Advances for flexibles drive growth

While many packaging material markets are still flat or declining, the flexible film sector seems set to power ahead. Pundits put this down to the changing lifestyle of consumers - who are switching to packs such as pouches and away from bottles, rigid plastics containers and cans - but also because improved laminates and coatings are enhancing performance where it matters: in waste reduction and product integrity.

Indeed a recent global report from Industry Intelligence on speciality and high performance films forecast the demand for barrier, safety, decorative and micro-porous applications (where packaging is 65% of the market) is expected to reach about 11.1 million tonnes in 2019, from a base of about 7.5 million tonnes in 2012, growing at a CAGR of 5.7% from 2013 to 2019.

More layers
High barrier materials generally consist of multi-layer compositions, typically aluminium foil sandwiched between two or more plastics layers, which are then laminated or glued together by means of adhesives. While three and five-layer film compositions have been very common, more and more converters are moving to seven and nine-layer co-extrusion lines that provide more flexibility for desired functionality, thickness and cost without over-engineering the structure.

One technique is to use less expensive resins as bulking layers. Another is to split the barrier layer into two thinner layers, with one serving as a backup in case a pinhole occurs in the other. This approach also multiplies the number of material interfaces a permeate must cross, further reducing permeation rates.

Several technologies for splitting barrier materials into many layers are being introduced, which are showing better than linear improvements in barrier properties. In addition, usage of these films in semiconductors in photovoltaic (PV) systems, and the growing number of installations of PV systems, is expected to increase demand.

A good example of laminate development comes from Taiwanese company, Wapo Corporation, which has developed a nylon-based vacuum pack bag that allows fresh foods to be stored at room temperature, while extending their shelf life.

The Wapo bags are produced using plastics materials from Japan's Unitika. They have good gas barrier properties allowing moderate oxygen transpiration so the fresh food products are not attacked by harmful gases or exposed to premature oxidation. When vacuum-sealed, the bags are puncture resistant, water resistant and vapour resistant.The nylon content means even if the vacuum bags are stored in sub-zero temperatures, the material does not become brittle, nor do they burst from expansion after freezing.

In another Asian development, Kyodo Printing of Japan has reduced problems associated with using desiccants, it claims, with the development of OxyCatch oxygen and moisture absorbent packaging film. OxyCatch incorporates a high concentration of celium oxide-lineage oxygen absorber, and activates without the involvement of water, to help prevent product deterioration.

Used for pharmaceutical, cosmetics or food applications, the product works evenly throughout the package interior to absorb oxygen. The oxygen scavenging process is indicated by colour changes in the inner functional surface of the packaging film. The film colour starts out as a navy blue, indicating that the oxygen absorber is 'active'; when it reaches a grey tone it is 'inactive'.

Product safety is enhanced as the four-layer packaging film has an interior PET sealant layer, preventing the oxygen absorption layer from coming into direct contact with the product. As no iron powder is used in the film, the packaging does not react to metal detectors (unless the film composition includes aluminium).

OxyCatch is also available in an aluminium blister packaging format for pharmaceutical products and fine electronic parts.
In the UK, Ultimate Packaging and grower QV Foods enabled UK supermarket chain Asda to be the first retailer to offer Viridiflex packed potatoes into UK stores this summer; resulting in a significant increase in the shelf life of Extra Special Cornish Crystal Potatoes compared with conventional packs, the companies say.

Viridiflex is a laminate structure designed by Ultimate, working closely with Innovia Films and customers involved in the harvest and packing of fresh produce. Cellulose-based Natureflex film, manufactured by Innovia, is used as a component of Viridiflex, which can be formed into bags or used as lidding film, and has extremely high gloss, providing a degree of permeability to moisture. This controlled moisture release prevents dehydration on one side and mould growth on the other.

Unlike other modified atmosphere packaging (MAP) solutions the film works by drawing moisture away from fresh produce, creating an environment that can help to prevent decay. The film has enhanced oxygen barrier qualities that can be manipulated using Ultimate Packaging's Adapt MAP laser technology, which modifies the perforations in the film to optimise the shelf-life of various types of fresh produce.

Coating caution
Much debate has taken place on the subject of Food Contact Materials, and a rigorous approval process exists in the EU, through EFSA, The European Food Safety Authority, to ensure consumer safety. A major topic of debate has been nano-materials, used as coatings or additives. The tone of debate has been characterised by similar concerns to those expressed at the height of the furore over genetically modified foods. But as one spokesman for the Nanotechnology Industries Association (NIA) put it: "Many of these are the same materials we use already, just on a microscopic scale."

The science seems to back up the NIA view and EFSA has already approved three nano-materials. Silicon Dioxide, Titanium Nitride and Carbon Black are all authorised for use in plastics food contact material, the statement confirmed.

NIA's spokesman comments: "The three approved nano-materials for food packing are safe and have passed the strict EU assessment and authorisation process. The benefits these materials bring to packaging will be explored and commercialised by food packaging manufacturers."

Materials scientists at Rice University and the Massachusetts Institute of Technology (MIT) in the USA have created very thin colour-changing films that could act as part of inexpensive sensors for food deterioration or security during transit.

The films are made of nano-scale layers of hydrophobic polystyrene and hydrophilic poly2-vinyl pyridine, P2VP. In the liquid solution, the polymer molecules are diffused, but when the liquid is applied to a surface and the solvent evaporates, the block copolymer molecules self-assemble into a layered structure.

A photonic gel self-assembles from long polymer molecules. The new work combines these polymers into a self-assembled meta-material which, when exposed to ions in a solution, or in the environment, changes colour, depending on the ions' ability to infiltrate the hydrophilic (water-loving) layers. The micron-thick material is said to be so inexpensive to make that it could cover an area the size of a football field for about a hundred dollars. If the layer is inside a sealed food pack and the environment in that pack changes because of contamination or ageing, or exposure to temperature, an inspector would see that sensor change from blue to red and know immediately the food is spoiled.

However it is not just in the world of nano that exciting developments are happening. A new patent identifying plant-based coatings for packaging materials has been filed by Esseoquattro of Italy, which has an R&D group for packaging innovation based in the Food Quality & Safety Department at the University of Camerino.

Designed to control and inhibit the development of biogenic amines and so extend the shelf life of meat and fish, the coatings are made from the extract or essential oils of rosemary, oregano or salvia, or their mixture, and have the ability to prolong the preservation of fresh foods. They can be sprayed onto the inside of the packaging, to be in contact with the food, without the need for any fixing resins and can be spread uniformly on the material.

No barrier
With investment in reducing food waste and pharmaceutical safety and integrity set to remain high on the agenda, the prospects for further developments in plastics film formulation, lamination and coating technologies seem bright. Already these advances have pushed plastics pouches into areas such as juice and even alcoholic beverage packaging, where few thought they could succeed.

Likewise, the current expansion of research into nano and complementary technologies is already pushing back the barriers of film performance and could have a major impact on process costs. So the growth of this ubiquitous family of materials will continue.