Synthesis and evaluation of trimethylolpropane triacrylate crosslinked superabsorbent polymers for conserving water and fertilizers

Abstract

A series of superabsorbent polymers (SAP) were synthesized by free radical thermal copolymerization of acrylic acid and N‐isopropyl acrylamide monomers using trimethylolpropane triacrylate as crosslinker. They were characterized by FT‐IR and thermal stability (TGA/DTG), and evaluated for their water and fertilizer uptake and release characteristics under different crosslinker levels, temperature, pressure, and pH. The observed maximum absorption of water by the SAP was 1130 g/g of polymer. The release was modeled which showed a non‐Fickian mechanism. The water uptake of SAP was correlated with the average molecular weight between the crosslinks and crosslink density. Analysis of the weight loss data from TG in air revealed a zero order kinetics for the initial degradation step with an activation energy (AE) of 70.8 kJ/mol. The AEs for water uptake and release for thermal degradation were also determined through Arrhenius plots. The results inferred that the synthesized SAP can be exploited for commercial agricultural applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis and characterization of high performance superabsorbent hydrogels using bis[2-(methacryloyloxy)ethyl] phosphate as crosslinker

“…Unfortunately, no direct correlation between values of M c and q with polymer swelling capacity can be made. The same was observed in the work of Venkatachalam et al [11]. In the case of SAP5, which showed the highest swelling capacity value, the molecular weight between crosslinkings was approximately 24.793 millions with a q value of 140 724.…”

“…SPM was used to increase the osmotic pressure between the interior and the exterior of the hydrogel (due to the difference in the concentration of the K + counterion), as a mean to improve the water absorption capacity of the ionic hydrogel [18].The use of this crosslinker in combination with the above refered monomers has never been reported in hydrogel synthesis. NIPAM is known to increase the rate of decomposition of persulfates, and because of that it was used in all the hydrogels prepared in this work [11,19,20]. The different reaction conditions for SAP synthesis (SAP1 to SAP10) and the physical properties of the obtained products are presented in Table 1.…”

“…The polymer volume fraction (!) of the swollen polymer was determined taking into account the swelling capacity of the hydrogels in distilled water and the density of the polymer determined in a pycnometer using heptane, according to Equation (1) [10,11]:…”

“…To perform the urea loading tests, samples of dry hydrogel (0.005 g) were immersed in urea solutions with different concentrations (5, 10, 15 and 20 g/L) for approximately 24 hours (until reaching the maximum swelling) [11,15]. Subsequently, the swollen and loaded hydrogels were oven dried at 50°C to constant weight.…”

“…The amount of urea was determined gravimetrically, comparing the weight of the container before and after this process and taking into account a blank experiment with only 20 mL of water. The percentage of urea released was calculated using the Equation (10) [11]:…”