High-performance thermoplastics (HPTPs) are used in very demanding applications. Compared with the larger-volume engineering thermoplastics, HPTPs exhibit superior short- and long-term thermal, and chemical stability due to their higher melting or softening point and stronger inter- and intramolecular bonds. They also possess superior mechanical properties, particularly at elevated temperatures, including higher stiffness, strength, and resistance to creep, wear and fatigue. Most HPTPs can withstand long-term operating temperatures of at least 150°C and short-term use temperatures of greater than 250°C. However, their applications are limited by their high price of the resin compared to commonplace engineering plastics. For this reason, HPTPs are only used for high-performance components primarily used in the aerospace, defense, electrical/electronics, and chemical industries.
Polybenzimidazole (PBI) is probably the highest performing engineering thermoplastic on the market and offers the highest heat resistance and service temperature of any unfilled thermoplastic.1 It has a glass transition temperature of about 425°C (800°F) and no melting point and its heat deflection temperature at 264 psi (1.8 MPa) is about 815°F (425°C).1 It also possesses outstanding chemical resistance. However, PBI is quite expensive and difficult to manufacture, and, thus, is mainly used for the most demanding applications.
Thermoplastic polyimide, or TPI, is one of the most heat resistant engineering thermoplastics available that can be melt-processed by injection molding with great precision. It has one of the highest continuous operating temperatures for an unfilled thermoplastic (240°C / 464°F), and outstanding friction and wear resistance as well as high strength and stiffness at elevated temperatures. Its glass transition temperature is about 250°C (482°F) and its heat deflection temperature at 264 psi (1.8 MPa) is about 460°F (238°C).2
Polyaryletherketones (PAEKs) are one of the highest performing engineering thermoplastics having a unique combination of thermal stability, chemical resistance, and excellent mechanical properties over a wide temperature range
including high strength and stiffness along with outstanding toughness and fatigue resistance.
They also have one of the highest continuous operating temperatures
for unfilled thermoplastics (260°C / 500°F).3
Many experts rank PAEKs as one of the best commercial HPTPs.
Howerver, they are one of the most expensive thermoplastics.
Self-reinforced polyphenylene (SRP) is one of the stiffest and strongest melt-processable engineering thermoplastics on the market. It offers outstanding dimensional stability and, unlike many other HPTPs, it has excellent mechanical properties at very low temperatures and without fiber reinforcement. In addition, it possesses exceptional abrasion and solvent resistance, outstanding thermal-oxidative stability, and inherent flame resistance. Due to its high specific strength, SRP is an excellent candidate for light-weight high-performance applications.
Polyphenylene sulfide (PPS) is a popular semicrystalline, high-performance engineering thermoplastic that is known for its excellent heat resistance, good dimensional stability, and high mechanical strength. It also has good retention of mechanical properties and dimensional stability at elevated temperatures and outstanding resistance to chemicals which is one of the broadest of any advanced engineering plastic. On the downside, most grades are difficult to process due to their poor solubility in most solvents and high melting point.
Polyamideimides (PAIs) are one of the strongest melt-processable amorphous HPTPs that possess outstanding thermal, mechanical, and chemical properties. Some grades maintain their strength and stiffness up to 260°C (500°F) and can be operated in harsh thermal and chemical environments even under severe stress with little to no creep, wear, and chemical degradation. However, a postcure is often required to achieve maximum heat, wear and chemical resistance.
Polyarylates (PAR) are a family of aromatic polyesters that offer moderate high heat distortion temperatures, inherent ultraviolet light stability, and outstanding mechanical properties. BPS-PAr has a glass transition temperature of about 196°C (385°F) and a heat deflection temperature at 264 psi (1.8 MPa) of about 174°C (345°F).4 Its transparency is comparable to polycarbonate but it has better gloss retention and lower haze when exposed to UV due to the formation of a protective layer that essentially serves as a UV stabilizer.
Poly(ether)sulfones (PES, PPSU) are an important class of amorphous, transparent thermoplastics. These HPTPs are known for their high thermal, oxidative and hydrolytic stabilitiy. They can be easily molded, extruded, and thermoformed into a wide variety of shapes and products. PES has a glass transition temperature of about 216°C (422°F) and a heat deflection temperature at 264 psi (1.8 MPa) of about 215°C (420°F).5 PES can be continuously used at temperatures up to + 190°C (UL) without noticeably dimensional change or physical deterioration.5
Polyoxymethylene (POM), sometimes called polyformaldehyde or acetal, is one of the most important engineering plastics. It is a highly crystalline thermoplastic that is known for its high flexural and tensile strength, stiffness, hardness, and low creep under stress. It also has a low coefficient of friction, excellent chemical resistance and outstanding fatigue properties, but only moderate heat stability and insufficient flame resistance. POM and its copolymers are often an excellent choice for applications that require low friction, tight tolerances, and high impact and creep resistance. In many applications, POM ca be used as a replacement for metal parts.
1Quadrant Celazone Polybenzimidazole product data sheet, Duratron® CU PBI
2DuPont Aurum® PL450C Thermoplastic Polyimide data sheet
3Ensinger TECAPEEK natural technical data sheet, Version AE, 2/20/2018
4Emco Ardel® Polyarylate technical data sheet
5Mitsui Chemicals Polyethersulfone (PES) technical literature