Ultem® boasts (or could if it was able to talk) the highest dielectric strength of any commercially available thermoplastic at 830 V/mil (per ASTM D149). Table 1 shows example material properties that are significantly affected by the presence of fillers for each of these material grades.Įlectrical Property and Environmental Influences Comparisonĭue to their electrical properties, both materials are widely used for electrical components including semiconductor test sockets and electrical connectors. The effects of temperature on flexural modulus for 30% glass and carbon fiber-filled PEEK are depicted graphically in Figure 2. Note that while fiber reinforcement provides improved mechanical performance, it has a negligible effect on Tg. below.įor higher strength performance and increased dimensional stability, fiber-reinforced versions of both materials are standardly available. This softening behavior is depicted graphically in Figure 1. As a result, the maximum usable service temperature of amorphous materials is limited accordingly. This is because at a material’s Tg, the amorphous regions soften or rubberize and the crystalline regions remain unaffected. PEEK exhibits a glass transition temperature (Tg) of around 289F and Ultem experiences its Tg around 420F, yet PEEK is used continuously in applications seeing 480F (and at even higher temperatures for short periods), while Ultem’s max continuous operating temperature is commonly reported as 340F. This may sound like a useless factoid, but it has strong implications for performance at elevated temperatures, especially above each material’s glass transition temperature. Ultem® is amorphous while PEEK is semi-crystalline (and contains both amorphous and crystalline regions). Elevated Temperature PerformanceĪ key difference between PEEK and Ultem® is their different morphological structures. In this article, we will briefly compare key characteristics of these two materials to assist in the material selection process. If you are choosing between Ultem® (PEI) and PEEK, there is likely a demanding thermal or electrical requirement (or perhaps both) in your application.
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