Setting the Record Straight: True Facts About Thermoset Composites

Regulatory requirements are all challenging today’s plastic engineers to find new and innovative solutions.  As companies ask for better performing materials to satisfy these modern product and production requirements, thermoset composites are being developed to meet ever-evolving demands. 

Since their inception in the early 1900s, thermoset materials have, in fact, kept pace with modern production practices.  Unfortunately, there are still several outdated and incorrect perceptions about thermoset materials that may have prevented engineers from considering them. Here are a few facts about thermoset plastics that may broaden your search for the perfect material. 

Fact 1: Thermoset plastics can be injection molded.

Thermosets are often thought of as useful only for manual, compression molding methods.  However, these materials have been adapted for use in automatic injection molding systems for more than 60 years.  Thermoset technology has advanced so that they can run on highly efficient, fully automated robotic cells that deliver cycle times similar to thermoplastics.   

Fact 2: Thermoset plastics are more environmentally friendly than metals and thermoplastics.

Thermoset materials require significantly less energy to produce than metals and many thermoplastic resins, measurably reducing the carbon footprint associated with overall production process.  Renewable products (such as wood fibers and cotton) and post-consumer ingredients (such as pulverized glass and polystyrene) can all be re-introduced as functional raw materials. 

Read more about the environmental sustainability benefits of thermosets.

Fact 3: Thermoset scrap can be recycled to make new products.

Thermoset materials are cured to completion during processing, so they cannot be melted down and recycled like thermoplastics. However, thermoset composite scrap parts and mold runners, for example, can be ground into a particle classified powder and then successfully fed into virgin thermoset material. According to research by Plenco, an industry-leading plastics engineering company, thermoset phenolics have shown little or no property loss with up to 13% regrind content in some formulations.  

“For example, another popular injection molded thermoset, bulk molding compound (BMC), has been blended with as much as 7% regrind (as a filler replacement) for OEM-specified automotive valve cover applications,” said Len Nunnery, V.P. Marketing, Sales & Technical Service at Plenco.

Fact 4: Thermosets can be used for a wide variety of applications.

From the beginnings of plastics, Phenolic molding compounds have been touted as “the materials of a thousand uses” as they were utilized in countless items such as radios, cookware handles and telephones. Today, thermosets are being specified for a wide variety of high-strength, tight tolerance products where dimensional stability, low shrink, high heat resistance, electrical insulating properties, surface hardness and corrosion resistance are critical performance features. Popular durable goods made with thermosets include street-rated manhole covers, mounting components for electrical utility service, electrical switchgear components, pole-top electrical components, flame-resistant EV battery boxes, precision gears and pump components.  

For major appliance applications, polyester thermosets such as BMC can be pigmented to exhibit brilliant colors and high gloss whites.  These colorfast substrates eliminate expensive paint or clear coat requirements. BMCs have been formulated to provide direct food contact safety and microwave use capability.  Also, several grades of BMC have  been recognized for medical applications such as side rails for hospital beds and apparatus enclosures for curative dental tools that use heat and/or UV light to produce implants, bridges and dentures.

Read more about how the U.S. military uses thermoset for long-lasting pole bases on defense radar arrays.

Fact 5: Plastics engineering students need to know more about the performance and commercial benefits of thermosets.

Most universities with plastic engineering programs focus primarily on thermoplastic materials, their manufacturing methods and processing techniques.  Based on the performance-to-cost benefit associated with thermosets (relative to engineered thermoplastics), a broader understanding of thermoset technologies would better prepare future engineers to make the most appropriate material selections.  Thermosets provide superior Underwriters Laboratories (UL) flammability ratings without complicated and costly flame retardant additives.  These unique materials impart excellent creep resistance when compared to virtually all thermoplastics and allow for tighter production tolerances and wall thickness variations based on inherently low factors of shrink.        

“Tomorrow’s design engineers will be tasked with choosing the best performing, most cost-effective material.  These engineers will need to consider manufacturability, end use performance and sustainability, such as full platform carbon footprint.  In many cases, thermosets will be the clear answer,” Nunnery said.

Learn more about how to use thermosets in the Plenco Processing Guide.

Contact Ci-Dell to find thermoset solutions that address many design challenges in a wide range of industries.