Study On Preparation And Properties Of Polycaprolactone-based Shape Memory Composite And Bone External Fixation

As a branch of smart materials,shape memory polymers have the ability to memorize permanent shapes and be programmed into one or more temporary shapes,and then spontaneously recover from temporary shapes to permanent shapes after specific stimulation.Different to ordinary intelligent systems or devices,SMP do not rely on the complex sensing devices or response structures of the feedback system,and depend on its inherent sensitivity to changes in the surrounding environment,such as temperature,light,electricity,magnetism and p H.As a kind of shape memory polymer,shape memory polycaprolactone has the advantages of biodegradable,low glass transition temperature,good thermal stability and so on,so it has great potential in the field of biomedicine.In order to tackle the problems of bulkiness,poor air permeability,and unfriendly to human body caused by traditional fracture external fixation materials,this article ultilized shape memory polycaprolactone as the matric material,modified by chitosan and stearic acid to obtain a polymer composite with low transition temperature and high strength,and designed a cylindrical bne external fixation with both shape memory and shape adaptive characteristics.The shape recovery process controlled the tightness of the cylindrical structure to achieve fracture external fixation,and during rehabilitation the structure enabled small-scale activities to help recover.At first,the chitosan/polycaprolactone composite material is prepared in this research,its shape recovery rate can reach 95 %,and the recovery process takes only 5 s;meanwhile,the melting point of the composite is 65.34 ℃,which is lower than that of pure polycaprolactone,and thebiomass material chitosan improves the human friendliness of composite.In addition,the effect of stearic acid content on shape memory polycaprolactone was studied and found that the shape recovery rate ranged from 80 % to 85 %,and the recovery process also took only 5 s.In general,the storage modulus and yield strength of stearic acid/polycaprolactone at room temperature increase with the increase of stearic acid content,and the melting point shows a small downward trend with the increase of stearic acid content,which has great advantages in the application of bone fracture fixation.After successfully preparing and verifying the performance of polycaprolactonebased shape memory composites,different structural external fixation plates and external fixation device of fractures were designed for the application in the direction of fracture external fixation.Through the ABAQUS finite element software to simulate the compression and bending process of different structures,analyze the deformation effect.The results shows that the performance of the small-diameter internal concave quadrilateral structure is closest to that of commercial round hole structure,and its structure is more adaptable and comfortable.The dislocated concave triangular cylindrical structure is more stable during the bending process.Different structures can be selected according to different fixing parts,and have wide applicability.