Various plasticized CA/HEC and CA/PVOH polymer blend compositions
were produced using pCA (30 wt% triacetin), pHEC (25 wt
% glycerol) and pPVOH (25 wt% glycerol). Table 3 summarizes the
blend compositions, theoretical water-soluble fractions (WSF) and
plasticizer contents. Water-soluble polymer content was varied
from 38 to 75 wt%. The WSF was introduced here as a parameter to
account all water soluble material in blend, including triacetin
content in pCA. This parameter will be further considered to discuss
the water-response of these blends. For some formulations, MAgPLA
was added as reactive compatibilizer. We recently reported
that MAgPLA is an effective compatibilizer for PLA/PVOH blends [9].
Compatibilization is obtained as the result of the formation of covalent
bonds by reaction of the grafted maleic anhydride units with
the hydroxyl groups of PVOH. The amount of MAgPLA added was
fixed at 10 phr (parts per hundred parts of the blend). Although
differences on nature between CA and PLA are obvious, we expected
some affinity of PLA for the CA phase since the amount of
MAgPLA added falls within the composition range (