【作者】 邱求元；

【导师】 肖加余；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2007， 硕士

【摘要】 多面体低聚硅倍半氧烷(Polyhedral oligomeric silsesquioxane,POSS)是一种新颖的、具有三维笼状立体结构的有机—无机纳米杂化材料,不仅兼具有机材料优良的加工性、韧性与低成本,同时保留了无机材料耐热、耐氧化与优异的力学性能。通过POSS顶角的有机基团将POSS分子引入环氧树脂交联网络之中,可以有效提高环氧树脂的使用温度、抗氧化性能等。本文采用七苯基三硅烷醇POSS(TSP-POSS)对AFG-90树脂/甲基四氢苯酐(简记为AFG-90/MeTHPA)体系和AFG-90树脂/4,4′-二氨基二苯砜(简记为AFG-90/DDS)体系进行改性研究。探讨了POSS改性环氧树脂的机理及改性工艺。研究表明TSP-POSS改性AFG-90环氧树脂的较佳工艺方案为:TSP-POSS与AFG-90经超声分散后在110℃预反应15小时后加入固化剂进行固化,AFG-90/MeTHPA体系促进剂三乙胺(TEA)的较佳用量为0.3wt%,而促进剂TEA不适用于AFG-90/DDS体系。固化动力学研究表明,AFG-90/MeTHPA/TSP-POSS/TEA体系及AFG-90/DDS/TSP-POSS体系固化过程均可用拓展Prout-Tompkins方程描述,即反应为具有自催化特征的n(m)级复杂反应。同时FT-IR分析表明AFG-90环氧树脂经酸酐固化剂MeTHPA或芳胺固化剂DDS固化后环氧环基本发生开环反应,并分别形成酯结构与叔胺结构,而TSP-POSS在固化过程中其骨架结构并没有被破坏。通过扫描电镜观察发现,除TSP-POSS含量为10wt%的AFG-90/DDS/TSP-POSS体系存在未反应TSP-POSS的富集区,TSP-POSS在其它改性体系中均能较均匀地分散,没有观测到未发生化学反应TSP-POSS的富集区。通过静态及动态力学研究方法、热失重方法,对两类改性体系的热、力学性能进行了研究,发现TSP-POSS的引入使环氧体系的拉伸强度、弯曲强度及断裂延伸率略有降低,而拉伸模量与弯曲模量有所提高;但大幅度提高了改性体系玻璃化转变温度T_g、热变形温度、热稳定性能及储能模量E,同时降低了体系的热膨胀系数与损耗因子tanδ峰强度。其中,AFG-90/MeTHPA/TSP-POSS/TEA体系及AFG-90/DDS/TSP-POSS体系的玻璃化转变温度T_g提高幅度分别达到23.80℃和22.78℃。此外,化学流变学研究表明:AFG-90环氧树脂经TSP-POSS改性后室温粘度显著增加,而TSP-POSS的引入只对AFG-90/MeTHPA体系的初始粘度有影响,对低温反应初始阶段的粘度变化影响并不明显。在反应的初始阶段,粘度不高于2000mPa·s时,AFG-90/MeTHPA/TSP-POSS体系的化学粘度变化符合双Arrhenius经验公式。根据此公式预报的AFG-90/MeTHPA/TSP-POSS体系RTM注射温度为20℃～30℃。更多还原

【Abstract】 The emerging of polyhedral oligomeric silsesquioxane (POSS) organic-inorganic hybrid nanocomposites that combine the processibility and flexibility of typical organic thermoplastics with high service temperature and oxidation resistance of inorganic ceramics, has received great attentions recently. Generally, POSS cages which have the precise three-dimension size, can be incorporated into epoxy molecular network via copolymerization or grafting polymerization to improve the thermal properties and oxidation resistance of epoxy systems.In this paper, the triglycidyl p-aminophenol epoxy resin (AFG-90) was first modified by trisilanolphenyl polyhedral oligomeric silsesquioxanes (TSP-POSS) and then cured by two kinds of curing agents, 3-(or 4)- methyl-tetrahydrophthalic anhydride (MeTHPA) and 4,4’-diamino-diphenyl-sulfone (DDS), respectively. According to the thermal propertites of epoxy systems modified with TSP-POSS via differents technics, the proper modification technics is that TSP-POSS can be properly dispersed in AFG-90 resin by ultrasonic, the pre-reactive time of AFG-90 resin and TSP-POSS is 15 hours, and the loadings of catalyst triethylamine (TEA) of AFG-90/MeTHPA system is 0.3 wt%, while TEA is not compatible with the AFG-90/DDS system.The investigation of curing kinetics of modified epoxy systems indicates that the studied curing process can be described by the two-parameter expended Prout-Tompkins kinetic model with autocatalysis. The molecular structures of AFG-90/MeTHPA system and AFG-90/DDS system were characterized by Fourier transform infrared spectroscop. The results show that epoxy groups disappeared after cured by MeTHPA or DDS, ester and tertiary amine structures were formed, accordingly, while the structures of TSP-POSS cages were not destroyed. Phase separation was not observed in the epoxy systems modified by TSP-POSS by scanning electronic microscopy, except for the AFG-90/DDS system with TSP-POSS content of 10wt %.The thermal and mechanical properties of the epoxy systems modified by TSP-POSS were also measured. It shows that the glass transition temperature, thermal deformation temperature, the thermal dimensional stability, and bending storage module E of Epoxy/TSP-POSS increased with increasing content of TSP-POSS, while the thermal expansion coefficient and tanδpeak intensity decreased. The maximal enhancement of glass transition temperature of AFG-90/ MeTHPA system and AFG-90/DDS system were 23.80℃and 22.78℃, respectively. However, the flexural strength, tensile strength and breaking extension of Epoxy/TSP-POSS decreased with increasing content of TSP-POSS, while the flexural module and tensile module increased.Furthermore, the chemo-rheology investigation indicates that the viscosity of AFG-90 resin was greatly increased after modified with TSP-POSS, and the present of TSP-POSS in AFG-90/ MeTHPA had little influence on the initial viscosity, but no evidence was found that it had influence on the viscosity at the initial reaction stage. A rheological model based on dual-Arrhenius equation was established and used to simulate chemo-rheological behavior of the AFG-90/MeTHPA/TSP-POSS system. The viscosity estimated by the model was in good agreement with that of the experiment results at the initialization reaction stage. The rheological model shows that the optimum processing temperature of the resin system for RTM process is between 20℃and 30℃.更多还原