Preparation And Characterization Of Organic-inorganic Double-network Hydrogel Composites

As a functional polymer material,the superabsorbent gel has excellent properties such as water swelling,high water retention and high water resistance.Using grouting repair technology,in-situ synthesis of water-absorbing gel in concrete structure cracks,to solve the leakage of concrete structure with the technical idea of “blocking water with water”,which has important application value for exploring the application field of water-absorbing gel and improving the service life of concrete structure.However,the traditional water-absorbing gel has inherent defects such as low mechanical strength and poor toughness,which greatly limits its application in the field of concrete crack repair and plugging.The use of organic-inorganic hybridization is one of the common methods of polymer reinforcement.In this study,an organic-inorganic hybrid method was adopted,with polyacrylamide or sodium polyacrylate as the organic gel,sulphoaluminate cement or Portland cement clinker as the inorganic gel,and a double network structure design concept was introduced to synthesize organic-inorganic double-network hydrogels to enhance the mechanical properties of conventional hydrogels.The test mainly consists of two kinds of double-network hydrogels: polyacrylamide-sulphoaluminate cement(PAM/SAC)and sodium polyacrylate-silicate cement [P(AA-NaAA)/CC].The tensile properties,compressive properties,water swellability,cohesive properties and impermeability of cracks in different width mortars were investigated with emphasis on the prepared organic-inorganic double-network hydrogels.The network structure and composition of hybrid hydrogels were analyzed by microscopic characterization methods such as FT-IR,XRD and SEM.The research conclusions are as follows:(1)The mechanical properties study results show that the addition of cement can effectively improve the compression and tensile strength of the prepared organic-inorganic double-network hydrogel,but its tensile and compressive strain capacity decreases with the increase of cement dosage.For the PAM/SAC double-network hydrogel,when the compression deformation is 85%,the breaking strength is up to 60 MPa,and when the tensile deformation is 2500%,the tensile strength at break is 15 MPa.For P(AA-NaAA)/CC double-network hydrogel,when the compression deformation is 65%,the compressive fracture strength can reach 5.5MPa,and when the tensile deformation is 85%,the tensile strength at break reaches 0.268MPa;(2)The results of water swelling and swelling properties show that the two organic-inorganic double-network hydrogels prepared have both a certain water-swelling ability and a certain mechanical strength.And with the increase of cement content,the water absorption rate of the two organic-inorganic double-network hydrogels decreases,and the swelling and water(salt)absorption ability decreases.When SAC/AM=2.2,the water absorption ratio and volume expansion ratio of the PAM/SAC double-network hydrogel were 16 g/g and 300%,respectively.The water swelling rate can be described by first-order and second-order kinetic equations;when CC/AA=0.6,the maximum water absorption ratio of P(AA-NaAA)/CC double-network hydrogel is 28g/g.At the same time,it has excellent water retention capacity and cyclic water absorption performance;(3)The research on repairing cracks and plugging performance shows that when PAM/SAC double-network hydrogel is used to treat concrete with different crack width,the bond strength between it and cement mortar substrate can reach 1.2MPa.When the crack width is 1mm,the impermeability of the PAM/SAC double-network hydrogel reaches 0.9MPa;(4)Microscopic characterization analysis showed that the prepared organic-inorganic double-network hydrogel produced two network structures with different physical properties.Among them,an inorganic gel(rigid skeleton)mainly composed of cement hydration products is used as the first network,and a large amount of cross-linked polymer(flexible matrix)is used as the second network.The two networks interpenetrate and entangle each other to enhance mechanical strength.TGA analysis also showed that the addition of cement can significantly improve the thermal stability of the hydrogel.