Comparison of the mechanical performance and crystallinity of medium density polyethylene films manufactured on IBC and conventional blown film extrusion lines

摘要

A range of films was manufactured from a medium density polyethylene (MDPE) resin of MFI 2.0 (g/10min) and density 0.94 g/cm{sup}3 using a 75mm extruder fitted with a 290mm diameter Blown Film Die and a die gap of 0.9mm. The films were manufactured at different haul off rates and a constant blow up ratio of 1.24, using both conventional air ring and internal bubble cooling (IBC) systems. The line speed of the IBC extrusion line was approximately three times that of the conventional blown film line. Tensile analysis of the films at room temperature showed significant increase in break strength and break modulus in the machine direction for the IBC films, at all draw down ratios. Differential Scanning Calorimetric (DSC) analysis showed IBC quenched films to be more crystalline than the conventionally quenched blown films. The results also indicated the potential for significant down gauging of film thickness (by up to 25%), without reduction in film mechanical performance by using IBC systems in blown film extrusion processes.