Fig. 6 shows the results of DMTA tests in double cantilever
mode, over a temperature interval from 30 to 170 C, carried out
on essential oil-containing bioplastics prepared by compressionmoulding
at 90 C. As can be seen, biocide addition in concentrations
of up to 10 wt.% does not produce any remarkable change
in the thermo-mechanical response of the reference WG-based
bioplastic. It just seems to very slightly extend the temperature
interval over which the rubbery-like plateau appears. The thermosetting
potential, characterised by a further increase in |E| and corroborated
by an important decrease in the tand values at the
highest temperatures, remains (Fig. 6a). However, the glycerol-free
sample, with an essential oil content of 33 wt.%, is strikingly seen
to modify the bioplastic rheological behaviour after compressionmoulding
at 120 C. This system is characterised by an apparent
plateau region, which extends over a temperature interval of about
40 C, and the absence of thermosetting potentials. Moreover, it
exhibits a notable increase in |E| of more than one order of magnitude
(comparable to LDPE). According to previous results by
Zárate-Ramírez et al. (2011) an increase in the temperature of processing
(i.e. from 90 to 130 C) yielded an increase in the DMA profile
which was much less pronounced than that shown by the 33%