Engineers sometimes need temperature-resistant moldings that do not need to be of aerospace-grade quality. In these cases, they can choose from more affordable temperature-resistant polymers with good engineering properties. (For the lowest possible budgets, engineers might select a commodity polymer like ABS, which has a reasonable CST of 90 °C but which is also sold in various “high heat” ABS formulations resisting up to 110 °C.)

Nylon 66 is one of the more heat-resistant polyamides (PA) that is widely used in injection molding. With good mechanical strength and rigidity, nylon 66 has applications in the automotive industry for under-the-hood components like air intake manifolds. Glass-filled PA66 has a slightly higher CST, while PA46 is another good choice for high-temp applications.

The most temperature-resistant injection molding plastics come at a high cost but exhibit excellent thermal performance, both in terms of their continuous service temperature (CST) — how much heat they can withstand over long periods of time — and their resistance to even higher temperatures in short bursts.

3ERP has many years of experience making prototypes and production parts via injection molding, and we can mold parts in the above materials and many more besides. Request a free quote for your next batch of high-temperature plastic parts.

Polyetherimide (PEI), often known by the brand name Ultem, is a high-performance polymer often used as a slightly more affordable alternative to PEEK. As well as performing well in high temperatures, it offers good strength, ductility, and chemical resistance. Applications of PEI include medical components, throttle bodies, and thermostat housings.

For more information on our two-shot injection molding services and how we can assist with your next project, please contact MME Group today.

Polyphenylene sulfide (PPS) is another high-performance polymer with engineering applications. As well as having a high CST, it exhibits excellent UV and chemical resistance, making it suitable for outdoor use. PPS parts include gaskets, seals, and electrical insulation. Polyphenylsulfone (PPSU) is slightly weaker and less thermally resistant, but exhibits greater hardness.

So which are the best heat-resistant thermoplastics for injection molding? This article discusses some of the most popular thermally resistant injection molding materials, noting their respective advantages and applications, as well as discussing the complexities of using such materials during the injection molding process.

Injection molding can process a wide range of materials. In addition to metals and thermosets, injection molding is suited to a large number of thermoplastic polymers, from commodity polymers like ABS to high-performance materials like PEEK.

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Engineers will select a thermoplastic based on the requirements of the molded part. Some moldings need to be impact-resistant, some need to be food-safe, while others need to be flexible. Another property that engineers and product designers often require is heat resistance. Heat-resistant molded parts can be used in a range of situations, such as near engines, within powerful electronic parts, and in extreme outdoor environments.

For an ultra high-temp plastic like PEEK, the injection molding machine barrel will reach temperatures above 400 °C, with the molds around 160 °C. These high temperatures can pose certain issues, such as residue getting stuck in the barrel feeder areas. High-temp materials like PEEK often necessitate purging of the machine before use of a subsequent molding material.

While both two-shot injection molding and overmolding involve combining multiple materials to create a single part, they have key distinctions:

Polycarbonate (PC) is often used for its high-quality appearance — especially for transparent parts — and good impact resistance, but the thermoplastic also offers good heat resistance. PC can be molded for uses in electronics, automotive, and aerospace. It is also used for optical and lighting components like headlamp lenses.

Two-shot injection molding, also known as dual-shot or multi-shot molding, is an advanced manufacturing process that enables the production of complex, multi-material components in a single molding cycle. This technique involves injecting two different thermoplastics, which can vary in color, type, or hardness, into a single mold sequentially. The process utilizes a specialized machine equipped with two barrels that inject the materials into the mold cavities one after the other, allowing for the creation of integrated, multi-functional parts.

Polyoxymethylene (POM) or acetal is another engineering thermoplastic in a lower price bracket than ultra-premium materials like PEEK. It provides good stiffness and low friction, with a relatively high CST. Molded POM can be made into various engineering parts like gears and fasteners, as well as automotive and electronics parts.

Another molding consideration with high-temperature plastics is unwanted freezing off of the nozzle or mold gates. If temperatures are not quite high enough, gates or the machine nozzle can freeze off before the mold cavity is completely filled. Larger gates may mitigate this issue if it persists.

MME Group, a Seaway Plastics Company has extensive experience in two-shot injection molding. We offer comprehensive tooling and secondary operations, serving diverse industries like medical, aerospace, industrial, and defense. MME Group specializes in plastic and LSR injection molding, providing a full suite of services from in-house tooling to post-molding operations, including assembly, kitting, and packaging. Our capabilities in two-shot molding allow us to create parts that combine different thermoplastics in a single cycle, improving design and functionality while cutting down on the need for post-molding assembly. This process is highly efficient and economical for high-volume production, ensuring the delivery of high-quality, multi-material components.

Because the injection molding machine must melt down pellets of the chosen thermoplastics, high-temperature materials are necessarily more difficult to process. However, with the right setup, it is still possible to achieve high-quality moldings using these engineering materials.

Polyether ether ketone (PEEK) is a high-performance polymer used for engineering purposes. With a melting temperature of 343 °C, it is as robust and strong as it is difficult to process. Its extremely high CST makes it suitable for applications in demanding industries like aerospace. Example PEEK parts include bearings, pumps, and compressor plate valves.

Two-shot injection molding is versatile and finds applications across various industries such as automotive, industrial, consumer, aerospace, defense, and particularly in the medical field, including: