At this stage, it is worth recalling that CA is sensitive to thermal
and hydrolytic degradation during melt processing. Thus, for the
preparation of the blends, it was necessary to remove any residual
water from the plasticized HEC. Water removal already started
during HEC melt blending, where vapour generation was observed.
Water content was further reduced to negligible levels on a subsequent over-night drying at 80 C. Plasticized HEC (pHEC) used
hereafter was prepared from a premix containing 30 wt% glycerol
and 10 wt% water. In these conditions, the final glycerol content
was 25 wt%, as verified by TGA measurements which is in accordance
with the premix composition. Actually, after water evaporation,
the blend composition became HEC/glycerol 75/25 (w/w).