辐射环境下聚合物固体介质沿面绝缘击穿机理及其材料改性

Polymer materials are widely used in radiation environments, such as scientific research fields and nuclear power stations, where the high safety and reliability are demanded. The polymer insulating materials are inevitably exposed to various kinds of radiation. The changes in their physical and chemical properties could prematurely terminate the useful life of the dielectric. Outside and inside of the secondary shield in the containment vessel of nuclear power plants, the maximum dose rates of irradiation are 0.01 Gy/h and 1 Gy/h. The dose rate in nuclear power plants varies widely from 10 μGy/h to 10 kGy/h with a potential of total exposure 1000 kGy or greater (e.g. for a nuclear plant accident after forty years of normal operation, the total exposure is the result of 40 years of normal exposure plus the additional exposure of the undefined accident). The high reliability is based on construction safety and system safety during the use of electrical equipment. Accordingly, it is important to investigate the influence of radiation on polymeric insulating materials used in the radioactive environments. Presently, the researches on irradiation aging are mostly concentrated on electrical and mechanical performance, but the effect of radiation, especially the radiation aging theory is rarely studied. We measured the physical and electrical properties of gamma-ray irradiated PC and concluded that the electrical receptivity of PC was reduced obviously. We investigated the tracking resistance of gamma-ray irradiated polyethylene and modified polycarbonate materials, and the results revealed that the tracking resistance was improved by irradiation for cross-linking type materials, but the conclusions for degradation type materials were opposite.The last decade has witnessed significant developments in the area of nano-particulate and nano-dielectric materials which have property of particle-discharge resistance.Polyimide is widely used in aerospace electronics, variable-frequency motor, electric engineering, nuclear generator, with advantage of excellent thermostability, chemical property, mechanical property.Epoxy resin, silicone rubber and polyethylene are widely used in electric engineering, chemical, metallurgy and medical equipment. Whether the dielectric property of the polymers is changed by irradiation or not is worth investigating.In this research, diffident kinds of nanoparticles with special surface treatments will be filled into the polymer matrix (epoxy resin, silicone rubber and polyimide) to prepare nanocomposites. Varies of modern experiment technologies are used to observe the tracking failure processes and specimens' molecular structure in order to explore the breakdown mechanism. The researches can can establish the theoretical foundation on the reliable operation of nuclear energy and the national defense construction engineering.

随着核能、大功率电子束、大功率离子束技术的发展，在辐射环境下使用的聚合物绝缘材料在逐年增加，研究表明在辐射环境下有些聚合物材料容易发生过早绝缘破坏现象。聚合物基纳米复合电介质材料具有提高耐电晕强度、抑制局部放电作用，在电介质工程领域得到发展。本项目以开发新型绝缘材料为目的，选择具有特殊表面物化特征的无机纳米颗粒为填充物，以聚酰亚胺、环氧树脂、硅橡胶和聚乙烯为基体制备纳米复合电介质材料，进行放射线辐射环境下的沿面绝缘击穿实验，在绝缘击穿变化趋势研究的基础上，探讨其物理过程，认识导致绝缘击穿的主要因素，研究绝缘击穿与添加纳米颗粒的影响规律，掌握绝缘击穿过程中的宏观和微观影响因素，采用现代实验技术对试样的分子结构、绝缘击穿过程进行研究，深入探索击穿机理，揭示放射线辐射环境下纳米复合电介质材料的变化趋势，研究开发适合辐射环境使用的纳米复合绝缘材料，为保障核能安全利用和国防建设工程奠定理论基础。

采用不同粒径、浓度和热导率的无机纳米颗粒，以典型聚合物为基体制备了纳米复合电介质材料，开展不同辐射量下纳米复合介质的绝缘破坏试验，揭示聚合物基纳米复合介质在辐射环境下的绝缘破坏规律。获得了辐射环境下纳米复合绝缘材料的电气性能参数、外施电压特性、表面电荷等不同外界因素与内在因素对绝缘破坏过程的物理化学规律，认识了绝缘击穿与添加纳米颗粒的相互关系，掌握了复合绝缘材料绝缘击穿过程中的宏观和微观影响因素。解决了辐射环境下聚合物绝缘材料老化所导致的安全问题。取得的成果有：研制了高压脉冲电源、高分辨率的沿面放电光测量系统、表面电荷测量系统；获得了沿面放电的数值模型和沿面放电到绝缘击穿的转换判据；掌握了纳米复合材料微观结构变化过程、表面电荷积累特性和热累积效应对绝缘击穿的影响规律；揭示了辐射环境下聚合物、纳米复合电介质材料的绝缘性能演变规律和击穿机理；确定了适合于辐射环境的新型高性能纳米复合绝缘材料的最佳制备方案，为保障核能安全利用和国防建设工程奠定了理论基础。