Plastic insluator for Antenna what type?

[VK6TU]

I plan on making a few antennas in the future that will require a insulator to fit into some aluminium tube that will be suitable for RF.
I am wondering what would be the best type plastic to use?

Some options are
HDPE
Polyurethane
Acetal Delrin®
Teflon

Acrylic
Nylon

And possibly more in many colours.
This site shows a good range of options
http://stores.ebay.com.au/Warlond-Plasti...7675.l2563

As I have a lathe I will be able to machine to the correct size but I want to make sure the insulator is suitable for RF and UV.

Thanks

Michael
VK6TU