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 crosslinked
starch-based trays may be further improved through the use
of certain plasticisers and nanoparticles.