Researchers at the University of Sheffield have transformed ordinary polyurethane packaging foam into a super foam that not only refuses to be crushed but also actually increases in thickness when stretched.
Under the same stresses conventional foam loses its resilience and its protective qualities so the super foam’s benefits for the packaging industry are obvious.
The secret lies in a new ‘cooking’ technique and in the cooking oil that has to be organic. Olive oil, for example, will do nicely.
Similar foams have been developed before but no one has yet found a cost-effective way to manufacture them. This one is different because almost any conventional packaging foam will do as the main ingredient.
The current manufacturing process, which is still being refined, consists simply of subjecting that ordinary foam to an industrial cooking process using inexpensive and easily obtainable ingredients.
Dr Fabrizio Scarpa of the University’s Department of Mechanical Engineering is leading the research project. “I decided to research this subject because I was interested in the mechanical and acoustic properties of negative Poisson’s ratio cellular materials,” he says. “These solids expand in all directions when pulled in only one, unlike ‘normal’ materials.
“The breakthrough came when we started to use particular combinations of temperature and compression ratios on samples of normal open cell polyurethane packaging foam. The dynamic crush resilience of the new foam we created was remarkable – and its acoustic absorption properties were better than conventional foam too.
“We can produce small quantities of the super foam in our labs here at the university but we’re seeking a packaging industry partner to develop a full scale manufacturing process.” Although the foam is hard to destroy when used in packaging, it can be safely recycled.