Thermoset Plastics vs. Ultem Plastics

Thermoset plastics are a popular type of molding compound used in many engineered plastic applications. Once thermoset plastics are heated and start to set, the curing process chemically alters the material so it can’t be reground or reused. Thermoset materials are cost-effective and durable, making them an ideal choice for many manufacturing projects. Conversely, thermoplastics can be returned to a ground state and recast or reused multiple times without altering the chemical structure of the material. This blog will discuss the differences between thermoset plastics and Ultem®, a specific type of thermoplastic.

What is Ultem?

Of all the different thermoplastic materials used for manufacturing goods, Ultem is one of the most advantageous for high-heat applications. This polyetherimide compound features a high melting point for a thermoplastic, which means it can be used to produce parts that stay rigid and reliable at temperatures up to 340°F. The high melting has led some engineers to choose Ultem in situations where a thermoset plastic might traditionally be used. Ultem also features good dielectric properties, high strength, rigidity, and resistance to most chemical damage.

Some of the most common applications for Ultem include:

  • Circuit boards
  • Electrical insulators
  • Electronic insulators
  • Eyeglasses
  • Food prep equipment
  • Jet engine components
  • Manifolds
  • Medical components
  • Microwaves
  • Sterilization equipment

Thermoset Plastic Advantages Over Ultem

Despite the benefits offered by Ultem and other thermoplastics, thermoset plastics remain advantageous in many applications. Manufacturing with thermoset materials presents many key advantages that are valuable during manufacturing and during the lifecycle of the product. The advantages of thermosets over Ultem include:


Thermoset compounds are less expensive than thermoplastics, which reduces overall production costs. Lower material costs also allow for a greater margin of experimentation and modification without exceeding a set budget.


Thermoset compounds can be molded into products with any geometry. No matter how complex the product design is, manufacturers can use thermosets to create solid, tough pieces with a high degree of structural integrity. This is ideal for parts that face extreme end-use environments and need to meet tight tolerances for complex configurations.

Physical Properties

Thermoset materials offer a wide variety of beneficial characteristics. After the curing process, thermoset parts have a high degree of rigidity and can withstand impact damage. The products are also strong and resistant to heat damage. Because of the excellent manufacturability thermoset plastics offer, they can be molded to extremely tight tolerances. This is ideal for electronic product components or complex mechanical assemblies with little room for error or misalignment.


Thermoset plastics feature an excellent strength-to-weight ratio. That means the products offer a high degree of strength while still being light and easy to handle. They dampen sound, resist creep, and have a low coefficient of friction that mitigates damage from abrasion. Thermosets are ideal for parts that need to retain quality and structural integrity long-term.


Thermoset products are stable and resistant to impact damage, UV radiation, fluid exposure, and heat. Some thermosets can retain their stability in environments that reach sustained temperatures of 500°F.

Thermoset Plastics and MCM Composites

At MCM Composites, we offer an extensive array of manufacturing services designed to create high-quality thermoset products. We offer thermoset injection molding and thermoset compression molding services for customers across industries. Contact us today or request a quote to see how our thermoset plastic molding capabilities can support your design.




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