They exhibit low permeability to various
substances, including water vapour, oxygen and carbon
dioxide, towards which the MMT platelets are effective
diffusion barriers. A 5% fraction of MMT in the PLA matrix
significantly improves the film barrier properties, because
it reduces the transmission of water vapour by more than
40%, of oxygen by almost 40% and of carbon dioxide by up
to more than 80%. The use of MMT as a component of the
films based on the PLA matrix eliminates to a great extent
the necessity to apply additional additives that reduce the
gas transmission.
A further reduction in the transmission of water vapour,
oxygen and carbon dioxide (by 10–27%) may be achieved
due to extrusion blow moulding of the nanocomposite PLA
film. The largest decrease in the transmission of these
substances occurs when the blow moulding ratio is 4. This
reduction in permeability is caused mainly by a more
parallel ordering of the MMT platelets within the PLA
matrix, induced by the film blowing. Thus, the diffusion
path of a substance elongates, which improves the barrier
properties of the blown films.
The presented experimental results confirm effectiveness
of the extrusion blow moulding as a method for
favourable modification or creation of beneficial barrier
properties of nanocomposite films based on the PLA matrix,
which are considered as prospective materials for food
packaging, being biodegradable under conditions of
industrial composting.