Barrier Properties of Coated and Laminated Polyolefin Films for Food Packaging

The food packaging industry demands polymer films possessing a defined barrier against permeation of gases, moisture and flavor.The objective of this study was to assess the differences between the barrier properties of coated and un-coated polyolefine films.Eight types of packaging films are prepared by standard industrial procedure by cast film extrusion processing with chill rollers: biaxially oriented polypropylene (BOPP), BOPP coated by acrylic copolymer, metallized BOPP by aluminum, and low-density polyethylene (LDPE).The influence of lamination and metallization on the gas molecules (CO2, O2 and N2) was determined by Lyssy's method.The moisture transparency was assessed according to the gravimetric method.The substantial differences between the barrier properties of the coated and un-coated films were estimated.It was estimated that the lamination process improves the oxygen barrier but not necessarily the moisture barrier, due to the different mechanisms for oxygen and moisture permeability.The obtained barrier properties data were considered from a practical point of view.It was concluded that films based on metallized BOPP has excellent barrier properties and can be used to over wrap food products.