Q: I’m involved in is currently looking at your non-conductive fasteners to isolate an SMA Connector. But have several questions for finding the right solution regarding torque, preload heating and cooling, and locking features.

A: Thanks for all the questions and interest. I will answer all your questions:

How is torque calculated, do they relax and lose preload?  
Torque is a tricky measurement at best and based on many factors that are hard to know.  On polymers its best to do a quick test to get some empirical information.  We typically recommend breaking few parts, measuring the torque and torque to about 60-70% of that break load.

How is the preload effected when heated then cooled (cycled)? 
Depends on the heating a cooling and the polymer. Glass reinforced polymers will hold their tension better.

How do the non-conductive fasteners adhere to staking material and other locking feature such as a locking insert?  
I’m not sure what you mean by adhere to staking material, but most of the polymers we offer are fluorinated based and generally don’t stick to anything.  Locking insert are not used on polymer parts. Perhaps a nylon patch could be used but is not very common.

Additionally, the PEEK material mentioned low outgassing, what about the others (PFA, PTFE, PVDF, etc? All these fluorinated polymers have very low outgassing.

Q: Looking to change to a non-conductive material for use in a high
impact application. Would Alumina or Zirconia ceramic fasteners be a good fit?

A: We could certainly quote you some ceramic hardware, however ceramics may not be the best non-conductive choice for a high impact environment.  Ceramic fasteners are generally strong but brittle. This makes them susceptible to failure from impacts.

Depending on the temperatures in your application, you might want to consider a polymer like PEEK screws.  Glass fiber re-inforced PEEK screws offer nearly double the strength of natural PEEK.  A polymer fastener like PEEK will be much tougher than ceramics and will still offer non-conductivity. In addition, PEEK is a VERY stable polymer and is creep resistant, depending on the temperature you are operating at.