Modified polyether-ether-ketone resin composite material as well as preparation method and application thereof

Abstract

The invention provides a modified polyether-ether-ketone resin composite material as well as a preparation method and application thereof, and belongs to the field of high-molecular polymer materials. The modified polyether-ether-ketone resin / glass fiber composite material with a continuous chemical gradient interface is prepared through the interface bonding design of the polyether-ether-ketone oligomer containing the phenylacetylene functional group, the respective plasticizing and co-extrusion composite process and the reverse gradient structure design with the hard outside and the tough inside; the composite material is used for a high-performance robot exoskeleton device, and the problems that the strength and toughness of a traditional composite material are difficult to maximize at the same time, layers of a multi-layer or gradient material are easy to strip and lose efficacy, and a high-performance complex component is tedious in preparation process and low in efficiency are solved. The composite material provided by the invention has excellent mechanical properties and anti-aging and anti-fatigue properties, shows certain heat resistance during high-temperature heating, and shows great application potential in the field of high-end medical devices.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a modified polyether ether ketone resin composite material, its preparation method, and its application. Background Technology

[0002] Polyetheretherketone (PEEK), as a high-performance thermoplastic resin with excellent comprehensive properties, has shown great application potential in high-end fields such as aerospace, automotive, and medical devices. Preparing composite materials using PEEK as the matrix and glass fiber or similar reinforcing phases is a mainstream approach to further improve its mechanical properties. However, its inherent high chemical inertness and high melt viscosity lead to poor interfacial bonding with reinforcing fibers, and traditional processing methods struggle to ensure both strength and toughness, let alone create an internal performance gradient. This severely restricts its application in advanced scenarios such as complex working conditions and biomimetic structures.

[0003] To improve the overall performance of PEEK composite materials, existing technologies have been improved from different perspectives. CN121271207A discloses a light-resistant polyether ether ketone composite material and its preparation method. By adding specific light stabilizers and optimizing the processing technology, the yellowing and degradation of the material under ultraviolet light are suppressed to meet the needs of long-term exposure scenarios. This preparation method, which solves the weather resistance problem of the material surface through physical blending and conventional molding processes, can only address the change of a single property. It does not take into account the interface problem between the reinforcement and the matrix in the composite material, and it cannot improve its mechanical properties. CN121136142A discloses a quartz fiber reinforced PEEK resin-based microwave-transparent composite material and its molding method. The method involves layering quartz fiber cloth and PEEK powder, and then molding the composite material using a precise multi-stage heating and pressing molding process. By optimizing the process parameters, the wettability of the high-viscosity PEEK melt on the fiber fabric is improved, thereby enhancing the interlayer bonding and final performance. However, the interfacial bonding relies entirely on the physical wetting of the fiber by the resin melt under high temperature and high pressure and the mechanical interlocking formed by subsequent cooling. It lacks a stronger chemical bonding mechanism. Furthermore, this process mode is essentially a discrete, discontinuous step-by-step operation, which limits production efficiency and consistency, making it difficult to achieve integrated near-net-shape molding of complex structures or long-sized components.

[0004] In summary, achieving high toughness, strong interfacial bonding, and lightweight properties while maintaining the high strength of PEEK composites is key to meeting the demands of high-end applications. By designing a reactive bilayer formulation system, chemical bonding interfaces and gradient structures are constructed in situ during processing, fundamentally improving the overall performance of the material and simultaneously addressing the pain points of traditional composite materials, such as easy delamination between layers, unadjustable properties, and cumbersome processes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a modified polyetheretherketone (PEEK) resin composite material, its preparation method, and its applications. This invention utilizes interfacial bonding design of epoxy-functionalized PEEK oligomers, reconstruction through an independent dual-channel reactive co-extrusion process, and a reverse gradient structure design with an outer hard and inner tough structure to prepare a modified PEEK / glass fiber composite material with a continuous chemical gradient interface. This composite material is then used in high-performance robotic exoskeleton devices, solving the problems of maximizing both strength and toughness simultaneously in traditional composite materials, easy delamination failure between layers in multilayer or gradient materials, and cumbersome and inefficient fabrication processes for high-performance complex components.

[0006] This invention discloses a method for preparing modified polyetheretherketone resin composite materials, such as... Figure 1 As shown, the specific technical solution is as follows: Step 1: Hydroxyl-terminated polyether ether ketone oligomers are synthesized through monomer condensation reaction, and then capped with a capping agent to covalently graft phenylacetylene functional groups to the ends of the oligomer molecular chains, finally obtaining polyether ether ketone oligomers containing phenylacetylene functional groups as interfacial reactants.

[0007] Step 2: After pretreating the glass fiber with a coupling agent, weigh and premix it with polyetheretherketone resin and additives according to the outer shell layer formula and the inner core layer formula, and then perform vacuum drying.

[0008] Step 3: The outer shell layer and inner core layer materials are added to extruder No. 1 and extruder No. 2 for independent melting, plasticizing and homogenization. Each extruder is divided into five areas from the feed port to the die head to obtain the shell layer melt and the core layer melt. The shell layer melt and the core layer melt are accurately measured and then introduced into a co-extrusion die head, where they are combined to form a composite melt slab with a shell layer enclosing the core layer structure.

[0009] Step 4: The composite melt slab is calendered and uniformly cooled and shaped using a three-roll calender; then the shaped slab is annealed and cooled to room temperature to obtain the modified polyether ether ketone resin composite material.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By optimizing the fiber content design of the outer shell layer and adding high-toughness polymers to the inner core layer, combined with the covalent bond interface layer formed by in-situ click chemical reaction, a continuous performance transition from hard to tough is achieved from the outside to the inside of the material. This structure enables the outer shell layer to effectively disperse stress when the material is subjected to external impact, while the inner core layer absorbs energy through plastic deformation, thereby significantly improving toughness while maintaining high strength, meeting the dual requirements of the robot exoskeleton for load-bearing components that require both rigid support and impact resistance toughness.

[0011] 2. Introducing epoxy-functionalized polyether ether ketone oligomers allows for in-situ chemical reactions with the inner core material during co-extrusion, forming a stable covalent bond network at the interface. This chemically bonded interface not only significantly improves interlayer bonding strength and effectively prevents peeling failure, but also enables the penetration of components within a limited area, forming a gradient transition region and further alleviating interfacial stress concentration.

[0012] 3. The chemical bonding interface generated by the in-situ chemical reaction integrates the outer shell, gradient layer and inner core into a whole at the molecular scale. This integrated structure prevents abrupt changes or concentrations at the interface when stress is transferred from the high modulus outer shell to the high toughness inner core, thereby greatly suppressing early failure modes such as delamination and debonding. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the preparation process of the modified polyetheretherketone resin composite material of the present invention; Figure 2 This is a schematic diagram of the thermogravimetric curves of the sample in Example 1 of the present invention and the pure polyetheretherketone sample; Figure 3 This is a schematic diagram of the chemical structure of the polyether ether ketone oligomer containing phenylacetylene functional groups synthesized in Example 1 of the present invention; Figure 4 This is a schematic diagram of the infrared spectrum of the polyether ether ketone oligomer containing phenylacetylene functional groups synthesized in Example 1 of the present invention; Figure 5 This is a scanning electron microscope (SEM) schematic diagram of the cross-section of the composite material prepared in Example 1 of the present invention. Detailed Implementation

[0014] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0015] This invention proposes a method for preparing modified polyetheretherketone resin composite materials, such as... Figure 1 As shown, the specific technical solution is as follows: 1. Preparation of intermediate reactants Hydroxyl-terminated polyether ether ketone (PEEK) oligomer intermediates were prepared by solution polycondensation of specific monomers under a high-temperature inert atmosphere. These intermediates were then reacted with a phenylacetylene-containing acyl chloride compound in a polar aprotic solvent. After the reaction, the mixture was precipitated, separated, and dried to obtain the phenylacetylene-functionalized PEEK oligomer. The main chain chemical structure of this oligomer is completely identical to that of the composite matrix PEEK resin. This molecular structural identity ensures ideal thermodynamic compatibility between the oligomer and the matrix resin, enabling uniform dispersion and miscibility at the molecular level during subsequent melt blending without phase separation. This guarantees that the oligomer can be uniformly distributed within the outer shell resin phase. The phenylacetylene functional groups grafted to the ends of the oligomer molecular chains possess a highly conjugated rigid structure. This structure endows it with excellent thermal stability, allowing it to maintain the integrity of its chemical structure for extended periods without significant decomposition under the high-temperature conditions required for PEEK resin processing. Simultaneously, the phenylacetylene group can be activated under specific thermal conditions, undergoing a highly efficient click chemistry reaction characterized by rapid rate, high selectivity, and few side reactions. This allows it to form strong covalent bonds with functional groups such as amino groups, enabling the construction of a robust chemical bonding network between the shell and core layers of the composite material. This oligomer molecule also acts as a molecular bridge connecting the outer shell and inner core layer. One end is firmly anchored in the outer shell layer through the high compatibility with the resin matrix, which has a completely identical chemical structure, while the other end chemically bonds with the active reaction sites in the inner core layer during processing via the terminal phenylacetylene functional group, thereby strengthening the interface between the two phases.

[0016] 2. Raw material pretreatment and core layer preparation The reinforcing fibers were surface-treated with a silane coupling agent. Then, polyetheretherketone resin, the treated glass fibers, and other additives were weighed and premixed according to two formulations: one for the outer shell layer and the other for the inner core layer, followed by vacuum drying. The glass fibers were treated with an aminosilane coupling agent. The alkoxy group at one end of the molecule hydrolyzed and condensed with the silanol groups on the fiber surface, forming a strong Si-O-Si covalent bond. The amino group at the other end was introduced into the fiber surface. This process not only significantly improved the wettability and physical bonding between the hydrophilic glass fibers and the hydrophobic polyetheretherketone matrix, but also introduced highly reactive amino functional groups in situ onto the fiber surface. These amino groups can become active sites for chemical reactions with specific components in the outer shell layer during subsequent high-temperature melt co-extrusion, thus transforming the fiber from a simple physical reinforcement into a potential interfacial reaction participant. This achieves a synergistic active design from the microscopic fiber / resin interface to the macroscopic shell / core layer interface. The outer shell layer formulation uses polyetheretherketone (PEEK) resin as the matrix, incorporating a high proportion of surface-treated chopped glass fibers, along with PEEK oligomers containing phenylacetylene functional groups and small amounts of lubricants and antioxidants. The inner core layer formulation uses PEEK resin as the matrix, with a significantly reduced proportion of glass fibers, and introduces a larger proportion of polyethersulfone and polyaryletherketone (PAEK) block copolymers and appropriate additives. The outer shell layer relies on its high fiber content to provide stiffness and strength, while the inner core layer relies on toughening polymers to dissipate energy. The interfacial reactant in the outer shell layer acts as a connector between the two layers. The toughening copolymer in the inner core layer has moderate compatibility with the PEEK matrix, enabling it to form a micro-phase separation structure within the matrix, inducing crazes and shear bands under stress to enhance toughness. Because the melt viscosity of the outer shell layer increases with high fiber content, it is controlled within a certain range through formulation adjustments to ensure that the rheological behavior of the outer shell layer and the inner core layer materials in the molten state matches each other. This ensures that the two melt layers can flow synergistically and composite stably during co-extrusion. All raw materials must be thoroughly dried to remove moisture before mixing, as trace amounts of moisture can cause resin hydrolysis and degradation at high temperatures and may interfere with interfacial chemical reactions. The premixing process ensures the initial uniform distribution of various components in the resin, avoiding processing or performance defects caused by local aggregation. Since PEEK resin is extremely sensitive to moisture, trace amounts of residual moisture can trigger resin hydrolysis and degradation at processing temperatures above 300°C, leading to a decrease in molecular weight and severely deteriorating the mechanical properties of the matrix. At the same time, moisture can also interfere with or even inhibit the predetermined interfacial chemical reaction between epoxy functional groups and active groups such as amino groups. Therefore, it is necessary to reduce the moisture content of the materials to an extremely low level through thorough vacuum drying, thereby ensuring stable melt rheological properties, efficient interfacial chemical reactions, and consistent performance of the final product.

[0017] 3. Dual-channel co-extrusion and confined interface reaction After the outer shell and inner core materials are melted and plasticized separately, a composite melt slab is obtained through a co-extrusion die. Because the outer shell contains a high proportion of glass fiber, its plasticization process requires a high energy input to achieve full resin melting and effective wetting and dispersion of the fibers. Conversely, the inner core contains a large proportion of toughening copolymers, requiring relatively mild shear and heating conditions to form a microstructure conducive to toughness expression. Separate processing of the two materials is employed using independent equipment to obtain uniform and stable melts. The outer shell melt exhibits higher viscosity due to its high fiber content, while the inner core melt has lower viscosity due to its large amount of toughening copolymers. Therefore, before the melts enter the die, a minimum confluence angle design and throttling control of the core layer flow channel are used to ensure that the two melts meet at a matched flow rate in the die confluence area. The high-viscosity outer shell melt smoothly envelops the inner core melt from both sides, forming a stable laminar enveloping structure. The temperature of the die head provides activation energy for the interfacial reaction. The polyether ether ketone oligomer containing phenylacetylene functional groups in the outer shell melt is activated at the confluence interface and undergoes a click chemical reaction with the amino groups on the surface of the inner core glass fiber. The reaction is strictly confined to the micro-region where the two phase melts are in direct contact. A three-dimensional network connected by covalent bonds is rapidly formed at the interface. This chemically bonded network firmly anchors the two melt layers at the molecular scale. Subsequently, the composite melt flows through the flat shaping section of the die head. The melt experiences very little shear force at this stage and is mainly transported forward in a laminar flow manner. The thermal motion of the polymer molecular chains near the interface allows some components of the shell and core layers to diffuse across the initial interface in a limited manner. The diffusion is limited by the formed chemical cross-linking network and the thermodynamic compatibility of the two components themselves. Finally, an interpenetrating transition layer with a continuous gradient of component concentration and structure is formed in the interfacial region.

[0018] 4. Gradient cooling and stress relaxation shaping After uniform cooling and shaping in a calender, the composite melt slab is annealed and then cooled to room temperature to obtain a modified polyether ether ketone (PEEK) composite material. The calender rollers apply pressure to the slab to ensure uniform thickness and a smooth surface. Heat is conducted through the contact between the rollers and the slab, causing it to cool and solidify. A relatively uniform cooling rate transforms the entire slab from a molten state to a solid state. A fixed die is used to form the shell-core structure, preventing deformation of the melt due to its own weight or stress relaxation. The interior of the initially shaped slab is not yet stable. The shearing and stretching flow of the melt in the flow channel causes the polymer molecular chains to orient. The volume shrinkage accompanying the cooling of the material from a high-temperature melt to a solid generates shrinkage stress. The different shrinkage behaviors of the outer shell and inner core layers due to differences in composition and properties also introduce complex shear stresses at the interface. The presence of these residual internal stresses is the root cause of warping, dimensional instability, and even interface debonding or internal cracking in the later stages of product development. Furthermore, the microstructure of the toughening polymer added to the inner core layer also depends on the heating conditions after curing. Therefore, based on the dual objectives of eliminating internal stress and optimizing microstructure, programmed annealing is required for the calendered and shaped sheet material. This allows various internal stresses caused by uneven shrinkage to gradually dissipate through chain segment movement, and also promotes the formation of a better microstructure in the toughening polymer phase of the core layer. This significantly enhances its ability to absorb impact energy by inducing plastic deformation mechanisms such as crazes and shear bands. Annealing also benefits the perfection and stability of the polyetheretherketone matrix's own crystal structure, improving the material's heat resistance and long-term dimensional stability. For interfacial regions constructed through chemical bonding and interpenetrating networks, the thermal environment of annealing enhances the mobility of molecular chain segments at the interface. This not only helps to further stabilize the already formed covalent bonds but also makes the physical entanglement across the interface tighter, thereby improving the interface's durability in complex environments and long-term use. After the annealing process, excessively rapid cooling of the material may reintroduce thermal stress. Therefore, a slow and controlled cooling method is required to uniformly reduce the material from the annealing temperature to room temperature.

[0019] The following are some specific embodiments of the present invention, and Table 1 shows the raw material information used in the embodiments.

[0020] Table 1 Raw Material Information Table

[0021] Example 1 S1: Under nitrogen protection, 218.2 g of 4,4'-difluorobenzophenone, 116.1 g of hydroquinone, 182.0 g of anhydrous potassium carbonate, and 1000 g of diphenyl sulfone were added sequentially to the reactor. The temperature was slowly raised to 180°C and mechanically stirred for 90 min. Then, the system was heated to 320°C for polycondensation reaction and held for 180 min. After the reaction, the viscous system was quickly poured into vigorously stirred deionized water to obtain a strip-shaped or granular crude product. This product was mechanically pulverized and washed five times with deionized water. Then, it was soaked in 1 mol / L hydrochloric acid at 60°C for 60 min, washed again with deionized water until neutral, and then dried in a vacuum drying oven at 100°C for 24 h. 500 g of the dried solid was taken and dissolved in 3000 mL of NMP. 150 mL of triethylamine was added to form a mixed system. 180 g of 4-fluorophenylacetylene was dissolved in 500 mL of NMP. In NMP, under nitrogen protection and an ice-water bath, the mixture was slowly added dropwise to the above mixture while continuously stirring. After the addition was complete, the ice bath was removed, and the reaction system was heated to 80°C and stirred continuously for 6 hours to carry out the end-capping reaction. Subsequently, the reaction solution was poured into a 1:1 mixture of methanol and water to precipitate the product. The solid was collected by filtration and washed three times with methanol. The solid was then placed in a vacuum drying oven and dried at 80°C for 48 hours to obtain a powdered polyether ether ketone oligomer containing phenylethynyl functional groups. Its chemical structure is as follows: Figure 2 As shown.

[0022] S2: Immerse 1000g of chopped glass fibers in a mixed solution of 50g of silane coupling agent KH550 and 950g of ethanol, and treat in a constant temperature water bath at 60℃ for 30min. Then transfer the fibers to a forced-air drying oven and dry at 120℃ for 120min. Weigh out 565g of polyetheretherketone resin, 400g of dried glass fibers, 20g of the oligomer obtained in S1, 3g of polytetrafluoroethylene micro powder, and 2g each of hindered phenolic antioxidant 1076 and phosphite antioxidant 168. As the outer shell layer formulation; weigh 665g of polyetheretherketone resin, 150g of dried glass fiber, 200g of polyethersulfone and polyaryletherketone block copolymer, 3g of polytetrafluoroethylene micro powder, and 2g each of hindered phenolic antioxidant 1076 and phosphite antioxidant 168 as the inner core layer formulation; place each component of the outer shell layer and the inner core layer in a high-speed mixer and premix at 800rpm for 5min, then place them in a vacuum drying oven at 150℃ for 4h and seal for later use.

[0023] S3: The outer shell and inner core layer formulations prepared in S2 are added to twin-screw extruders No. 1 and No. 2 for independent melt plasticization and homogenization. The temperature of extruder No. 1 is set in zones: from zone 1 to zone 5 and the die head, the temperatures are 300℃, 360℃, 380℃, 375℃, 370℃, and 365℃ at the die head, respectively. The temperature of extruder No. 2 is set in zones: from zone 1 to zone 5 and the die head, the temperatures are 300℃, 355℃, 370℃, 365℃, 360℃, and 355℃ at the die head, respectively. The melt output from both extruders is pumped through a gear pump at a shell melt to core melt volume ratio of 6:4 and fed into a co-extrusion die with a 15° confluence angle design, a throttling dam in the core layer flow channel, and a horizontal relaxation zone. The die head temperature is 350℃, and the pressure at the die head front is adjusted to 9MPa to obtain a composite melt slab with a shell layer encapsulating a core layer.

[0024] S4: The composite melt slab is extruded from the die at a speed of 1.2 m / min and directly fed into a three-roll calender for hot calendering and preliminary shaping. The temperature of the upper, middle and lower rollers is set to 200℃. The calendered and shaped slab is placed in a hot air circulating oven and annealed at 220℃ for 6 hours. Then the heating is turned off, and the slab is slowly cooled with the oven to below 60℃ before being taken out and equilibrated in a 25℃ environment for 24 hours to obtain the modified polyether ether ketone resin composite material.

[0025] The phenylacetylene-functionalized polyether ether ketone oligomer prepared by S1 was subjected to infrared spectroscopy in the range of 400–4000 cm⁻¹. The scanning results are as follows: Figure 3 As shown, it can be seen that at 830cm -1 and 860cm -1 The presence of out-of-plane bending vibrations of CH at the corresponding substitution of the benzene ring indicates that the benzene ring is mainly a 1,4-para-substituted structure; at 1225 cm⁻¹ -1 The presence of an asymmetric stretching vibration peak corresponding to an aromatic ether bond nearby indicates that p-xylphenol and 4',4-difluorobenzophenone underwent a successful condensation reaction; at 1495 cm⁻¹ -1 and 1595cm -1 A stretching vibration peak corresponding to the benzene ring skeleton appeared nearby; 1650 cm⁻¹ -1 A stretching vibration peak corresponding to the C=O in the benzophenone structural unit appeared nearby, originating from the PEEK molecular chain; at 2215 cm⁻¹ -1 The presence of stretching vibration peaks corresponding to the carbon-carbon triple bonds nearby indicates that the phenylacetylene group was successfully grafted to the end of the PEEK oligomer; while at 3400 cm⁻¹... -1 The absence of obvious broad peaks nearby indicates that the terminal hydroxyl groups in the raw material intermediate have been completely capped by the acyl chloride and converted into phenylacetylene groups.

[0026] Example 2 The preparation method according to Example 1 differs in that: S1: The polycondensation reaction temperature is 310℃ and the time is 150min. 4-fluorophenylacetylene is replaced with 3-(phenylacetyl)benzoyl chloride. The end-capping reaction temperature is 60℃ and the reaction time is 4h. S2: The temperature of the constant temperature water bath is 50℃, the amount of glass fiber added in the outer shell layer is 300g, the amount of glass fiber added in the inner core layer is 100g, the amount of polyethersulfone and polyaryletherketone block copolymer added is 150g, the amount of polytetrafluoroethylene micro powder added is 2g, and the amount of hindered phenolic antioxidant 1076 and phosphite antioxidant 168 added is 1g each; S3: The second zone of the No. 1 extruder is 370℃, the die head temperature is 360℃, the second zone of the No. 2 extruder is 365℃, the die head temperature is 355℃, the temperature of the co-extrusion die head is 320℃, and the die head pressure is 7MPa; S4: The temperature of the upper, middle and lower rollers is set to 180℃, the annealing temperature is 180℃, the annealing time is 2h, and the other steps are the same.

[0027] Example 3 The preparation method according to Example 1 differs in that: S1: The polycondensation reaction temperature is 330℃ and the time is 210 min. 4-fluorophenylacetylene is replaced with 4-phenylacetylene isocyanate. The end-capping reaction temperature is 90℃ and the reaction time is 8 h. S2: The temperature of the constant temperature water bath is 70℃, the amount of glass fiber added in the outer shell layer is 420g, the amount of glass fiber added in the inner core layer is 200g, the amount of polyethersulfone and polyaryletherketone block copolymer added is 250g, the amount of polytetrafluoroethylene micro powder added is 5g, and the amount of hindered phenolic antioxidant 1076 and phosphite antioxidant 168 added is 5g each; S3: The temperature of the second zone of the No. 1 extruder is 385℃, the die temperature is 375℃, the temperature of the second zone of the No. 2 extruder is 375℃, the die temperature is 365℃, the temperature of the co-extrusion die is 360℃, and the die pressure is 11MPa. S4: The temperature of the upper, middle and lower rollers is set to 220℃, the annealing temperature is 240℃, the annealing time is 8h, and the other steps are the same.

[0028] Example 4 The preparation method according to Example 1 differs in that: S1: Polycondensation reaction temperature is 325℃, time is 200min, end-capping reaction temperature is 75℃, reaction time is 5h; S2: The temperature of the constant temperature water bath is 65℃, the amount of glass fiber added in the outer shell layer is 370g, the amount of glass fiber added in the inner core layer is 140g, the amount of polyethersulfone and polyaryletherketone block copolymer added is 230g, the amount of polytetrafluoroethylene micro powder added is 4g, and the amount of hindered phenolic antioxidant 1076 and phosphite antioxidant 168 added is 4g each. S3: The temperature of the second zone of the No. 1 extruder is 382℃, the die temperature is 372℃, the temperature of the second zone of the No. 2 extruder is 372℃, the die temperature is 362℃, the temperature of the co-extrusion die is 345℃, and the die pressure is 10MPa; S4: The temperature of the upper, middle and lower rollers is set to 205℃, the annealing temperature is 225℃, the annealing time is 7h, and the other steps are the same.

[0029] Comparative Example 1 The preparation method according to Example 1 differs in that: S2: Eliminate the distinction between the outer shell layer and the inner core layer formulation. Weigh 1170g of polyetheretherketone resin, 600g of treated glass fiber, 20g of the oligomer prepared in S1, 200g of polyethersulfone and polyaryletherketone block copolymer, 5g of polytetrafluoroethylene micro powder, 4g each of hindered phenolic antioxidant 1076 and phosphite antioxidant 168, and put all components into a high-speed mixer at once. Premix at 800rpm for 15min, and then vacuum dry at 150℃ for 4h. S3: Feed the dried mixture into the twin-screw extruder from the same feed port at a feeding speed of 10 kg / h. High-shear mixing is carried out throughout the process. The barrel temperature is 370°C throughout the process, and the screw speed is 250 rpm. All other steps are the same.

[0030] This comparative example prepared a polyetheretherketone resin composite material with uniform components and no macroscopic property gradient.

[0031] Comparative Example 2 The preparation method according to Example 1 differs in that: S1: Do not synthesize oligomers containing phenylacetylene groups; S2: Replace the oligomer with an equal amount of polyetheretherketone resin powder, and the remaining steps are the same.

[0032] This comparative example shows a composite material where the outer shell and inner core layers are bonded together by physical interaction rather than by click chemistry.

[0033] Comparative Example 3 The preparation method according to Example 1 differs in that: S2: The outer shell layer formulation and the inner core layer formulation are respectively fed into two identical single-screw extruders and extruded into sheets; S3: The extruded outer shell sheet and inner core sheet are closely aligned and placed together in a hot press mold. They are then hot-pressed at 330℃ and 5MPa for 30 minutes to bond them together. After cooling and demolding, they are annealed. The remaining steps are the same.

[0034] This comparative example was prepared by distributing independent extrusion, followed by secondary hot-pressing bonding assembly of the composite material.

[0035] Experimental Example 1 According to the standard ASTM D638-22 "Test Method for Tensile Properties of Plastics", the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were cut into standard dumbbell shapes of 115mm×19mm×3mm. They were stretched at a rate of 5mm / min using a universal testing machine until the specimens broke. The tensile strength, tensile modulus and elongation at break of the specimens were recorded.

[0036] According to the standard ASTM D790-17 "Test Method for Bending Properties of Unreinforced and Reinforced Plastics and Electrical Insulators", the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were cut into standard rectangles of 127mm × 12.7mm × 3mm. The samples were pressurized with a universal testing machine at a beam displacement rate of 1.3mm / min until the sample broke, and the bending strength and bending modulus were recorded.

[0037] According to the standard ASTM D6110-18 "Charpy Impact Strength Test Method for Notched Plastic Specimens", the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were cut into standard notched Charpy impact specimens of 80mm×10mm×4mm. A V-shaped notch with a depth of 2mm and a notch root radius of 0.25mm was machined at the center of the specimen thickness. A pendulum impact testing machine with a pendulum energy of 5.5J was used to release the pendulum to impact the specimen once. The impact energy absorbed by the specimen at fracture was recorded, and the impact strength was calculated.

[0038] Table 2 Mechanical properties of the examples and comparative samples

[0039] As can be seen from Table 2, the mechanical properties of the example samples are significantly better than those of the comparative samples. Compared with pure PEEK material, the tensile strength, flexural strength and modulus of the example samples are significantly improved, indicating that the effective combination of the gradient structure of the high-fiber outer shell and the high-toughness inner core layer with the chemical interface can endow PEEK-based composite materials with ultra-high rigidity and load-bearing capacity. Comparative Example 1 is a homogeneous composite material with a single formulation and completely uniform blending of all components. Due to the lack of a gradient structure in the sample, although its tensile and flexural strengths are higher than those of pure PEEK due to the overall reinforcement effect of the fibers, its elongation at break is extremely low, and its impact strength is worse than that of pure PEEK. This indicates that this simple physical blending method will impair the ductility of the material to some extent. Comparative Example 2 is a composite material in which there is no click chemical bonding between the outer shell layer and the inner core layer. Since the outer shell layer formulation does not use PEEK oligomers containing phenylacetylene functional groups, the material cannot undergo efficient click chemical reactions at the interface during co-extrusion. Although the gradient distribution is retained inside the sample, the interlayer bonding depends on physical action, and this interface is very fragile under dynamic load, resulting in a significant decrease in the impact resistance of the material. Comparative Example 3 is a composite material obtained by step extrusion followed by secondary hot pressing and bonding and then annealing. Its artificial bonding interface is an obvious weak part, with all mechanical properties being the lowest. This indicates that this secondary bonding process cannot achieve material integration. Its weak interface leads to stress transfer failure, causing the material to preferentially peel off from the bonding layer under stress, resulting in extremely poor mechanical properties.

[0040] Experimental Example 2 According to standard ISO 13003:2003 "Fiber-reinforced plastics—Determination of fatigue properties under cyclic loading", the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were cut into standard rectangles of 127mm × 12.7mm × 3mm and subjected to fatigue testing using a hydraulic servo fatigue testing machine. The test was set to sinusoidal load control mode, stress ratio R = 0.1, test frequency 5Hz, and the maximum stress was set to 50% of the static bending strength of the material in Example 1. Cyclic loading was performed, and the number of cycles experienced by the specimen until complete fracture was recorded.

[0041] According to the standard ASTM D5229 / D5229M-20 "Test Method for Moisture Absorption Properties and Humid / Heat Condition Effects of Polymer-Based Composite Materials", the specimens for mechanical testing in Experiment Example 1 were placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity. The specimens were exposed to this environment for 2 weeks. Then, the specimens were removed and conditioned for 24 hours at 25°C and 50% relative humidity. Subsequently, the tensile, bending and impact properties of the specimens were tested according to the method in Experiment Example 1. The retention rate of each data was calculated to evaluate the material's resistance to humid heat aging.

[0042] Table 3. Durability of the Examples and Comparative Samples

[0043] As shown in Table 3, the fatigue resistance of the sample in the examples is significantly better than that of all the comparative samples, and its strength retention rate after humid heat aging is comparable to that of pure PEEK. This indicates that the gradient interface structure constructed by the phenylacetylene-based click chemical reaction effectively transfers the load and blocks environmental erosion. Comparative Example 1 is a homogeneous composite material with a single formulation and completely uniform blending of all components. It lacks a performance gradient and a strong-toughness synergistic mechanism, resulting in a low fatigue life. In a humid heat environment, moisture easily penetrates uniformly, causing a decline in the overall performance of the material. Comparative Example 2 is a composite material without the aforementioned click chemical bonding between the outer shell layer and the inner core layer. Under cyclic loading, its physical bonding interface becomes a preferential channel for fatigue crack initiation and propagation. At the same time, in a humid heat environment, moisture easily accumulates at the interface, leading to plasticization and loss of bonding force. Therefore, its fatigue resistance and aging resistance are both poor. Comparative Example 3 is a composite material produced by step extrusion, secondary hot pressing bonding, and annealing. Its artificial bonding interface has inherent defects, becoming a focus of stress concentration and moisture erosion under dynamic load and humid heat environment, leading to rapid interface degradation. Therefore, its overall durability is the worst.

[0044] Experimental Example 3 Take 10 mg each of the composite material powder sample obtained in Example 1 and pure PEEK resin powder, and place them in corundum crucibles respectively. Perform thermogravimetric analysis (TGA) in a simultaneous thermal analyzer according to standard ASTM E1131-25, "Standard Test Method for Compositional Analysis of Thermogravimetric Analysis." The test atmosphere is high-purity nitrogen, the flow rate is 50 mL / min, and the temperature is increased at a constant rate of 10 °C / min from 30 °C to 800 °C. Record the curve of sample mass change with temperature. Figure 4 As shown.

[0045] The composite material sample prepared in Example 1 was rapidly fractured after being immersed and frozen in liquid nitrogen, exposing a fresh cross-section. A cut sample was taken along the cross-section, and the fracture surface was sputter-coated with gold before being sent to a field emission scanning electron microscope to observe the microstructure of the cross-section. An accelerating voltage of 10 kV was used. The results are as follows: Figure 5 As shown.

[0046] from Figure 4As can be seen from the thermogravimetric curve of the pure PEEK sample under nitrogen atmosphere, it exhibits a single main weight loss stage, decomposing at around 550℃. The weight loss process is intense and concentrated, with the main mass loss completed within a temperature range of approximately 50℃. The final char residue at around 800℃ is extremely low. This is because PEEK, as a linear thermoplastic polymer, mainly generates volatile small-molecule products during pyrolysis in an inert atmosphere, leaving almost no residue. In contrast, the sample from Example 1 exhibits a broader main weight loss stage with a slightly lower initial decomposition temperature and a slower weight loss rate, maintaining a high char residue of approximately 40% at 800℃. This is due to the thermal decomposition of interfacial oligomers and additives, which shifts the initial decomposition earlier. The high content and uniform dispersion of inert glass fibers act as a physical barrier, effectively hindering heat transfer and the diffusion of pyrolysis products, thereby slowing down the overall decomposition process of the PEEK matrix. The final large amount of residue mainly comes from the glass fibers themselves and a small amount of carbon layer generated by the restricted pyrolysis on the fiber surface, indicating that the material is not easy to continue burning at extreme high temperatures, produces less combustible volatiles during combustion, and has lower flame retardancy and fire risk. At the same time, the physical skeleton function of the glass fiber reinforcement network at high temperatures is preserved, which can prevent the component from catastrophic melting and dripping or overall collapse at high temperatures. This shows that the sample of Example 1 can be well applied to high-end medical devices such as robotic exoskeletons.

[0047] from Figure 5 As can be seen, high-density white rod-shaped objects are visible on the upper and lower sides of the sample, which are short-cut glass fibers dispersed in the PEEK matrix. This region has a high fiber content, with fibers randomly or slightly oriented within the matrix. The high-content rigid glass fiber network provides the composite material with excellent tensile strength and flexural modulus, bearing the main mechanical load and acting as a supporting external skeleton. There are no obvious cracks or sharp phase boundaries between the outer shell and the inner core layer, exhibiting a smooth transition in fiber density from high to low. This is because the phenylacetylene oligomer in the outer shell layer undergoes a click chemical reaction with the amino groups on the surface of the fibers in the inner core layer at high temperature, generating a covalent network in the micro-region where the two-phase melts meet. Excessive diffusion of polymer chains was controlled, preventing component mixing, while achieving strong molecular-level anchoring. This gradient transition layer effectively transferred stress, avoided interlayer delamination, and significantly improved the fatigue resistance of the material. In the inner core layer of the middle region of the sample, the number of glass fibers was significantly reduced, reducing brittleness, and the matrix exhibited a relatively rough microporous or pitted texture. This texture was caused by the added polyethersulfone and polyaryletherketone block copolymer. The copolymer formed a micro-phase separation structure in the PEEK matrix. This structure can induce crazes and shear bands when subjected to impact, effectively dissipating energy and thus giving the material high impact strength. This core layer structure mainly acts as a tough core, preventing rapid crack propagation.

Claims

1. A modified polyetheretherketone resin composite material, characterized in that: The composite material comprises an outer shell layer and an inner core layer; the outer shell layer comprises polyetheretherketone resin, chopped glass fibers treated with an aminosilane coupling agent, polyetheretherketone oligomers containing phenylacetylene functional groups, polytetrafluoroethylene micropowder, hindered phenolic antioxidant 1076, and phosphite antioxidant 168; the inner core layer comprises polyetheretherketone resin, polyethersulfone and polyaryletherketone block copolymer, chopped glass fibers treated with an aminosilane coupling agent, polytetrafluoroethylene micropowder, hindered phenolic antioxidant 1076, and phosphite antioxidant 168; the outer shell layer and the inner core layer form a strong interface with gradient interpenetrating bonding in the interface region through covalent bonds.

2. The modified polyetheretherketone resin composite material according to claim 1, characterized in that: The amount of polytetrafluoroethylene micro powder added is 0.2~0.5wt%; the amount of hindered phenolic antioxidant 1076 and phosphite antioxidant 168 added is 0.1~0.5wt%.

3. The modified polyetheretherketone resin composite material according to claim 1, characterized in that: The composite material has tensile strength and flexural strength both >200 MPa, tensile modulus and flexural modulus both >10 GPa, and fatigue resistance >0.75 × 10⁻⁶. 6 Second-rate.

4. A method for preparing a modified polyetheretherketone resin composite material according to any one of claims 1 to 3, characterized in that, It is prepared according to the following method: S1: Hydroxyl-terminated polyether ether ketone oligomers are synthesized through monomer condensation reaction, and then capped with a capping agent to covalently graft phenylacetylene functional groups to the end of the oligomer molecular chain, finally obtaining a polyether ether ketone oligomer containing phenylacetylene functional groups as an interfacial reactant. S2: After pretreating the glass fiber with a coupling agent, it is weighed and premixed with polyetheretherketone resin and additives according to the outer shell layer formula and the inner core layer formula, and then vacuum dried. S3: The outer shell layer and inner core layer materials are added to extruder No. 1 and extruder No. 2 for independent melting, plasticizing and homogenization. Each extruder is divided into five areas from the feed port to the die head to obtain the shell layer melt and the core layer melt. The shell layer melt and the core layer melt are accurately measured and then introduced into a co-extrusion die head, where they are combined to form a composite melt slab with a shell layer enclosing the core layer structure. S4: The composite melt slab is calendered and uniformly cooled and shaped using a three-roll calender; then the shaped slab is annealed and cooled to room temperature to obtain the modified polyether ether ketone resin composite material.

5. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: The capping agent in S1 is one or more of 4-fluorophenylacetylene, 3-(phenylacetyl)benzoyl chloride, or 4-phenylacetylbenzene isocyanate.

6. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: The polycondensation reaction in S1 is carried out at a temperature of 310~330℃ and a reaction time of 150~210 min; the end-capping reaction is carried out at a temperature of 60~90℃ and a reaction time of 4~8 h.

7. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: The pretreatment temperature of S2 is 50~70℃; the glass fiber content in the outer shell layer formulation is 30~42wt%; the glass fiber content in the inner core layer formulation is 10~20wt%, and the glass fiber content in the inner core layer does not exceed 50% of the glass fiber content in the outer shell layer; the amount of polyethersulfone and polyaryletherketone block copolymer added is 15~25wt%.

8. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: The confluence angle of the two melts in the co-extrusion die described in S3 is ≤15°.

9. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: In the No. 1 extruder, the temperature in the second zone is 370~385℃, and the die temperature is 360~375℃; in the No. 2 extruder, the temperature in the low-temperature zone is 365~375℃, and the die temperature is 355~365℃; the temperature of the co-extrusion die is 320~360℃, and the melt pressure at the front end of the die is 7~11MPa.

10. The method for preparing a polyetheretherketone resin composite material according to claim 4, characterized in that: The temperature of the upper, middle and lower rollers of the three-roll calender described in S4 is 180~220℃, the annealing temperature is 180℃~240℃, and the processing time is 2~8 hours.

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