I make large coils. 3 to 6" diameter. Back 50 years ago I used ceramic or bakelite coil forms. Today I am using ABS, PVC, and Acrylic forms but they expand with temperature different than copper.
Copper = 17x10^-6/C while ABS= 63x10^-6/C.
I am about to get some coil forms printed in 3201 PA-F Nylon. I like the high milting point of Nylon but cannot find any numbers on thermal expansion. There are many different types of Nylon with good to bad expansion numbers.

What would you wind coils on?
I am looking for fiberglass tubs with 3 to 6 inch diameter but cannot find any. I think it matches copper very well.
Any ides will help.
RonS

 

Have you seen these guys? https://www.rockwestcomposites.com/tubing/round-tubing/fiberglass-tubing

Or - https://www.compositewarehouse.com/index.php?route=product/product&path=25_28_35&product_id=64

 

Mineral filled or glass filled polymers have much lower thermal expansion than infilled polymers.

 

One of my beloved materials is quartz because the full shelves of it. Or more appreciating, the quartz-glass. Pure quartz is crystall, but quartz glass is polimorph. It linear expansion factor is around 5.5E-7/°C (for comparizon, stainless steel (1.01-1.73)E-5. If You ask for kapron (nylon 6) it is around 4E-5. The best ever seen material is Zerodur, with alpha=6E-9, but I cannot to suggest where to buy it. Rather good is also Sitall ceramics with 1.5E-7 but it is rather expensive material from astronomic mirrors. Try to never use the polypropylene and polyethylene (12E-5). Typical fiber-glass value is 5.4E-6. The best way is to wind the bobbin with rather large expansion of wire then wire is springing along with coil form. Or other words, copper alpha is effectively diminished.