Insulating varnish is an important insulating material in the motor manufacturing process. It is involved not only in the motor manufacturing and processing process, but also in the upstream materials of motor products. Whether for environmental protection itself or for the occupational health and safety of operators, the improvement of the safety and environmental protection of insulating varnish is an inevitable and irreversible trend.
Currently, traditional solvent-based insulating varnishes used by various motor manufacturers in China contain large amounts of flammable, explosive, and toxic solvents such as benzene and ketone esters. After application, these varnishes release large amounts of harmful substances, threatening human health and polluting the environment. Therefore, they are gradually being replaced by water-based insulating varnishes. However, users of insulating varnishes may have some blind spots in their understanding of water-based varnishes and the process requirements for their use, requiring a deeper understanding and adaptation. Ms. Can will share some simple information about water-based insulating varnishes with you today.
What is water-based insulating varnish?
Water-based insulating varnish refers to insulating varnish that uses water as its main solvent. Water-based insulating varnishes include both water-soluble and water-emulsion types. Improper handling of water-based insulating varnishes can lead to some adverse reactions, mainly manifested in the following ways:
(1) The polar groups of water-based paint should be reduced to a low level during the curing process of insulating paint; otherwise, hydrolysis in a humid environment will seriously affect the insulation and mildew resistance of the paint film.
(2) The corrosiveness of water or ionic groups to metals can cause damage to metal parts to varying degrees. Anti-flash erosion technology is used in the paint manufacturing process, which can solve the corrosion of metal parts to a certain extent, but at the same time it will reduce the insulation performance of the cured product.
(3) The mechanical strength and bonding strength are relatively poor compared to traditional insulating varnish. Under the action of electromagnetic force and mechanical stress, the winding may become loose or deformed.
Typical applications of water-based insulating varnishes
● Alkyd resin type water-based insulating varnish. This is the most widely used type of insulating varnish. Because alkyd has low heat resistance and weak breakdown voltage, but it is cheap and readily available, it is mainly used for insulation treatment of small and medium-sized low-voltage motors and electrical appliances.
●Water-based polyester insulating varnish. The synthesis method of this type of varnish using water-based polyester is basically similar to that of water-based alkyd resin. However, due to the introduction of more heat-resistant materials, the electrical insulation properties of this type of varnish are also superior to those of water-based alkyd resin. It can be used as a water-based insulating varnish of current Class F and above.
●Water-based epoxy insulating varnish. Epoxy resin varnishes have excellent mechanical strength and electrical properties, good chemical resistance, good moisture resistance, low shrinkage, and good adhesion and compatibility with other materials, but they are expensive. This type of insulating varnish not only has good performance but is also safe and environmentally friendly, with a lower overall cost. Its overall performance can meet the requirements of Class F insulating varnishes, making it well-suited to the insulation performance requirements of small and medium-sized motors.
●Water-based polyimide insulating varnish. A high-performance polymer with excellent thermal stability, outstanding mechanical properties, and good electrical properties. It has been applied in domestic electromagnetic wire production lines and has entered the practical verification stage in motor manufacturing.
Precautions for using water-based insulating paint
Undried water-soluble insulating varnish may cause leakage or even burn out the machine, so it must be completely dried to achieve the purpose of insulation.
● The viscosity of the paint must meet the requirements. Different sizes and models of motors have different viscosity requirements for the paint, and the specific process parameters need to be determined through verification.
● The air vents of the kiln must be unobstructed to ensure that water vapor can be discharged in time, allowing the paint film to dry and cure fully.
● The drying temperature should be above 120℃. The larger the motor and the more complex its structure, the longer the drying time will be.
● If the drying time is too long or the temperature is too high, the insulating sleeve may turn yellow or even black. A suitable insulating hose should be selected to prevent this problem from occurring.
●After exiting the kiln, the withstand voltage and insulation resistance should be checked to ensure that it is completely dry.
● Water-soluble insulating varnish should not be mixed with other types of insulating varnish, otherwise it may turn milky white or even deposit.
