【作者】 李建；

【导师】 黄志雄； 秦岩；

【作者基本信息】 武汉理工大学 ， 材料学， 2009， 博士

【摘要】 环氧片状模塑料（ESMC）是在不饱和聚酯树脂片状模塑料（SMC）的基础上研究出来的一种新型模压料,可应用于高强度、高腐蚀、高绝缘部件的生产。而ESMC的增稠体系和固化体系是制约ESMC发展的关键因素。目前国内外的环氧树脂存在粘度太大不易浸润纤维、无法化学增稠、固化时间长等缺点,难以满足模压工艺要求。因此迫切需要对环氧片状模塑料的增稠体系、固化体系和流变体系进行深入的理论和实验研究,以制备适合模压工艺生产的环氧基片状型模压材料,拓展模压制品的使用领域。针对ESMC的树脂体系,本文采用“二步法”合成出了一种粘度较低、可化学增稠的低分子量环氧树脂,并使用Gaussian03量子化学软件,采用DFT方法,利用量子化学中的价键理论和分子轨道理论分析阐释其合成机理,揭示其微观反应本质,为环氧树脂的合成提供了理论依据。利用MgO和α—甲基丙烯酸混合物、二异氰酸酯预聚物可与含羟基环氧树脂发生化学反应的原理,采用控制反应温度和反应物含量的方法来增稠环氧树脂。并通过傅立叶红外光谱和差热式扫描分析方法对环氧树脂的增稠进行了表征,探讨了环氧树脂的化学增稠机理。结果表明,在MgO和α—甲基丙烯酸混合体系中,α—甲基丙烯酸中的端羧基先与氧化镁进行的一种酸碱成盐反应,这种酸碱成盐反应伴随着大量的放热,放出的热量在MgO这种催化剂的影响下又促进了α—甲基丙烯酸中的端羧基与环氧树脂发生酯化反应,进而达到增稠的目的;对于二异氰酸酯预聚物体系,在较低温度（≤50℃）的情况下,环氧树脂中的羟基与异氰酸酯基反应生成氨基甲酸酯结构;在温度超过90℃的情况下异氰酸酯基会发生自聚反应,生成含六元杂环的异氰脲酸酯;在更高的温度下（≥210℃）环氧基与异氰酸酯基反应生成含五元杂环的嗯唑烷酮。随着反应继续进行,分子链进一步扩展形成网状结构,体系的粘度不断的增加。针对ESMC固化体系,本文将环氧树脂液体型快速固化剂包囊在微小的（5-500u）胶囊中,制备出室温不固化、升温可快速固化的环氧树脂潜伏性微胶囊固化剂。分别通过测试ESMC体系等温DSC曲线和升温DSC曲线,建立了分步等温动力学理论模型和升温动力学理论模型。通过等温模型确立了环氧片状模塑料的固化工艺:凝胶温度(T_gel),固化温度(T_cure),后处理温度(T_treat)。通过升温模型计算出了引发体系温度和转化率的关系,并得到了ESMC固化过程特征温度参数:峰始温度（T_o）,峰值温度（T_p）,峰终温度（T_f）。本文结合增稠体系和固化体系,确立了ESMC的片材生产工艺和模压工艺。ESMC片材制备工艺主要分为四个步骤:①树脂糊的制备与上糊;②粗纱的切割与沉降;③粗纱的浸渍与片材收卷;④片材熟化与存放。而ESMC的最佳模压工艺参数为:模压温度150℃、加压时机15s、模压时间15s、保压时间30min。而针对ESMC的流变特性,本文开展了片材流动性、纤维分布和纤维取向研究,其中的关键影响因素主要有纤维含量和长度、填料的含量和粒径、模压温度、保压时间、铺料面积和闭模速度等。同时以现有的Hele-shaw模型和滑移挤压流动模型为基准,建立了适合于环氧片状模塑料在热模具中的数学流动模型和传热模型。为ESMC的流动特性研究提供了理论依据。最后,本文对ESMC制品的结构与性能进行了分析研究。研究表明制品在各流动方向上的弯曲强度有很显著的差别。当纤维含量为30%,长度为24mm;填料含量为150份,粒径为500目;模压温度为150℃,加压时机为15s,合模时间为15s,保压时间30min为时,ESMC综合力学性能最佳。而且纤维含量和长度、填料种类、含量和粒径对ESMC的体积电阻、介电特性、耐电弧特性和漏电起痕特性也具有显著影响。更多还原

【Abstract】 Epoxy sheet molding compound（ESMC） is a kind of new compressed material,which is developed from unsaturated polyester sheet molding compound（SMC）.It can be used to produce high-strength,high-corrosion-resistance and high-insulation parts.Inefficient thickening system and high-temperature and slow curing velocity of epoxy resin are key factors to restrict the development of ESMC.The molding process of ESMC needs epoxy resin have low viscosity to immerse fiber and have special group to be chemically thickened and have short curing time.So,it is critical to study the thickening system,curing system and fluid rheology system of ESMC.The molded ESMC can widen the application area of compression molding parts.A kind of epoxy resin（EP-LM） with low-viscosity and low molecular weight was synthesized by means of "two-step synthesis process" in this article.And it could be chemically thickened.Gaussian03 software based on quantum chemistry theory was applied to analyze the synthesis mechanism of EP-LM by the method of DFT on the basis of valence bond theory and molecular orbital theory.The reaction nature of EP-LM on the microscopic level was carefully revealed,which provided an evidence for synthesizing epoxy resin.By controlling the reaction temperature and the weight content of reactors,epoxy resin could be thickened by MgO andα-methyl acrylic acid compound and diisocyanate prepolymers.The thickening mechanism was studied by fourier transform infrared spectroscopy and differential scanning calorimetry.In the system of MgO andα-methyl acrylic acid compound,MgO reacted with the terminated carboxyl ofα-methyl acrylic acid to yied a kind of salt and released a great amout of heat.Then the terminated carboxyl ofα-methyl acrylic acid reacted with epoxy resin to yield a kind of ester under the condition of existing heat and MgO catalyst.In the system of diisocyanate prepolymers,when the temperature was below 50℃,the hydroxyl group of EP-LM reacted with isocyanate groups to yield carbamate;when the temperature was beyond 90℃,diisocyanate prepolymers would self-polymerize;and when the temperature was beyond 210℃,the epoxy group of epoxy resin would react with isocyanate groups to yield oxazolidine- menthanone.As the reaction continued,the network structure formed and the viscosity of the system increased.In this study,a kind of microcapsule curing agent（5-500u） was prepared by spraying hot curing agent and PEG-6000 into 0℃methyl methacrylate solution.Epoxy resin with this kind of microcapsule curing agent would not be cured at room temperature and would be quickly cured at high temperature.The isothermal kinetic model and the temperature-rising kinetic model were established by testing DSC curves of the curing system,and then the curing process including gel temperature(T_gel),curing temperature(T_cure) and post-treating temperature(T_treat) was obtained.The relationship between the initial curing temperature and the conversion rate was calculated on the basis of temperature-rising kinetic model,and the special temperature spots including the initial curing temperature（T₀）,the peak temperature （T_p） and the finishing temperature（T_f） of the whole curing process were predicted.On the base of thickening system and curing system,the process of manufacturing ESMC sheets and molding ESMC parts were determined.The process of producing ESMC sheets was divided into the following four steps:①preparing and spraying of resin paste;②cutting and dropping of glass fiber;③impregnating of chopped glass fiber and ESMC sheets rolling-up;④thickening and storing of ESMC sheets.And the optimum molding parameters were list as follows:molding temperature 150℃,dwell time 15s,clamping time 15s and pressure holding time 30min.The rheology property,fiber distribution and fiber orientation of ESMC in hot die were systematically researched.The critical factors affecting the theology properties of ESMC included the weight content and length of chopped fiber,the weight content and diameter of filler,molding temperature,pressure keeping time,the feeding area and the velocity of closing mold and so on.At the same time,on the basis of Hele-shaw flowing model and Slip-extrusion flowing model,a new mathematic flowing model for ESMC in hot die was established.It provided an evidence for studying the rheology properties of ESMC.At last,the structure and properties of ESMC were studied in this article.Results showed that the flexural strength of ESMC parts was different at different direction of fiber orientation.When the weight content of glass fiber was 30%,the length of chopped fiber was 24 mm,the weight content of filler was 150%,the diameter of filler was 500eyes,the molding temperature was 150℃,the dwell time was 15s,the clamping time was 15s and the pressure holding time was 30min,the mechanical properties of ESMC parts was optimum.And the weight content and length of chopped fiber,the weight content and diameter of filler had great effect on volume resistance,dielectric properties,voltaic arc property and leakage tracking resistance of ESMC.更多还原