Using Thermosets in High Temperature Applications
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Thermosets are used in molding applications requiring an end-part or product assembly to remain dimensionally stable within challenging and aggressive environments. One of the main benefits of using a thermoset in a molded application is thermosets’ heat resistance and high deflection temperatures that allow the molded components to exhibit excellent dimensional stability, durability, strength, and creep resistance while exposed to elevated operating temperatures. Thermoset materials offer heat resistance up to 400F-500F continuous operating temperatures, depending on the material formulation, whereas thermoplastic molding materials such as a nylon or ABS may melt or disfigure, jeopardizing the integrity of the product or assembly. (more…)
BMC, or Bulk Molding Compound, is a common type of moldable thermoset material or composite. BMCs are unsaturated polyesters or vinyl esters, and may be injection or compression molded with thermoset molding machines. The properties of BMC molded parts exhibit exceptional dielectric strength, electrical insulation, heat resistance, and chemical resistance. These beneficial material properties lend BMC materials to be molded in a variety of safety-critical applications and component assemblies within the Electrical, Automotive, and Industrial markets. In its raw state, BMC resembles a play-dough like form usually filled with glass fibers and or minerals dispersed within the resin system. Molding wise, BMCs are more commonly injection molded, but can also be compression or transfer molded. Injection molding BMCs require the use of a molding machine stuffer or ram to help inject material into the screw and barrel to preheat and plasticize prior to injecting into the molds. 
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). 
Why are thermoset composites like phenolic and bulk molding compound commonly used material in automotive applications? Molded thermoset parts and components have excellent material properties with regards to resistance against high temperatures, corrosion, and chemicals and automotive fluids. Processing wise, thermosets may be injection molded, or compression molded. 
Phenolics, or phenolic molding compounds, are a type of thermoset composite or plastic molding material. Phenolics have history dating back to the very first plastic, bakelite, that derived from Leo Baekeland in the early 1900s. Despite a long history, phenolics thermosets are still commonly molded today for various applications and end products. The physical properties of molded phenolics provide a molded part or component exceptional dielectric strength, electrical insulation, heat resistance, and chemical resistance. These properties allow phenolics to be molded for a variety of safety-critical components in Electrical, Automotive, and Industrial markets. In its raw state, phenolic is similar to thermoplastics such as nylons or ABS in a granular-like form, filled with glass fibers, minerals, or bead fillers dispersed within the resin. Molding wise, phenolics are generally injection molded, but can also be compression or transfer molded. Injection molding phenolics require the use of a molding machine with a screw and barrel to plasticize the material prior to injection. 
BMCs are unsaturated polyesters or vinyl esters, and can be injection or compression molded with thermoset molding machines. The properties of BMC molded parts include exceptional dielectric strength, electrical insulation, heat resistance, and chemical resistance. These end properties lend BMC to be molded for a variety of safety-critical components in Electrical, Automotive, and Industrial markets. In its raw state, BMC resembles a play-dough like form usually filled with glass fibers and or minerals dispersed within the resin system. Molding wise, BMCs are generally injection molded, but can also be compression molded. Injection molding BMCs require the use of a molding machine stuffer or ram to help injection material into the screw and barrel. 
