Method of joining plastic pipe

A polyethylene graft copolymer fitting, for use solely in joining polyethylene pipe sections to produce a pipe joint assembly wherein the fitting is less stiff than and can creep with the pipe sections which it joins, the combined fitting and pipe sections forming a pipe joint which is at least as strong as the pipe itself, said fitting comprising:

• a. an annular insert portion having an outer diameter substantially the same as the inner diameter of the pipe section to be joined thereto, and
• b. a shoulder portion having a larger diameter than the insert portion, the fitting formed of a polyethylene graft polymer comprising the reaction product of a polyethylene polymer or copolymer having a density of 0.940-0.950, with from about 5.0 to about 15.0% by weight of the polyethylene of a butyl rubber and from about 0.30 to about 2.5% by weight of the polyethylene of a bifunctional phenolic composition having ortho functionality and the para position of the phenol ring substituted with an inert hydrocarbon radical selected from the group consisting of alkyl, aryl, alkaryl and aralkyl radicals of up to 16 carbon atoms.