Understanding which material for screws is important for design success. In this post, we worked with Extreme Bolt & Fastener to offer their insights into understanding polymers.
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.
| Usable Temperature Limit Guide | ||
| Materials | Usable Temperature Limit (°F) | Usable Temperature Limit (°C) |
| PI (Vespel®) | 572 | 300 |
| PAI (Torlon®) | 527 | 275 |
| PEEK (Victrex®) | 500 | 260 |
| PTFE | 500 | 260 |
| PVDF (Kynar®) | 300 | 150 |
| Nylon (Reference) | 212 | 100 |
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 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 a 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.
| Material | Ultimate Tensile |
| PEEK Extreme | 47,900 |
| PEEK Glass Fiber | 22,800 |
| PEEK Unfilled | 16,000 |
| Vespel® | 12,500 |
| Torlon® Unfilled | 22,000 |
| PVDF | 5000 – 8000 |
| PFA | 3600 |
| PTFE | 3900 |
Top Picks
We you need fasteners with multiple capabilities, here are our top picks.
| High corrosion & temperature | PTFE |
| Moderate corrosion/moderate temperatures | PEEK – Temperature PVDF – Strength |
| General corrosion, high temperature, and strength | PEEK |
To view the selection of Extreme Bolt products, visit our dedicated page here.
Works Cited
Extreme Bolt & Fastener. (2024). Which Polymer Is Right for You? Retrieved from When Materials Matter Blog: https://www.extreme-bolt.com/blog/which-polymer-is-right-for-you/
