Synthesis,Characterization And Properties Of Gum Arabic-Based Hydrogels

Hydrogel which can absorb aqueous solution hundreds times of its own weight without being dissolved is a polymer functional material with network structure.As a new functional material,it has been widely used in water-saving agriculture,biological medicine,daily chemical industry and sewage disposal.In recent years,with the concern of the eco-environment and the cost of hydrogel raw materials,the synthesis of environmentally friendly composites using inorganic clay minerals and natural polymers has become a research hotspot in the field of hydrogel technology.In this paper,two kinds of gum arabic-based composite hydrogels were prepared by microwave irradiation using natural polymer gum arabic?GA?and clay mineral sepiolite?ST?,acrylic acid?AA?and 2-acrylamide-2-methylpropionic sulfonic acid?AMPS?,water-soluble ammonium persulfate?KPS?as initiator and N,N'-methylene bisacrylamide?MBA?as crosslinking agent.The composition,structure,morphology and thermal stability of the composite hydrogel were characterized by FTIR,XRD,SEM and TG.The synthetic conditions and water absorption properties of the hydrogel were studied,and the formation mechanism of the hydrogel was discussed.The experimental results of this paper are as follows:1.GA-g-PAA/ST composite hydrogels were prepared by free radical polymerization using AA,GA and ST as raw materials under microwave irradiation.XRD,FTIR and SEM analysis showed that GA and ST participated in the graft copolymerization to form a hydrogel with three-dimensional network structure.TG analysis showed that the hydrogel had good thermal stability,and the thermal stability of the hydrogel could be significantly improved by introducing ST into the hydrogel.The optimum synthetic parameters of GA-g-PAA/ST were AA=3.9mL,?GA?=7.5%,w?ST?=10%,N=75%,w?MBA?=0.25%,w?APS?=1%,P=135W,t=4 min.Under these conditions,the ionized water absorbed by GA-g-PAA/ST hydrogel was 559 g/g and the saline was 71 g/g.Hydrogels have a certain responsiveness to salt solution and pH solution,and have good sensitivity and reversibility in NaCl-BaCl₂ solution and pH=2.0-7.0 solution.The water absorption behavior of hydrogels in salt solutions with different concentration and in solutions with different pH conforms to quasi-second-order kinetics model.Hydrogels have good water retention and repetitive water absorption properties.2.GA-g-PAA/AMPS/ST composite hydrogels were prepared by free radical polymerization using AA,AMPS,GA and ST as raw materials under microwave irradiation.XRD,FTIR and SEM analysis showed that GA and ST participated in the graft copolymerization to form a hydrogel with three-dimensional network structure.TG showed that the hydrogel had good thermal stability.The optimum synthetic parameters of GA-g-PAA/AMPS/ST were n?AMPS?:n?AA?=1:3,w?GA?=5%,w?ST?=5%,N=85%,w?KPS?=1%,w?MBA?=0.35%,P=195W,t=3 min.Under these conditions,the absorption of ionized water and saline by GA-g-PAA/AMPS/ST was 710 g/g and 92.3 g/g,respectively.Compared with GA-g-PAA/ST gel,the water retention rates of hydrogels at40,60 and 80?were 2.6%,8.6%and 10.1%higher respectively.Compared with GA-g-PAA/ST,the water absorption rate of GA-g-PAA/AMPS/ST increased by about 5%after 5 times of repeated using.Figure[40]table[7]reference[71]...