Nanoclays modified with crustacean shells
The shells of crabs and lobsters might not be the obvious source of packaging inspiration, but scientists at Sheffield Hallam University, UK, think otherwise. By modifying nanoclays with molecules from the shells of crustaceans, the team is making progress towards creating natural fibre-based packaging that is a viable alternative to petroleumbased polymers.
The research is part of the four-year European Sustainpack project. Dedicated to creating packs that are more easily degradable and recyclable, and produce less carbon dioxide emissions in manufacturing, Sustainpack brings together packaging research associations, academia and industry from 13 European countries. The scheme, which is due to end in 2008, aims to encourage widespread use of biopolymers, paper and board for packaging.
Professor Chris Breen of Sheffield Hallam's Materials and Engineering Research Institute says, 'Developing sustainable packaging that can compete with petrochemical-based polymers is extremely challenging. Clay containing nanocomposites have been attracting interest for several years because they offer increased mechanical and barrier properties [in] biopolymer films and coatings.'
Breen and his team dispersed natural clays, such as montmorillonite, into natural polymers, such as starch, to create these composites. At the nanoscale, the clay particles have a high surface area, producing water resistant materials.
'When a molecule like water encounters one of these particles it has to make a detour, the equivalent of about one kilometre in our terms. Imagine having to do that every few hundred yards. It is this tortuous path that slows down the movement of water molecules through the nanocomposite barrier film,' explains Breen.
To make the clay particles more compatible with the polymers, the researchers are using a range of unusual modifiers, including chitosan derived from the shells of crabs and lobsters. The aim is to optimise formulations that meet properties, price and coating capability requirements.
Breen does not foresee any environmental or health concerns surrounding the use of nanoclays, particularly in food packaging. He says, 'Clays are used in many different products. You may take kaolin as a remedy for an upset stomach, and clay is present in washing powders and cosmetics. In these formulations, the particles are most likely micro rather than nanosized. The clays only become nanoparticles when they are successfully confined via their interaction with the polymer.'
Moreover, he explains that the extraction and purification of natural clays has become a far more eco-friendly process. 'The use of water, electricity and fuel has been driven down to make the clays economically attractive.'
With trials underway on sample packs, and support from fellow Sustainpack partners such as Sainsbury's, Breen envisages that prototypes will be ready by May 2008.