 Water-Based Varnishes
During the past 2-3 decades, a significant amount of research has been done in developing water-based polymers. Besides being abundant in nature, water has no detrimental health effect on environmental impact. With the concerns about organic solvents affecting the ozone layer in the stratosphere, and causing chronic health problems, more and more companies are switching to water-based products.
The majority of polymers used in industrial applications, however, are not soluble in water. These polymers, being organic in nature, dissolve readily in organic solvents like toluene or xylene. There are, however, a number of ways that polymers can be made water soluble or water dispersible. Several articles, symposia and text books have been published on this topic.
Practical ways of incorporating water solubility and/or water dispersibility in organic polymers include:
- Incorporation of Functional Groups - Functional groups such as Carboxyl (-COOH) and hydroxyl (-OH) impart water solubility/dispersibility. Incorporation of such functional groups is common in water-based alkyds, polyesters, epoxies, as well as polyurethanes. To further improve their water solubility/miscibility, cosolvents like glycol ethers are incorporated into the formula.
- Water-Based Emulsions - Emulsions by definition contain two immiscible (non-mixing) liquids in which one liquid is dispersed in the other. Surfactants (emulsifying agents) are used to make stable emulsions. When an organic polymer is emulsified in water, the resulting formulation acts like an aqueous solution; which can be readily diluted with water. Emulsions with very small droplets as the dispersed phase, appear clear like true solutions. These are commonly known as "microemulsions".
- Water-Based Dispersions - In contrast to emulsions, dispersions are solid particle/polymers dispersed/ suspended in a liquid phase. These products are formulated with surfactant
and dispersing agents to form stable products.
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Regardless of the physical form, water-based polymers used in electrical insulation applications require heat cure to crosslink the polymer and remove the last traces of residual water. Water-based varnishes are increasingly being used in impregnating stators and transformers. These products not only offer workers safety and low VOC's, but also give excellent electrical and mechanical properties. Dolphon BC-365 and a lower temperature cure version, BC-365-LTC, are being used successfully throughout the world. For more information on Dolph water-based varnish lines, contact our Customer Service Department.
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