Studies On The Mechanical Properties Of Physical Gel

Hydrogels are ideal biomaterials because of their good chemical and physical properties,such as high water content,high tensile strength and biocompatibility.They have been applied to many fields,such as artificial cartilage,cornea et al.Physically crosslinked hydrogel is low toxic,higher water content and the raw material is natural,so it is much better for biomaterials.The number and position of crosslinking points and the position of water molecules of hydrogel are changing under the deformation,leading to the variation of compress strength.The constitutive relations of hydrogel are not well because the effects of water under different states are not discriminated.The objectives of this paper are to discriminate water under different states in physically crosslinked hydrogels,and calculate the content respectively by molecular dynamic simulations.The stress-strain behavior of hydrogel under uniaxial compress deformation has also been studied,and the variations of water content under different states with increasing deformation are investigated.The work is helpful to perfect constitutive relations of hydrogel,promote the application of hydrogel in many fields.Firstly,a new classification rule is proposed,and then the freezing and free water content in ethylene glycol and glycerol solutions are calculated by this rule.The influence of concentration and temperature on the freezing water content is studied.It is found that the freezing water content is increasing with increasing concentration within a certain range,and then keeps constant.With increasing temperature,the freezing water content decreases.Secondly,the classification rule is applied to the carrageenan.The non-freezing water,freezing water and free water content by molecular dynamic simulations.The swelling dynamic property of carrageenan is studied by adding water step by step.The influence of temperature on the water content under different states in the carrageenan is also analyzed.Finally,the mechanical properties of glucan hydrogel are studied.The stress-strain behavior of hydrogel under uniaxial compress deformation and the variation of water content under different states are studied.The change of free water content as a function of strain was also analyzed,and the curve indicates the water content under different states has significant influence on the mechanical properties of hydrogel.Then the temperature dependency for the mechanical properties is studied.It is found that the compression strength decreases with increasing temperature.The influence of water content on the mechanical properties is also investigated.The results show the mechanical properties decreases with increasing water content.