Photo, thermal, and ultrasonic degradation of EGDMA‐crosslinked poly(acrylic acid‐co‐sodium acrylate‐co‐acrylamide) superabsorbents

Abstract

Superabsorbent polymers (SAPs) based on acrylic acid (AA), sodium acrylate (SA), and acrylamide (AM) were synthesized by inverse suspension polymerization using ethylene glycol dimethacrylate as the crosslinking agent. The equilibrium swelling capacities and the rates of swelling of SAPs varied with the AM content and followed first‐order kinetics. The photodegradation of SAPs in their equilibrium swollen state was carried out by monitoring their swelling capacity and the residual weight fraction. The SAPs degraded in two stages, wherein the swelling capacity increased to a maximum and then subsequently decreased. Thermogravimetric analysis of the SAPs indicated that the copolymeric superabsorbents had intermediate thermal stability between the homopolymeric superabsorbents. The activation energies of SAPs with 0, 20, and 100 mol % AM content were determined by Kissinger method and were found to be 299, 248, and 147 kJ mol−1, respectively. The ultrasonic degradation of the superabsorbents was carried out in their equilibrium swollen state, and the change in the viscosity with ultrasonication time was used to quantify the degradation. The ultrasonic degradation of AA/SA superabsorbent was also investigated at various ultrasound intensities. The degradation rate coefficients were found to increase with the intensity of ultrasound. The ultrasonic degradation of AA/SA/AM (20% AM) was also carried out, and degradation rate was found to be more than that of the AA/SA superabsorbent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Photo and Thermal Degradation of a Cationic Superabsorbent Polymer

“…The observation of the dry weights along with the swelling capacity supports the proposed degradation phenomenon. These results are in accordance with the photodegradation of poly(acrylic acid-co-sodium acrylateco-acrylamide) SAPs [17] .…”

“…The synthesis routes of the monomer-based SAPs are well established, but there are only a few studies reporting their degradation [16][17] .The SAPs constitute a significant part of domestic waste, making the degradation studies of the synthetic SAPs important. Li and Cui [16] subjected acrylic acid and acrylamide-based SAP to ultravioletinduced decomposition and quantified the degradation by measuring the weight of the SAP at the end of the degradation.…”

“…Their study, although the first report of its kind, did not provide information about the changes in the swelling capacity of the SAPs during the degradation. In our previous study, we had adopted an improved technique for the photodegradation of poly (acrylic acid-co-sodium acrylate-co-acrylamide) SAPs [17] .…”

“…Although, most of the SAPs commercially produced are anionic (based on acrylic acid and its derivatives) [2] , a wide variety of other superabsorbent polymers have been synthesized [5][6][7][8][9] . The cationic monomers have also been polymerized, either independently [10] or with anionic SAPs to obtain amphoteric SAPs [11][12][13][14][15] .The synthesis routes of the monomer-based SAPs are well established, but there are only a few studies reporting their degradation [16][17] .The SAPs constitute a significant part of domestic waste, making the degradation studies of the synthetic SAPs important. Li and Cui [16] subjected acrylic acid and acrylamide-based SAP to ultravioletinduced decomposition and quantified the degradation by measuring the weight of the SAP at the end of the degradation.…”

“…Their study, although the first report of its kind, did not provide information about the changes in the swelling capacity of the SAPs during the degradation. In our previous study, we had adopted an improved technique for the photodegradation of poly (acrylic acid-co-sodium acrylate-co-acrylamide) SAPs [17] .The changes in the swelling capacity as well as the residual weights of the SAPs were measured during the degradation and a possible mechanism of the degradation of SAPs was proposed. The SAPs were found to undergo degradation in two stages.…”