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Shipping boxes 
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Roll labels 
Paper cans 
Sample boxes A barrier film is a barrier layer integrated into the packaging that protects food, cosmetic products or industrial goods from external influences such as oxygen, water vapour, UV radiation or even mineral oils. Functional barriers prevent certain substances from penetrating the packaging from the outside and, for example, prevent aromas from escaping from the packaging. Barrier layers can be divided into organic and inorganic barriers.
In order for the barriers used to be fully effective against oxygen and water vapour, they must be integrated into the packaging in a significant thickness. The layer thickness of the barrier is specified in micrometres (µm) and should be between 2 and 10 µm for organic barriers such as EVOH. An inorganic barrier such as aluminium should be used in layer thicknesses of 6–12 µm. Vapour-coated barriers such as AlOx or SiOx are applied in very thin layers (a few hundred nanometres).
Barrier measurement
The performance of a barrier is specified in different units of measurement and depends on the material being tested. The permeation of a material can be measured using different test methods. The principles for this are defined in various DIN, ASTM, ISO or EN standards. A permeation test is carried out under strictly defined parameters, in which the temperature, humidity and ambient pressure must be constant. The test then determines how much of the substance in question penetrates the material within a certain period of time, relative to the surface area. The following diagram serves as a simplified schematic of the barrier performance of common plastics and special barriers:
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Common substances used to test the permeation (permeability to gas and vapour) of a film/packaging are oxygen and water vapour (moisture). The test results are given in the following units:
- Oxygen permeation (OTR): cm³/m²/24h*bar*
- Water vapour transmission rate (WVTR): g/cm³/m²/24h*bar*
The performance of a barrier film can be divided into four different categories. A distinction is made between ‘low barrier’, ‘medium barrier’, ‘high barrier’ and ‘ultra-high barrier’. The following values can be used as guidelines for classification:
Source: Innoform ‘Guidelines for barrier classes’
Factors influencing barrier performance
The performance and suitability of a barrier also depend on a number of factors. These include, for example:
- the filling material,
- the material composition (e.g. 25PE / 5EVOH / 65PE),
- the thickness of the barrier layer,
- moisture,
- the ambient temperature,
- mechanical stress,
- or further processing steps such as deep drawing or sterilisation processes.
In the case of organic barriers such as EVOH, for example, it has been shown that the barrier performance deteriorates as soon as the humidity or temperature rises significantly. In this case, the decline in barrier performance depends on the composition of the EVOH (i.e. the ratio of ethylene to vinyl alcohol). In contrast, inorganic barriers such as aluminium or aluminium oxide do not exhibit this sensitivity to changes in humidity and temperature.
Damage to the barrier film caused by mechanical stress or deformation can lead to a complete loss of barrier performance. Therefore, the results of a permeation test on barrier films should not automatically be regarded as a measure of the barrier effect of the finished packaging. The barrier performance of the entire material composite should always be considered, not just that of the barrier film/barrier layer used.
The most important criterion for or against a packaging is not the maximum barrier performance, but the suitability of the barrier used for the respective filling material.
Mineral oil barrier MOSH/MO
When evaluating conventional films, barrier films and barrier papers, testing focuses primarily on the permeation of gases and vapours. In addition to these standard tests, however, it is also essential to carry out a risk analysis with regard to permeability to components found in mineral oils. MOSH (saturated mineral oil hydrocarbons) and MOAH (aromatic mineral oil hydrocarbons), collectively referred to as MOH, are particularly toxicologically significant in this context. Residues in food often originate from various sources such as recycled cardboard, mineral oil-containing printing inks or machine oils used during production. Various plastic barriers serve as protection against the migration of MOSH/MOAH. Plastics such as PP (polypropylene), PET (polyethylene terephthalate) and functional barriers such as aluminium, AlOx or EVOH have proven to be effective barriers against mineral oil components. The effectiveness of a barrier depends on factors such as layer thickness, storage duration and storage temperature. The penetration time of the barrier should always be longer than the product's shelf life.
Recyclable barrier films
In order to properly assess the recyclability of barrier films, it is essential to consider the entire material composite (e.g. PET/AL/PE) of the packaging used. Aluminium as a single material is characterised by excellent recyclability. However, this property is severely limited when aluminium is used in combination with various plastic films, such as PET (polyethylene terephthalate) and PE (polyethylene). In such cases, the mix of different materials cannot be recycled because sorting and separation via mechanical recycling is not possible. Such non-recyclable composites are then usually sent for thermal recycling.
In contrast, certain high-barrier coatings such as SiOx or AlOx, which are applied in very thin layers, do not impair the mechanical recycling of other components, such as polyethylene. Organic barriers, such as EVOH, can be efficiently separated and recycled within mono-material composites (e.g. PE/EVOH/PE).
Sources as of 3 April 2024:
- Innoform;
- BASF;
- DLG,
- Federal Institute for Risk Assessment,
- Fraunhofer Institute for Process Engineering and Packaging IVV
