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Generally, plastics that can be used above 150°C are called heat-resistant plastics. Heat-resistant plastics can not only withstand high temperatures above 150°C, but also their mechanical properties will not be affected at such high temperatures.
Heat-resistant plastics play an important role in many industries. Their thermal stability, along with other favorable properties, make them suitable replacements for metals in countless applications.
Although metals tend to withstand higher temperatures than plastics, in some cases plastics may be a better material choice. (Typically, replacing metal parts with plastic parts can reduce the weight of the part, prolong the life of the part and improve the performance of the part.)
This article will explore the types of heat-resistant plastics and several common types of heat-resistant plastics.
Heat-resistant plastics are generally divided into two categories: thermosets and thermoplastics.
Thermosets are plastics that cure when heated and cannot be reshaped after curing. Thermoplastics are plastics that melt when heated, become solid when cooled, and remelt when cooled. The structural integrity of thermoplastics is affected by factors such as the intrinsic glass transition temperature (Tg) and melting point of different materials. There are some high-performance thermoplastics that can be selected to maintain their short-term structural capabilities above 150°C and 250°C.
In addition to heat resistance, they can exhibit chemical resistance, corrosion resistance, light weight, electrical and heat resistance, and other desirable properties, depending on their composition. These various qualities make them suitable for a wide range of industrial applications.
There are different types of heat-resistant plastics, each with specific advantages and disadvantages for different applications.
PTFE has a low coefficient of friction and high chemical resistance. It also has excellent flexural strength, electrical resistance, weather resistance and thermal stability. Teflon gaskets are suitable for -200°C to 260°C. Provides excellent strength, weather resistance and electrical insulation in hot and humid environments.
PTFE performs well at very high and very low temperatures, but its mechanical properties are often not the same as plastics at room temperature. It is sensitive to creep, abrasion and radiation, and the fumes can be toxic. Also, it is worth noting that PTFE is very expensive to process.
Polyetheretherketone is a high-performance engineering thermoplastic with a semi-crystalline structure. It has chemical resistance, abrasion resistance, fatigue resistance, creep resistance and heat resistance. The material is tough enough to withstand harsh environments and is used by manufacturers as a metal replacement in many applications because it maintains strength and adaptability under extreme environmental conditions. PEEK has a melting point above 371°C and can withstand temperatures as high as 310°C for a short period of time. What’s more, it has the highest tensile and flexural strength of any high-performance polymer.
Disadvantages of PEEK include sensitivity to sulfuric, nitric, chloric, halogen and sodium, and low resistance to UV radiation. They are also expensive and therefore should only be used in demanding applications.
Polyetherimide is one of the few amorphous thermoplastics on the market. It is strong, chemically resistant, flame retardant, and has the highest dielectric strength of any high-performance thermoplastic. The material has a very high melting point of 219°C and a maximum continuous operating temperature of 170°C.
Polyamide-imide is another high-performance thermoplastic with high temperature resistance, high thermal stability, excellent chemical resistance and high temperature wear resistance up to 275°C. Polyamide-imides also exhibit high tensile and compressive strengths. Polyamide-imides can be processed by injection and compression molding techniques. Polyamide-imide also has excellent dimensional stability due to its high compressive, impact and creep resistance.
Heat-resistant plastics are currently widely used in the manufacture of components and products used in the industry. Examples include heat- and impact-resistant parts for the aerospace, automotive and glass industries; heat-, radiation-resistant, highly insulating or certain conductive parts for the electrical and semiconductor industries; sterilization and hydrolysis-resistant parts for the medical device industry ; Radiation protection and anti-radiation components for the nuclear industry and X-ray technology industry; various components for the chemical industry, etc.
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