Manufacture of biodegradable packaging foams from agar by freeze-drying

Abstract

Cellular foams were made from the aqueous solution of agar by freeze-drying. A narrow range (5-20 degrees C min(-1)) of freezing rate was required to avoid damage to the microstructure of the agar foams. The size of cells in the foam decreased with increasing freezing rate. Agar foams of more than 4 wt% agar content absorbed more energy than a polystyrene foam in compression tests. Foams with a higher agar content absorbed more energy. The behaviour of agar foams in compression tests could be explained by the modified beam theory for cellular foams. Agar foams were thermally stable up to 200 degrees C, and were also stable in a humid environment.