Thermoset Injection Molding – What Is It, What To Expect?

Many of our customers or prospective customers ask about thermoset molding. What is it? Can you injection mold thermosets? How does it differ from thermoplastic injection molding (ie, nylon, ABS, PP)? How does it process?

The answer is thermoset injection molding is quite similar to traditional injection molding with thermoplastics. Thermoset materials such as phenolics are gathered in a material hopper, and then fed through a hot screw and barrel at around 170F-240F depending on the material formulation. The material is injected into an even hotter mold (around 350F) via sprue and runner system, feeding the cavity or cavities and filling the molded part. Other thermoset materials such as Bulk Molding Compounds (BMCs), which are unsaturated polyesters and vinyl esters are fed to the screw and barrel using a hydraulic stuffer ram, and injected, molded, and cured the same way as phenolics.

Below is a video of a recent sampling on a thermoset injection molded part using a glass-filled phenolic material.