Additives, for example antioxidants, ultra violet stabilizers, carbon black, processing aids, colorants, etc., may be added to the blend prior to forming pipe, fittings and accessories. [0053] The preferred method of determining ESCR's for blended HDPE compositions having similar density and MI values is derived from the formula: ESCR=Ae???B(PI), where PI=Mw/Mn; M w=weight average molecular weight