Acrylics can be very brittle, ebonite should work better. But you can also try PET (polyethylene), PBT (polyester) and Acetal (delrin) which may work out to be the best materials. Not sure about PVC, Nylon, or Teflon they may not be very dimensionally stable.
Someone once said metals work pretty good.
You should also use dissimilar materials for the mating threaded parts.