EFFECT OF SILICA FILLERS ON CHARACTERIZATION OF CELLULOSE-ACRYLAMIDE HYDROGELS MATRICES AS CONTROLLED RELEASE AGENTS FOR UREA FERTILIZERS

Controlled Release Urea Fertilizers-based hydrogels matrices was synthesized by graft copolymerization of
acrylamide onto the rice straw cellulose backbones in the presence of silica fillers using simultaneous graft
copolymerization by gamma irradiation as initiator. Evidence of the silica presence on grafted cellulose was obtained
from FTIR. X-ray diffraction analysis showed that the crystalline was reduced through silica fillers added. The effect
of silica content on grafting efficiency, gel fraction, Young modulus, swelling degree, and urea loading were
examined. It was found that grafting efficiency and gel fraction decrease with increasing silica added inversely with
Young modulus. Water swelling and loading urea fertilizers into hydrogels matrices were conducted and the results
showed that swelling degree and urea fertilizers loading increased first and then decreased with increasing silica
added. The effect of the silica fillers had implications in the mechanism of controlled release urea fertilizers that
diffusion-controlled mechanism became dominant, which attributed to the decreasing of urea diffusion coefficient.
Keywords: silica fillers; hydrogels; gamma irradiation; controlled release urea fertilizers