Casting resins are pourable plastics used to cast parts, make molds or form structures in place. Typically, casting resins are mixed with a hardener, catalyst or activator and then poured into the sprue of open molds. Some casting resins contain acrylic, polyimide, polyurea, and silicone adhesives. Others contain thermoplastic materials with trimellitic anhydride or thermosetting resins such as melamine. Casting resins are used in a variety of applications, including semiconductors; generators and motors; coils and transformers; and switches and circuit breakers.

Many casting resins are made of polymers or elastomers. Thermoset resins are cross-linked polymers cured using heat or pressure. Elastomers are synthetic compounds or rubber materials that provide a high degree of flexibility and elasticity. Some polymers and elastomers are designed for electronics applications and are used as thermal interface materials, encapsulants, and potting compounds. Typically, thermal interface materials are used between a heat-generating electrical device and a heat sink to improve heat dissipation. Encapsulants are used to seal or cover circuits from mechanical and environmental ingress.  Potting compounds are dielectric resins used to fill containers or pockets containing electronic components. Casting resins that contain polymers and elastomers are also used in optical and photonics applications, and in mold fabrication and tooling.

Casting resins are pourable plastics used to cast parts, make molds or form structures in place. Typically, casting resins are mixed with a hardener, catalyst or activator and then poured into the sprue of open molds. Some casting resins contain acrylic, polyimide, polyurea, and silicone adhesives. Others contain thermoplastic materials with trimellitic anhydride or thermosetting resins such as melamine. Casting resins are used in a variety of applications, including semiconductors; generators and motors; coils and transformers; and switches and circuit breakers.

Many casting resins are made of polymers or elastomers. Thermoset resins are cross-linked polymers cured using heat or pressure. Elastomers are synthetic compounds or rubber materials that provide a high degree of flexibility and elasticity. Some polymers and elastomers are designed for electronics applications and are used as thermal interface materials, encapsulants, and potting compounds. Typically, thermal interface materials are used between a heat-generating electrical device and a heat sink to improve heat dissipation. Encapsulants are used to seal or cover circuits from mechanical and environmental ingress.  Potting compounds are dielectric resins used to fill containers or pockets containing electronic components. Casting resins that contain polymers and elastomers are also used in optical and photonics applications, and in mold fabrication and tooling.

Casting resins vary in terms of mechanical and physical properties. Bond shear strength is the maximum shear load per unit cross-section that an adhesive joint can withstand before mechanical failure or breakage occurs. Tear strength measures the bond strength of adhesives on thin flexible sheets by pulling the flexible material from the mating surface at an angle. The stress, which is concentrated along the edge of the sheet, is expressed in pounds per inch width or pounds per linear inch. Other mechanical properties for casting resins include bulk density, impact toughness, and water absorption. Physical properties include viscosity, process temperature, shrinkage, and melt flow. 

There are several important electrical and optical properties for casting resins. Electrical resistivity, the inverse of conductivity, is the longitudinal electrical resistance (ohm-cm) of a uniform rod of unit length and unit cross-sectional area. Dielectric strength is the maximum voltage field that a material can withstand before electrical breakdown occurs. The dielectric constant is the relative permittivity of a material compared to a vacuum or free space. The index of refraction measures the speed of light in a material, while transmission is the amount of light transmitted through a material.

Casting resins vary in terms of thermal properties. The deflection temperature is the temperature range to which a material can be exposed without deflection under a given stress of 264 psi or 1.8 MPa. Thermal conductivity is the linear heat transfer per unit area through a material for a given applied temperature gradient. The coefficient of linear expansion is the amount of linear expansion or shrinkage that occurs in a material with a change in temperature.