meanwhile,the toughness of the modified resin is improved.Thus,an epoxy resin system with desirable liquid oxygen compatibility and toughness was obtained.更多还原