Abstract: Pipe or tubing of crosslinked polyethylene (“PEX”) containing less than 2% by wt. carbon black provides improved resistance to oxidizing agents such as chlorine and hypochlorous acid in water. The pipe may be further protected with a thin tubular core (inner layer) of high density polyethylene or chlorinated polyethylene. The pipe may optionally have an oxygen barrier layer, such as poly(ethylene-co-vinyl alcohol) (“EVOH”), contiguously disposed radially outward from the carbon-containing PEX layer. The pipe is suitable for potable water applications and for hot water radiant heating systems.

Abstract: A multi-layered pipe of arbitrary length and cross-section is produced by co-extrusion of a segmented thermoplastic copolyester elastomer (COPE) outer body over the exterior surface of an annular tubular core of CPVC/PVC having a wall thickness, measured in the radial direction, in the range from about 0.95 mm (38 mils) to about 1.375 mm (55 mils). The COPE is cohesively bonded to the annular core coextensively with essentially the entire length of the pipe. Though the COPE is easily degraded in contact with water, and CPVC and blends of CPVC with less than 25% by weight of PVC are typically rigid when extruded as pipe, a laminated pipe of COPE and CPVC/PVC with the specified wall thickness and overall dimensions which in the laminated pipe satisfy an applicable plumbing code (SDR-11 in the U.S.) has essentially the same performance characteristics as commercially available CPVC pipe which is a monolayer and not a laminate.