US Patent RE39968 PTFE tube

The present invention relates to a polytetrafluoroethylene (PTFE) tube, and more particularly to a PTFE tube for a flexible hose. In particular the invention relates to a PTFE tube having a smooth bore for use in the production of a lined hose assembly farther comprising hose braids, external hose protection and end fittings. The PTFE tube comprises external roots and peaks, which tube is obtainable from a non-convoluted tube having an original wall thickness W0 and an internal diameter ID by a process in which a region of the tube is thinned to provide external convolutions with a root wall thickness W1 characterised in that the convoluted PFTE tube has an improved resistance, of greater than 7.6%, to permeation by comparison with the non-convoluted tube, the comparison being made between tubes of (i) equal nominal bore ID; and (ii) equal weight of PTFE per unit length.