【作者】 沈浮；

【导师】 杜伯学；

【作者基本信息】 天津大学 ， 高电压与绝缘技术， 2008， 硕士

【摘要】 聚合物材料以其优异的机电性能被广泛的应用于各种电力、电子设备中,而在选择绝缘材料时必须要考虑设备的运行环境。宇宙空间及核电站中存在的各种高能放射线会改变绝缘材料的电气性能。实际运行中,除辐射之外聚合物材料还会经常应用在强磁场环境下,磁场对其电气性能的影响不容忽视。所以研究强磁场环境下聚合物材料表面绝缘击穿和放射线辐射量的影响具有理论意义和实用价值。试验采用经60Co放射源照射的聚萘二甲酸丁二醇酯(PBN)和聚对苯二甲酸丁二醇酯(PBT)作为试样,辐射率为10 kGy/h,辐射量达到100 kGy和1000 kGy。试验中设置磁场与电场正交,磁通密度为249 mT,使得E×B与材料表面的相对角是0,90,180,270和360度。本文主要研究了磁场环境下聚合物介质的表面击穿与伽玛线辐射对绝缘击穿时间和放电量的影响。结果表明:相对角为180度时,PBN和PBT的击穿时间均出现极小值而放电量均出现极大值;相对角为0/360,90/270度时,PBN和PBT的击穿时间均有所增长而放电量均有所下降;随辐射量的增加,PBN的击穿时间延长,放电量减少,而PBT的趋势相反。比较相同条件下的放电痕迹可发现, PBT放电痕迹的面积明显大于PBN;随辐射量的增加,PBN放电痕迹的面积减小,而PBT放电痕迹的面积增大;当相对角为90/270度时,PBN、PBT放电痕迹均有明显弯曲;相对角为180度时PBN放电痕迹的面积小于其0/360度时放电痕迹的面积,而PBT呈现相反的趋势。本文从材料化学结构的角度(PBN和PBT主链上苯环数量不同)进一步探讨了辐射环境下聚合物材料绝缘性能的变化机理,推测分子主链上的苯环数量对辐射反应结果(交联占优或降解占优)有较大的影响。更多还原

【Abstract】 Polymers are widely used as insulating materials because of their excellent dielectric properties. The selection of the proper polymer dielectric for a desired application depends on the operating conditions. The polymer insulations used in space power and nuclear power station are exposed to kinds of radiations which can change their electrical performance. Polymers inevitably operate under radiation with combined environments such as magnetic field. Therefore, it is necessary to investigate the dielectric properties of the polymers under these conditions.Polybutylene naphthalate (PBN) and polybutylene terphthalate (PBT) are employed as experimental samples. The samples were radiated in air up to 100 kGy and then up to 1000 kGy by using a 60Co gamma source. The magnetic flux density (MFD) was 249 mT. The electric field was perpendicular to the magnetic field, which made relative angles between the sample surface and the direction of E×B as 0, 90, 180, 270 and 360 degree respectively.This paper investigates effects of magnetic fields on surface breakdown of gamma-ray radiated polymer dielectrics. Obtained results indicated that the time to tracking failure of both PBN and PBT showed a minimum value and the amount of cumulative charges showed a peak value when the relative angle was 180 degree. The time to tracking failure of both PBN and PBT delayed and the amount of cumulative charges decreased when relative angles were 0/360 and 90/270 degree. The carbonized area was smaller at 180 degree than that at 0/360 degree for PBN whereas the tendency was opposite for PBT. With the increasing of the total dose of the radiation, the time to tracking failure increased for PBN but decreased for PBT; the amount of cumulative charges decreased for PBN but increased for PBT; the carbonized area decreased for PBN but increased for PBT. Comparing the molecular formulas of PBN and PBT, it is suggested that the amount of phenyl in the main chain plays a key role in determining the types of the radiation reactions in which one is crosslinking reaction and the other is degradation reaction.更多还原