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Case Study: Thermoset Plastics

September 29th, 2021

Successfully manufacturing a plastic molded component for its intended application relies on not only designing the tooling and component correctly but also selecting the correct material for the job. In situations where a part needs superior thermal stability, structural integrity, and chemical resistance, thermoset plastics may be answer.

What are Thermosets?

Thermoset plastics are synthetic materials that strengthen when heated, but which can’t be remelted or reformed after they have been cured. This distinguishes them from thermoplastic materials, which can be ground down to be remelted and reprocessed. The difference lies in the chemical reaction that takes place when thermoset materials are cured—thermoset molecules have three or more reactive ends that form chains interlocking in three dimensions. When those bonds are set, they can’t be reversed by the application of heat.

Components made from thermoset plastic are resistant to extremes of temperature (both hot and cold); won’t degrade when exposed to chemicals, oils, and automotive fluids; are corrosion and steam resistant; have excellent chemical and dimensional stability; and have a high strength-to-weight ratio. There are different types of thermoset plastics such as epoxies, phenolics, melamines, and diallyl phthalates (DAP), which exhibit different characteristics. Thermoset can also be reinforced with other materials such as fiberglass for added strength. It can be molded using compression, transfer, or injection molding processes; the recommended process will depend on the type of part and type of material preferred.

Its unique combination of qualities makes thermoset plastic suitable for applications in automotive, aerospace, electronics, telecom, and military equipment. However, thermosets aren’t limited to these industries—they can be found in all kinds of products, including domestic products like cooking utensils.

Examples of Thermoset Parts

At Southwest Plastics, we routinely work with both thermoset and thermoplastic materials. Some examples of parts we’ve made from thermoset plastic include:

Shaft for a water pump: This part is made from E2738, a short glass fiber epoxy, a material selected for added strength. The shaft connects to a rubber impeller that turns to propel water or other liquids. As thermoset is impervious to water as well as highly strong and durable, this is an ideal application for the material.

Pump filter: This cage for a pump filter is made from FM4004, a type of phenolic thermoset. This is another example of a part that needs to remain structurally sound when in constant contact with water.

Aircraft antenna: This fin-shaped antenna housing and its mount are made with FM4007. The antenna attaches underneath the aircraft and must withstand large temperature fluctuations and 700 mph winds during flight.

Expertise and Innovation

At Southwest Plastics, we’re experienced at producing custom parts for the most exacting clients, including the military. We conform to ASTM D5948 (formerly MIL-M-14) specifications. In addition to our existing capabilities, we’re also improving our finishing department into a clean room facility that will allow us to meet the standards necessary to produce medical devices and sensitive parts for the aerospace industry. As an industry leader for over 55 years, we continually add to our knowledge and capabilities to serve our customers in the aerospace, automotive, defense, electronics, healthcare, and telecom sectors.


As a U.S. company based in Southern California, we provide our clients superior quality, competitive pricing, and fast turnaround times without the uncertainty inherent in working with overseas manufacturers. We handle every project with the utmost in expertise and customer service, ensuring that your finished product is manufactured to the highest quality standards from the best possible material for the job. For more information about thermoset plastics or to learn more about how Southwest Plastics can help reliably meet your manufacturing needs, contact us here.

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