Patent ID: 7255134

Claim:
A pipe of crosslinked polyethylene (“PEX”) having a wall of substantially uniform thickness in the range from 1.78 mm to 17.29 mm having dispersed therein from 0.1 to about 1.25% by weight of carbon black having a particle size less than 27 nm (nanometers), and wherein said PEX is crosslinked by a method selected from the addition of AZO compounds and silane grafting process said pipe including, an inner tubular core of protective polymer selected from the group consisting of high density polyethylene (“HDPE”) and chlorinated polyethylene (“CPE”) contiguous with the inner surface of the crosslinked PEX, the core having a substantially uniform wall thickness in the range from 0.025 mm (1 mil) to 1.52 mm (0.06″), and a maximum wall thickness in the range from about 28 to 100 times smaller than the nominal diameter of the pipe in the range from 7 mm (0.25″) to 152 mm (6″), ratio 28 being attributable to small diameter non-SDR-9 piping, and ratio 100 being attributable to the larger diameter SDR-9 pipe, wherein the HDPE has a density in the range from 0.941 g/cc to 0.963 g/cc, and the chlorinated polyethylene (“CPE”) has a chlorine content in the range from 5 to about 50% by weight.