Synthesis and Characterization of Cellulose-Based Hydrogels Using Citric Acid as a Crosslinker
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Date
2018-06-06
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AAU
Abstract
Incorporation of synthetic polymers along with natural polymers to prepare hydrogels can
improve the performance of these materials. The objective of this study was to synthesize
and evaluate a hydrogel using sodium carboxymethyl cellulose (NaCMC), polyethylene
glycol (PEG), and citric acid. The Fourier Transform Infrared analysis of these raw materials
confirms that the functional groups involved in the crosslinking reaction are present. The
effect of preparation conditions such as polymer composition, reaction temperature (65-95
℃), reaction time (8-24 hours) and citric acid concentration (10-20%) on the swelling degree
was evaluated. The results demonstrated that superabsorbent hydrogels were produced
with swelling degree typically ranging from 215% to 5595%. The swelling degree was
significantly influenced by the temperature, concentration of crosslinker, time and polymer
composition. In addition to their high swelling capacity, Thermogravimetric analysis of
NaCMC based hybrids that were prepared by blending with 20 wt.% PEG has shown good
stability. Response surface methodology was used to optimize the synthesis process. The
optimum hydrogel with swelling degree of 6748% was synthesized at 72.38 ℃ temperature,
8 hours of reaction time, 16.54% citric acid concentration, and 80% NaCMC and 20% PEG
composition. Influence of ionic strength and pH of the external solution on the swelling
behavior of the hydrogel was investigated. Urea as an agrochemical model was loaded onto
the obtained hydrogel to study the slow release of the nutrient. The hydrogel was
responsive to the variation of ionic strength and pH of the external solution. Due to its
considerable slow urea release and good water retention capacity, it could be used in
agricultural application.
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Keywords
Carboxymethyl cellulose, Superabsorbent hydrogel, Slow release, Swelling