Study On The Construction And Toughness Of Fiber Structure Composite Hydrogel

Hydrogels have broad application prospects,especially in the fields of structural bio-materials,but the lack of toughness greatly limits their functional applications.In recent years,researchers at home and abroad have proposed a series of composite toughening strategies,among which the representative is to introduce the light-weight reinforced structure of fibers and fabrics into the soft hydrogel matrix.However,most research reports tend to develop fiber/fabric composite hydrogels using different hydrogel matrix,different fiber types and different knitting modes（ordinary/3D weaving,knitting,non-woven and 3D printing,etc.）,while there is a lack of systematic research on the interface between hydrogel matrix and fiber.Due to the easy de-bonding of the gel matrix-fiber interface,the insufficient strength of the interface and the instability of the interface,the strengthening effect of the fiber/fabric is often unable to give full play,thus the performance improvement,performance stability and application of the composite hydrogel materials are limited.In order to further study and improve the interfacial strength,stability and toughness of fiber-reinforced composite hydrogels,this paper proposes to use poly（acrylamide-co-acrylic acid）-Fe³⁺chemical/ion reinforced dual-crosslinked hydrogels as matrix,which are tough and have stronger infiltration of precursor solution and easier control of gel curing.While the non-alkali plain glass fiber fabric is used as macro-scopic continuous fiber reinforcement.The interfacial strength,stability and tearing toughness of silane-chemical-reinforced fiber-reinforced hydrogels were further improved by balancing the cross-linking density and distribution gradient of COO^--Fe³⁺ion coordination cross-linking network,as well as the silane infiltration modification concentration of the fabric reinforcement,in the glass fiber fabric composite dual-crosslinked hydrogels.The main research contents are as follows:（1）Preparation and characterization of dual-crosslinked hydrogel matrixThe preparation of poly（acrylamide-co-acrylic acid）-Fe³⁺dual-crosslinked hydrogel matrix was studied.By combining the viscosity test and curing parameter test of the hydrogel precursor solution,as well as the swelling test,water content test,uni-axial tensile test and type Ⅲ（trouser type）tear test of the dual-crosslinked hydrogel with different acrylic component content and different iron ion crosslinking concentration,the preparation process parameters of the relatively optimal toughness matrix were determined by quantitative comparison and characterization as follows:curing temperature 55℃,initiator content 1.0wt%,and the iron ion crosslinking concentration is 0.01 M,the content ratio of acrylic acid to acrylamide is 1:12,and the tensile and tear test speed is 50 mm/min,besides.Among them,the tensile fracture work of the relatively optimal toughness dual-crosslinked hydrogel matrix is 39.794±0.993 MJ/m³,the fracture energy is 13.436±0.250 kJ/m²,the water content is 67.05±0.70%,the elastic modulus is 2.819±0.053 MPa,and the fracture strength is 5.380±0.177 MPa.（2）Modification and characterization of glass fiber fabric reinforcementThe glass fiber reinforcement modified with silane was studied.The silane modification effect of the fabric was characterized qualitatively and quantitatively by combining static water Contact Angle test（CA）,Fourier Transform Infrared spectroscopy（FTIR）and Scanning Electron Microscopy test（SEM）,uni-axial tensile test of glass fiber bundle and fabric,and type Ⅲ（trouser type）tear test.In addition,the interfacial strengthening effect of silane modified glass fiber was quantitatively characterized by the 180°interface stripping test of fabric composite dual-crosslinked hydrogel and the pull out shear test of single fiber bundle with mono and dual-crosslinked hydrogel matrix.Finally,the optimum interface modifying parameters of glass fiber reinforced fabric were preliminarily determined.Among them,the contact Angle of the fabric（average increased from 42.2°to 129.1°）,the tensile properties of the single fiber bundle（average tensile strength increased from 23 N to 30 N）and the fabric（average tensile strength increased from 260.00 N to 354.75 N）,and the tearing properties of the fabric（tearng toughness increased from 26.79±2.02 kJ/m² to 115.97±6.24 kJ/m²）all showed an increasing trend with the increase of silane concentration.However,the interfacial shear properties of glass fiber bundles with mono and dual-crosslinked hydrogel matrix increased first and then decreased with the increase of silane concentration,and the 1.0 wt%silane modified fiber bundles showed the highest interfacial shear strength.（3）Study on preparation and toughness of composite hydrogel reinforced by modified fabricThe preparation process parameters and toughness of glass fiber fabric composite dual-crosslinked hydrogel were studied.The effects of different conditions(Fe³⁺secondary cross-linking time,deionized water dialysis,matrix thickness,tearing velocity,silane concentration and tearing width)on the tearing toughness of the composite hydrogel were characterized and compared by swelling test,water content test,SEM test and type Ⅲ（trouser type）tear test.For the preparation of composite hydrogels,the experiment explored and determined that the mold gasket with a thickness of 0.10 mm was used to prepare fabric composite hydrogels,and 0.01 M ferric chloride was used for secondary ion cross-linking.In the process of ion cross-linking,under the cross-linking state that the gel matrix tends to shrink to make the composite hydrogels start to be less than the theoretical total thickness（the total thickness of gasket and fabric）,full deionic dialysis balance for 48 h was performed to ensure that the ion cross-linking network inside and outside the gel matrix was reorganized as fully as possible while maintaining the volume shrinkage characteristics of the matrix.In addition,the optimal silane modified concentration of the composite hydrogel was determined to be 1.0 wt%,the optimal tear testing speed was 50 mm/min,the saturated tear width was 65mm,and the corresponding saturated tear toughness reached 806.951±9.954 kJ/m²,which was far higher than that of a single component,and is 1.49 times of the common fabric composite hydrogel,and it also maintains high water content of 50.492±1.168%.