Abstract: A pressure pipe resin is disclosed comprising from 90 to 99.9 wt %, based on the total weight of the resin, of a polyethylene, and from 0.1 to 10 wt %, based on the total weight of the blend, of an ionomer.

Abstract: A process of manufacture of pipes and of fittings comprising a first stage of utilising a propylene polymer based compound comprising: from 76 to 98 parts by weight of a crystalline homopolymer of propylene or of a crystalline statistical copolymer (A) of propylene which may contain up to 1.5% molar of monomer units derived from ethylene and/or from an alpha-elefin containing from 4 to 6 carbon atoms; from 24 to 2 parts by weight of a statistical copolymer (B) containing from 40 to 70% molar of monomer units derived from ethylene and/or from an alpha-olefin containing from 4 to 6 carbon atoms, so as to obtain a pipe or a fitting, and a second stage of annealing said pipes or fittings by heating for a perior of between one hour and three days at a temperature between 110 and 155° C.