Improved barrier properties of PP/LDPE composite film: effect of montmorillonite and poly (lactic acid)

Abstract

In this research, the properties of polypropylene (PP) were improved for single layer film application by incorporating low density polyethylene (LDPE), poly(lactic acid) (PLA) and montmorillonite (MMT). The polymer composites was prepared by melt blending using a twin screw extruder and the film was produced by cast film extruder. The addition of LDPE in PP improved the elongation at break and tear strength. The PP/LDPE blend at the ratio of 80:20 (w/w) was selected for blending with PLA and MMT and the PP/LDPE/PLA/MMT composite showed the increased tensile modulus while the elongation at break decreased with increasing PLA and MMT contents. The morphological structure of nanocomposite was examined by using X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). For the barrier properties, the incorporation of PLA and MMT in PP/LDPE blend tended to decrease the oxygen permeability but increase the water vapor permeability. The 80/20/25/3 PP/LDPE/PLA/MMT composite film exhibited the good balance of mechanical and gas permeability properties and had a potential to be used as a food packaging. Moreover, the PP/LDPE/PLA/MMT composite as a new effective film could yield the decreased tomato loss weight at a low temperature storage (14-20 ºC) rather than PP film.