Wacker offers silicone resins for impregnating electric motors

BERLIN—Wacker Chemie A.G. has released new silicone-based special resins and a new silicone rubber for the impregnation of electric motors and in the coil winding industry, respectively.

Wacker dropped the curtain on the new resins—Silres H60A/B and Silres H62C, as well as Elastosil N2076, a silicone rubber that has applications in products for drip impregnation—at the trade show CWIEME, taking place in Germany May 14-16.

The Elastosil, which cures at room temperature, has uses in dipping and vacuuming processes as well. The room-temperature curing allows electrical coil windings to be permanently protected from moisture and environmental influences.

"The product is one-component and crosslinks with sufficient humidity to form a flexible elastomer of medium hardness, which permanently protects electrical windings of transformers or choke coils from moisture, dirt and deposits," Wacker said.

The product is weather- and UV-resistant, flame-retardant, electrically insulating and heat-stable.

The Silres compounds were developed for the impregnation of electric motors. The H60A/B is a "fast-curing two-component phenyl silicone resin formulated without an inhibitor" with a hardness of 65 Shore D. The product is free of solvents and reactive crosslinkers.

"The high crosslinking speed of the silicone resin is comparable to organic impregnation resins," Wacker said. "At 150°C the gelling time is around 13 minutes. At this temperature the material is completely hardened after six hours."

The cross-linked resin is transparent and has a non-sticky hydrophobic surface. With a dielectric strength of 27 kV/mm, measured according to IEC 60243-1, "it is a very good electrical insulator," Wacker said.

The Silres H62C "has proven itself for decades as an impregnation agent in traction engines."

"Electric rail vehicles and drive motors for hybrid and electric cars are among the preferred areas of application," Wacker said. "Unlike many organic impregnation resins, the ready-to-use product contains neither solvents nor reactive thinners. The liquid formulation is usually applied at temperatures between 60°C and 80°C and cured at temperatures between 170°C and 200°C."

The H62C contains an inhibitor to delay the crosslinking reaction.

"This is particularly advantageous if the resin is used in the classic dipping or vacuum printing process," Wacker said. "In such cases, the resin must remain liquid until the motor winding is completely saturated. Such processes are mainly used for large machines, for example for impregnating traction motors for rail vehicles or for diesel-electric large dump trucks for opencast mining."