High-toughness mechanically compatible bone screw and preparation method thereof

Abstract

The application provides a high-toughness mechanically adaptive bone screw and a preparation method thereof, relates to the technical field of orthopedic implant medical devices, and comprises the following steps: preparing a carbon fiber-polyether ether ketone core mold; preparing a variable-thickness carbon fiber-polyether ether ketone prepreg; conveying the variable-thickness carbon fiber-polyether ether ketone prepreg and an organic film after heat sealing to the surface of the carbon fiber-polyether ether ketone core mold, and layer by layer laying on the carbon fiber-polyether ether ketone core mold to be compacted, molded and prepared into a preform; heating the preform to a specified temperature, extruding and molding through a screw structure mold, and then demolding and heat treating to prepare the bone screw. The application uses the organic film as a toughening layer and designs a coaxial laminated structure, the thickness gradually decreases from the central cylinder to the outer peripheral layer of the screw body, the performance in the aspects of bending fatigue performance and fracture toughness is obviously improved, the relative modulus is significantly lower than that of the bone screw prepared by a traditional scheme, and is closer to the modulus of cortical bone, thereby reflecting the advantages in mechanical adaptation.

Description

Technical Field

[0001] This application relates to the field of orthopedic implant medical device technology, and more specifically, to a high-toughness mechanically adaptable bone screw and its preparation method. Background Technology

[0002] Internal fixation surgery for fractures of the spine, limbs, and pelvis is one of the most common treatment methods in orthopedic clinics. As the core implantable device with the largest usage and widest application in this type of surgery, bone screws directly determine the success rate of the surgery and the patient's postoperative quality of life due to their mechanical properties, biocompatibility, and long-term service stability.

[0003] Currently, the mainstream bone screws used in clinical practice are mostly made of titanium alloy and stainless steel. Although they have high strength and rigidity, they have inherent defects that are difficult to overcome: First, the elastic modulus of metal materials (titanium alloy is about 110 GPa) is much higher than that of human cortical bone (10-30 GPa). Long-term implantation will produce a serious stress shielding effect, causing the bone tissue around the implant to undergo disuse bone resorption due to lack of mechanical stimulation, which will eventually lead to screw loosening, breakage, or even secondary fracture.

[0004] To address the aforementioned issues, polyetheretherketone (PEEK), a semi-crystalline high-performance thermoplastic engineering plastic, has gradually become a research hotspot in the field of orthopedic implants due to its excellent biocompatibility, chemical stability, absence of metal artifacts, and elastic modulus (approximately 3-4 GPa) closer to that of human bone. However, the tensile strength, flexural strength, and rigidity of pure PEEK materials are insufficient to meet the mechanical requirements of internal fixation in load-bearing areas. Introducing continuous carbon fibers to prepare carbon fiber-reinforced PEEK (CF-PEEK) composites can significantly improve the material's mechanical properties, making its strength and rigidity approach those of human cortical bone, thus becoming an ideal material to replace metal bone screws. However, existing CF-PEEK bone screws still suffer from insufficient fracture toughness and poor interlaminar properties. CF-PEEK composites have a typical layered structure, with interlaminar bonding mainly relying on the resin matrix, resulting in low bonding strength. Under cyclic loading in the human body, interlaminar microcracks are prone to develop and rapidly propagate, ultimately leading to brittle fracture of the screw. Summary of the Invention

[0005] To address the aforementioned problems, this application employs a method for preparing a high-toughness mechanically adaptable bone screw, comprising the following steps: Preparation of carbon fiber-polyetheretherketone mandrel; Preparation of variable thickness carbon fiber-polyetheretherketone prepreg; After heat-sealing the variable thickness carbon fiber-polyetheretherketone prepreg and organic film, the prepreg is conveyed to the surface of the carbon fiber-polyetheretherketone core mold and then laid layer by layer on the carbon fiber-polyetheretherketone core mold and compacted to shape, thus obtaining the preform. After the preform is heated to a specified temperature, it is extruded and shaped using a screw structure mold, and then the bone screw is obtained after demolding and heat treatment.

[0006] Optionally, the preparation method of variable thickness carbon fiber-polyetheretherketone prepreg is as follows: preheated continuous carbon fiber is conveyed to an impregnation mold and impregnated with molten polyetheretherketone resin. Whenever the carbon fiber-polyetheretherketone prepreg leaving the impregnation mold reaches the corresponding layer laying length, the mold exit gap is reduced, and after continuous traction, it is wound to obtain variable thickness carbon fiber-polyetheretherketone prepreg.

[0007] Optionally, preheating includes preheating the carbon fiber surface by infrared radiation preheating, with the preheating temperature of infrared radiation preheating being 100-150°C. Before the continuous carbon fiber passes through the infrared radiation preheating process and enters the impregnation mold, it also passes through a heating roller with the temperature of the heating roller set to 100-150°C. The temperature inside the impregnation mold is 350-400℃, the pressure is 0.5-8MPa, and a corrugated tension roller is also installed inside the impregnation mold. The outlet gap of the impregnation mold is 0.1-0.3mm.

[0008] Optionally, in the variable thickness carbon fiber-polyetheretherketone prepreg, the carbon fiber is T700S-12K, the melt index of the polyetheretherketone granular resin is 60-100g / 10min (380℃, 5kg), the variable thickness carbon fiber-polyetheretherketone prepreg is a unidirectional prepreg, and the total volume content of the carbon fiber in the variable thickness carbon fiber-polyetheretherketone prepreg is 40-60%.

[0009] Optionally, the carbon fiber-polyetheretherketone prepreg is wound with 5-10 layers, and the thickness of each layer ranges from 0.1-0.3 mm; The organic film includes polyetherimide film or polyethersulfone film, with a thickness of 0.01-0.2 mm, the number of winding layers is the same as the number of winding layers of prepreg, the heat sealing temperature is 270-330℃, and the heat sealing time is 8-20 s.

[0010] Optionally, the laminated tape, which is thermally synthesized from carbon fiber-polyetheretherketone prepreg and organic film, is conveyed to the laying head of an automatic tape laying machine under a tension of 7-20N. The laying head then conveys the tape to the surface of the mandrel under the action of a flexible pressure roller, and continuously and repeatedly lays it layer by layer onto the rotating carbon fiber-polyetheretherketone mandrel for compaction and shaping to form a preform.

[0011] Optionally, the preform is heated to a specified temperature and then extruded and shaped using a screw structure mold. After demolding and heat treatment, a bone screw is obtained. The precast body is heated to 290-350℃, and after reaching the specified temperature, it is held for 10-30 minutes. The temperature of the screw structure mold is 180-220℃, and the setting time is 6-20s; The heat treatment temperature is 170-250℃, the duration is 2-12h, the cooling rate during the cooling process is 0.2-2℃ / min, and after cooling to 120-160℃, it is naturally cooled to room temperature.

[0012] Optionally, the preparation of carbon fiber-polyetheretherketone (PEEK) mandrels includes: processing carbon fiber-PEEK rods with prepreg by pultrusion or hot pressing, and then cutting them to obtain carbon fiber-PEEK mandrels.

[0013] Optionally, during the pultrusion process, the molding die includes a preheating zone, a hot melt zone, and a cooling zone. The temperature of the preheating zone is 90-190℃. In the hot melt zone, the carbon fiber-polyetheretherketone mandrel is heated to the molding temperature using prepreg, which is 350-380℃. The temperature of the cooling zone is 20-40℃, and the diameter of the pultrusion rod is 2-6mm.

[0014] This application also provides a high-toughness mechanically adaptable bone screw, prepared using any of the aforementioned methods for preparing high-toughness mechanically adaptable bone screws, comprising, from the inside out: Carbon fiber-polyetheretherketone core mold; A multilayer variable thickness carbon fiber-polyetheretherketone prepreg and organic film composite layer is used. In the composite layer, the thickness of the carbon fiber-polyetheretherketone prepreg decreases layer by layer, while the thickness of the organic film remains unchanged. Each layer of the composite layer includes one layer of carbon fiber-polyetheretherketone prepreg and one layer of organic film.

[0015] The beneficial effects of the high-toughness mechanically adaptable bone screw and its preparation method provided in this application are as follows: (1) By using an organic film as a toughening layer, crack propagation and / or crack displacement can be inhibited during load fracture, dissipating more energy and improving the fracture toughness of the screw; the addition of the organic layer can reduce the elastic modulus of the screw to match the human skeleton, effectively avoiding the stress shielding effect; the coaxial laminated structure design, with the layer thickness gradually decreasing from the central cylinder to the outer periphery of the nail body, and the continuous fiber composite thick inner layer ensures that the screw has sufficient rigidity; overcoming the disadvantages of poor interlayer bonding in traditional composite products, and improving the overall physical and mechanical properties of the nail body.

[0016] (2) Compared with the schemes of carbon fiber-polyetheretherketone prepreg with uniform thickness in each layer, the scheme of carbon fiber-polyetheretherketone prepreg with progressively thicker layers from the inside out, the scheme of carbon fiber-polyetheretherketone prepreg without varying thickness, the scheme of carbon fiber-polyetheretherketone prepreg without organic film toughening layer, and titanium alloy bone screws, the bone screws prepared by the design scheme of carbon fiber-polyetheretherketone prepreg with progressively thinner layers from the inside out provided in this application show significantly improved performance in terms of bending fatigue properties and fracture toughness. Among them, the fracture toughness of the bone screws prepared by the technical solution of this application is 177.8 MPa.m. 1 / 2 In summary, after 2.5 million cycles, the maximum bending moment is above 20 N·m, and the relative modulus is significantly lower than that of the bone screw prepared by the screw design scheme without the addition of the organic film layer. It is closer to the modulus of cortical bone, demonstrating the advantage in mechanical adaptation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a schematic diagram of the layup of the variable thickness carbon fiber-polyetheretherketone prepreg and organic film provided in this embodiment.

[0019] Explanation of reference numerals in the attached figures: 1-Core mold; 2-First variable thickness carbon fiber-polyetheretherketone prepreg layer; 3-Second variable thickness carbon fiber-polyetheretherketone prepreg layer; 4-Third variable thickness carbon fiber-polyetheretherketone prepreg layer; 5-First organic film layer; 6-Second organic film layer; 7-Third organic film layer. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] Example 1: In this embodiment: (1) Using the pultrusion molding process, carbon fiber-polyetheretherketone core mold prepreg (carbon fiber-polyetheretherketone unidirectional prepreg, carbon fiber is T700S / 12K, the volume content of carbon fiber in the prepreg is 62%, the melt index of polyetheretherketone resin is 80g / 10min (380℃, 5kg), the width of the prepreg is 3.2mm, the thickness is 0.16mm, the carbon fiber-polyetheretherketone core mold prepreg can be the same material as the carbon fiber-polyetheretherketone prepreg used for winding and coating reinforcement on the carbon fiber-polyetheretherketone core mold, the term "carbon fiber-polyetheretherketone core mold prepreg" is used only to distinguish it from the carbon fiber-polyetheretherketone prepreg used for winding and coating reinforcement) is continuously pultruded through the molding die to form carbon fiber-polyetheretherketone rods of unlimited length. The diameter of the pultruded rod is 4mm, and then it is cut into carbon fiber-polyetheretherketone core molds with a length of 70mm (diameter of 4mm). The molding die includes a preheating zone, a hot-melt zone, and a cooling zone. The preheating zone is set at 140°C. The carbon fiber-polyetheretherketone unidirectional prepreg is heated to the molding temperature of 365°C in the hot-melt zone and then enters the cooling zone, which is set at 25°C.

[0022] (2) An infrared radiation preheating device is used to preheat, soften, and remove moisture from the carbon fiber surface at 125°C. Before the continuous carbon fiber enters the impregnation mold after the infrared radiation preheating process, it also passes through a heating roller with a temperature of 125°C. At the same time, a twin-screw extruder heats and melts polyetheretherketone resin (granular, melt index of 80g / 10min (380°C, 5kg)) at a processing temperature of 370°C and then conveys it to the impregnation mold. Under the action of high temperature and high pressure, the preheated carbon fiber is fully impregnated in the mold. The temperature in the impregnation mold is 375°C and the pressure is 4MPa (gauge pressure, i.e., relative pressure).

[0023] Remove the unstable part at the front end, adjust the initial impregnation die exit gap to 0.20mm, and after each corresponding winding layer length of the prepreg is pulled, the die exit gap is reduced by 0.02mm until the exit gap is reduced to 0.1mm and the corresponding length of the layer is pulled, and then the variable thickness carbon fiber-polyetheretherketone prepreg is obtained by winding. The number of winding layers of the carbon fiber-polyetheretherketone prepreg is 6.

[0024] The total volume content of carbon fiber in the variable thickness carbon fiber-polyetheretherketone prepreg is 50%. This "total volume content" refers to the proportion of carbon fiber to the total volume of the variable thickness carbon fiber-polyetheretherketone prepreg wound on the same carbon fiber-polyetheretherketone mandrel.

[0025] (3) After stacking the carbon fiber-polyetheretherketone prepreg and the polyetherimide film, place them in a heat sealing device and heat seal them at 300°C for 15s, then allow them to cool naturally to room temperature. After cooling, the heat-sealed tape is conveyed to the laying head of the automatic tape laying machine under a tension of 14N. The heating system is then turned on, and the tape is laid layer by layer along the 90° direction (0° is defined as the length of the carbon fiber-polyetheretherketone core mold / fiber orientation direction) under the action of the flexible pressure roller. The six layers (the thicknesses of the first layer (innermost layer) to the sixth layer (outermost layer) are 0.40mm, 0.38mm, 0.36mm, 0.34mm, 0.32mm and 0.30mm respectively) are compacted and shaped on the surface of the rotating carbon fiber-polyetheretherketone core mold to form a preform. The width of the heat-sealed tape used for laying is 70.00 mm, the thickness of the carbon fiber-polyetheretherketone prepreg is 0.20 mm, 0.18 mm, 0.16 mm, 0.14 mm, 0.12 mm and 0.10 mm respectively, and the thickness of the polyetherimide film is 0.2 mm.

[0026] (4) The above preform is first placed in a muffle furnace and the temperature is raised to 320°C and kept constant for 20 minutes. Then it is shaped by a screw extrusion mold with a mold temperature of 200°C and a shaping time of 14 seconds. After demolding, it is placed in a precision oven and heat-treated at 210°C for 7 hours. Then, it is cooled to 140°C at a rate of 1°C / min. The oven power is turned off and the bone screw is naturally cooled to room temperature to obtain the bone screw.

[0027] Example 2 In this embodiment: (1) Using a pultrusion molding process, carbon fiber-polyetheretherketone (PEEK) core molds are continuously pultruded through a molding die using a prepreg (carbon fiber-PEEK unidirectional prepreg, carbon fiber is T700S / 12K, the volume content of carbon fiber in the prepreg is 62%, the melt index of PEEK resin is 80g / 10min (380℃, 5kg), the width of the prepreg is 3.2mm, and the thickness is 0.16mm) to produce carbon fiber-PEEK rods of unlimited length. The pultruded rods have a diameter of 6mm and are then cut into carbon fiber-PEEK core molds with a length of 70mm (diameter of 6mm). The molding die includes a preheating zone, a hot melt zone, and a cooling zone. The preheating zone is set at 90℃. The carbon fiber-PEEK unidirectional prepreg is heated to the molding temperature of 350℃ in the hot melt zone and then enters the cooling zone, where the temperature is set at 20℃.

[0028] (2) An infrared radiation preheating device is used to preheat, soften, and remove moisture from the carbon fiber surface at 100°C. Before the continuous carbon fiber enters the impregnation mold after the infrared radiation preheating process, it also passes through a heating roller with a temperature of 100°C. At the same time, a twin-screw extruder heats and melts polyetheretherketone resin (granular, melt index of 80g / 10min (380°C, 5kg)) at a processing temperature of 370°C and then conveys it to the impregnation mold. Under the action of high temperature and high pressure, the preheated carbon fiber is fully impregnated in the mold. The temperature in the impregnation mold is 350°C and the pressure is 0.5MPa (gauge pressure, i.e., relative pressure).

[0029] Remove the unstable part at the front end, adjust the initial impregnation die exit gap to 0.18mm, and after each corresponding winding layer length of the prepreg is pulled, the die exit gap is reduced by 0.02mm until the exit gap is reduced to 0.1mm and the corresponding length of the layer is pulled, and then the variable thickness carbon fiber-polyetheretherketone prepreg is obtained by winding. The number of winding layers of the carbon fiber-polyetheretherketone prepreg is 5.

[0030] The total volume content of carbon fiber in the variable thickness carbon fiber-polyetheretherketone prepreg is 60%. This "total volume content" refers to the proportion of carbon fiber to the total volume of the variable thickness carbon fiber-polyetheretherketone prepreg wound on the same carbon fiber-polyetheretherketone mandrel.

[0031] (3) After laminating the carbon fiber-polyetheretherketone prepreg and the polyethersulfone film, place them in a heat sealing device and heat seal at 270°C for 8 seconds, then allow them to cool naturally to room temperature. After cooling, the heat-sealed tape is conveyed to the laying head of the automatic tape laying machine under a tension of 7N. The heating system is then turned on, and the tape is laid layer by layer along the 90° direction (0° is defined as the length of the carbon fiber-polyetheretherketone core mold / fiber orientation direction) under the action of the flexible pressure roller. The thicknesses of the first layer (innermost layer) to the fifth layer (outermost layer) are 0.19mm, 0.17mm, 0.15mm, 0.13mm and 0.11mm respectively) until it is compacted and shaped on the surface of the rotating carbon fiber-polyetheretherketone core mold to form a preform. The width of the heat-sealed tape used for laying is 70.00 mm, the thickness of the carbon fiber-polyetheretherketone prepreg is 0.18 mm, 0.16 mm, 0.14 mm, 0.12 mm and 0.10 mm respectively, and the thickness of the polyethersulfone film is 0.01 mm.

[0032] (4) The above preform is first placed in a muffle furnace and the temperature is raised to 290°C and kept constant for 10 minutes. Then it is shaped by a screw extrusion mold with a mold temperature of 180°C and a shaping time of 6 seconds. After demolding, it is placed in a precision oven and heat-treated at 170°C for 2 hours. Then, it is cooled to 120°C at a rate of 0.2°C / min. The oven power is turned off and the bone screw is naturally cooled to room temperature to obtain the bone screw.

[0033] Example 3 In this embodiment: (1) Using a pultrusion molding process, carbon fiber-polyetheretherketone (PEEK) core molds are continuously pultruded through a molding die using a prepreg (carbon fiber-PEEK unidirectional prepreg, carbon fiber is T700S / 12K, the volume content of fiber in the prepreg is 62%, the melt index of PEEK resin is 80g / 10min (380℃, 5kg), the width of the prepreg is 3.2mm, and the thickness is 0.16mm) to produce carbon fiber-PEEK rods of unlimited length. The pultruded rods have a diameter of 2mm and are then cut into carbon fiber-PEEK core molds with a length of 70mm (diameter of 2mm). The molding die includes a preheating zone, a hot-melt zone, and a cooling zone. The preheating zone is set at 190℃. The carbon fiber-PEEK unidirectional prepreg is heated to the molding temperature of 380℃ in the hot-melt zone and then enters the cooling zone, where the temperature is set at 40℃.

[0034] (2) An infrared radiation preheating device is used to preheat, soften, and remove moisture from the carbon fiber surface at 150°C. Before the continuous carbon fiber enters the impregnation mold after the infrared radiation preheating process, it also passes through a heating roller with a temperature of 150°C. At the same time, a twin-screw extruder heats and melts polyetheretherketone resin (granular, melt index of 80g / 10min (380°C, 5kg)) at a processing temperature of 370°C and then conveys it to the impregnation mold. Under the action of high temperature and high pressure, the preheated carbon fiber is fully impregnated in the mold. The temperature in the impregnation mold is 400°C and the pressure is 8MPa (gauge pressure, i.e., relative pressure).

[0035] Remove the unstable part at the front end, adjust the initial impregnation die exit gap to 0.30mm, and after each corresponding winding layer length of the prepreg is pulled, the die exit gap is reduced by 0.02mm until the exit gap is reduced to 0.12mm and the corresponding length of the layer is pulled, and then the variable thickness carbon fiber-polyetheretherketone prepreg is obtained by winding. The number of winding layers of the carbon fiber-polyetheretherketone prepreg is 10.

[0036] The total volume content of carbon fiber in the variable thickness carbon fiber-polyetheretherketone prepreg is 40%. This "total volume content" refers to the proportion of carbon fiber to the total volume of the variable thickness carbon fiber-polyetheretherketone prepreg wound on the same carbon fiber-polyetheretherketone mandrel.

[0037] (3) After laminating the carbon fiber-polyetheretherketone prepreg and the polyetherimide film, place them in a heat-sealing device and heat-seal at 330°C for 20s, then allow them to cool naturally to room temperature. After cooling, the heat-sealed tape is conveyed to the laying head of the automatic tape laying machine under a tension of 20N. The heating system is then turned on, and the tape is laid layer by layer along the 90° direction (0° is defined as the length of the carbon fiber-polyetheretherketone mandrel / fiber orientation direction) by the laying head under the action of the flexible pressure roller. Ten layers are laid continuously and repeatedly (the thicknesses of the first layer (innermost layer) to the tenth layer (outermost layer) are 0.40mm, 0.38mm, 0.36mm, 0.34mm, 0.32mm, 0.30mm, 0.28mm, 0.26mm, 0.24mm, and 0.22mm, respectively) until it is compacted and shaped on the surface of the rotating carbon fiber-polyetheretherketone mandrel to form a preform. The width of the heat-sealed tape used for laying is 70.00 mm, the thickness of the carbon fiber-polyetheretherketone prepreg is 0.30 mm, 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm, 0.20 mm, 0.18 mm, 0.16 mm, 0.14 mm, and 0.12 mm, respectively, and the thickness of the polyetherimide film is 0.1 mm.

[0038] (4) The above preform is first placed in a muffle furnace and the temperature is raised to 350°C and kept constant for 30 minutes. Then it is shaped by a screw extrusion mold with a mold temperature of 220°C and a shaping time of 20 seconds. After demolding, it is placed in a precision oven and heat-treated at 250°C for 12 hours. Then, it is cooled to 160°C at a rate of 2°C / min. The oven power is turned off and the bone screw is naturally cooled to room temperature.

[0039] Example 4 In this embodiment, the carbon fiber-polyetheretherketone mandrel is prepared by hot pressing, and all other processes and process parameters are consistent with those in Example 1.

[0040] In Examples 1-3, carbon fiber-polyetheretherketone mandrels are directly formed into rods via pultrusion. In this example, hot pressing requires forming a sheet followed by machining into a rod. The hot pressing employs a unidirectional layup method and includes: Carbon fiber-polyetheretherketone prepreg is placed in a mold and subjected to vacuum hot pressing. After demolding, carbon fiber-polyetheretherketone laminate is obtained. Vacuum hot pressing includes: starting the vacuum system and sequentially passing through pre-pressing, preheating, heating, heat preservation and pressurization, and cooling. The pre-compression pressure is 2 MPa, and the time is 5 min; The preheating temperature is 150℃ and the time is 60 min; The heating rate is 4℃ / min, and the temperature after heating is 365℃; The temperature for heat preservation and pressurization is 365℃; the pressure is 4MPa; and the time is 30 min. The cooling rate is 2℃ / min, and the temperature after cooling is 130℃; After cooling is complete, allow it to cool naturally to room temperature.

[0041] Comparative Example 1 The difference from Example 1 is that, in this comparative example, the carbon fiber-polyetheretherketone prepreg layer wound around the core mold gradually thickens from the inside to the outside, while the other process parameters remain the same as in Example 1.

[0042] The initial impregnation die exit gap is adjusted to 0.10 mm. After each corresponding winding layer length is pulled, the die exit gap is increased by 0.02 mm until the exit gap increases to 0.20 mm and the corresponding layer length is stretched. Then, the variable thickness carbon fiber-polyetheretherketone prepreg is obtained by winding.

[0043] Comparative Example 2 The difference from Example 1 is that, in this comparative example, the carbon fiber-polyetheretherketone prepreg layer wound around the mandrel has the same thickness from the inside to the outside, while all other process parameters remain the same as in Example 1: Adjust the exit gap of the impregnation mold to 0.15mm, pull the carbon fiber / polyetheretherketone prepreg to the length required for winding 6 layers, and then wind it up to obtain carbon fiber / polyetheretherketone prepreg of equal thickness.

[0044] Comparative Example 3 The difference from Example 1 is that the preform prepared in this comparative example does not include the carbon fiber-polyetheretherketone prepreg layer and the organic film toughening layer. The carbon fiber-polyetheretherketone core mold with a diameter of 8.2 mm is prepared using the process of Example 1. The carbon fiber-polyetheretherketone core mold is used as the preform and is extruded and shaped by a screw structure mold using the same process as in Example 1. After demolding and heat treatment, the bone screw is obtained.

[0045] Comparative Example 4 The difference from Example 2 is that the preform prepared in this comparative example does not include an organic thin film toughening layer, and the thicknesses of the carbon fiber-polyetheretherketone prepreg are 0.19 mm, 0.17 mm, 0.15 mm, 0.13 mm and 0.11 mm, respectively. All other process parameters are consistent with those in Example 2.

[0046] Comparative Example 5 In this comparative example, titanium alloy bone screws were manufactured using CNC machine tools through machining processes such as turning and milling. Appropriate threading cutters, V-cutters, milling cutters, parting cutters, and titanium alloy finishing rods were selected and installed in their respective positions. The screw tip and thread outer diameter were precision turned sequentially at a speed of 2500 r / min and a feed rate of F0.02 mm / r; the thread was precision turned at a speed of 800 r / min and a feed rate of F2.75 mm / r; and the ball end was precision turned at a speed of 3000 r / min and a feed rate of F0.02 mm / r. After machining, the parts were transferred to the fitter's workshop for preliminary treatment (removal of residual burrs and rounding), post-treatment, fine cleaning, and drying to obtain the titanium alloy bone screws.

[0047] The performance of the bone screws prepared in Examples 1-4 and Comparative Examples 1-5 was tested, and the results are shown in Table 1.

[0048] The bending / pull-out performance test method is conducted in accordance with YY / T0119.5-2014 Spinal Internal Fixation System Components Part 5: Test Method for Static and Fatigue Bending Strength of Metal Spinal Screws; The fracture toughness test method was conducted according to GB / T4161-2007, the KIC test method for plane strain fracture toughness of metallic materials.

[0049] The relative modulus is calculated based on the modulus of cortical bone (i.e., the relative modulus of cortical bone is 1).

[0050] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-5

[0051] Example 5 To illustrate the structure of the high-toughness mechanically adaptable bone screw provided in this application, through... Figure 1 This application demonstrates the process of heat-sealing variable thickness carbon fiber-polyetheretherketone (CFPE) prepreg and organic film onto the surface of a CFPE core mold, and then laying them layer by layer onto the CFPE core mold and compacting them for shaping. In this embodiment, to clearly illustrate the structure, the core mold of the preform is wrapped with only three layers of variable thickness CFPE prepreg and three layers of organic film. The CFPE prepreg layers, from the inside out, are: first CFPE prepreg layer 2, second CFPE prepreg layer 3, and third CFPE prepreg layer 4. The organic film layers, from the inside out, are: first organic film layer 5, second organic film layer 6, and third organic film layer 7.

[0052] In this embodiment, the thicknesses of the first variable thickness carbon fiber-polyetheretherketone prepreg layer 2, the second variable thickness carbon fiber-polyetheretherketone prepreg layer 3, and the third variable thickness carbon fiber-polyetheretherketone prepreg layer 4 decrease sequentially. Furthermore, the first variable thickness carbon fiber-polyetheretherketone prepreg layer 2 is connected to the second variable thickness carbon fiber-polyetheretherketone prepreg layer 3, and the second variable thickness carbon fiber-polyetheretherketone prepreg layer 3 is connected to the third variable thickness carbon fiber-polyetheretherketone prepreg layer 4.

[0053] The first organic thin film layer 5, the second organic thin film layer 6, and the third organic thin film layer 7 have the same thickness, and the first organic thin film layer 5 is connected to the second organic thin film layer 6, and the second organic thin film layer 6 is connected to the third organic thin film layer 7.

[0054] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing a high-toughness mechanically adaptable bone screw, characterized in that, Includes the following steps: Preparation of carbon fiber-polyetheretherketone mandrel; Preparation of variable thickness carbon fiber-polyetheretherketone prepreg; After heat-sealing the variable thickness carbon fiber-polyetheretherketone prepreg and organic film, the prepreg is conveyed to the surface of the carbon fiber-polyetheretherketone core mold and then laid layer by layer on the carbon fiber-polyetheretherketone core mold and compacted to shape, thus obtaining the preform. After the preform is heated to a specified temperature, it is extruded and shaped using a screw structure mold, and then bone screws are obtained after demolding and heat treatment.

2. The method for preparing the high-toughness mechanically adapted bone screw according to claim 1, characterized in that: The preparation method of the variable thickness carbon fiber-polyetheretherketone prepreg is as follows: preheated continuous carbon fiber is conveyed to an impregnation mold and impregnated with molten polyetheretherketone resin. Whenever the carbon fiber-polyetheretherketone prepreg leaving the impregnation mold reaches the corresponding layer laying length, the mold exit gap is reduced, and after continuous traction, it is wound up to obtain the variable thickness carbon fiber-polyetheretherketone prepreg.

3. The method for preparing the high-toughness mechanically adapted bone screw according to claim 2, characterized in that: The preheating includes preheating the carbon fiber surface by infrared radiation preheating, with the preheating temperature of infrared radiation preheating being 100-150℃. Before the continuous carbon fiber enters the impregnation mold after passing through the infrared radiation preheating process, it also passes through a heating roller with the temperature of the heating roller set to 100-150℃. The temperature inside the impregnation mold is 350-400℃, the pressure is 0.5-8MPa, and a corrugated tension roller is also provided inside the impregnation mold. The outlet gap of the impregnation mold is 0.1-0.3mm.

4. The method for preparing the high-toughness mechanically adapted bone screw according to claim 1, characterized in that: In the variable thickness carbon fiber-polyetheretherketone prepreg, the carbon fiber is T700S-12K, the melt index of the polyetheretherketone granular resin is 60-100g / 10min (380℃, 5kg), the variable thickness carbon fiber-polyetheretherketone prepreg is a unidirectional prepreg, and the total volume content of carbon fiber in the variable thickness carbon fiber-polyetheretherketone prepreg is 40-60%.

5. The method for preparing the high-toughness mechanically adapted bone screw according to claim 1, characterized in that: The carbon fiber-polyetheretherketone prepreg has 5-10 winding layers, with each layer having a thickness ranging from 0.1-0.3 mm. The organic film includes polyetherimide film or polyethersulfone film, with a thickness of 0.01-0.2 mm, the number of winding layers is the same as the number of winding layers of prepreg, the heat sealing temperature is 270-330℃, and the heat sealing time is 8-20 s.

6. The method for preparing the high-toughness mechanically adapted bone screw according to claim 5, characterized in that: The laminated tape, which is thermally synthesized from carbon fiber-polyetheretherketone prepreg and organic film, is conveyed to the laying head of the automatic tape laying machine under a tension of 7-20N. The laying head then conveys the tape to the surface of the mandrel under the action of a flexible pressure roller, and continuously and repeatedly lays it layer by layer onto the rotating carbon fiber-polyetheretherketone mandrel for compaction and shaping to form a preform.

7. The method for preparing the high-toughness mechanically adapted bone screw according to claim 6, characterized in that: After the preform is heated to a specified temperature, it is extruded and shaped using a screw structure mold. After demolding and heat treatment, bone screws are obtained. The preform is heated to 290-350℃, and after being heated to the specified temperature, it is kept at that temperature for 10-30 minutes. The temperature of the screw structure mold is 180-220℃, and the setting time is 6-20s; The heat treatment temperature is 170-250℃, the duration is 2-12h, the cooling rate during the cooling process is 0.2-2℃ / min, and after cooling to 120-160℃, it is naturally cooled to room temperature.

8. The method for preparing the high-toughness mechanically adapted bone screw according to claim 1, characterized in that: The preparation of the carbon fiber-polyetheretherketone (PEEK) core mold includes: processing the carbon fiber-PEEK core mold with prepreg by pultrusion or hot pressing to prepare carbon fiber-PEEK rods, and then cutting them to obtain the carbon fiber-PEEK core mold.

9. The method for preparing the high-toughness mechanically adapted bone screw according to claim 8, characterized in that: In the pultrusion process, the molding die includes a preheating zone, a hot-melt zone, and a cooling zone. The temperature of the preheating zone is 90-190℃. In the hot-melt zone, the carbon fiber-polyetheretherketone mandrel is heated to the molding temperature using prepreg, which is 350-380℃. The temperature of the cooling zone is 20-40℃. The diameter of the pultrusion rod is 2-6mm.

10. A high-toughness mechanically adaptable bone screw, characterized in that: Prepared using the method for preparing high-toughness mechanically adapted bone screws as described in any one of claims 1-9, comprising, from the inside out: Carbon fiber-polyetheretherketone core mold; A multilayer variable thickness carbon fiber-polyetheretherketone prepreg and organic film composite layer, wherein the thickness of the carbon fiber-polyetheretherketone prepreg decreases layer by layer in the composite layer, while the thickness of the organic film remains constant, and each layer of the composite layer includes a layer of carbon fiber-polyetheretherketone prepreg and a layer of organic film.

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