An efficient preparation method for superabsorbent polymers

A copolymer superabsorbent was prepared by inverse microemulsion polymerization, using cyclohexane as the continuous phase, water as the dispersed phase, N,N-methylene bisacrylamide as the crosslinking agent, ammonium persulfate (APS) as the initiator and OP-10 and SDS as complex surfactants. The synthetic variables (amount of crosslinking agent and initiator, water/oil ratio, monomer/surfactant ratio, and AA/AM ratio), and their effects on the absorbencies of the synthesized superabsorbents were studied. The relationships between the water absorbency and absorption time as well as the water retention capacity of the water superabsorbent were studied. The experimental results of superabsorbent polymers (SAPs) showed the maximum water absorbency of 1432 g/g, and the water absorbency of 722 g/g within 15 min. The water retention in the soil was greatly enhanced using the above superabsorbents. SEM indicated an irregular, undulant, and microporous surface of the superabsorbent, which was convenient for the penetration of water into the polymeric network. SAPs can be considered for watermanaging materials for agriculture and horticulture purposes in desert and drought-prone areas.

Section: Resultssupporting

confidence: 93%

Preparation of poly(AA‐AM) water superabsorbent by inverse microemulsion polymerization

Wan

Yao

2008

“…SEM photograph of GG displays dense and smooth surface of the backbone. As is evident from Figure , grafting and crosslinking of PA chains onto the backbone resulted in homogeneous but fractured topography …”

Section: Resultsmentioning

confidence: 59%

“…Consequently, the less expanded network of hydrogel absorbs less water, manifesting in low WAC values. This phenomenon is often referred to as charge screening effect . Alkaline degradation of the backbone polymer could also be another reason for the observed behavior.…”

Section: Resultsmentioning

confidence: 99%

pH‐sensitive crosslinked guar gum‐based superabsorbent hydrogels: Swelling response in simulated environments and water retention behavior in plant growth media

Chandrika

Singh

Sarkar

et al. 2014

Crosslinked guar gum-g-polyacrylate (cl-GG-g-PA) superabsorbent hydrogels were prepared to explore their potential as soil conditioners and carriers. The hydrogels were prepared by in situ grafting polymerization and crosslinking of acrylamide onto a natural GG followed by hydrolysis. Microwave-initiated synthesis under the chosen experimental conditions did not exhibit any significant improvement over the conventional technique. The optimization studies of various synthesis parameters, namely, monomer concentration, crosslinker concentration, initiator concentration, quantity of water per unit reaction mass, particle size of backbone, and concentration of alkali were performed. The hydrogels were characterized by wide-angle X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and solid-state 13 C-NMR spectroscopy. Swelling behavior of a candidate hydrogel [GG-superabsorbent polymer (SAP)] in response to external stimuli, namely, salt solutions, fertilizer solutions, temperature, and pH, was studied. The GG-SAP exhibited significant swelling in various environments. The effect of GG-SAP on water absorption and the retention characteristics of sandy loam soil and soil-less medium were also studied as a function of temperature and moisture tensions. The addition of GG-SAP significantly improved the moisture characteristics of plant growth media (both soil and soil-less), showing that it has tremendous potential for diverse applications in moisture stress agriculture.

“…Figure 1 shows that the water absorbency of the superabsorbent composite crosslinked with Na 2 WO 4 increases as the reaction temperature increases from 60 to 90°C and decreases with further increases in the reaction temperature. When the temperature is below 90°C, as the reaction temperature increases, the rate of decomposition of the initiator in polymerization increases, and this results in a loss of crosslinking efficiency 10. With the same crosslinker content, the water absorbency increases with the reduction of the crosslinking efficiency according to Flory's network theory 11.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of a salt‐resisting superabsorbent based on poly(acrylic acid) with sodium tungstate as a crosslinker

Liu

Zhang

Zhu

et al. 2008

A novel salt-resistant superabsorbent polymer was synthesized by solution polymerization from the monomer acrylic acid (AA) with potassium persulfate as the initiator. Sodium tungstate was first employed as a crosslinker in the preparation to achieve a better crosslinked polymer (WPAA). In addition to the xerogel WPAA, sodium hydroxide and tris(2-hydroxyethyl)amine (TEA) were introduced for the preparation of WPAA-sodium and WPAA-TEA hydrogels, respectively. The effect on the water absorbency of factors such as the reaction temperature, degree of neutralization of AA, and amounts of the crosslinker sodium tungstate and the initiator were investigated. The crosslinked xerogels were characterized with infrared spectroscopy. These crosslinked superabsorbent composites with sodium tungstate were characterized with thermogravimetric analysis and scanning electron microscopy. The water absorbencies of these superabsorbent composites in water and saline solutions were investigated. Results obtained from this study showed that under the same synthesis conditions, in comparison with superabsorbent composites with an aluminum salt as a crosslinker and styrene as a graft copolymer, the salt resistance of the superabsorbent composite synthesized with sodium tungstate as a crosslinker was obviously enhanced. Moreover, the WPAA-TEA xerogel had absorbency values of 223.6 and 81.9 g/g for distilled water and a 0.9 wt % NaCl solution, respectively, and it showed better salt resistance and a better water-absorbing rate than the WPAA-sodium xerogel because of the modification with triethanolamine.