Category Archive: Thermoset

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.




Thermoset Plastics vs. Thermoplastics

While you may have heard the terms thermoset plastic and thermoplastics used synonymously, they are two different products. Composed of polymer powders, they each react differently when exposed to heat. While thermoset plastics are cured by heat, they can only be formed once and are not suitable for exposure to extremely variable or high temperatures. Engineered thermoplastics, however, remain pliable and can be ground and reformed without changing the chemical composition.

The Basics

Thermosets are a popular alternative to metal. Often they are comparable in strength and rigidity, but have greater corrosion resistance with less weight than metal. Thermoset plastics are not only heat-resistant, creep resistant, and ideal for tight tolerances, but they also have higher impact resistance and durability than thermoplastics. They can be less expensive to source and form than either metal or engineered thermoplastics, and the fact that they do not require finishing makes them even more cost and time-efficient. 

MCM works with most types of thermoset plastics, such as:

  • Carbon fiber epoxy resin 
  • Phenolics 
  • BMC (bulk molded compounds) 
  • Fluoropolymers, 
  • Melamine  
  • Urea-formaldehyde

Thermoplastics include Polyethylene, Acrylonitrile Butadiene Styrene (ABS), Polymide (Nylon), Polycarbonate, Polypropylene, and High Impact Polystyrene (HIPS).

Their Differences

While thermoplastics are more suited to some applications like plastic bags, plastic films,  clothing, carpeting, and flexible packaging, there are some distinct advantages to choosing thermosets over thermoplastics.


Thermosets can be less expensive to procure and fabricate than either metals or thermoplastics and do not require finishing. Using a single mold, they can be formed into complex geometries or multi-part components, providing economies in production time and cost. Injection molding of thermosets requires less heat and pressure than thermoplastics, making them more cost-efficient to produce.


Unlike thermoplastics, thermoset plastics are heat stable, retaining their shape and chemical composition when reheated. Thermosets also have an exceptional strength-to-weight ratio, temperature resistance, corrosion resistance, and UV stability. 

Physical Properties

Resistance to high heat, petrochemicals, fire, and corrosion make thermosets extremely versatile. They exhibit low creep and exceptional dimension retention, strength, rigidity, and low fluid absorption, as well as antimicrobial qualities. Thermosets also possess excellent electrical and sound insulating qualities. 

Surface Finish

The efficient process used for forming thermosets produces high-gloss surfaces without additional finishing or coating. The resulting finish is also much harder than that of thermoplastics. 


Thermosets can be formed into any geometry using a variety of molding processes such as injection molding, and compression molding. Highly complex shapes and multi-part components are easily created from thermoset plastics. 

Their Applications

Both thermoset plastics and thermoplastics can be easily formed, making them attractive alternatives to metals in a variety of sectors and industries. The aerospace and automotive industries, as well as the energy sector, including oil, gas, and solar, have seen huge benefits by leveraging the exceptional versatility of thermosets and thermoplastics. Electrical components, durable manufactured goods, and heavy-duty construction equipment manufacturers routinely use thermosets and thermoplastics. While thermoplastics are highly flexible and recyclable, thermosets will be preferred in applications requiring strength at temperatures up to 500° F.

Applications that make extensive use of thermoset plastics include but aren’t limited to:

  • Aerospace components
  • Appliance parts
  • Arc shielding
  • Connector housings
  • Electrical and electromechanical components
  • Food grade parts & food and beverage processing equipment
  • Marine applications
  • Medical devices and equipment
  • Outdoor furniture
  • Outdoor lighting
  • Parts that require insert molding
  • Public transportation seating

Thermoset Plastics From MCM Composites

MCM Composites, LLC is an industry leader in thermoset plastic molding, including injection molding and compression molding. We also offer secondary services for injection molded parts such as tapping, drilling, coating, and multi-piece assembly. Our experienced team works with both customers and suppliers to determine the ideal material for the specific application.

MCM Composites produces over 1,000 different parts for customers throughout the United States, Canada, China, Mexico, and the Caribbean in our ISO 9001:2015 certified mold shop. We are committed to providing the highest quality thermoset plastic components in strict conformance with our customers’ specifications. For more information about our capabilities, contact us today or request a quote