Frontal Polymerization Synthesis And Characterization Of Konjac Glucomannan-Based Superabsorbent Polymers

Frontal polymerization（FP） which also named low-temperature combustion synthesis is a novel preparation method of high efficiency,energy saving,convenient which converts the monomer into polymer through the heat release by the reaction itself. Superabsorbent material based on carbohydrates has caught redoubled attention for its biodegradability so that it has practical significance to water resources utilization,and apply in the field of health,medical,food anti-staling and so on.This study is the first synthesis of konjac glucomannan superabsorbent polymers （SAP） with special pore structure by frontal polymerization.Effects of konjac glucomannan（KGM）,initiator,crosslinking agent,environment temperature,water, acrylamide and kaolin on front velocity,front temperature and the absorbent properties of SAP were investigated.The polymers were also characterized by SEM,FT-IR and DSC.The main results were as follow:1.A stable front formed and propagated down in the test tube as the KGM/AA ratio was between 7.5×10^-3 and 1.25×10^-2 and maximum temperature(T_max) was almost same in different levels.When KGM/AA ratio was 1×10^-2,the distilled water absorption rate was highest.Front velocity and T_max increased with increasing the amount of initiator.The amount of initiator should be as low as possible to obtain less homopolymerization and highest water absorption rate of SAP under the premise that reaction can be propagate. Besides,the dependence of the front velocity on the initiator amount fitted a power function.The amount of crosslinking agent mainly affected the water absorbency and microstructure more than front velocity and T_max.Higher environment temperature could reduce heat loss,resulting in higher front velocity and T_max,but the water absorption rate of SAP decreased accordingly.2.Front velocity of all samples increased after adding acrylamide into reaction mixture.Front velocity and T_max increased with increasing the amount of acrylamide. Oppositely,water absorbency decreased.Water in reaction system was both solvent and diluent.The increase of water results in decrease of heat release and increase of heat loss. Effect of water on front velocity,especially T_max was remarkable.Front velocity and T_max decreased with increasing the amount of water,and the water absorption rate of SAP showed the opposite trend.3.T_max decreased with increasing the amount of kaolin,but water absorbency in distilled water and physiological saline of SAP increased,up to 1941g/g and 93g/g respectively.4.SAP samples were characterized by SEM,FT-IR and DSC.Porous structure was observed in all three kinds of SAP by SEM,but not quite the same.The DSC curves of swelling KGM-acrylic acid polymers indicated that higher water absorbency corresponding to lower enthalpy.The DSC curves of KGM-acrylic acid-kaolin polymers showed that exothermic peak move to lower temperature when Kaolin/AA ratios were 0.20 and 0.30,which prompted increasing amount of kaolin declined the thermal stability of SAP.5.SAP synthesized by frontal polymerization has advantages of short reaction time, high efficiency and high water absorbency by comparison with traditional solution polymerization.