Novel Silicone Resin For C-class Vacuum Pressure Impregnation

Vacuum pressure impregnation (VPI) technique is considered as one of the most effective techniques for fabricating high-performance insulating materials used for large and medium high-voltage electric machines and apparatuses today. Resins consequently are the material guarantee for VPI technique. But present high-performance resins cannot meet the requirments of VPI technique in terms of manufacturability. Silicone resin is expected to be the most promising candiate for developing high-performance VPI resins owing to its outstanding integrated property.This thesis gives the first presentation of preparing a novel high-performance silicone (PEh), of which the base resin (branched poly(methylphenylvinylsiloxane), PMPVSi) and the novel diluent (end-capped hydrogen-functionalized hyperbranched polysiloxane, EHFHPSi) react with each other to form a compact crosslinking network in the existence of Karstedt catalyst. Based on the theoretical calculation the effect of the mass ratio of PMPVSi and EHFHPSi on the properties of PEh was systematically discussed to give an optimal mass ratio.In order to further improve the thermal and dielectric properties of original base resin, two kinds of polyhedral oligomeric silsesquioxane (POSS), reactive octavinyl-polyhedral oligomeric silsesquioxane (POSSv) and non-reactive octa (trimethylsiloxy)-polyhedral oligomeric silsesquioxane (POSSm), were synthesized and introduced to develop two new ternary silicone hybrids (PEPv and PEPm). The structure and properties of these two hybrids were systematically discussed to give a clear understanding of the effect of chemical bonding and physical bonding on the properties of materials.Results show that the viscosity of both ternary silicone hybrids can meet the requirment of VPI technique, showing desirable processability. In addition, the properties of both hybrids were closely related to the content of POSSv or POSSm. Compared with binary PEh system, the thermal and dielectric properties of both ternary silicone hybrids were dramatically improved, depending on the different curing behavior and reinforcing mechanism. Specifically, in PEPv system, there is a hydrosilation reaction between POSSv and EHFHPSi, meaning that POSSv is introduced to the base resin via the hydrosilation reaction, and thus leading to greatly improved properties, especially for the hybrid with 2wt% POSSv. On the other hand, POSSm is incorporated into the base resin through a physical route, so the modification effect is not better than that of POSSv.