Reactive Extrusion and Barrier Properties of PP/PET Films.

The barrier polypropylene (PP) films were prepared via reactive blending of PP with polyethylene terephthalate (PET) in an intermeshed co-rotating twin-screw extruder. Films were prepared via extrusion through a flat die followed by postextrusion stretching. The effects of compatibilizer, PP-g-MA, content and draw ratio were investigated. SEM micrographs showed that the dispersed phase inclusion size decreases significantly upon the addition of compatibilizer. Morphological studies of the films have shown that laminar morphology was developed in the machine direction rather than in transverse direction. The optimum morphology was observed at 5% compatibilizer concentration. Tensile tests showed that melt stretching has resulted to the inferior properties except modulus. Mechanical properties of blends decreased significantly upon the addition of PET and increased as the compatibilizer content was raised to 10%. Higher contents, however, showed no improvement, as it just improves the physical properties of the blends. Blending results in 200% improvement in the oxygen barrier properties. Permeability of the stretched films and compression moulded films showed 25-35% improvement in the oxygen barrier properties. The maximum barrier property of the extruded films was observed at 5% compatibilizer and draw ratio of 2. Higher contents (up to 15%) resulted in decreased oxygen barrier properties.