【作者】 霍莉；

【导师】 高俊刚；

【作者基本信息】 河北大学 ， 分析化学， 2009， 博士

【摘要】 液晶环氧树脂融合了液晶有序与网络交联的优点,具有优异的机械、热、电,光等方面性能,特别是耐热性、尺寸稳定性、抗冲击性,取向方向、介电性能优异,特别适用于对性能要求高的微电子封装材料,航空航天,军事国防等领域,是一种深具潜力的功能材料,也可以用来制备高性能复合材料。本论文合成了一系列以双酚-S和双酚-F为介晶基元的新型液晶环氧树脂,并对其固化机理、动力学及改性通用环氧树脂进行了较系统的研究,对液晶环氧树脂进一步发展有指导意义。以乙二醇单烯丙基醚、3-溴1-丙烯、6-1-己烯、对羟基苯甲酸乙酯,双酚-S和双酚-F为原料,经不同的方法分别合成了以双酚-S和双酚-F为介晶基元的一系列新型的不同长度不同柔性链基团的不饱和末端基的液晶化合物和液晶环氧化合物,用DSC、FTIR、1H-NMR、POM、XRD对其进行了表征,测定了其熔点、清亮点,得到其液晶区域范围和形态织构。探讨了分子结构对液晶行为的影响,为合成新型液晶化合物或设计新型的液晶功能高分子材料提供思路。用示差扫描量热分析(DSC)、FTIR、动态力学谱(TBA), POM等方法研究了新型的p-BEASPA、p-SBPEPB等液晶环氧树脂和不同的固化剂(4,4-二氨基二苯醚(DDE)、4,4-二氨基二苯甲烷(DDM)、4,4-二氨基二苯砜(DDS)和甲基四氢苯酐(MeTHPA)以及相应的羟基(-OH)催化固化体系的固化行为；通过等转化率方法(主要采用Ozawa方程,Kissinger方程和Friedman方程)计算了反应活化能Ea和转化率α的关系；探讨了合适的动力学模型(主要为Sestak-Berggren模型和JMA模型),求得了各固化反应体系的动力学的参数和相应的热力学参数(m, n, A, k,ΔS);证明了羟基(-OH)催化能降低环氧树脂的固化反应的活化能Ea,同时讨论了固化反应的分子历程。通过观察固化产物织构,证明液晶有序结构已经固定在固化系统中。对通过非等温自催化Sestak-Berggren模型所预测的动力学参数和实验数据之间出现偏差的情况,探讨了扩散对非等温动力学的影响,并在Sestak-Berggren方程中引入了扩散因子f’(a)用来描述非等温的固化反应,修正后的动力学关系式理论值和实验值能很好的符合,丰富了非等温动力学方法。利用合成的液晶环氧树脂改性普通环氧树脂,研究了共混体系的热性能、力学性能、形态、固化动力学,得到了固化反应的活化能,反应级数等动力学参数。研究了液晶环氧树脂与普通环氧树脂不同配比对固化反应和产物热性能和力学性能的影响,发现适度加入液晶环氧树脂能提高普通环氧树脂的玻璃化温度Tg,抗冲强度,热分解温度也有所提高,该研究为液晶增韧环氧树脂提供了固化反应的工艺参数和实验数据。以上工作,为液晶坏氧化合物的合成与固化反应提供了理论依据,有望推动热固性液晶树脂领域方面研究的完善,对实际工业生产有一定指导意义。更多还原

【Abstract】 Liquid crystalline thermosets (LCTs) can form high-orderly and deep-crosslinked polymeric materials. Compared to ordinary epoxy resins, liquid crystalline epoxy resins (LCER) have capabilities of heat-resistant, a relatively low coefficient of thermal expansion and higher dimensional stability, higher dielectric strengh and lower dielectric dissipation. Therefore, it can be applied in many industrial scopes as adhesive, matrix for advanced composites, electronic packaging material, et al. In this article, some novel LC epoxy resins based on bisphenol-S and bisphenol-F mesogen were synthesized and their curing behaviors, kinetics and reaction mechanism were investigated.A series of novel LC compounds which have different length and different flexible groups aromatic unsaturated or epoxy end group based on bisphenol-S and bisphenol-F mesogen were synthesized from bisphenol-F, bisphenol-S,3-bromopropene,6-brome-1-hexene, allyl 2-hydroxyethyl ether. Their molecular structures and liquid crystalline behaviors and textures were characterized by FTIR, DSC,1H NMR, POM and XRD. The melting point and cleaning point were mensurated.Curing behaviors and curing morphology of these novel LCERs with different curing agents (such as DDM, DDS, DDE, and MeTHPA) and catalyzed activation of hydroxyl group for curing reaction were characterized by DSC, FTIR, TBA, POM, XRD and 1HNMR. Curing process and cure kinetics were investigated by isothermal and non-isothermal DSC. The relationships of the apparent activation energy Ea with the conversionαin the curing process were determined by the isoconversional method (Ozawa’s equation, Kissinger equation, Friedman equation) and the overall curing reactions can be described by autocatalytic kinetic model. Some parameters (the even reaction orders m, n, the pre-exponential factor A, the rate constant k) and the activation entropy AS were evaluated. The results show that the hydroxyl group has catalyzed activation and can decrease the Ea for curing system in DSC experiment. The curing reaction molecular mechanism was proposed further.The curing reactions were evaluated used an non-isothermal autocatalytic kinetic model of Sestak-Berggren equation, which there are some deviations for those theoretically calculated with experimental data at higher heating rates and last stages of curing reaction. The diffusion effect in the non-isothermal curing reaction was discussed and a diffusion factor f’(α) was proposed and introduced into Sestak-Berggren equation, which is possible to describe and predict the non-isothermal curing reaction of epoxy resin. The theoretical values agree very well with the experimental data according modified Sestak-Berggren equation.The ordinary epoxy resin were modified with the novel synthetical LCER, The thermal properties, mechanics properties, morphology and curing kinetics of the mixed systems were studied. The effect of the different liquid crystalline contents on curing reaction and the heating rate and curing conversion rate were discussed. The curing process, thermal behavior and morphological structure of these systems were investigated by DSC and torsional braid analysis (TBA) and scanning electron microscope (SEM). The results show that the glass transfer temperature Tg and the mechanical properties increases with adding of LCER and has a best content.So these studied results will impel the development of LCTs fields and provide instruction to practical production.更多还原