Insulating varnish, also known as insulating paint, is a paint with excellent electrical insulation. It has good electrical properties, thermal properties, mechanical properties and chemical properties. There are two kinds of varnishes and paints.
1. Composition of insulating paint
Insulating varnish is composed of base material, flame retardant, curing agent, auxiliary agent, solvent and pigment and filler. The base material is generally polyester, polyesterimide, silicone, epoxy resin, etc. Flame retardants include inorganic flame retardants and organic flame retardants.
Commonly used pigments and fillers include titanium dioxide, iron oxide red, carbon black, chrome yellow, mica powder, talcum powder, barium sulfate, calcium carbonate and silicon dioxide. The purpose of adding pigments and fillers to the paint is to improve the performance of the paint and prepare the required color.
In addition, some additives such as initiators, stabilizers, anti-aging agents, etc. are also required components in insulating varnishes.
Second, the influence of pigments and fillers on the quality of insulating paint
The addition of pigments and fillers in the insulating paint improves some properties of the paint, endows the paint with various colors, and to some extent also reduces the preparation cost of the insulating paint.
Among pigments and fillers, talc powder is favored in the insulating paint industry because of its good suspension, easy dispersion, low corrosion, and low cost. The following will take common pigment and filler talcum powder as an example to illustrate the influence of pigment and filler on the insulating paint system.
1. Moisture content. If the moisture content of the talcum powder exceeds the standard, it will affect the production and processing costs and storage problems, and directly affect the appearance and stability of the talcum powder. When applied to insulating varnish, it will affect the solid content and insulating properties of the insulating varnish, as well as the gel time of the insulating varnish.
Because talcum powder contains a lot of water in its molecules, the water is not easy to remove, and it takes a long time for the water to be separated out during drying. Therefore, it is necessary to strictly control the moisture content of talc powder during the production and processing process.
2. Granularity. Particle size is an important indicator to determine the quality of talcum powder. Different industries have different requirements for the particle size of talc powder. When applied to insulating paint, the smaller the particle size of talc powder (larger mesh number), the better. The larger the particle size, not only The moisture content will exceed the standard, and it will affect the gradual change performance of the insulating paint, and it will also cause the talcum powder to easily settle and not easy to filter.
3. Whiteness. It will affect the appearance of talcum powder, and when it is applied to insulating paint, it will affect the appearance color of insulating paint.
4. pH value. It is also an important indicator of talcum powder. When applied to insulating paint, the pH needs to be within a safe range.
5. Settling speed. Applied to the insulating varnish industry, the slower the settling speed, the better the coating effect of the insulating varnish.
6. Loss on ignition. It determines the purity and fire resistance of talcum powder, and it is used in the insulating varnish industry, which will affect the solid content and stability of insulating varnish.
