The water resistance of cross-linked corn starch foams can be increased by the addition of corn husk fibre, beeswax or kaolin. Moreover, a more uniform and improved surface quality can be obtained by incorporating fibre, while the addition of beeswax encourages foaming. Conversely, incorporating combinations of these additives, most notably the triple combination of fibre, kaolin and beeswax, improves the water resistance and surface quality of the trays. The addition of the triple combination also improves the tensile and flexural properties of the trays. Despite the higher density and lower elasticity of KFB compared to EPS, the present findings demonstrate that KFB can be used as an alternative to EPS trays in applications where contact with moist food occurs for shorter periods.
Thermal analyses showed, cross-linking caused decrease in Tm of starch foam from 163.4 °C to 146.8 °C. The kaolin and beeswax additives suppressed crystallisation and incorporation of fibre to the foams caused shifting of the endothermic peaks to higher temperatures. FT-IR analyses showed that incorporating the additives increase intermolecular hydrogen bonding.
The density, elasticity and water absorption properties of cross-linked starch-based trays may be further improved through the use of certain plasticisers and nanoparticles.