A high water absorbing copolymer, based on the graft copolymerization of cassava starch and AM, was successfully prepared by
reactive batch processing using a specially designed batch reactor.
The reactor has a Reynold number of 224.7 and can mix the mixture
effectively even at low water content. The highest obtained water
absorption capability of the saponified starch-g-PAM copolymer
was 605 g/g when prepared with a reaction time and temperature of 140 min and 80
◦
C, a KPS concentration of 1.5 wt% of starch
and a starch:AM (w/w) ratio of 1:1. The FT-IR spectra confirmed
the formation of saponified starch-g-PAM copolymer by exhibiting all the characteristic bands of both starch and AM units. The
starch granules, as viewed by SEM, had irregularly oval shaped
particles of variable sizes with a smooth surface. However, the
graft copolymers exhibited coarse porous structures and a broad
network, which may contribute to the higher water absorption
capability of the copolymer and the SAPCs over the SAP. The bentonite clay SAPC exhibited the highest water absorption capability
(ca. 730 g/g), significantly higher than that of the unfilled graft
copolymer SAP (606 g/g). This is due to larger hydration of bentonite
powder than those of the China clay and silica