Which Polymer Is Right for You?

PEEK, PVDF and PTFE all offer lightweight, electrical & thermal insulation and great corrosion resistance. But when it comes to strength, temperature, purity and corrosion, each has its niche. The newsletter points out which is best to use in different conditions.

TEMPERATURE
PEEK and PTFE screws offer excellent high temperature resistance to 500°F, far exceeding that of PVDF and nylon. For extreme temperatures up to 572°F requiring the best strength possible, Vespel is the ultimate choice.ULTRA PURITY
PVDF materials are approved by the FDA, USDA, NSF, 3A Dairy and USP Class VI. In addition, PVDF screws are resistant to ultraviolet and standard sterilization, making them ideal for pharmaceutical, food, and semiconductor applications.

CORROSION
PTFE fasteners score top marks for corrosion resistance: offering protection from most organic materials, acids and bases – even hydrochloric acid. Useable to 500°F, PTFE fasteners are ideal for high temperature corrosion resistance but are relatively weak. PVDF screws also offer a high level of chemical resistance and more strength than PTFE but but are generally reserved for lower temperature applications below 300°F. PEEK screws offer less corrosion resistance than PVDF but still can be considered to have very good corrosion resistance relative to other more common polymer fasteners.

STRENGTH
When it comes to strength, PEEK screws are ideal. PEEK offers higher strength than PTFE, PFA, PVDF and Vespel. While nature PEEK is very strong, fiber reinforced PEEK, like PEEK Extreme and glass filled PEEK fasteners are can be nearly as strong as some steel fasteners.

TOP PICKS
We you need fasteners with multiple capabilities, here are our top picks.

PEEK Screw Strength vs FDA Approved PTFE Screws

Q: I work in the food industry and need a larger sized polymer fastener sized 1/4-20 x 2.5″. I tried PTFE but it isn’t does not seem to have enough strength. It also needs to be FDA approved and offer moderate corrosion resistance.

A: Not knowing the specific strength requirements of your application, I would suggest a PEEK fastener. PEEK screws are FDA approved and offers decent corrosion resistance. PEEK is also much higher strength than PTFE which will be important in a larger bolt. PTFE only can provide a yield strength of 1450 psi compared to PEEK screws which offer 13,600 psi in yield.

Lightweight & High Strength PEEK Screws

Q: I need a fastener that is very low weight and offers good wear resistance for a robotics application. I need about 40 ksi in strength.

A: For your application I would actually suggest an engineered polymer fasteners since your strength requirement isn’t high enough to necessitate a metal . PEEK Extreme screws are made of a carbon fiber reinforced PEEK polymer. These screws provide one the highest tensile strengths of any polymer, with an ultimate tensile greater than 47 ksi. In addition, PEEK screws are very lightweight, far lighter than any metal fastener and will provide excellent wear resistance.