Regulation Of Crystalline Structure And Strengthening And Toughening Behaviours And Mechanisms Of CF/PEEK

Traditional orthopedic implants are medical metals,however,metal materials can cause artifacts during scanning or magnetic resonance imaging,and excessive modulus of elasticity can cause stress shielding.Carbon fiber reinforced polyetheretherketone composite(CF/PEEK)is expected to become one of the important materials in the field of orthopedic implantation due to its good biocompatibility,corrosion resistance,fatigue resistance,X-ray transmission and excellent mechanical properties,and its modulus is close to that of cortical bone compared with metal materials,which can reduce stress shielding.CF/PEEK materials are mainly divided into two categories,short carbon fiber reinforced polyetheretherketone composites(S-CF/PEEK)and the other is continuous carbon fiber reinforced polyetheretherketone composites(C-CF/PEEK).S-CF/PEEK has the advantages of low cost,simple molding process and high production efficiency.However,in order to ensure the mechanical properties of S-CF/PEEK,increasing the content of carbon fiber often leads to more difficult processing and a decrease in material toughness,so how to achieve the strength and toughness of S-CF/PEE at the same time needs further research.The mechanical properties of C-CF/PEEK are significantly better than S-CF/PEEK,but C-CF/PEEK is an anisotropic material,and carbon fiber has a relatively poor effect on the mechanical properties of composite materials in the vertical direction,so it is of great significance to improve the transverse mechanical properties of composite materials by regulating crystallization to construct a good interface between the fiber and the matrix,thereby increasing the interaction pressure between the two.In addition,the specific performance requirements of orthopedic materials are different,and the anisotropy of C-CF/PEEK brings a lot of freedom to the design.For example,the mechanical properties of the product can be changed by changing the plying method,including ply angle and ply sequence,to meet the specific user requirements.In this paper,S-CF/PEEK composites were prepared by PIF,the mechanical properties of the composites were tested,the influence of different molding processes on the mechanical properties of the materials were compared,and the tensile modulus,impact strength and flexural modulus of the composites after PIF molding could be increased by up to about 105%,110% and 90%,respectively.At the same time,in order to explore the relationship between the change of microstructure and the macroscopic mechanical properties,SEM,SAXS,DSC and DMA tests were carried out on S-CF/PEEK,which verified that the spherulites in the S-CF/PEEK matrix and carbon fiber were oriented along the flow direction after PIF molding,which improved the strength of the composite material and improved the crystallinity of the material due to orientation induction.Under certain temperatures and pressures,the multilayer-oriented structure formed by PEEK polymer can intervene in the crack growth path,effectively improving the toughness of the material.During the molding process,a rigid amorphous region was formed after the crushing,slipping and rearrangement of PEEK crystal lamellae,thereby improving the thermal stability and toughness of the material.PIF molding provides an effective path for the preparation of S-CF/PEEK with both strength and toughness.In addition,the melting temperature and crystallization temperature of C-CF/PEEK crystallization studies were determined by thermodynamic characterization such as TGA and DSC,and the exploration range of C-CF/PEEK crystallization was 360 ℃-410 ℃ and 260 ℃-290 ℃,respectively.The thermal history elimination effect was better when the melting temperature was above 380 ℃,and the crystal growth space and size were further increased when the melting temperature was further increased to 400 ℃ and above,and the crystal growth space and size were further increased at 400 ℃ and above,and 260 ℃-290 ° at 400 ℃ melting temperature Transcrystallinities could be formed within the crystallization range of 260 ℃-290 °,but the growth of transcrystallinities was inhibited when the degree of subcooling was large.Through DSC and rheological tests,it was found that mild crosslinking caused by short-term heat treatment slowed down the crystallization rate of PEEK.However,its influence was mainly on the nucleation and growth of spherulites but had no obvious effect on transcrystallinities.POM and AFM were used to characterize the surface morphology of transcrystallinities and shear flow-induced formation of PEEK cylindrites,and the growth mechanism of transcrystallinities and cylindrites was further explored.In addition,in order to further explore the orthopedic application of C-CF/PEEK,the cytotoxicity of PEEK and C-CF/PEEK was tested by MTT,and the RGRs of the two were 95.3% and 88.3%,respectively,and there was no cytotoxicity.The simulation results show that the bone plate prepared by C-CF/PEEK can be used as a load-bearing structure to protect the fracture site,and the addition of ±45° and 90° patriarchy can improve the stress concentration and stress occlusion of the bone plate,which provides a theoretical basis for the practical application of C-CF/PEEK.