Why permeability and barrier properties are a critical consideration for sustainable packaging

As packaging manufacturers and brand owners look to develop packaging that can be labelled as ‘sustainable’, the core functionality of the packaging must be maintained. The pack still needs to preserve the quality of its contents – providing protection both from physical damage and commonly, providing a barrier to oxygen and moisture vapor. The barrier and permeability of the pack materials is often critical in determining the shelf life of the packaged product. The limited shelf life provided by sub-optimal materials can lead to more frequent, less economic pack deliveries and greater product waste through spoilage. The use of ‘sustainable’, but compromised materials may complicate your supply chain with no overall benefit to the environment.

Sustainability options

There are several areas that are being considered for sustainable packaging. These include:

• Light-weighting through improved pack design, manufacturing process controls and transportation
• A reduction in the complexity of the materials used in a pack, making them easier to be recycled
• Producing a more durable/functional pack which can be re-used/re-filled
• Reducing the susceptibility of the product to damage or environmental deterioration, thereby reducing the barrier requirement from the packaging

Barrier coatings on paper-based materials or mono-plastic materials are often considered to be two of the
more sustainable packaging options. They can be made to work, but their limitations in terms of barrier and
permeability performance in relation to traditional multilayer structures need to be understood.

Barrier coatings
Functional and barrier coatings may be used to prevent paper-based packaging from simply getting wet or
provide some resistance to staining from greasy foods. A more demanding requirement is to limit the
ingress of oxygen or moisture vapor to extend the shelf life of the product. In essence, coatings are used to
mitigate the poor performance of paper – when compared with most plastics – in applications that require
some barrier performance.

Mono-plastics
Polyethylene is a popular mono-plastic material, and is an inherently good moisture barrier. In applications
which require an enhanced oxygen barrier, a mono-plastic material will often need to incorporate a thin
barrier layer of a second high barrier plastic, such as ethylene-vinyl alcohol copolymer (EVOH).
Care needs to be taken to ensure that the barrier layer does not undermine the recyclability credentials of
the final pack.

Permeability properties
Knowing the water vapor and oxygen transmission rates of
‘sustainable’ alternative packaging materials is critical in
determining their suitability for the packaging of moistureand
oxygen-sensitive products.
However, a word of caution when looking at the permeability
rates quoted for barrier coated papers. The act of folding or
creasing a coated paper may have a marked effect on its
barrier performance unless the coating remains intact
through the conversion and subsequent handling processes.