HDPE for Corrugated Pipe Holds Back Crack Growth.

A new HDPE for large-diameter corrugated pipe is said to have excellent processability combined with improved crack-growth resistance. Fortiflex CP52-35 from Solvay Polymers, Inc., Houston, is similar in melt index (0.35) and density (0.952 g/cc) to standard corrugated-pipe resins but exceeds the new NCTL (notched constant tensile load) ESCR test soon to be required by the American Association of State Highway and Transportation Officials (AASHTO), which regulates highway drainage pipe. AASHTO will require NCTL performance of 24 hr at 15% applied yield stress (ASTM D5397). CP52-35 HDPE exceeds that standard, whereas a typical HDPE corrugated-pipe resin lasts only 6 hr. By the traditional D1693 Bent-Strip ESCR test, CP52-35 has an F50 rating of 45 hr vs. 10 hr for the standard resin.