| Epoxy resin is widely used in the area of mechanical, electrical and national defense industry because of its excellent mechanical and electrical properties, high resistant to corrosion, humidity and aging. It is very important to develop a high performance epoxy-based non-solvent varnish, improve its insulation properties of motors, electrical appliances, and meet the need of special motor markets. However, the epoxy resin with curing agent and styrene as dilution agent is very unstable before curing, and there are few cross linkage positions between epoxy resin and polystyrene. Thereby, it can not be widely used in the dipping varnish, especially in the insulation of high-power motors and electrical appliances. In the presence, unsaturated epoxy resins were synthesized by inducing vinyl group into epoxy via molecule design, and the non-solvent unsaturated epoxy insulating varnish was prepared with styrene as thinner. Compared with the commercial non-solvent epoxy-anhydride insulating varnish, the former holds the insulation properties, and its storage stability, adhesion strength and thermal stability are improved obviously. It provides a new route to develop a high performance non-solvent varnish based on epoxy resin. At the same time, DSC, DMA and TGA were used to analysis the curing, glass transition, and thermal decomposition of unsaturated epoxy insulating varnish. The DSC results showed that the curing temperature range of non-unsaturated epoxy varnish is narrower than that of epoxy resin-acid anhydride system. The DMA results showed that there is one glass transition in the cured product of non-solvent unsaturated epoxy insulating varnish, whereas there are two glass transitions in the epoxy-anhydride system. It is because there is a copolymerization reaction between the unsaturated epoxy resin and styrene , whilst the cured product of epoxy-anhydride system is a simple mixture of two phases. The TGA results showed that the thermal decomposition kinetics of non-solvent unsaturated epoxy varnish in nitrogen is a 1.5 order reaction, and that of the non-solvent epoxy–anhydride system is a 2 order reaction. |
PDF Full Text Request