Investigation On Structure Form And Electrical Tree Discharge Characteristic Of PP

Polypropylene (PP) has superior chemical corrosion-resistant, mechanical properties, insulation performance and breakdown field, and it is extensively used to power capacitors insulation materials. But PP also has the disadvantages itself that its toughness is poor, its low temperature resistance is poor and its molding shrinkage is big, so that the application in the field of high-voltage insulation is limited. Polypropylene is a crystalline polymer, its crystalline morphology play a critical role in its performance. Therefore, the research on the impact on characteristics of polypropylene crystalline morphology has increasingly become a hot spot.Four different types of polypropylene were used as the base material in this paper, and mixed the nucleating agent CA202. PP/CA202 material is prepared by melting process. And surface modified montmorillonite as the nanofiller, maleic anhydride grafted polypropylene (PP-g-MAH) as the compatibilizer, on this basis, PP/MMT nanocomposite is prepared by melting intercalation process. And the relationship between crystalline morphology and electrical treeing of PP, PP/CA202 material and PP/MMT nanocomposite are researched.The paper has showed that nucleating agent and montmorillonite has played a role as out-of-phase nucleation, and the lamellar structure of montmorillonite stoped the growth of grain through observing the crystalline morphology of PP, PP/CA202 material and PP/MMT nanocomposite by polarized light microscopy (PLM). It has studied on electrical treeing resistance of PP, PP/CA202 material and PP/MMT nanocomposite by digital shooting system. The results have shown that: in the AC voltage, the electrical tree of polypropylene had small occurrence probability and longer initiation period. After the initiation period, the electrical tree had fast growth rate and got longer length after 240min at the applied voltage. On the other hand, the electrical tree of PP/CA202 material mixed with nucleating agent had relatively large occurrence probability and shorter initiation period. But then the electrical tree had slower growth rate and got shorter length after 240min at the applied voltage. The PP/MMT nanocomposite had the worst electrical tree resistance and got the longest length after 240min at the applied voltage. In the DC short-circuit voltage, comparing to polypropylene, the PP/CA202 material mixed with nucleating agent have improved the DC short-circuit electrical treeing resistance. And the relationship between electrical tree development and crystalline morphology had been observed through polarized light microscopy (PLM), and gotten single-branch electrical tree developing along the ball boundary.The PSD characteristics of polypropylene, PP/CA202 material and PP/MMT nanocomposites had been researched with PSD measurement system. And the insulation resistance of the different samples had been tested with impedance meter. The results have showed that: compared to polypropylene, PP/CA202 material has the bigger density of traps, and it has new shallow traps in the material. Therefore, the PP/CA202 material can restrain the growth of the electrical tree through making the free trip shorter, reducing the carrier energy in the course of the campaign and the number of the electron.