UP Emulsion: A Novel Electrical Insulating Material

Abstract

Unsaturated polyester (UP) resins are used extensively in electrical impregnation applications. The major disadvantage of UP resins is that reactive diluents such as styrene, vinyl toluene and diallyphthalate must be used to maintain low viscosity for application. Approximately 30-75% of the reactive diluent is lost during the curing cycle as a volatile organic compound (VOC). The use of waterborne polyester resins is a competing technology. However even waterborne polyesters typically contain a co-solvent which contributes to VOC emissions. The presence of a co-solvent can also lead to low flashpoints and safety concerns. Epoxy resins on the other hand do not contain VOC's but are significantly more expensive than UP resins and are high viscosity for application on electrical devices. The current invention describes the utilization of UP Emulsion along with crosslinking agents for a high performance impregnation material. The emulsion particle size is less than one micron for long-term shelf life and has an application viscosity of only 300–600 cP at greater than 60% solids content. This UP emulsion product offers properties such as superior coating quality, high bond and dielectric strengths, and excellent corrosion / moisture resistance. The other advantages of emulsion products are that they are easy to use and cleanup, low VOC, no HAPS, no odor and low viscosity.