Q: What would be the highest strength polymer fastener I can use to 400F?
A: For this application, probably the best option for you would be PEEK fasteners. PEEK screws are usable to 500F and are available in three levels of strength. Unfilled natural PEEK fasteners offer 16,000 psi tensile strength, glass fiber reinforced PEEK fasteners offer 22,800 psi and finally the highest is PEEK Extreme fasteners which offer 47,900 psi of ultimate tensile strength.