| L-polylactic acid(PLLA)is a kind of polymer synthesized by L-lactic acid.It has the advantages of non-toxic,non-irritating,high strength,good biocompatibility,complete biodegradation,renewable and processable,and can be completely decomposed by the natural micro-organisms,water,acid,alkali or other effects and ultimately generate carbon dioxide and water,as well as non-toxic and harmless to the human body,widely used in surgical suture and orthopedic materials.L-polylactic acid-based composites are ideal materials in the field of bone repair,which not only meet the requirements of strength and degradation,but also can overcome or avoid the harm caused by secondary operation.While the shortcomings of L-polylactic acid in hydrophilicity and mechanical properties bring great challenges to the academic community.modified L-lactic acid-based composite materials has becomes the focus of the field of bone repair research.Nano-hydroxyapatite(n-HA)-the main component of bone tissue,has a good biological activity,can promote bone tissue repair.L-lactic acid and nano-hydroxyapatite with hydrophilic groups containing JMXRJ modifier,by solution blending,to enhance the hydrophilic properties and binding capacity,respectively.With the carbon fiber as the reinforcement,carbon fiber reinforced modified PLLA matrix composite is prepared.The effects of JMXRJ and n-HA contents on the properties of modified PLLA were investigated by orthogonal design.The chemical structure was analyzed by infrared spectroscopy.XRD was used to analyze the crystallization behavior of JMXRJ and n-HA,and the thermal properties were analyzed by DSC,the hydrophilicity was analyzed by contact angle,the polarized light microscopy was used to observe the change of crystal grains during isothermal crystallizatio.The crystallization behavior of modified PLLA at different cooling rates was simulated by BP neural network and predicted the DSC curves of modified PLLA at other cooling rates to get the theoretical guidance foundation of the composite molding process.The molding process was carried out under a pressure of 10 MPa for 30 min,and the temperature was raised to 160?at a heating rate of 5?/ min.The pressure was maintained for 60 min and then reduced to 95?at a rate of 5?/ min.And finally the temperature of the carbon fiber reinforced PLLA matrix composites was prepared at room temperature,which had good bioactivity,biodegradability and high strength.It was expected to be a new type of bone repair material to meet the requirements of clinical bone repair.The mechanical properties of the composites under different formulations were tested,and the best recipe for the requirements of bone repair materials was selected.The moisture absorption performance of carbon fiber reinforced modified PLLA composites was studied at ambient temperature of 37±1? with simulated body fluid(SBF)as a medium for 12 weeks.The results show that the addition of n-HA particles inhibits the degradation of PLLA and relieves the degradation rate of the matrix.The mass loss rate and volume change rate of the composites increase with the time;the pH of the SBF medium is within the allowable range of the human body's pH.After 12 weeks,the mechanical properties of the bone are still degraded.Hemolysis experiments and cytotoxicity experiments show that carbon fiber reinforced modified PLLA matrix composites meet the biological material evaluation technology standards,can be used as bone repair materials,used in the field of biomedical. |
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