The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus

viz. an inlaid pan-mill

was used. Melt indexer

capillary rheometer

Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress

as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than for unmilled HDPE.The apparent shear viscosity of HDPE decreased with increasing times of milling.After milling

the flow activation energy decreased and thus the sensitivity of viscosity to temperature was reduced.Die pressure and torque during single screw extrusion were reduced significantly after milling.Plasticizing time as measured in a Brabander mixer decreased markedly with increasing milling times.