Best Heat-Resistant Plastics for Injection Molding : Material Properties, Advantages, Disadvantages, and Applications
- Best Heat-Resistant Plastics for Injection Molding : Material Properties, Advantages, Disadvantages, and Applications
- What are heat-resistant plastics?
- What is heat-resistant plastic injection molding?
- Classification of heat-resistant plastics
- Innovation in heat-resistant plastics
- How to measure the heat resistance of plastic injection molded products?
- Properties and applications of all injection-molded heat-resistant materials
- Why choose Elimold’s injection molding services?
- in conclusion
Among plastic materials, different types of plastics exhibit varying heat resistance; some have very low heat resistance, while others have relatively high heat resistance. Heat-resistant plastics generally refer to plastic products with a heat distortion temperature above 200℃. Furthermore, heat-resistant plastics have significantly transformed industries requiring materials with high thermal stability and resistance to deformation. These new polymers retain their properties even at high temperatures. Compared to other standard materials such as metals, heat-resistant plastics offer advantages. They are lightweight, chemically inert, and easy to mold. Therefore, innovation has driven the application of heat-resistant materials in high-performance environments, ensuring they remain a key factor in the development of modern technology. This article will delve into the applications, advantages , disadvantages , material properties , and selection methods of heat-resistant plastics suitable for injection molding .
What are heat-resistant plastics?
Heat-resistant plastics (or high-temperature plastics) are plastics that maintain good mechanical properties, dimensional stability, and excellent electrical properties at high temperatures, typically with heat distortion temperatures above 100°C, and sometimes even above 300°C. These are specially designed polymer materials that retain their mechanical strength, dimensional stability, and functional properties even when exposed to high temperatures during processing or use. Unlike general plastics, these materials have higher transition temperatures or melting points, robust molecular structures, and stronger resistance to heat distortion, oxidation, and long-term thermal aging. Therefore, they can operate continuously or intermittently at high temperatures without softening, warping, or degrading. Traditional, non-heat-resistant plastics, on the other hand, will fail under thermal stress.
What is heat-resistant plastic injection molding?
Heat-resistant plastic injection molding operates on the same principle as ordinary injection molding, except that it uses heat-resistant plastic materials. It typically employs thermoplastic molding, also known as thermoplastic injection molding, a process for mass-producing plastic parts and products. This technology is characterized by its ability to continuously melt and solidify thermoplastic materials without altering their original properties. It can produce plastic products with high precision, stable physical properties, and a smooth appearance.
The injection molding process for durable plastics is similar to that of conventional injection molding. Both involve melting granular or pellet-like thermoplastic material under high temperature and pressure using an injection molding machine. The molten plastic becomes a homogeneous liquid , which is then injected into a mold by a large screw system. Molds for mass production of plastic materials are typically made of steel and are precisely designed to form the desired product shape. After the injection molding machine has completely filled the mold, the molten plastic is cooled and solidified by a cooling system located within the mold. Finally, the mold is opened, the solidified portion is separated and ejected, resulting in the final product.
Classification of heat-resistant plastics
Based on their heat resistance, plastics can be divided into the following four categories :
| Low heat resistant plastics | Resins with a heat distortion temperature of less than 100℃. Specific varieties include: PE, PS, PVC, PET, PBT, ABS, and PMMA, etc. |
| Medium heat resistant plastics | Resins with a heat distortion temperature between 100 and 200℃. Specific varieties include: PP, PVF, PVDC, PSF, PPO, and PC, etc. |
| High heat resistant plastics | Resins with heat distortion temperatures between 200 and 300°C. Specific varieties include: polyphenylene sulfide (PPS) with a heat distortion temperature up to 240°C, chlorinated polyether with a heat distortion temperature up to 210°C, polyarylsulfone (PAR) with a heat distortion temperature up to 280°C, PEEK with a heat distortion temperature up to 230°C, POB with a heat distortion temperature up to 260–300°C, fusible polyimide (PI) with a heat distortion temperature of 270–280°C, amino plastics with a heat distortion temperature of 240°C, polypropylene (EP) with a heat distortion temperature up to 230°C, and polyphenol phosphite (PF) with a heat distortion temperature up to 200°C. |
| Ultra-high heat resistant plastics | Resins with a heat distortion temperature greater than 300℃. There are very few types, including: polyphenylene ester with a heat distortion temperature of up to 310℃, polybenzimidazole (PBI) with a heat distortion temperature of up to 435℃, and infusible polyimide (PI) with a heat distortion temperature of up to 360℃. |
Innovation in heat-resistant plastics
Materials scientists and engineers are working to develop new polymers to overcome the limitations of traditional heat-resistant materials. The aim is to improve the thermal stability and performance of injection-molded products to withstand harsher application environments. A significant change is the emergence of high-performance blends and composites. Different polymers are also incorporating reinforcing materials such as carbon fibers or glass to form more heat-resistant composites with mechanical properties superior to ordinary heat-resistant plastics. A key material innovation is the development of plastic materials with operating temperatures exceeding 400°C, which also offer better resistance to oxidation and chemical attack. The emergence of modern polymers with higher thermal stability, mechanical and chemical durability is a result of continuous advancements in heat-resistant plastics technology across various industrial sectors.
How to measure the heat resistance of plastic injection molded products?
Indicators for measuring the heat resistance of plastic products include heat distortion temperature, Martin’s heat resistance temperature, and Vicat softening point, with heat distortion temperature being the most commonly used. For the same type of plastic, the relationship between these three heat resistance indicators is as follows: Vicat softening point > Heat distortion temperature > Martin’s heat resistance temperature. The following are several types of indicators for judging the heat resistance of plastic products.
| Heat distortion temperature (HDT) | Under specified loads (0.45/1.8/8 MPa), the temperature at which a plastic specimen deforms upon heating is determined by placing the specimen on a simply supported beam, applying a constant bending stress, and heating at a rate of 2℃/min or 12℃/min. The temperature at which the deformation at the midpoint of the specimen reaches 0.25% is recorded. HDT (Heat Deformation Temperature) is an important indicator of a material’s heat resistance; however, it only reflects the theoretical high value of the material under load and does not reflect actual long-term requirements. |
| Vicat softening temperature (VST) | Under specific conditions, the temperature at which a plastic sample is indented to a certain depth by a needle (the indenter has a circular end face with a cross-sectional area of 1 mm²) is called the Vicat softening temperature (when the indenter is applied under a load of 10 N for method A/50 N for method B). This temperature reflects the material’s heat resistance and deformation performance under static load. However, this only reflects the material’s self-damaging heat limit. In practical applications, there are always loads, and the self-damaging temperature is at extremely low loads, so it has no heat resistance reference value. |
| Glass transition temperature (Tg) | The critical temperature at which amorphous plastics transition from a glassy (hard and brittle) state to a highly elastic (soft and tough) state reflects the change in the mobility of molecular chain segments and is an important processing indicator for plastics. This temperature reflects the material’s heat resistance under full load pressure; however, in reality, application pressure is never fully applied. |
| Melting temperature (Tm) | The temperature at which crystalline plastics melt. It is an important temperature indicator for plastic injection molding. |
| Embrittlement temperature (Tb) | The embrittlement temperature (Tb) is the critical temperature at which a polymer material transitions from ductile (deformation) fracture to brittle fracture, reflecting the material’s impact resistance at low temperatures. It is the temperature at which the probability of specimen failure is 50% under specified test conditions. It is also the minimum service temperature for plastics. While this reflects a certain critical value for low-temperature applications, the load requirements in actual applications are much higher, and many industries have specific requirements for low-temperature notched impact strength. |
Properties and applications of all injection-molded heat-resistant materials
We have compiled the key properties and typical applications of commonly used heat-resistant plastics in injection molding. The table covers all industry-recognized heat-resistant materials with significant commercial value.
| Heat-Resistant Material | Key Thermal/Mechanical Properties | Typical Applications |
| PEEK (Polyetheretherketone) | Continuous use up to ~250 °C; excellent mechanical strength, chemical resistance, wear resistance, and dimensional stability | Aerospace components, medical implants, semiconductor equipment, oil & gas parts |
| PPS (Polyphenylene Sulfide) | Continuous use up to ~200–220 °C; inherently flame-retardant, chemically inert, low moisture absorption | Automotive under-hood parts, electrical connectors, pump and valve components |
| PEI (Polyetherimide) | Glass transition ~217 °C; high stiffness, excellent flame resistance, good electrical insulation | Medical device housings, aircraft interiors, electrical and electronic enclosures |
| LCP (Liquid Crystal Polymer) | High heat resistance (~240 °C short-term); very low thermal expansion, excellent flow for thin walls | Micro-connectors, SMT electronic components, precision electrical parts |
| PAI (Polyamide-imide) | Continuous use up to ~250 °C; extremely high strength, wear resistance, and creep resistance | Bearings, seals, high-load mechanical parts, aerospace components |
| High-Temperature Nylons (PA46, PA6T, PA9T) | Continuous use ~150–200 °C; high stiffness, good fatigue and chemical resistance | Automotive engine parts, gears, electrical connectors |
| PBI (Polybenzimidazole) | Continuous use up to ~300 °C; highest heat resistance among thermoplastics, excellent strength at temperature | Aerospace, semiconductor manufacturing, extreme-temperature insulation |
| PSU (Polysulfone) | Continuous use ~160–180 °C; good hydrolytic stability, transparency, and toughness | Medical devices, sterilizable housings, food-contact components |
| PES (Polyethersulfone) | High heat and chemical resistance; excellent dimensional stability under steam | Medical sterilization components, membranes, electrical parts |
| PTFE (Polytetrafluoroethylene) | Continuous use up to ~260 °C; outstanding thermal stability, ultra-low friction, chemical inertness | Seals, gaskets, insulating parts, chemical processing equipment |
| Phenolic (Thermoset) | Excellent heat resistance and flame retardancy; rigid and dimensionally stable | Electrical components, automotive brake and clutch parts |
| Polyimide (PI) | Exceptional thermal stability (>300 °C); excellent electrical insulation and chemical resistance | Aerospace insulation, flexible circuits, high-temperature films |
Why choose Elimold’s injection molding services?
Elimold specializes in injection molding services for a wide range of industries. We offer a diverse range of plastic materials, color options, and finishes to meet your specific needs. Our experienced team will work closely with you to determine the best solution for your unique requirements, ensuring your parts are produced quickly, efficiently, and to the highest quality standards.
Whether you need assistance with design, prototyping, or mass production, we have the expertise and resources to help you get the job done. Elimold’s injection molding services offer fast turnaround times and high-quality parts to meet your unique needs. Contact us today to learn more about how we can help you achieve your production goals.
in conclusion
Heat-resistant plastics are a class of plastics that are crucial for use under high temperatures and extreme conditions. They possess properties such as thermal stability, light weight, and chemical resistance, surpassing traditional materials like metals and ceramics. While the initial cost of heat-resistant plastics may be higher, their advantages, including high efficiency, lightweight construction, and low maintenance, make them increasingly attractive to various industries. As continuous innovations improve the performance and functionality of heat-resistant plastics across a wide range of applications, these materials are expected to become even more important in modern technological development.