Hydroxyapatite-nano calcium silicate-polyether-ether-ketone composite material and preparation method thereof

Abstract

The invention provides a hydroxyapatite-nano calcium silicate-polyether-ether-ketone composite material and a preparation method thereof, and relates to the technical field of bone implant materials. According to the composite material, polyether-ether-ketone is used as a continuous matrix, and hydroxyapatite and nano calcium silicate are used as bioactive phases to be uniformly dispersed in the matrix; the content of each component in percentage by mass is as follows: 10%-20% of hydroxyapatite, 1%-10% of nano calcium silicate and 70%-90% of polyether-ether-ketone; the length-diameter ratio of the hydroxyapatite is 1.5 to 40. According to the invention, polyether-ether-ketone is taken as a matrix, hydroxyapatite and calcium silicate particles are synergistically introduced as a composite reinforcement phase, so that the material is endowed with excellent biological activity, osteoconductivity and osseointegration ability while the mechanical strength and modulus of the material are remarkably improved, and the crystallization property and biocompatibility of the material are further optimized; the prepared composite material has excellent comprehensive performance and is suitable for an implant for bone defect repair of a bearing part.

Description

Technical Field

[0001] This invention relates to the field of bone implant materials technology, and specifically to a hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material and its preparation method. Background Technology

[0002] In orthopedics, plastic surgery, and oral and maxillofacial surgery, implant materials are crucial for repairing bone defects and restoring joint function. Currently, commonly used implant materials are mainly classified into metallic, inorganic non-metallic, polymeric, and composite materials. Metallic materials, such as stainless steel, titanium and titanium alloys, and cobalt-chromium-molybdenum alloys, have advantages such as high strength and good wear resistance. However, their elastic modulus is significantly higher than that of human bone tissue (e.g., the elastic modulus of titanium alloys is approximately 110 GPa, while the elastic modulus of human cortical bone is approximately 7-30 GPa), which can easily lead to a "stress shielding" effect, causing surrounding bone resorption and implant loosening. Long-term implantation may also cause local tissue reactions, allergies, or systemic toxicity due to the release of metal ions (such as nickel, chromium, cobalt, and aluminum ions). Furthermore, metallic implants are expensive and can interfere with medical imaging (e.g., producing artifacts on CT and MRI scans), affecting postoperative evaluation. Inorganic non-metallic materials, such as hydroxyapatite (HA), bioglass, and calcium phosphate ceramics, have good biocompatibility and osteoconductivity, but they generally have mechanical defects such as high brittleness, poor toughness, and insufficient fatigue strength, making it difficult to withstand the physiological loads of weight-bearing parts. At the same time, their elastic modulus is still relatively high, and the degradation rate is difficult to match the rate of new bone growth, which may lead to premature fracture of the implant or long-term retention that hinders bone remodeling.

[0003] Polyetheretherketone (PEEK), a semi-crystalline thermoplastic polymer, has an elastic modulus (approximately 3-4 GPa) similar to that of human cortical bone, effectively mitigating stress. It also possesses excellent radiopaqueness and magnetic resonance imaging compatibility, ensuring no impact on postoperative imaging follow-up. Furthermore, PEEK exhibits good chemical resistance, fatigue resistance, and relatively low manufacturing costs. It has already found successful applications in spinal fusion devices, joint prostheses, and other fields. However, PEEK itself is a bioinert material with a lack of surface bioactivity, making it difficult to form strong chemical osseointegration with host bone tissue. This limits its long-term stability and osteoinductive capacity, which has become a major bottleneck for its further widespread application in orthopedics.

[0004] To improve the bioactivity of PEEK, bioceramics are often incorporated into the composite. Current research indicates that calcium silicate (CS) possesses good biodegradability and ion release activity (e.g., Si). 4+ Ca 2+ It can promote cell proliferation, angiogenesis, and osteogenic differentiation, but its degradation rate is too fast and its mechanical strength is insufficient. Hydroxyapatite (HA) is the main inorganic component of human bone tissue. It has excellent osteoconductivity and chemical stability and can directly bond with bone, but it is brittle. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention combines HA and CS with PEEK. CS activates cellular biological responses through controlled ion release, HA provides a stable bone bonding interface, and PEEK acts as the matrix, providing primary mechanical support and structural maintenance. This synergistic effect promises to create a novel bone repair composite material with excellent mechanical compatibility, bioactivity, and long-term stability, thereby systematically addressing multiple clinical challenges such as stress shielding and ion release in metallic materials, the brittleness of inorganic ceramic materials, and the bioinertness of pure PEEK.

[0006] The first aspect of the present invention is to provide a hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material, wherein the composite material uses polyetheretherketone as a continuous matrix, and hydroxyapatite and nano-calcium silicate are uniformly dispersed in the matrix as bioactive phases; the content of each component by mass percentage is: hydroxyapatite 10-20%, nano-calcium silicate 1-10%, polyetheretherketone 70-90%; the aspect ratio of the hydroxyapatite is 1.5-40.

[0007] Preferably, the content of each component is: 12-20% hydroxyapatite, 2-8% nano-calcium silicate, 75-85% polyetheretherketone, and further, 17-20% hydroxyapatite.

[0008] Preferably, the hydroxyapatite is acicular hydroxyapatite with an aspect ratio of 10-40; further, the aspect ratio of the acicular hydroxyapatite is 20-40.

[0009] Preferably, the average particle size of the hydroxyapatite is 4-5 μm.

[0010] Preferably, the average particle size of the polyetheretherketone powder is 45-55 μm.

[0011] Preferably, the average particle size of the calcium silicate powder is 100-500 nm.

[0012] A second aspect of the present invention is to provide a method for preparing the above-mentioned composite material, the method comprising the following steps: Step 1: Raw material pretreatment and mixing: Dry the hydroxyapatite powder, nano calcium silicate powder and polyetheretherketone powder, then place them in a mixing device and mix thoroughly for 0.5-2 hours to obtain a uniform composite powder; Step 2, Compression Molding: The composite powder is loaded into a mold and molded using a compression molding process. The maximum molding temperature is 360-400℃, and the product pressure range is 0.1-0.5MPa. Step 3, Post-processing: Cool and demold the molded blank to obtain the hydroxyapatite-nano calcium silicate-polyether ether ketone composite material.

[0013] Preferably, in step one, the drying is carried out under vacuum conditions, at a temperature of 120-150°C, for 3-6 hours.

[0014] Preferably, in step two, the molding process includes a multi-stage heating and pressurization procedure. Further, the molding process includes a multi-stage heating process from room temperature to the highest molding temperature, and applies different molding pressures at different temperature stages.

[0015] Compared with the prior art, the present invention has the following beneficial effects: PEEK was modified to simultaneously enhance its bioactivity, osseointegration capacity, and mechanical adaptability. A ternary composite material was constructed by introducing hydroxyapatite (HA) and calcium silicate (CS) into the PEEK matrix. First, the introduction of hydroxyapatite provides the composite material with excellent osteoconductivity and chemical stability. As the main inorganic component of human bone, it can directly form a strong chemical bond with the host bone tissue, laying a stable interfacial foundation for bone integration.

[0016] Secondly, the incorporation of calcium silicate significantly enhances the material's bioactivity and metabolic responsiveness. It can undergo controlled degradation in physiological environments, continuously releasing calcium ions (Ca). 2+ ) and silicate ions (SiO4) 4- These ions have been shown to effectively stimulate osteoblast proliferation and differentiation, promote collagen deposition and angiogenesis, thereby endowing materials with active osteoinductive potential.

[0017] Third, PEEK, as a continuous matrix, plays a crucial role in structural support and performance regulation. On the one hand, PEEK itself has an elastic modulus that matches that of human cortical bone, effectively transferring loads and mitigating stress shielding effects, ensuring the overall mechanical compatibility and long-term service reliability of the composite material. On the other hand, the PEEK matrix encapsulates HA and CS particles, preventing the excessively rapid aggregation or degradation of bioactive particles, thereby regulating ion release kinetics and material degradation behavior, making the bioactive effects more durable and controllable.

[0018] Fourth, in natural bone tissue, hydroxyapatite crystals are mainly arranged in an orderly manner in the form of needles or plates within collagen fibers. This structure endows bone with excellent mechanical properties. Therefore, when needle-shaped hydroxyapatite (HA) is used as a reinforcing phase, its microstructure more closely resembles the biomineral morphology of natural bone, providing osteoblasts with a more familiar template for adhesion and growth, thus inducing a better cellular response from a physical morphology perspective. Compared to granular hydroxyapatite, the high aspect ratio hydroxyapatite of this invention has unique advantages in improving mechanical properties. Due to its high aspect ratio, it can form a through-networked reinforcing framework in the matrix through mutual contact and overlap, achieving a qualitative change in the reinforcing phase from "discrete distribution" to "continuous load-bearing." When the material is under stress, this network can efficiently transfer stress from the polymer matrix to the more rigid hydroxyapatite network through a large contact surface, thereby improving the material's mechanical properties. In particular, needle-shaped hydroxyapatite with an aspect ratio of 10-40 has a more significant aspect ratio, making it easier to form a continuous three-dimensional reinforcing network. This can maximize the continuous load-bearing effect, improve stress transmission and dispersion capabilities, effectively avoid stress concentration, and ultimately achieve a decisive improvement in the mechanical properties of composite materials.

[0019] Fifth, the combination of the three components produces a significant synergistic enhancement effect. HA and CS are functionally complementary, promoting osteoogenesis from the perspectives of stable binding and activation, respectively; while PEEK provides support from the perspectives of mechanical load-bearing and structural stability. This ternary system not only significantly improves the bioinertness of the PEEK surface, but also retains its excellent processability, radiation permeability, and fatigue resistance, ultimately resulting in a new generation of orthopedic implant composite material that combines good mechanical properties, promotes osteogenic activity, and has long-term stability.

[0020] This invention introduces a biphasic bioactive component of hydroxyapatite and calcium silicate, which is then combined with a PEEK matrix to synergistically enhance the material's osteointegration capacity. Hydroxyapatite provides a stable osteoconductive interface, while the degradation products of calcium silicate activate cellular bioactivity, together overcoming the bioinertness of pure PEEK.

[0021] The composite material of this invention retains an elastic modulus similar to that of human cortical bone, effectively mitigating stress shielding effects. By optimizing the content and dispersion of active components, it imparts bioactivity while maintaining good mechanical strength, toughness, and fatigue resistance.

[0022] In this invention, the encapsulation of calcium silicate by the PEEK matrix can regulate its degradation rate, avoiding early performance degradation caused by the rapid dissolution of the active phase, thereby ensuring the long-term mechanical stability and biological function durability of the implant in the in vivo environment.

[0023] The molding process used in this invention is mature and controllable, suitable for large-scale preparation of orthopedic implants with complex shapes, and the material is radiopaque, which has significant clinical application value and socio-economic benefits. Detailed Implementation

[0024] Example 1 (I) Materials and Instruments Material: Polyetheretherketone (PEEK) powder with an average particle size of 50 μm.

[0025] Instruments: Vacuum drying oven, molding machine.

[0026] (II) Material Preparation PEEK powder was placed in a vacuum drying oven and dried at 120℃ for 6 hours. The dried powder was then loaded into a mold and placed in a compression molding machine for hot pressing. The molding process parameters were as follows: the temperature was increased to 290℃ at 3℃ / min, a pressure of 0.125MPa was applied and held for 100 minutes; then the temperature was increased to 375℃ at 1.5℃ / min, a pressure of 0.375MPa was applied and held for 60 minutes; subsequently, the temperature was decreased to 270℃ at 5℃ / min, a pressure of 0.375MPa was applied and held for 45 minutes; finally, the temperature was decreased to 180℃ at 1.5℃ / min, a pressure of 0.250MPa was applied and held for 60 minutes; after cooling to room temperature, the mold was removed to obtain pure PEEK sheet.

[0027] (III) Performance Testing and Results Mechanical properties of the material were tested, and the results were used as a benchmark for subsequent comparison of composite material properties (data shown in Table 1).

[0028] Example 2 (I) Materials and Instruments Materials: Polyetheretherketone powder (average particle size 50μm), calcium silicate powder (average particle size 100-500nm).

[0029] Instruments: Same as in Example 1, except for the addition of a ball mill as a mixing device.

[0030] (II) Material Preparation PEEK powder and calcium silicate powder were weighed at a mass ratio of 80:20. The mixed powders were placed in a mixing device and mixed for 2 hours to obtain a uniform composite powder. The subsequent drying and molding processes were the same as in Example 1.

[0031] (III) Performance Testing and Results A series of tests were conducted on the material to evaluate the extent to which the addition of CS alone improved the material's properties (data are shown in Table 1).

[0032] Example 3 (I) Materials and Instruments Materials: Polyetheretherketone powder (average particle size 50 μm), needle-shaped hydroxyapatite powder (average diameter 4.5 μm, aspect ratio 20-40), calcium silicate powder (average particle size 100-500 nm).

[0033] Instruments: Same as in Example 2.

[0034] (II) Material Preparation PEEK powder, needle-shaped HA powder, and CS powder were weighed at a mass ratio of 80:12:8. The three powders were mixed in a mixing device for 2 hours to obtain a uniform composite powder. The composite powder was dried at 120°C for 6 hours and then molded into shape using the same process parameters as in Example 1.

[0035] (III) Performance Testing and Results The material was tested, and its comprehensive performance data are shown in Table 1 below.

[0036] Example 4 The difference between this embodiment and Example 3 is that the hydroxyapatite used is in the form of short rods with an average particle size of 4.5 μm and an aspect ratio of 1.5-3.

[0037] Example 5 The difference between this embodiment and Embodiment 3 is that the mass ratio of each component in the composite material is: PEEK 80%, needle-like HA 15%, and CS 5%.

[0038] Example 6 The difference between this embodiment and Example 5 is that the hydroxyapatite used is in the form of short rods with an average particle size of 4.5 μm and an aspect ratio of 1.5-3.

[0039] Example 7 The difference between this embodiment and Embodiment 3 is that the mass ratio of each component in the composite material is: PEEK 80%, needle-like HA 18%, and CS 2%.

[0040] Example 8 The difference between this embodiment and Example 7 is that the hydroxyapatite used is in the form of short rods with an average particle size of 4.5 μm and an aspect ratio of 1.5-3.

[0041] Performance testing and data analysis The materials prepared in the above embodiments were subjected to uniform testing, and the testing methods are as follows: A three-point bending test was conducted according to standard ISO 178 to test the bending strength and bending modulus of the material.

[0042] Testing instruments: Instron electronic universal testing machine, vernier calipers.

[0043] The bending test employs the simply supported beam method, placing the specimen on two supports and applying a concentrated load at the center of its span, causing it to bend at a constant speed until the specimen breaks or the deformation reaches a predetermined value, thus determining its bending performance. According to national standard GB / T 9341-2008, the three-point loading test (three-point bending test) involves placing a rectangular cross-section specimen across two supports and applying a load to the specimen using a loading head, with the point of application of the loading head equidistant from the two supports.

[0044] Under bending load, the specimen will undergo bending deformation. The distance by which the top or bottom surface of the specimen deviates from its original position after deformation is called deflection *s*, measured in mm. The deflection of the specimen increases with increasing load. Bending strength σ f It is the maximum bending stress that the specimen withstands during the bending process, expressed in MPa, and is calculated by the following formula: ; In the formula, F is the maximum applied load (N); L is the span of the specimen (mm); b and h are the width and thickness of the specimen (mm), respectively. The core data of the test results are summarized in Table 1.

[0045] Table 1. Flexural modulus of the materials used in each embodiment

[0046] The experimental data clearly show that the elastic modulus of the polyetheretherketone (PEEK)-based composite material with the addition of inorganic components hydroxyapatite (HA) and nano-calcium silicate (CS) is significantly higher than that of the pure PEEK matrix material without inorganic components (Example 1). This reinforcing effect follows the classical mixing law principle of composite material mechanics. The microscopic mechanism is that the high-modulus inorganic dispersed phase forms a stress-bearing skeleton in the polymer matrix. When the material is under load, the stress is effectively transferred from the low-modulus PEEK matrix to the high-modulus inorganic particles through the two-phase interface, thereby macroscopically inhibiting the slippage and deformation of polymer molecular chains and improving the overall stiffness of the composite material. Furthermore, in the system containing HA as an inorganic filler, the elastic modulus of the composite material increases with the gradual increase of the HA mass fraction. This experimental phenomenon indicates that increasing the hydroxyapatite content can effectively enhance the stiffness of the PEEK-based composite material and significantly improve its elastic deformation capacity.

[0047] Simultaneously, it can be observed that the elastic modulus of PEEK composites modified with needle-shaped HA as inorganic filler is significantly higher than that of PEEK composites modified with short rod-shaped HA. Compared to short rod-shaped particles with low aspect ratios, needle-shaped hydroxyapatite exhibits superior reinforcing performance due to its extremely high aspect ratio. This advantage is realized during the hot pressing process: the molten PEEK matrix encapsulates and impregnates the needle-shaped hydroxyapatite particles. Under the action of melt flow and shearing, the slender particles are more likely to orient and make contact and bridge with each other, assembling in situ in three-dimensional space to form a continuous, penetrating rigid inorganic network structure. On the one hand, the network generates a strong physical interlock with the matrix through its huge specific surface area, constraining the movement of PEEK molecular chains; on the other hand, it establishes an efficient micro-stress transmission path, allowing external loads to be quickly dispersed to the entire high-modulus skeleton through interfacial shear stress.

[0048] From the perspective of adapting biomedical materials to the mechanical properties of human bone, pure PEEK material has a low elastic modulus and poor compatibility with the mechanical properties of human bone tissue. Direct application in bone repair and replacement can easily lead to stress shielding effects, resulting in bone atrophy and implant loosening. However, this study, by controlling the mass fraction of HA, achieved precise and controllable adjustment of the elastic modulus of the PEEK / HA / CS composite material. This helps reduce the modulus mismatch between the implant material and bone tissue, minimizes the stress shielding effect, and promotes osseointegration and long-term implant stability. Therefore, it provides an important basis for designing orthopedic implant materials with better biocompatibility with human bone.

Claims

1. A hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material, characterized in that: The matrix is ​​polyetheretherketone (PEEK) as a continuous matrix, and hydroxyapatite and nano-calcium silicate are uniformly dispersed in the matrix as bioactive phases. The content of each component by mass percentage is: hydroxyapatite 10-20%, nano-calcium silicate 1-10%, and PEEK 70-90%. The aspect ratio of the hydroxyapatite is 1.5-40.

2. The hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 1, characterized in that: Hydroxyapatite 12-20%, nano-calcium silicate 2-8%, polyetheretherketone 75-85%.

3. The hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 2, characterized in that: Hydroxyapatite 17-20%.

4. The hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 1, characterized in that: The needle-shaped hydroxyapatite is needle-shaped hydroxyapatite with an aspect ratio of 10-40.

5. The hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 4, characterized in that: The aspect ratio of the needle-like hydroxyapatite is 20-40.

6. The hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 1, characterized in that: The average particle size of the hydroxyapatite is 4-5 μm; the average particle size of the polyetheretherketone powder is 45-55 μm; and the average particle size of the calcium silicate powder is 100-500 nm.

7. A method for preparing the hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material according to claim 1, characterized in that: Includes the following steps: Step 1: Raw material pretreatment and mixing: Dry the hydroxyapatite powder, nano calcium silicate powder and polyetheretherketone powder, then place them in a mixing device and mix thoroughly for 0.5-2 hours to obtain a uniform composite powder; Step 2, Compression Molding: The composite powder is loaded into a mold and molded using a compression molding process. The maximum molding temperature is 360-400℃, and the product pressure range is 0.1-0.5MPa. Step 3, Post-processing: Cool and demold the molded blank to obtain the hydroxyapatite-nano calcium silicate-polyether ether ketone composite material.

8. The method for preparing the hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 7, characterized in that: The molding process includes multiple stages of heating and pressurization.

9. The method for preparing the hydroxyapatite-nano-calcium silicate-polyetheretherketone composite material as described in claim 8, characterized in that: The compression molding process includes a multi-stage heating process from room temperature to the highest molding temperature, and different molding pressures are applied at different temperature stages.

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