There are many ways to measure the heat resistance of thermoplastics.
These include heat deflection temperatures (HDT) which are normally measured under a load of 264 or 66 psi, melt temperatures, and glass transition temperature (Tg).
However, over time it has been determined that one of the most useful physical properties of a high-temperature resistant thermoplastic is that of the glass transition temperature. (Tg is the temperature at which a material begins to soften.)
Temperature Resistance of Thermoplastics
|PAI||Polyamideimide (Torlon®)||527°F (275°C)|
|PI||Polyimide (Aurum®)||482°F (250°C)|
|PPS||Polyphenylene Sulfide||198°F (92°C)|
|PVC||Polyvinyl Chloride||176°F (80°C)|
|PA||Polyamide 6/6,6||167°F (75°C)|
|PA||Polyamide 4,6||133°F (56°C)|
By means of independent tests, Minnesota Rubber and Plastics has published performance results that demonstrate continuous use temperature above the Tg. The same is true for heat deflection temperatures. However, it is important to remember that performance ultimately depends upon the application. Normally, a material is in danger of failure when it begins to soften (Tg). Therefore, as a general guide, the Tg must be a major consideration when selecting a high temperature resistant thermoplastic.
A material listing helps to clarify and place into perspective common thermoplastic materials showing the Tg of several high performance materials.