Nightjar cpb wrote:

The only thing PTFE will stick to is PTFE.

Not according to 3M

http://multimedia.3m.com/mws/media/79749O/3m-scotch-weld-structural-plastic-adhesive-dp-8005.pdf

True it has its lowest shear strength when bonding PTFE rather than
other plastics, and it's about £15 a tube (plus you need a special 10:1
plunger to get it out, for DIY you could probably mix it with a spatula,
rather than wasting a lot filling the special mixing nozzles).