Effect of blown film processing parameters on sharkskin melt fracture of linear low-density polyethylene

A study to evaluate the effect of various processing parameters of blown film extrusion on the melt fracture of linear low density polyethylene resin was conducted. A correlation between the barrel/die temperature, air cooling rate and take off speed on the onset of sharkskin was made. Melt fracture was measured by both qualitative and quantitative methods i.e. by traditional visual inspection techniques, and also with a hazemeter to obtain % clarity and a water immersion test to check for the type of surface defect. Capillary rheometer studies were carried out over a range of shear rates and temperatures to obtain a processing window for the resin.; The severity of melt fracture decreased as the die temperature and air cooling rate was increased. Melt fracture and surface roughness increased with an increase in the output rate and take off speed (draw down rate). It was observed that melt fracture occurred above a critical shear stress of 0.1 MPa. With an increase in the extensional rate, the melt fracture increased.