Sandwich panels with a core of expanded corn only weigh half as much as chipboard but have the same mechanical properties.
Moira Burnett
Professor Alireza Kharazipour had the idea of using popcorn many years ago. In a research project, he and his team have now successfully developed especially lightweight sandwich panels with a popcorn core. These panels have the same mechanical properties as chipboard, but weigh only half as much. Possible uses for these panels include furniture making and, theoretically, insulation, as popcorn grains have very low thermal conductivity.
The panels could also be of interest in the manufacture of cars, boats and exhibition stands. When asked if the use of popcorn in construction is not in conflict with food production, Kharazipour has this response: "Considerable quantities of maize are already used in materials today. Cornstarch, in particular, is used in glue and bio-based plastics. Besides, we also use low-quality maize products, such as cracked corn, which would not be considered edible."
Lightweight composite popcorn panel
For this project, the researchers employed two different methods. In the single-step method, popcorn for the core and woodchip and wood fibre for the top layer were bonded with glue, scattered and compressed into a panel in a single operation. In the two-step method, the researchers first produced the composite popcorn panel, then clad it with plywood, thin fibreboard and thin chipboard, aluminium and high-pressure laminate. A four to eight percent mixture of urea-formaldehyde resins or methane diisocyanate was found to be most suitable for bonding.
Tests on the mechanical characteristics of finished sandwich panels revealed that they have similar properties to conventional chipboard but with a much lower weight. Panels manufactured using the single-step method achieved the same bending properties as the reference chipboard, with half the bulk density. Panels produced with the two-step method and coated with plywood or aluminium were in fact more stable than the reference boards.
Popcorn grains bind formaldehyde
"The ability of popcorn grains to bind formaldehyde at temperatures of 70 ° C and above is extremely interesting. As a result, this problematic gas is not released during production nor during use," Professor Kharazipour tells us. He sees a need for further development where protection against high humidity is concerned, and in industrial production. "Popcorn-based panel material is generally very attractive to companies, as they don't need to make extensive alterations to machines or purchase new ones. However, we still have to determine the optimum processing parameters," says Kharazipour.
The project was sponsored by the German Federal Ministry of Food and Agriculture (BMEL) through its lead partner the Agency for Renewable Resources (FNR, Fachagentur Nachwachsende Rohstoffe e. V.). The final report is available at fnr.de under funding code 22014313.