【作者】 郑芸；

【导师】 江平开；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 绝缘是电机可靠运行的保障,绝缘处理技术以及绝缘材料的性能是决定绝缘结构性能的重要因素。真空压力浸渍(V.P.I.)技术是现代最先进的绝缘处理技术,广泛应用于大容量电机的对地主绝缘中。V.P.I.技术包括云母带、V.P.I.树脂、V.P.I.设备和V.P.I.工艺等几大要素,其中V.P.I.树脂作为主绝缘材料的重要组成部分,对V.P.I.绝缘质量和运行的安全可靠性起着决定性的影响,因此开发新型的综合性能优良的V.P.I.树脂是电机技术发展进步的一个重要课题。本文以新型脂环族环氧化合物为基体树脂,采用甲基六氢邻苯二甲酸酐为固化剂,乙酰丙酮金属络合物为促进剂,并选择无毒或低毒且挥发性低的反应性硅氧烷化合物为环氧树脂活性稀释剂,在降低环氧树脂粘度的同时,利用硅氧烷的同步水解缩合反应形成长链-Si-O-Si-结构,并结合纳米技术对环氧树脂进行增强增韧改性,系统研究了环氧树脂的固化反应机理,通过对环氧V.P.I.树脂配方工艺的优化,研究了不同组分和含量对环氧树脂固化反应、固化物微观结构以及绝缘性能、耐热性、机械性能等的影响,制备了新型无毒环保的环氧V.P.I.树脂,一方面可以用于大容量电机的主绝缘,另一方面可以用于高温电机如H级绝缘。本文研究比较了含有环氧基、氨基或乙烯基的反应性硅氧烷,包括:γ-缩水甘油醚氧丙基甲基二乙氧基硅烷(GPMDS)、β-(3,4环氧环已基)乙基三乙氧基硅烷(ECETES)、γ-缩水甘油醚氧丙基三甲氧基硅(GPTMS)、β-(3,4环氧环已基)乙基三甲氧基硅烷(ECETMS)、γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MAPTMS)、乙烯基三乙氧基硅烷(VTES)和苯胺甲基三乙氧基硅烷(PMTES)对环氧V.P.I.树脂固化反应及固化物性能的影响,结果表明:在乙酰丙酮铝存在情况下,GPMDS的加入能够有效降低环氧树脂的粘度,改善其加工性能,且对固化反应没有明显的影响,固化物表现出良好的绝缘性、耐热性和机械性能。有机硅氧烷对环氧树脂固化反应和固化物性能的影响比较复杂,与其反应性基团(环氧基、乙烯基或氨基)以及烷氧基的结构有密切关系。环氧基和乙烯基硅氧烷对环氧树脂体系的影响主要取决于烷氧基的结构,含有甲氧基的硅氧烷水解缩合反应活性高,在乙酰丙酮铝促进作用下对环氧树脂固化交联反应影响比较大;而含有乙氧基的硅氧烷水解缩合反应活性比较低,对固化反应和固化物性能影响比较小;氨基硅氧烷中的氨基在较低的温度下能够与酸酐固化剂反应生成羧酸,从而促进环氧树脂固化反应,导致体系储存性降低,但对固化物绝缘性能没有不良影响。本文系统研究了GPTMS改性环氧树脂(GPTMS-EP)体系中环氧树脂固化与硅氧烷水解缩合同步反应之间的相互影响及对固化物性能的影响,结果表明:GPTMS-EP体系的固化反应和固化物性能与促进剂关系密切,乙酰丙酮铝(Al(acac)3)的促进作用使硅氧烷的水解缩合反应先于环氧树脂的固化反应而发生并影响后者的反应深度,在环氧树脂微观结构中产生相分离,从而导致固化物性能下降;而在乙酰丙酮钕(Nd(acac)3)存在的情况下,GPTMS对环氧树脂固化反应没有明显的影响,GPTMS-EP固化物表现出良好的耐热性、绝缘性和机械性能,Nd(acac)3是更适合于GPTMS-EP体系的潜伏性促进剂。本文通过差示扫描量热分析(DSC)和升温红外分析(Heating-FTIR)研究了乙酰丙酮金属络合物对环氧树脂固化反应的促进机理,结果表明,在一定温度下,乙酰丙酮金属络合物与酸酐反应形成过渡化合物,攻击环氧树脂开环从而引发固化反应。本文通过动态DSC方法研究了环氧树脂固化过程,推算了其理论凝胶温度和固化温度,并通过Kissinger、Friedman-Reich-Lev等方法研究了环氧V.P.I.树脂的固化反应动力学,计算了不同V.P.I树脂体系的固化反应参数;结果表明环氧V.P.I.树脂是复杂反应体系,且GPTMS和GPMDS可以降低环氧树脂的凝胶温度和固化反应温度。本文在有机硅氧烷(GPMDS)改性的基础上,采用纳米二氧化硅增强增韧环氧V.P.I.树脂,研究了纳米二氧化硅及其表面改性对环氧V.P.I.树脂固化反应、玻璃化转变和介电行为、耐热性能、热机械性能和微观结构等的影响。研究表明:纳米二氧化硅与环氧树脂基体具有良好的相容性,固化物性能取决于纳米二氧化硅的含量及其在环氧树脂基体中的分散情况。未经表面改性的纳米二氧化硅容易团聚,分散困难,在含量不高的情况下(不超过3 wt%)可以提高环氧V.P.I.树脂的强度和韧性,且对环氧树脂的耐热性没有明显的影响,但是由于大量的羟基被吸附在纳米二氧化硅表面而引入环氧V.P.I.树脂中,导致环氧树脂固化物直流电导和介质损耗增加,绝缘性能下降;而经过GPMDS表面处理的纳米二氧化硅(T-silica)分散性良好,受到冲击时作为应力集中点吸收部分能量,起到明显的增强增韧效果;T-silica在树脂基体中作为物理交联点,可明显提高环氧树脂固化物的玻璃化转变温度和耐热性,固化物具有良好的绝缘性能。更多还原

【Abstract】 Groundwall insulation is employed to separate the copper conductors from the grounded stator core in the electric machines. The performances and service life of the groundwall insulation of the stator is critical to the service life of electric machines. At present,the vacuum pressure impregnation process (V.P.I.) is one of the most promising technologies for the groundwall insulation of electric machines and are widely adopted by many leading electrical equipment manufacturers around the world. Groundwall insulation systems for vacuum-pressure-impregnated (V.P.I.) coils of high voltage stators are usually glass-backed mica paper tape system. The coils are insulated with mica paper tape and then vacuum-pressure-impregnated with the impregnating resin. Therefore, the performance of the impregnating resin is one of the key factors accounting for the evolution of the groundwall insulation. Accordingly, the availability of an impregnating resin with improved dielectric properties as well as excellent mechanical performances and thermal stability for the V.P.I process is eagerly desired from the viewpoint of the moter/ or generator technology development.In this study, multifunctional-reactive silicon compounds with very low toxicity have been used as reactive diluents for epoxy impregnating resin based on a kind of cycloaliphatic epoxy resin and methyl-hexahydrophthalic anhydride (MHHPA) system, with the catalysis of aluminum (III) acetylacetonate (Al(acac)3). This is based on the following considerations: firstly, the organosiloxane are effective diluents since they have very low viscosities and are mutually soluble with the epoxy resin at all temperatures; secondly, the existence of the reactive groups like epoxide, amino, or vinyl groups enables the diluents to be involved in the cross-linking networks of the epoxy resin; and at last, the reactivity of Si-OR makes the structure design possible. It can be expected that polysiloxane may be produced in the cross-linking network of the cured epoxy resin via synchronous reactions, which could improve the toughness of the epoxy matrix. Besides, nano-silica particles have been employed to enhance the epoxy impregnating resin. To develop an eco-friendly epoxy impregnating resin system for groundwall insulation of large generators, the curing reaction mechanism has been fully studied, the formulation and the curing techniques have been optimized, and the influence of different constitution on the curing reaction, microstructure, and final performances have been studied and characterized.In this paper, influences of different reactive organo-siloxanes on the curing reaction and performances of epoxy V.P.I. resin have been studied and compared. The results show that: in the presence of Al(acac)3, the addition of GPMDS can obviously reduce the epoxy viscosity, improve the processability and toughness without imparment to the insulating properties and thermal stabilities. The influences of organo-siloxanes on the curing reaction and performances of epoxy V.P.I. resin are very complicated and greatly related to the reactive structures (epoxide, amino, or vinyl groups) and the silicon structures.In this paper, the interaction between the hydrolysis/condensation of (3-glycidoxypropyl) trimethoxysilane (GPTMS) and the curing reaction of epoxy resin have been studied, as well as the influences on the properties of the cured samples. The results show that the influence of GPTMS on the curing reaction of epoxy resin is very complicate and is greatly influenced by the catalysts. With the catalysis of Nd(acac)3, the incorporation of GPTMS into epoxy resin has a slight influence on the curing reaction, and considerable enhancement in toughness have been obtained without impairments to thermal stability and insulating properties. Differently, with the catalysis of Al(acac)3, the hydrolysis and condensation of GPTMS prior to the curing polymerization of epoxide and anhydride can been greatly facilitated and detected by the DSC analysis which induces phase separation and inhomogeneity in the micro-morphologies of the cured sample and accordingly decreased glass transition temperature, thermal stability, insulating and mechanical performances.DSC and Heating-FTIR have been employed to study the accelerating mechanism of Al(acac)3 on the curing reaction between the epoxy resin and MHHPA. The results show that the catalytic mechanism is that Al(acac)3 first reacts with MHHPA to form a carboxylic anion as a transition state at elevated temperatures, then the carboxylic anions attack the epoxide groups to initiate the curing reaction. Kissinger’s and Friedman-Reich-Lev’s methods have been employed to study the curing kinetics of the epoxy V.P.I. resin. The results show that the epoxy V.P.I. resin is a complicate reacting system, and the introduction of GPTMS or GPMDS into the system can lower down the gel temperature and the curing temperature.Nano-silica particles have been introduced into epoxy resin to achieve good toughness and mechanical strength. The results have shown that with the incorporation of GPMDS, the nano-silica particles exhibit good compatibility with the epoxy matrix and the enhancement is determined by the concentration and dispersion of nano-silica particles. Nano-silica particles without surface treatment are easy to aggregate and hard to disperse, thereby enhancement can be obtained only at low silica loadings (no more than 3 wt%) when there’s no great aggregations. The incorporation of untreated nano-silica particles results in decreased volume resistivity and increased dielectric loss due to the large amount of–OH groups adhered to the particle surface. Surface treatment of nano-silica with GPMDS can improve the dispersion of the nanosilica particles, and accordingly improve the toughness, strength, the glass transition temperature, the insulating properties, and the thermal stabilities of the epoxy/nano-silica composites.更多还原