Permeability

The gas transmission

The crossing of aeriform substances happens only through the packaging material discontinuities

Four different types of discontinuity can be distinguished in the structure of plastic materials:

• Cracks and/or rupture: as a consequence of abrasions; any type of gas flow may be referred to this type of discontinuity, also the crossing of liquid and even of microorganisms;
• Holes and pipes: as a consequence of drillings or a non-uniform distribution of bulks, pigments and welding defects;
• Inter molecular gaps: these material gaps are a consequence of the nature and morphology of the polymer, they have unsteady dimensions because subject to molecular motions;
• Intra molecular gaps: in molecules of big dimensions it is possible that there is a sufficient space for the crossing of gas substances or fumes; also these discontinuities can vary their dimensions due to thermic motions.

Permeability and Shelf life

• Texture alteration
• Flavours loss
• Oxygen intake
• Undesirable volatile compounds intake

These are phenomena that can influence the SHELF LIFE of a pre-packaged product and they are involved in content-container interactions.