Homogeneous synthesis of chitin-based acrylate superabsorbents in NaOH/urea solution

• Published in: Carbohydrate polymers 2013-04, Vol.94 (1), p.261-271
• Main Authors: Liu, Tingguo, Qian, Liwu, Li, Bin, Li, Jing, Zhu, Kunkun, Deng, Hongbing, Yang, Xiaohong, Wang, Xin
• Format: Article
• Language: English
• Subjects: acrylic acid; adsorption; Alkali-freezing; Applied sciences; Chitin; emissions; Exact sciences and technology; Fourier transform infrared spectroscopy; freeze-thaw cycles; gels; Graft polymerization; hydrocolloids; Hydrogels; industrial applications; Natural polymers; neutralization; nitrogen; Physicochemistry of polymers; polymers; scanning electron microscopy; sodium hydroxide; Starch and polysaccharides; Superabsorbent polymers; thermal stability; urea; X-ray diffraction
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.01.010

► Chitin was dissolved in NaOH/urea solution and directly involved in synthesis reaction. ► Chitin based superabsorbent was synthesized under homogeneous conditions with better water absorption properties. ► Acrylic acid used directly without prior neutralization with NaOH. ► The polymerization reaction can carry out in a small beaker without nitrogen protection. ► Products exist as hydrogel without excess reagent emissions, which is conducive to reducing the environmental pollution. A modified freezing–thawing cyclic (FTC) process was applied to dissolve the chitin in NaOH/urea solution. A transparent homogeneous solution was obtained. It was utilized directly for preparing the superabsorbent polymers (SAPs) by grafting copolymerization under static solution conditions without nitrogen protection. The acrylic acid was used conveniently without prior neutralization. The final products existed as hydrogels without excess reagent emissions. The adsorption capacity and yield of SAP that was prepared in the optimum conditions was 2833g/g and 81.65%, respectively, higher than one-time FTC program prepared with 2527g/g and 15.44%. Furthermore, it formed a uniform and transparent gel without any residual chitin particles. The regenerated chitin and SAPs were characterized by SEM, FTIR, XRD, and TG. The samples prepared by the new method presented a more amorphous state with good thermal stability, suggesting that this convenient preparation method for a potential industrial application's pathway.