Abstract:
Literature data on the rheological behavior of a reaction
mixture during the graft copolymerization of acrylic acid
onto gelatinized starch are scarce. Yet, such information
is important for process design. In this work, continuous
torque recording was found to be a suitable method to
monitor the apparent viscosity. Reactions were performed
in a bench scale reactor at ambient conditions with the
monomer to starch ratio as the main variable. Apparent
viscosity of the reaction mixture increased rapidly, which
could be fitted with good accuracy with a first order exponential
growth model. The maximum viscosity of 18 Pa s
was seen at the intermediate monomer to starch ratio of
1.0, a phenomenon that is in accordance with literature
data. Starch thixotropy is influenced by the grafting of
poly-acrylic acid, until it has almost disappeared at the
highest monomer to starch molar ratio of 2.0.
