Polyolefin resin blends for crack-resistant pipe

A blow molded pipe produced from a resin blend comprising from about 30 to about 70 wt. % of a low-molecular-weight, high-density polyethylene, and from about 30 to about 70 wt. % of a high-molecular-weight, low-density ethylene copolymer produced using a bridged indenoindolyl Group 4 metal complex having open architecture, wherein the ethylene copolymer has a weight-average molecular weight within the range of 150,000 to 500,000,

• wherein the blend has a density from 0.94 to 0.96 g/cm3, a weight-average molecular weight (Mw) by gel permeation chromatography greater than 200,000, rheological polydispersity (ER) of less than 1.5, and a viscosity enhancement factor (VEF), calculated from its melt viscosity (η*) at 190° C. and 0.025 radians per second, of less than 2, wherein the pipe exhibits a notched constant tensile (NCTL) value of greater than 500 hours to failure, and wherein the low molecular-weight, high-density polyethylene is produced using a polysiloxane-supplied Ziegler-Natta catalyst.