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Thermoplastics vs. thermosets: What’s the difference?

When designing a part, it’s important to understand critical differences between comparable materials. For instance, mistakenly using a thermoplastic instead of a thermoset to create a product that’s meant to withstand high temperatures would have disastrous results. 

The terms “thermoplastic” and “thermoset” appear in many of the same conversations regarding plastic part manufacturing, but they’re not interchangeable. This article breaks down the major differences between thermoplastics and thermosets, as well as key advantages and best applications for each material.

Thermoplastics: What you need to know

Mechanical/chemical properties

A thermoplastic is any plastic material with a low melting point that becomes molten when heated, solid when cooled, and can be re-melted or molded after cooling. The curing process is completely reversible, and doing so will not compromise the material’s physical integrity.

Thermoplastics are usually stored as pellets to facilitate easy melting during the injection molding process. Common examples of thermoplastics include acrylic, polyester, nylon, and PVC.

Advantages of thermoplastics

Thermoplastics are strong, shrink-resistant, and relatively easy to use. Their inherent flexibility makes them an excellent choice for manufacturers who require shock-absorbent products that can withstand wear and tear while retaining their shape.

Thermoplastics are generally more cost-effective than thermosets because they’re easier to process. This is because thermoplastics are made in higher volumes and don’t require post-processing. Plus, thermoplastic molds can be made from affordable materials like aluminum or fiberglass. Because thermoplastics are highly compatible with injection molding processes, they are ideal for making repeatable parts in high volumes.

Additionally, thermoplastics are some of the more environmentally friendly plastics on the market, as they are highly recyclable by design. As an added benefit, manufacturing with thermoplastics  produces fewer toxic fumes than working with thermosets.

Common thermoplastics applications

Manufacturers often use thermoplastics for prototyping because if the final product doesn’t meet certain standards, they can easily melt the part down and start over without producing a lot of scrap material.

water bottle pet

Beyond part prototyping, thermoplastics can be used to create a range of common products — from trash bags, cookware, and clothing to children’s toys and mechanical parts.

Thermosets: What you need to know

Mechanical/chemical properties

In contrast to thermoplastic, a thermoset is any plastic material that hardens once cured by heat and cannot be reshaped after the curing process. During curing, valence bonds in the polymer cross-link together to form three-dimensional chemical bonds that cannot be undone, even under extreme heat.

Thermosets are usually stored in liquid form in large containers. Common examples of thermosets include epoxy, silicone, and polyurethane.

Advantages of thermosets

Thermosets offer a wide range of benefits; overall, they are strong, stable, and chemical-resistant. They won’t warp, degrade, or break down easily in extreme temperatures.

Due to their strength and durability, thermosets are often used to reinforce another material’s structural properties. Among the most impact-resistant materials on the market, they are frequently used to seal products to protect them against deformation.

Common thermosets applications

While thermoplastics offer a more diverse range of high and low functionality applications, thermosets can be used to create high-performance products in a wide variety of industries.

small housing unit 3D printed with EPX 82

Thermosets are ideal for building anything that comes into contact with extreme temperatures on a regular basis, such as kitchen appliances and electronics parts.

Start building with us

The crucial difference between thermoplastics and thermosets boils down to how they react to heat. Thermoplastics can be molded and remolded in the presence of heat without losing structural integrity, while thermosets can be molded only once. Of the two, thermoplastics are better suited for all-purpose products that need to be strong and flexible, while thermosets make better high-performance products. An experienced manufacturing partner can help you decide which material best fits your needs.

When you partner with Fast Radius, you partner with a dedicated team of engineers and manufacturing experts who will help you take your project to the next level. We’ll match your vision with optimal materials, manufacturing processes, and post-production services to ensure that you end up with a product of unmatched quality. Contact us today for a quote.

Ready to start working with thermoplastics or thermosets? Take a look at the Fast Radius resource center for more information on the materials and processes we offer.

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