# 1988 Bath
Studies are reported on the performance of pipes produced fmm selected blends of polyethylene materials. The pipes were tested at a single temperature of 80°C and at irternal pressures designed to induce slit-mode failure. It is shown that blending the wrong polyethylene resins can substantially reduce performance of good stress craek resistant pipe materials. Blecding should therefore not be undertaken, and it should be clarified that the oarrie~9 used in masterbatches do not down-rate pipe performance. Studies on the microstructure of un-blended and blended polyethylene resins reveal that the size of the spherulitio structures cannot be used as a guide to stress crack resistance.