What Is Heat Resistant Plastic?
Heat-resistant plastics have a short-term exposure resistance of 250 ºC (482 ºF) or continuous use at temperatures beyond 150ºC (302 ºF) or more. These materials exhibit remarkable mechanical properties that are closely similar to metal ones. Plastics comprise long molecular chains. The bonds between these chains are severed when the plastics are heated, melting the material into molten form.
Heat-resistant thermoplastics are categorized into two major classes – thermoplastics and thermosets. High-performance thermoplastics are materials that turn to liquid when heated, harden when cooled, and re-melted again after cooling. In contrast, thermosets are polymers that harden upon exposure to heat and cannot take another shape after curing. Variables like glass transition temperature (Tg) and inherent melting point affect thermoplastics’ structural integrity.
Manufacturers often improve the heat resistance of plastics with additives, such as glass fiber, which is one of the commonly used additives for enhancing the temperature resistance of plastics. These fibers also help increase overall material stiffness and strength.
Standard Methods of Characterizing Heat Resistance of Plastics
There are various ways of characterizing a plastic’s heat resistance. They provide critical insight into a plastic material’s thermal capabilities and stability for effective material selection, assessing the application suitability and product design. These methods include:
- Heat Deflection Temperature (HDT): This measures the temperature at which a plastic deforms under a predefined load. Plastic material softens at this temperature, losing its ability to support a load without deformation. This test helps product designers assess the suitability of plastics for structural applications that require high dimensional stability in environments with heat exposure.
- Continuous Use Temperature (CUT): CUT defines the highest temperature at which a plastic material can function continuously over a more extended period without significant degradation or losing its mechanical properties. It provides insight into a plastic material’s long-term thermal stability in different applications.
- Glass Transition Temperature (Tg): Tg refers to the temperature at which an amorphous plastic changes to a rubbery or viscous state. It indicates the temperature range at which a plastic material experiences significant changes in mechanical properties like stiffness and ductility—Tg helps to examine the processing conditions and thermal properties of plastic materials.
Why Choose Heat Resistant Plastics?
Plastics are indispensable machining materials with different uses across industries. However, the question is – why choose plastics as the suitable option for high-temperature applications when metals can perform better over a wider temperature range? We will discuss reasons why you should pick these groups of plastics for your applications:
Corrosion Resistance: Some plastic resins exhibit better resistance to corrosion than metals when subjected to different chemicals. Moreover, this attribute is crucial for applications involving corrosive environments and high temperatures, as in the chemical industry.
Low Weight: Plastics have considerably lower weight than metals. As a result, manufacturers in the automotive and aerospace sectors employ these heat-resistant plastics to produce lightweight parts and components for optimized overall efficiency.
Insulation: Plastics are ideal materials capable of functioning as electrical and thermal insulators. Hence, they are perfect for applications where high temperatures can affect the operations of an electrical part or where electrical conductivity could spoil sensitive electronics.
Manufacturing Flexibility: Product designers manufacture plastic components with high-volume production technologies like CNC machining, 3D printing, and injection molding. These heat-resistant plastics allow complex designs and a higher degree of design flexibility.
Typical Heat-Resistant Plastics
| Property | PBI | PEI | PEEK | PTFE | pDCPD |
|---|---|---|---|---|---|
| Tensile Strength (MPa) | 170-230 | 100-120 | 90-100 | 20-35 | 30-40 |
| Heat Deflection Temp. (°C) | 425-450 | 170-215 | 335-350 | 260-290 | 130-150 |
| Cost (Relative) | Very High | Moderate | High | Moderate | Low |
| Chemical Resistance | Excellent | Fair to Good | Excellent | Excellent | Good to Fair |
| Moisture Absorption | Low | Moderate | Very Low | Very Low | Low |
| Other Special Properties | Exceptional thermal stability, flame resistance | Good dimensional stability, flame retardant | Excellent wear resistance, radiation resistance | Excellent chemical resistance, low friction | Good impact strength, low density |
Heat-resistant or high-temperature polymers are materials that can maintain their mechanical properties at extremely high temperatures. Here are the notable high temp polymers:
Polyether Ether Ketone (PEEK)
PEEK is a semi-crystalline, high-performance engineering thermoplastic with excellent chemical, creep, fatigue, heat, and wear resistance. Manufacturers often use this resin as an ideal replacement for metal in several applications, irrespective of the temperature involved, due to its high strength and ability to adapt to harsh environments.
PEEK exhibits the highest flexural and tensile strength. It has a 371ºC melting point and can withstand temperatures above 310ºC for short periods. This high-performance polymer is often used for different medical devices because it exhibits similar durability to metals. Solid PEEK resin is compatible with CNC machining, and it is easy to machine using injection molding and extrusion methods. Its versatility makes it a worthy material every engineer should have in their inventory.
Nevertheless, this popular engineering thermoplastic has various limitations, such as susceptibility to specific acids and weather resistance.
Polyetherimide (PEI)
Polyetherimide (PEI) is a popular commercially available amorphous thermoplastic on the market today. It has remained a staple in the manufacturing industry since it’s a strong plastic with desirable chemical and flame resistance. ULTEM (the branded name for Polyetherimide) is famous among high-performance thermoplastic materials because it has the highest dielectric strength. This plastic exhibits minimal shrinkage when exposed to heat or during processing.
PEI is perfect for making components like food sterilization equipment, aircraft parts, and circuit boards due to its maximum continuous operating temperature of 170 ºC and extremely high melting point of 219 ºC. Polyetherimide exhibits excellent creep resistance and performs well when subject to different fuels and coolants. Hence, it is one of the few plastics used in commercial aerospace for airplane seat covers and fire blockers. Nevertheless, it is susceptible to cracking when exposed to polar chlorinated solvents. ULTEM is quite expensive and exhibits lower impact strength.
Polybenzimidazole (PBI)
Polybenzimidazole (PBI) is an engineering thermoplastic with high heat and wear resistance and mechanical and strength property stability. PBI material has 393ºC as its highest continuous service temperature in inert environments, 343 ºC in air, and a blistering 537 ºC as its short-term exposure. PBI fibers do not have melting points and do not burn or stick to other plastics.
Manufacturers often use PBI for critical applications, including astronaut spacesuits, racecar driver suits, and protective apparel for firefighters because of its high stability and good heat resistance.
Although PBI offers exceptional mechanical strength, it is costly and challenging to manufacture. As a result, fabricators often employ diamond tools to shape this material at the risk of increasing machining costs. From a design perspective, the elevated notch sensitivity of PBI is a significant setback. Product engineers must avoid sharp corners and edges and smooth all surface finishes.
Polytetrafluoroethylene (PTFE)
PTFE, or Teflon, is another popular heat-resistant thermoplastic on the market today. It is a soft, low-friction plastic with excellent chemical resistance. Manufacturers often use it in hot and cold temperatures due to its high flexural strength, good electrical insulating power, and adequate weathering resistance.
Teflon is a highly versatile resin suitable for numerous high-temperature applications because of its excellent chemical inertness and is highly insoluble in most solvents. PTFE exhibits a large operating temperature range and is one of the thermoplastic materials with the highest melting point at 327ºC.
This heat-resistant material is quite famous for its commercial applications. It is ideal for protecting pipes from corrosive chemicals, coating heat exchangers, and providing insulation for electrical components. However, PTFE has inferior mechanical properties to comparable plastics at room temperature, even though it performs well at extremely low and high temperatures. Despite being reasonably expensive to process, Teflon can make toxic fumes and is susceptible to creep, radiation, and abrasion.
Polydicyclopentadiene (pDCPD)
This material is a custom-engineered thermoset resin formulated to provide a unique combination of corrosion, heat, and chemical resistance with excellent stiffness and impact strength. This polymer integrates the high-performance attributes of top-engineering thermoplastics with the molding flexibility of a thermoset. It exhibits a maximum heat deflection temperature of about 120 ºC.
Polydicyclopentadiene is a unique material with no part size or weight limitations. As a result, production delays won’t occur due to parts with variable wall thickness, molded stiffening ribs, and other factors. However, the applications of pDCPD are still limited because it is a relatively new material. Nevertheless, it has proven useful in corrosion-resistant chemical process equipment, water treatment equipment, and septic tanks.
Applications of Heat Resistant Plastics
Product engineers and manufacturers often use heat-resistant plastics for numerous applications across different industries where parts are subject to high temperatures. Typical industry applications of the engineering-grade polymers discussed above include:
Aerospace
Since heat-resistant plastics can withstand extreme temperature variations, they are widely used in making parts and components of aircraft and spacecraft. Interior components, insulation materials, and electrical connectors are typical aircraft components made with heat-resistant plastic.
Automotive
In the automotive sector, fabricators often use high-temp materials for engine components like radiator tanks, valve covers, and intake manifolds. These plastic materials can withstand very high melting temperatures produced within the engine.
Medical Industry
Typical applications of heat-resistant plastics in the medical industry include sterilizable components like surgical instruments, instrument trays, sterilization equipment, and autoclave housings.
Electronics
Heat-resistant plastics are crucial materials used to create electronic devices and their components, especially those with high power consumption. Electronics manufacturers use heat-resistant plastics for components like housings and precision electrical connectors to ensure operational safety and prevent heat-related damage.
Energy
Manufacturers in the energy sector utilize heat-resistant plastics for different applications, such as components of power-generating machinery like turbines and broilers and insulating material for electrical wiring.
Food and Chemical Processing
Heat-resistant plastics are suitable for making food and chemical processing equipment since they can withstand high temperatures, corrosive environments, and sterilization procedures. Typical applications of these plastics in these industries include piping systems, packaging materials, pumps, containers, valves, and conveyor belts.
AT-Machining Your Reliable Manufacturer for Heat-Resistant Plastic Needs
Heat-resistant plastics play a significant role in product manufacturing in different industries. They offer advantageous properties, including thermal stability, low weight, corrosion, and wear resistance, making them ideal substitutes for metals in many applications. However, understanding these engineering plastics helps to derive peak benefits for your projects.
AT-Machining is your best bet if you need top-quality, heat-resistant plastic parts and components. We are experts in manufacturing non-metallic components. We leverage our modern CNC facility and extensive manufacturing experience to meet the specific requirements of your projects. Our experts have in-depth knowledge of the different heat-resistant plastics. Contact us today, and let experts help you choose the perfect heat-resistant plastic for your products.
