Nylon is not as slippery as many plastics, and it does swell but usually from absorbing water.

Are you looking to simply reduce friction on the end face of a top hat ? If so, it might be worth considering using UHMWPE tape, it's commonly sold as "glide tape" by 3M amongst others. It's extremely abrasion resistant and nearly as slippery as PTFE.

I haven't used the tape myself, Delrin (acetal homopolymer) or plain acetal copolymer have worked well enough for my tinkering.