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.

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.

A mold is a hollow metal block into which molten plastic is injected to from a certain fixed shape. Although they are not illustrated in the figure shown below, actually there are many holes drilled in the block for temperature control by means of hot water, oil or heaters.

Molding condition means cylinder temperature, injection speed, mold temperature etc. set in a molding machine to obtain required moldings, and the number of combinations of conditions is innumerable. Depending on the conditions selected, the appearances, dimensions, and mechanical properties of the molded products change considerably.

The screw is rotated to melt plastic introduced from the hopper and to accumulate molten plastic in front of the screw ( to be called metering ) . After the required amount of molten plastic is accumulated, injection process is stared.

While molten plastic is flowing in a mold, the machine controls the moving speed of the screw, or injection speed. On the other hand, it controls dwell pressure after molten plastic fills out cavities.

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.

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.

The position of change from speed control to pressure control is set at the point where either screw position or injection pressure reaches a certain fixed value.

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.

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.)

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.

A molding consists of a sprue to introduce molten resin, a runner to lead it to cavities, and products. Since obtaining only one product by one shot is very inefficient, a mold is usually designed to have multiple cavities connected with a runner so that many products can be made by one shot.

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.

Injection molding machine is divided into 2 units i.e. a clamping unit and an injection unit. The functions of the clamping unit are opening and closing a die, and the ejection of products. There are 2 types of clamping methods, namely the toggle type shown in the figure below and the straight-hydraulic type in which a mold is directly opened and closed with a hydraulic cylinder.

The method is suitable for the mass production of products with complicated shapes, and takes a large part in the area of plastic processing.

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.

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.

Specialize in CNC machining, 3D printing, urethane casting, rapid tooling, injection molding, metal casting, sheet metal and extrusion

For the properties when reprocessed materials are used, please refer to "reprocessing capability" in the plastic data base.

If the length of the runner to each cavity is different in this case, the cavities may not be filled simultaneously, so that dimensions, appearances or properties of the moldings are often different cavity by cavity. Therefore the runner is usually designed so as to have the same length from the sprue to each cavity.

Molten plastic flows into a mold through a sprue and fills cavities by way of runners and gates. Then, the mold is opened after cooling process and the ejector rod of the injection molding machine pushes the ejector plate of the mold to further eject moldings.

The standard molding conditions for our materials are shown below. Please click the mouse at the following names of plastics.

Injection molding is a method to obtain molded products by injecting plastic materials molten by heat into a mold, and then cooling and solidifying them.

Sprues and runners among moldings are not products. These portions are sometimes discarded, but in other cases they are finely reground and reused as materials for molding. These materials are called reprocessed materials.

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.

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.

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.

Reprocessed materials are not solely used as materials for molding but usually used after blending with virgin pellets, since there is possibility of deterioration in various characteristics of the plastics because of the initial molding process. The maximum allowable limit for the ratio of reprocessed materials is about 30 %, because too high ratio of reprocessed materials may spoil the original properties of the plastics used.

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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.

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.