Evaluation of interfaces of filled polymeric insulating materials with the Dielectric Spectroscopy

在高压技术中，绝缘系统越来越多地由合成材料制成，通常是填充有微观尺寸颗粒的聚合物。因此，内界面显著地影响绝缘材料的性质。新的发展表明，填充有纳米尺寸颗粒的聚合物具有改善的抗树枝化、抗高压电弧以及抗漏电起痕和抗侵蚀性。据推测，这些改进是由于界面的特殊性质，即颗粒和聚合物之间的界面周围的区域。到目前为止，这种界面只能间接证明与纳米填料的聚合物绝缘材料的不同性能相比，未填充的材料。最近，通过原子力显微镜的测量，可以首次直接验证界面相的存在。但是，到目前为止，尚不清楚界面相的性质、界面相的结构以及自由电荷载流子的作用（如果有的话）。界面相的形成取决于填料、基体材料，特别是填料颗粒的表面处理。界面相可以通过其介电性质来识别和表征，即介电常数和介电损耗因子由介电谱确定。在介电谱中，材料的温度和施加场的频率在很宽的范围内变化。因此，不同的极化机制可以相互区分，揭示了所研究的绝缘材料的结构。该项目的目的是使用介电谱来表征具有微米和纳米级填料的聚合物绝缘材料，以增强对颗粒与聚合物之间相互作用的理解，并开发一个模型，然后可以用来解释聚合物绝缘材料的介电性能以及它们在电应力下的行为。因此，有可能系统地影响填充绝缘材料的性能。

In high voltage technology, insulation systems are increasingly made of synthetic materials, usually polymers filled with particles of microscopic size. Thereby, the inner interfaces influence the properties of the insulating material significantly. New developments indicate that polymers filled with particles of nanometric size have improved resistance to treeing, to high-voltage arcing as well as to tracking and erosion. It is assumed that these improvements are due to the special properties of the interphase, i.e. the area around the interface between particles and the polymer. So far, such interphase could only be demonstrated indirectly by the different properties of polymeric insulating materials with nanometric fillers compared to the unfilled material. Quite recently the existence of an interphase could be directly verified for the first time by measurements with the Atomic Force Microscopy. But, so far it is not certain, what are the properties of the interphase, what structure the interphase has and what is the role of free charge carriers, if any.The development of interphases depends on the filler, the matrix materials, and in particular the surface treatment of the filler particles. Interphases can be identified and characterized by their dielectric properties, i.e. the permittivity and the dielectric loss factor determined by the dielectric spectroscopy. In a dielectric spectroscopy the temperature of the material and the frequency of the applied field are varied over a wide range. Thus, the different polarization mechanisms can be distinguished from each other, revealing the structure of the investigated insulating material. The aim of the project is to use the dielectric spectroscopy to characterize polymeric insulating materials with micro- and nanosized fillers to enhance the understanding of the interaction between the particles and the polymer and to develop a model, which can then be used to explain the dielectric properties of polymeric insulating materials as well as their behavior under electrical stress. So, it would be possible to influence systematically the properties of filled insulating materials.