What Is The Different between PEI And PEEK?

Both PEEK and PEI are high-performance plastics that can withstand high temperatures and are widely used in aerospace, automotive, and electronic and electrical fields. But there are differences in their performance

Temperature resistance performance of PEEK and PEI:

PEEK material has a higher service temperature than PEI.

Although the glass transition temperature of PEEK at 143°C is lower than that of PEI at 217°C, the long-term service temperature of PEEK can reach up to 260°C and the short-term service temperature can reach up to 300°C, while the long-term service temperature of PEI is 170°C and the short-term service temperature is 200°C.

Although the operating temperature of PEI is lower than that of PEEK, it has already exceeded that of most engineering plastics.

The wear resistance of PEEK and PEI

The coefficient of friction of pure PEEK is 0.38, and that of pure PEI is 0.41. The coefficients of friction of the two are quite close.

However, the friction coefficient of the modified bearing gradePEEK has been greatly reduced.

As high-temperature resistant plastics, we need to study their wear resistance at high temperatures.

PEEK has excellent self-lubricating properties. As a crystalline material, the crystalline zone can maintain good strength at high temperatures. After exceeding the glass transition temperature, the friction coefficient of PEEK will increase. PEEK reinforced with carbon fibers has a very slow decline in wear resistance when the temperature exceeds Tg. Moreover, the carbon fibers wear out and turn into graphite, further maintaining the wear resistance of PEEK.

However, the crystallinity of PEI is low. As an amorphous material, it softens rapidly after exceeding the Tg temperature, and is prone to adhesive wear and plastic deformation, resulting in a rapid decrease in friction.

The corrosion resistance of PEEK and PEI

The corrosion resistance of PEI

The corrosion resistance of these two materials is equally excellent.PEI has excellent corrosion resistance to a variety of chemical substances, including most hydrocarbons, alcohols and all halogenated solvents. In terms of acid resistance, PEI shows good tolerance to dilute acids such as 30% concentration sulfuric acid, hydrochloric acid and phosphoric acid, with relatively small mass loss and decline in mechanical properties. In terms of alkali resistance, PEI has excellent resistance to dilute alkali solutions such as sodium hydroxide and potassium hydroxide and can be used stably at room temperature for long periods ‌. However, PEI has poor tolerance to concentrated acids and strong alkalis, and high temperatures gradually erode PEI, causing the surface to become brittle, discolor, and even molecular chain breakage ‌.

The corrosion resistance of PEEK

PEEK has excellent chemical resistance and remains stable in common chemicals except concentrated sulfuric acid. PEEK is resistant to irritating chemicals including H2S, and thus is widely used in downhole oil and gas applications. PEEK is also radiation-resistant, showing high levels of radiation-resistant ‌.

PEEK is more than twice as resistant to strong acids as PEI ‌ in terms of acid resistance.

PEEK also excels in alkali resistance and is suitable for reusable medical components that repeat autoclave cycles ‌.

Comparison of processing difficulty