Influence of Calcium Oxide (Quicklime) On the Hydrostatic Pressure Resistance of Microporous Polyethylene Films

The adverse effects of using calcium oxide (CaO) (quicklime) as a water absorber on polyethylene (PE) microporous film under actual production conditions are studied. A twin-screw extruder was used for compounding the calcium carbonate (CaCO3)/PE blend into pellets containing low-density polyethylene, linear low-density polyethylene, ground calcium carbonate, antioxidants, and lubricant. Two dehumidifying methods, hot air and CaO absorber, were used before film casting in a production line equipped with a stretching unit. Physical properties of two microporous films were compared with hydrostatic pressure, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared analyses. The microporous film with CaO dehumidifier showed lower hydrostatic pressures on average with much greater variation and is prone to degradation versus the hot air dried resin. The results indicate that adverse effects occur due to the high alkaline basicity of CaO.