Using Molded Thermosets in Electrical Applications

Why are thermosets commonly used as a molding material for electrical parts and component assemblies? Thermosets are implemented in electrical applications due to the materials’ exceptional electrical stability, high dielectric strength, and resistance to arc and track which protect internal components from electrical charge and risk of fire or product failure. Parts including circuit breakers, terminal blocks, and electrical connectors are molded from thermoset materials to ensure product safety. Whereas a thermoplastic can degrade, disfigure, or ignite; thermosets such as unsaturated polyester BMC and phenolic molding compounds remain durable and strong when exposed to such electrical elements. From a cost comparison, thermosets are a commercial option available at a low cost per lb. compared to engineered thermoplastics with similar type of electrical and heat resistant properties. Common thermoset materials used in electrical applications include both phenolic and bulk molding compounds (BMC).
 
Electrical components and assemblies require materials that not only protect internal components and electronics, but also allow for safe handling by users and service technicians. Molding electrical parts with a thermoset composite can provide a host of safety benefits to the end parts and product assembly. Components requiring a thermoset due to potential exposure to electrical arc and track damage include switches, circuit breakers, contacts, electrical connectors, and fuses. Aside from arc and track resistance, thermoset molded parts are heat resistant up to 400-500 degrees depending on material formulation, allowing the parts to continue operating at peak performance in high temperatures or under thermal shock conditions without degradation. Many thermoset material formulations are also UL 94 rated for flammability with a V0 or 5VA designation. Lastly, thermosets are used in many applications as electrical insulators to resist the flow of electrical charges or currents that can cause physical or chemical damage or degradation to parts and assemblies.