Clay packs in protein
A lightweight, biodegradable, aerogel made from clay and milk protein could provide a feasible alternative to plastic packaging foam, claim USA scientists.
The aerogel created at the Case Western Reserve University (CWRU), Ohio, USA, is typically formed of ~50wt% sodium montmorillonite and ~50wt% casein. To process the material, an aqueous clay dispersion is slowly added to an aqueous casein solution and blended together with water. The material’s imperviousness to water is achieved by then adding a reactive molecule of 1-10wt% of glyceraldehyde before being freeze dried. The sample was then cured at 80ºC for 24 hours.
The researchers claim nanoparticles of sodium montmorillonite are ideal to add to many different types of polymers to improve their mechanical and thermal properties. Furthermore, the team states the clay used is more hydrophilic (readily absorbs/dissolves in water) than other clays and therefore interacts well with the casein to create a stronger, more network-like structure, as the glyceraldehyde crosslinks with casein chains.
The use of clay in the foam material also ‘allows a desirable low flammability, good water solubility and high aspect ratio’ says Professor David Schiraldi, researcher and inventor at CWRU and Chief Scientific Officer at Aeroclay Inc.
To ensure the product does not smell like sour milk, samples are kept in fridges to prevent mould and a ‘sniff-test’ is carried out.
The main benefit of the foam, they claim, is its lightness and ease of biodegradability compared to synthentic foams. Schiraldi elucidates, ‘The casein/clay product is designed to degrade away, not fill up landfill space, or consume [a] significant amount of oil. The biodegradation of the materials was tested at the US Department of Agriculture (USDA) in an activated landfill system.’
Bor-Sen Chiou, a Bioproduct, Chemistry and Engineering researcher at the USDA, who studied the biodegradation of the material says, ‘Approximately 24-30% of the aerogels degraded after 45 days. The USDA uses a standard protocol which models landfill degradation.’
The next step of the research collaboration will look at scaling up more efficiently and the use of a lower cost dairy protein.
The patented product is now licensed by AeroClay Inc.