Study On Preparation And Properties Of N-HA/PVA Gel As Articular Cartilage Repair Material

Poly vinyl alcohol(PVA)hydrogel composite is a promising articular cartilage repairing material.In this dissertation,n-HA/PVA gel composite was prepared by in situ synthesis of nano-HA from PVA solution and combined with freezing/thawing method. The micro-morphology and structure were characterized by many experimental techniques such as TEM,SEM,XRD and FTIR.The mechanical and biotribological properties of n-HA/PVA composite were systemic studied.The main contents and results are as follows:1.n-HA/PVA gel composite was prepared by in situ synthesis of nano-HA from PVA solution and combined with freezing/thawing method.PVA solution also acted as dispersant to inhibit grain growth,decrease crystallinity degree and improve dispersibility of nano-hydroxyapatite.The results of micro-morphology showed that the nano-hydroxyapatite tents to agglomeration with the increase of nano-hydroxyapatite content in the composite.2.The change behaviors of tensile and compressive stress of the gel composite with the strain are accorded with non-linear characteristics.Both tensile strength and compressive strength of the composite increase with the rise of PVA solution and freezing/thawing cycle times.The tensile and compressive strength firstly increase and then tend to reducing with the increase of n-HA content.The tensile modulus of the composite increases linearly and compressive modulus increase exponentially with the rise of strain.Both storage and loss modulus of the gel composites increase with test frequency,PVA content and freezing/thawing cycles.The change behavior of their modulus with the rise of HA content represent increase firstly and then decrease.The maximum value of the storage and loss modulus reached while n-HA content in the composites is 6%.3.The stress relaxation speed of the gel composites decreases rapidly with the rise of relaxation time and increases with the rise of initial strain.At the same initial strain, the stress relaxation speed of the gel composites increases firstly and then tent to decrease.However,the normalized equilibrium relaxation modulus decreases firstly and the increases with the improvement of HA content.The generalized Maxwell model is established to characterize the stress relaxation behavior of the n-HA/PVA gel composites.The stress relaxation mechanism of the composites are:(1)Water rapid extrusion of the composites and the instantaneous change of bond length and bond angle of PVA result in rapid stress relaxation;(2)The movements of network structure and polymeric chain segment cause moderate and slow speed stress relaxations.4.The change behavior of the gel composites friction coefficient with different influence factors is revealed by Hertz contact theory and elasto-hydrodynamic lubrication theory, The friction coefficient of the gel composites increases with the rise of load and decreases with rise of radium of stainless steel ball and sliding speed.The friction coefficient decreases firstly and then increases with the rise of n-HA content.The minimum value is 0.0458 while n-HA content is 4.5%.The friction coefficient of the gel composites is lower in bovine serum than that in distilled water and physiological saline.5.The mechanical and bio-triblogical properties of the gel composites can be controlled by varation of processing conditions.For the n-HA/PVA gel composites used as an articular cartilage,the optimum preparation process of n-HA/PVA gel composites is 6wt%HA in 20wt%PVA matrix by 5 freeze/thaw cycle times.n-HA/PVA gel composite is a promising articular cartilage repairing material which possesses similar mechanical and biotribological properties to that of natural articular cartilage.