Flexible packaging Flashcards
What is flexible packaging and for which applications is it used?
Any package or part of package of which the shape can be changed. It includes bags, pouches, liners and wraps. Very often used in the food industry
Which three basic principles for barriers do you know? Please give a brief explanation of these principles!
1) Penetration through defects = The barrier must be defect and pore free to be successful. Otherwise penetration will occur.
2) Principle of diffusion = The penetrant must have a certain solubility in order to pass through the material from the high concentration to low concentration side. We can understand what barrier materials to use if we understand the sorption and desorption properties (Permeation = SxD)
3) Principle of tortuosity = this is the use of crystals, pigments or minerals within the barrier that make the path through the material more difficult and therefore slow the rate of transmission
What are the most important barrier properties for flexible packaging?
Having a low permeability to gases and vapours – oxygen and water vapour can affect the shelf life of many packaged goods. Therefore the most important properties are water vapor transmission rate (measured in g/m^2 per day), oxygen transmission rate (cm^3/m^2 per day).
However it is hard to find a barrier that is good against both so often need multiple layers.
What possibilities do you have to create a barrier and which materials can be used?
Can use aluminium foil, metallised film, metallised paper, coated papers etc. Barrier films usually made of Polypropylene (water vapor barrier), Polyetheylene (water vapor), Polyamide (O2). Can also use starch and cellulose as bio alternative but not as effective.
Hard to have a barrier which repels both as hydrophilic barriers block hydrophobic components and vice versa.
Which coating techniques can be used to produce a coated barrier paper and what is the benefit of a pre-coating?
Can use curtain coater which follows the contours of the paper which means we may need to use more coating. Rod coating applies an even layer.
If these methods are combined to pre coat we get many advantages such as consistent coating profile and good surface quality. By pre coating we will in grooves of the paper allowing the coating to be more uniform.
