Synthesis and characterization of novel gels based on carboxymethyl cellulose/acrylic acid prepared by electron beam irradiation

The formation of hydrogels based on carboxymethyl cellulose (CMC) and acrylic acid (AAc) monomer in aqueous solutions under the effect of electron beam irradiation was investigated. Preliminary experiments showed that the formation of hydrogels is largely dependent on the quantities of water and the amount of CMC. Also, it was found that the formation of hydrogels depends on the concentration of AAc as well as the electron beam irradiation dose as indicated from the determination of gel fraction. The obtained hydrogels were characterized by infrared spectroscopic analysis (IR), and thermogravimetric analysis (TGA). The IR spectra of pure CMC or CMC/AAc hydrogels showed the presence of hydrogen bonding, however, hydrogels possess more extensive H-bonding than pure CMC. Also, the intensity of the absorption bands due to H-bonding was found to increase with increasing irradiation dose indicating that the linkage between CMC and AAc inside the hydrogels is through hydrogen bonding. The complete miscibility between CMC and AAc components inside the hydrogels were confirmed by SEM micrographs. The TGA thermograms and percentage mass loss at different decomposition temperatures show that CMC possesses lower thermal stability than CMC/AAc composites within the heating temperature range investigated up to 500 degreesC. Also, the rate of thermal decomposition reaction of CMC was found to proceed through four maxima at 100, 220, 300 and 440 degreesC corresponding to evaporating moisture, breaking of hydrogen bonding, melting and thermal degradation, respectively. These findings were confirmed by the calculated activation energies of the thermal decomposition reaction. (C) 2004 Elsevier B.V. All rights reserved.