Thermally resistant unsaturated polyester resin with low dielectric loss based on special benzyl alcohol terminated hyperbranched polysiloxane for producing high efficiency motors using vacuum pressure impregnation technique

Abstract

Motors with higher efficiency and smaller size are the premise for producing higher performance electrical products and achieving an energy-saving world, so the motors should be fabricated with Vacuum Pressure Impregnation (VPI) technique and the matrices for the motors should be high performance resins that have higher thermal resistance and lower dielectric loss. However, available resins for common motors do not simultaneously have VPI processing characteristics, high thermal resistance and low dielectric loss. Herein, based on unsaturated polyester (UP), the common VPI resin for which the thermally resistant level is as low as F level (155 °C), a unique high performance resin is developed by co-polymerizing UP resin with a novel benzyl alcohol terminated hyperbranched polysiloxane (Vi-HPSi). The structure and integrated performances of Vi-HPSi/UP resins were intensively studied. Results show that Vi-HPSi/UP resin not only meets the strict processing requirements of VPI technique, but also has better curing features, thus endowing Vi-HPSi/UP resins with higher crosslinking density and reduced free volume than the UP resin. In addition, compared with the UP resin, Vi-HPSi/UP resins have much better toughness and bond strength, greatly improved thermal stability, and reduced dielectric loss. Typically, for the Vi-HPSi/UP resin with 20 wt% Vi-HPSi (20Vi-HPSi/UP), its initial degradation temperature is as high as 331 °C, about 80 °C higher than that of the UP resin, and this is also the highest value among modified UP resins reported; while the dielectric loss of 20Vi-HPSi/UP is about 0.62 times of that of the UP resin. These attractive performances demonstrate that the Vi-HPSi/UP resin has great potential for fabricating new generation motors with higher efficiency for cutting-edge applications.