DSC was used to characterize the degree of crystallinity of
each blend. The blends with the highest proportion of PVOH,
50:50 and 0:100, were the only blends that exhibited crystallinity.
The degree of crystallinity within each substrate was 4%
and 31% respectively.
Crystallinity within blends was investigated to assess whether
blend crystallinity exhibited an affect on the rate and extent of
substrate solubilisation (Arshady, 2003). The starch used in this
study was predominantly gelatinized amylose (P90%) and has an
amorphous structure. Permeation of liquids into amorphous structures
is more favourable due to a disordered structure compared to
an ordered, densely packed crystalline structure. PVOH has been
reported to crystallise after processing (Chiellini et al., 2003). The
crystallinity within the 50:50 substrate is minimal but this may
have been enough to significantly reduce accessibility to the starch
phase, as indicated by the reduced hydrolysis rate in Table 2. The
crystallinity within the 0:100 substrate would reduce the rate of
media permeation throughout the substrate and as a result reduce
the rate of solubilisation.