Modified PTFE sliding block material with ultralow friction coefficient and preparation method thereof

Abstract

The invention discloses a modified PTFE sliding block material with an ultralow friction coefficient and a preparation method of the modified PTFE sliding block material, and belongs to the technical field of building shock insulation support materials.The PTFE sliding block is prepared from 70-80 parts of PTFE resin, 5-10 parts of polyphenylene sulfide, 3-8 parts of polyether-ether-ketone, 1-3 parts of polyimide, 2-5 parts of silicon dioxide, 1-5 parts of carbon fibers and 1-2 parts of graphite. According to the invention, a plurality of high-performance fillers are scientifically proportioned and synergistically act with a PTFE matrix, so that the friction coefficient of the sliding block is as low as 0.01-0.07, the wear rate of the sliding block is reduced by 30-50% compared with that of pure PTFE, meanwhile, the sliding block has excellent mechanical strength, creep resistance and high and low temperature resistance, the preparation process is simple and controllable, complex equipment is not needed, and the preparation method is suitable for industrial production. The PTFE sliding block is simple in preparation process, suitable for large-scale industrial production, capable of being widely applied to shock insulation support scenes such as bridges and buildings, capable of solving the technical problems that an existing PTFE sliding block is prone to creep deformation and high in abrasion rate and friction coefficient, and has important application value and market prospects.

Description

Technical Field

[0001] This invention relates to the field of building seismic isolation bearing materials, and in particular to a modified PTFE slider material with an ultra-low friction coefficient and its preparation method. Background Technology

[0002] In the field of engineering construction, friction pendulum seismic isolation bearings are widely used in large-scale engineering structures such as bridges and high-rise buildings as important seismic resistance and disaster reduction components. Their working environment is usually below 25MPa and the sliding speed does not exceed 1m / s. In this type of application scenario, the slider is the core functional component of the friction pendulum seismic isolation bearing, and its performance directly determines the seismic isolation effect, service life and safety reliability of the bearing. Under the same pressure conditions, the higher the pressure bearing capacity of the slider, the smaller the volume of the bearing-related connecting parts, which can significantly reduce the overall cost of engineering construction. Therefore, the development of high-performance slider materials has important engineering significance.

[0003] The performance of slider materials depends primarily on the choice of matrix resin. Currently, polytetrafluoroethylene (PTFE), commonly known as the "King of Plastics," is a commonly used low-friction material in engineering. This material has excellent chemical inertness, corrosion resistance, electrical insulation, and high-temperature resistance. Furthermore, its amorphous portion is extremely easy to slide, making it one of the polymer materials with the lowest coefficient of friction. Therefore, it is widely used as a coating, composite material filler, and friction material. However, the plate-like crystal structure of PTFE is connected by van der Waals forces, resulting in inherent defects in pure PTFE materials, such as high wear rate and easy creep during friction. It is also prone to deformation during long-term use, making it difficult to meet the requirements of engineering fields for the long-term stability and durability of slider materials, thus limiting its application in high-end seismic isolation bearings.

[0004] To fully leverage the inherent advantages of PTFE materials and compensate for their inherent defects, the industry commonly employs composite modification of PTFE by adding modified fillers. Through the synergistic effect of different materials, the friction coefficient of PTFE is reduced, its wear resistance is improved, and its overall performance is enhanced. Various PTFE modification schemes have emerged in existing technologies. For example, Tianjin University of Technology, in its research paper "Preparation and Performance Study of Modified Polytetrafluoroethylene Composites," disclosed a technique for modifying PTFE by adding carbon nanofibers and polyphenylene ester. This technique improves the interfacial bonding force between different components through silanization of CF, or forms chemical bonds between the fibers and the matrix through fluorination, thereby creating a cross-linked network. This achieves the effects of improving the mechanical properties and thermal stability of the composite material, and reducing the friction coefficient and wear rate.

[0005] However, existing modification technologies still have significant shortcomings: on the one hand, the filler modification process is usually quite complex, such as the silanization or fluorination of carbon nanofibers, which involves complicated steps and increases the difficulty and cost of production processes; on the other hand, the friction coefficient and wear index of the modified PTFE composite material still have room for further optimization, making it difficult to meet the requirements of high-end seismic isolation bearings for ultra-low friction and ultra-long service life, thus limiting its large-scale industrial application. Therefore, developing a PTFE-type slider material for building friction pendulum bearings with a reasonable formula, simple process, excellent mechanical properties and ultra-low friction coefficient has become an urgent technical problem to be solved in this field, and has extremely important application significance and market value. Summary of the Invention

[0006] The purpose of this invention is to provide a modified PTFE slider material with an ultra-low coefficient of friction and its preparation method, in order to solve the technical problems of existing PTFE slider materials, such as high coefficient of friction, high wear rate, easy creep, insufficient mechanical strength, and complex modification process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A modified PTFE slider material with an ultra-low coefficient of friction is composed of the following raw materials in parts by weight: 70-80 parts PTFE resin, 5-10 parts polyphenylene sulfide, 3-8 parts polyether ether ketone, 1-3 parts polyimide, 2-5 parts silica, 1-5 parts carbon fiber, and 1-2 parts graphite.

[0008] The selection of raw materials and the design of the formulation in this invention are based on the following scientific principles and performance requirements: PTFE resin: As the matrix material of the composite material, the present invention preferably uses suspended polytetrafluoroethylene resin. This type of resin has the characteristics of uniform particle size and good molding performance, which can provide good basic lubrication performance and chemical stability for the composite material, ensuring the core function of the slider.

[0009] Polyetheretherketone (PEEK): PEEK materials themselves possess excellent self-lubricating properties, wear resistance, mechanical properties, thermal stability, and chemical inertness. When added to the PTFE matrix as a dispersed phase, it can play a dual role: First, it provides high strength and rigidity support, effectively dispersing external forces through the skeletal effect, inhibiting the breakage of PTFE carbon chains and interlayer slippage, and preventing local deformation or breakage of the slider under stress; Second, its toughness and the lubricity of PTFE form a synergistic effect, significantly reducing the wear rate of the composite material.

[0010] Carbon fiber: As a reinforcing phase dispersed in the PTFE matrix, it restricts the slippage of PTFE molecular chains through physical cross-linking, thereby improving the structural stability of the material. At the same time, carbon fiber has high thermal conductivity, which helps to quickly disperse frictional heat during friction and avoid the deterioration of material performance caused by local high temperature. In addition, the high modulus of carbon fiber can effectively improve the creep resistance of PTFE material, ensuring that the slider maintains good dimensional stability under long-term load or high temperature environment.

[0011] Silica: The present invention preferably uses spherical nano-silica, which plays a dual role in composite materials: on the one hand, it acts as a support, improving the load-bearing capacity and rigidity of the composite material, reducing the deformation under external force, and enhancing the resistance to plastic deformation; on the other hand, on the friction mating surface, spherical nano-silica is conducive to promoting the formation of the transfer film and can make the surface of the transfer film smoother, thereby further reducing the coefficient of friction; in particular, the present invention adds spherical nano-silica to the composite material to reduce the roughness of the relative surface, achieving a dual reduction in the coefficient of friction and wear, and the spherical nano-silica acts as a "ball bearing".

[0012] Polyphenylene sulfide (PPS) materials are characterized by good dimensional stability, high mechanical strength, and excellent thermal stability. The rigid chain structure composed of sulfide bonds and benzene rings in its molecular structure can play a role in fixing the skeleton of the composite material and enhancing the overall strength of the material. During friction, PPS can effectively resist and support the load, and improve the plastic deformation resistance of PTFE molecular chains and the plastic flowability under harsh working conditions.

[0013] Polyimide (PI) materials have excellent wear resistance and low surface energy properties. During friction, they can enhance the bonding strength between the PTFE transfer film and the mating surface, effectively reduce the coefficient of friction and wear rate, and ensure that the composite material maintains stable performance under dry friction or high load conditions.

[0014] Graphite: Graphite has a typical layered structure. During friction, its layered slippage can quickly form an initial lubricating film, significantly shortening the break-in period of the slider. Meanwhile, the low surface energy of PTFE can enhance the stability and durability of the transfer film. The synergistic effect of the two further optimizes the lubrication effect of the composite material.

[0015] The preparation method of the modified PTFE slider with ultra-low friction coefficient described in this invention includes four steps: pretreatment, dispersion and stirring, molding, and sintering. The process parameters of each step have been repeatedly optimized to ensure stable and controllable material properties. The specific steps are as follows: Step 1, Pretreatment: Place PTFE resin, polyphenylene sulfide, polyether ether ketone, polyimide, silica, carbon fiber, and graphite in a drying equipment for drying. The drying temperature is controlled at 80-120℃ and the drying time is 2-4 hours to completely remove moisture from the raw materials and avoid moisture affecting the dispersion effect of the raw materials and the final material properties. Step 2: Dispersion and stirring. According to the above weight ratio, add all the pretreated raw materials into a high-speed mixer, control the stirring temperature at 15℃, the stirring speed at 300-800 r / min, and the stirring time at 30-90 minutes to ensure that all raw materials are fully and evenly mixed and improve the compositional uniformity of the composite material. Step 3, molding: The uniformly mixed material is added into a high-precision mold and cold-pressed. The molding pressure is controlled at 15-30MPa and the holding time is 10-30 minutes. The blank is obtained by pressing. This process can ensure that the blank has good surface quality and dimensional accuracy. Step 4, sintering: The molded blank is placed in a sintering furnace and sintered by slowly heating at a rate of 5-10℃ / min. The sintering temperature is 360-380℃, and the holding time is 2-4 hours. Then, it is naturally cooled to room temperature to obtain the modified PTFE slider product. The slow heating sintering method can effectively avoid the decomposition of PTFE resin and ensure that a strong bond is formed between various fillers and the PTFE matrix, thus ensuring the comprehensive performance of the material.

[0016] Compared with the prior art, the present invention has the following features and beneficial effects: This invention utilizes the synergistic lubrication effect of carbon fiber, silica, and polyetheretherketone (PEEK), combined with the initial lubricating film formation characteristics of graphite and the reinforcing effect of polyimide on the transfer film, to achieve a modified PTFE slider with a friction coefficient as low as 0.01-0.07. The wear rate is reduced by 30%-50% compared to pure PTFE sliders, far superior to pure PTFE sliders and existing modified products on the market. It can adapt to long-term use requirements in different environments, significantly extending the service life of seismic isolation bearings. The extremely low friction coefficient and significantly reduced wear rate further enhance the modified PTFE slider. The prepared modified PTFE slider not only retains the original high and low temperature resistance, chemical stability, and chemical corrosion resistance of PTFE material, but also significantly improves the material's hardness, mechanical strength, and creep resistance through the synergistic effect of fillers such as PEEK, carbon fiber, and polyphenylene sulfide. It maintains good dimensional stability and structural integrity under long-term loads or complex working conditions. This invention effectively solves the problems of easy deformation and poor stability of traditional PTFE sliders, exhibiting excellent comprehensive performance and strong stability. Through precise optimization of the selection and weight ratio of various raw materials, a complementary and synergistic mechanism is formed between the PTFE matrix and various fillers, resulting in a dense internal structure, stable mechanical properties, and performance indicators that meet the requirements of seismic isolation bearings for different types of buildings. The preparation process includes only four core steps: pretreatment, dispersion and mixing, molding, and sintering. It does not require complex raw material pretreatment processes or special equipment. The process steps are clear, parameters are easy to adjust, and production costs are moderate, enabling large-scale industrial production. This meets the large-scale demand for slider materials in the engineering field. The process is simple and controllable, suitable for large-scale production, and has significant economic and social value. It has good promotion and practical value, and its widespread application will generate good economic benefits. Detailed Implementation

[0017] To make the technical means, innovative features, objectives and effects of this invention easier to understand, the invention will be further described below.

[0018] The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the invention, and are illustrative and exemplary, and should not be construed as limiting the implementation or scope of the invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0019] This invention discloses a modified PTFE slider material with an ultra-low coefficient of friction, composed of the following raw materials in parts by weight: 70-80 parts PTFE resin, 5-10 parts polyphenylene sulfide, 3-8 parts polyetheretherketone, 1-3 parts polyimide, 2-5 parts silica, 1-5 parts carbon fiber, and 1-2 parts graphite. The PTFE resin is a suspension polytetrafluoroethylene resin, and the silica is spherical nano-silica. The PTFE slider can adopt a disc-shaped, rectangular, or polygonal structure, with chamfered or rounded edges to reduce stress concentration and prevent edge wear or cracking during reciprocating sliding. The working surface of the PTFE slider can be designed as a micro-groove or micro-protrusion array to store lubricating medium or debris, further improving lubrication and wear resistance. Metal inserts or reinforcing mesh can be pre-embedded inside the PTFE slider to improve overall load-bearing capacity and impact resistance, while facilitating connection with other components of the support. It can be designed using functionally graded materials.

[0020] A method for preparing a modified PTFE slider material with ultra-low friction coefficient includes four steps: pretreatment, dispersion and stirring, molding, and sintering. The specific steps are as follows: Step 1, Pretreatment: Dry all raw materials to remove moisture; Step 2: Disperse and stir, controlling the temperature and speed, to fully mix the pretreated raw materials evenly; Step 3, molding: using cold pressing molding process, with the help of high-precision molds to press and shape the blank; Step 4, sintering: Sintering is carried out by slow heating to ensure that the filler and PTFE matrix are fully bonded.

[0021] In the pretreatment step, the drying temperature is 80-120℃ and the drying time is 2-4 hours. In the dispersion and stirring step, the stirring temperature is 15℃, the stirring speed is 300-800 r / min, and the stirring time is 30-90 minutes. In the molding step, the molding pressure is 15-30 MPa and the holding time is 10-30 minutes. In the sintering step, the heating rate is 5-10℃ / min, the sintering temperature is 360-380℃, and the holding time is 2-4 hours, followed by natural cooling to room temperature.

[0022] Example 1 A modified PTFE slider material with an ultra-low coefficient of friction has the following raw material weight ratio: 70 parts PTFE resin, 5 parts polyphenylene sulfide, 3 parts polyether ether ketone, 1 part polyimide, 2 parts silica, 1 part carbon fiber, and 1 part graphite.

[0023] Preparation method: (1) Pretreatment: Place each raw material in a drying oven at 100℃ and dry for 3 hours to remove moisture; (2) Dispersion and stirring: Add the dried raw material to a high-speed mixer, control the stirring temperature at 15℃, the speed at 500r / min, and the stirring time at 60 minutes to mix evenly; (3) Molding: Add the mixture to a high-precision mold, apply a pressure of 20MPa, hold the pressure for 20 minutes, and cold press to form a blank; (4) Sintering: Place the blank in a sintering furnace, heat it to 370℃ at a rate of 8℃ / min, hold it for 3 hours, and cool it naturally to room temperature to obtain the finished product.

[0024] Example 2 A modified PTFE slider material with an ultra-low coefficient of friction has the following raw material weight ratio: 75 parts PTFE resin, 7 parts polyphenylene sulfide, 5 parts polyether ether ketone, 2 parts polyimide, 3.5 parts silica, 3 parts carbon fiber, and 1.5 parts graphite.

[0025] Preparation method: (1) Pretreatment: Place each raw material in a drying oven at 110℃ and dry for 2.5 hours to remove moisture; (2) Dispersion and stirring: Add the dried raw material to a high-speed mixer, control the stirring temperature at 15℃, the speed at 600r / min, and the stirring time at 70 minutes to mix evenly; (3) Molding: Add the mixture to a high-precision mold, apply a pressure of 25MPa, hold the pressure for 15 minutes, and cold press to form a blank; (4) Sintering: Place the blank in a sintering furnace, heat it to 375℃ at a rate of 7℃ / min, hold it for 3.5 hours, and cool it naturally to room temperature to obtain the finished product.

[0026] Example 3 A modified PTFE slider material with an ultra-low coefficient of friction has the following raw material weight ratio: 80 parts PTFE resin, 10 parts polyphenylene sulfide, 8 parts polyetheretherketone, 3 parts polyimide, 5 parts silica, 5 parts carbon fiber, and 2 parts graphite.

[0027] Preparation method: (1) Pretreatment: Place each raw material in a drying oven at 120℃ and dry for 2 hours to remove moisture; (2) Dispersion and stirring: Add the dried raw material to a high-speed mixer, control the stirring temperature at 15℃, the speed at 800r / min, and the stirring time at 90 minutes to mix evenly; (3) Molding: Add the mixture to a high-precision mold, apply a pressure of 30MPa, hold the pressure for 10 minutes, and cold press to form a blank; (4) Sintering: Place the blank in a sintering furnace, heat it to 380℃ at a rate of 10℃ / min, hold it for 4 hours, and cool it naturally to room temperature to obtain the finished product.

[0028] Example 4 A modified PTFE slider material with an ultra-low coefficient of friction has the following raw material weight ratio: 72 parts PTFE resin, 6 parts polyphenylene sulfide, 4 parts polyetheretherketone, 1.5 parts polyimide, 3 parts silica, 2 parts carbon fiber, and 1.2 parts graphite.

[0029] Preparation method: (1) Pretreatment: Place each raw material in a drying oven at 80℃ and dry for 4 hours to remove moisture; (2) Dispersion and stirring: Add the dried raw material to a high-speed mixer, control the stirring temperature at 15℃, the speed at 300r / min, and the stirring time at 30 minutes to mix evenly; (3) Molding: Add the mixture to a high-precision mold, apply a pressure of 15MPa, hold the pressure for 30 minutes, and cold press to form a blank; (4) Sintering: Place the blank in a sintering furnace, heat it to 360℃ at a rate of 5℃ / min, hold it for 2 hours, and cool it naturally to room temperature to obtain the finished product.

[0030] Example 5 A modified PTFE slider material with an ultra-low coefficient of friction has the following raw material weight ratio: 78 parts PTFE resin, 9 parts polyphenylene sulfide, 7 parts polyether ether ketone, 2.5 parts polyimide, 4 parts silica, 4 parts carbon fiber, and 1.8 parts graphite.

[0031] Preparation method: (1) Pretreatment: Place each raw material in a drying oven at 90℃ and dry for 3.5 hours to remove moisture; (2) Dispersion and stirring: Add the dried raw material to a high-speed mixer, control the stirring temperature at 15℃, the speed at 450r / min, and the stirring time at 50 minutes to mix evenly; (3) Molding: Add the mixture to a high-precision mold, apply a pressure of 18MPa, hold the pressure for 25 minutes, and cold press to form a blank; (4) Sintering: Place the blank in a sintering furnace, heat it to 365℃ at a rate of 6℃ / min, hold it for 2.5 hours, and cool it naturally to room temperature to obtain the finished product.

[0032] Performance testing The modified PTFE sliders prepared in Examples 1-5 above, as well as existing technology products such as pure PTFE sliders and modified PTFE sliders with added carbon nanofibers and polyphenylene ester, were subjected to performance comparison tests. The test items included friction coefficient, wear rate, tensile strength, flexural strength, and creep resistance. The test results are shown in the table below: The test results above show that the modified PTFE sliders prepared in Examples 1-5 of this invention have a friction coefficient reduced to an ultra-low range of 0.01-0.07, and a wear rate reduced by 30%-50% compared to pure PTFE sliders, and significantly lower than existing products. Simultaneously, tensile strength, flexural strength, and creep resistance are all significantly improved, with creep resistance improved by more than 50% compared to existing products, while maintaining the excellent original properties of PTFE material within the operating temperature range. Among these, the formulation and process parameters in Example 2 represent the optimal combination, resulting in the lowest friction coefficient (0.01-0.02) and the lowest wear rate (2.5 × 10⁻⁻⁶). 6 The material exhibits the best mechanical properties and creep resistance (mm³ / (N・m)), fully demonstrating the synergistic effect of the raw material formulation and the advanced nature of the preparation process of this invention.

[0033] The core innovations of this invention are as follows: First, by scientifically proportioning PTFE resin with polyphenylene sulfide, polyether ether ketone, polyimide, carbon fiber, silica, and graphite, a synergistic lubrication and enhancement effect of multiple materials is achieved, significantly reducing the coefficient of friction and wear rate. Second, the addition of spherical nano-silica utilizes the "ball bearing" effect of spherical nano-silica to further optimize friction performance. Third, the preparation process is simplified, eliminating the need for complex filler pretreatment steps and enabling large-scale production.

[0034] The raw material ratios and process parameter ranges described in this invention have been obtained through extensive experimental verification. Exceeding these ranges will lead to a decline in performance: for example, when the PTFE resin content is less than 70 parts, the lubrication performance of the material will be significantly reduced and the coefficient of friction will increase; when it is more than 80 parts, the mechanical strength and creep resistance will be insufficient; when the polyetheretherketone content is less than 3 parts, the skeleton support effect is not obvious, and when it is more than 8 parts, it will lead to a significant increase in material cost and an increase in the coefficient of friction; when the sintering temperature is less than 360°C, the PTFE resin and filler are not firmly bonded, and when it is more than 380°C, the PTFE resin is prone to decomposition, affecting the material performance.

[0035] The modified PTFE slider prepared by this invention can be adapted to the requirements of different types and working conditions of seismic isolation bearings by adjusting the raw material ratio and process parameters according to actual engineering needs, and has wide applicability and promotion value.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified PTFE slider material with an ultra-low coefficient of friction, characterized in that, It is composed of the following raw materials in parts by weight: 70-80 parts PTFE resin, 5-10 parts polyphenylene sulfide, 3-8 parts polyether ether ketone, 1-3 parts polyimide, 2-5 parts silicon dioxide, 1-5 parts carbon fiber, and 1-2 parts graphite.

2. The modified PTFE slider material with an ultra-low coefficient of friction according to claim 1, characterized in that, The PTFE resin is a suspension polytetrafluoroethylene resin.

3. The modified PTFE slider material with an ultra-low coefficient of friction according to claim 1, characterized in that, The raw material weight ratio is as follows: 72-78 parts PTFE resin, 6-9 parts polyphenylene sulfide, 4-7 parts polyether ether ketone, 1.5-2.5 parts polyimide, 3-4 parts silicon dioxide, 2-4 parts carbon fiber, and 1.2-1.8 parts graphite.

4. The modified PTFE slider material with an ultra-low coefficient of friction according to claim 1, characterized in that, The raw material weight ratio is as follows: 75 parts PTFE resin, 7 parts polyphenylene sulfide, 5 parts polyether ether ketone, 2 parts polyimide, 3.5 parts silicon dioxide, 3 parts carbon fiber, and 1.5 parts graphite.

5. The modified PTFE slider material with an ultra-low coefficient of friction according to claim 1, characterized in that, The silica is spherical nano-silica.

6. A method for preparing a modified PTFE slider material with an ultra-low coefficient of friction according to any one of claims 1 to 5, characterized in that, The process includes four steps: pretreatment, dispersion and mixing, molding, and sintering. The specific steps are as follows: Step 1, Pretreatment: Dry all raw materials to remove moisture; Step 2: Disperse and stir, controlling the temperature and speed, to fully mix the pretreated raw materials evenly; Step 3, molding: using cold pressing molding process, with the help of high-precision molds to press and shape the blank; Step 4, sintering: Sintering is carried out by slow heating to ensure that the filler and PTFE matrix are fully bonded.

7. The method for preparing a modified PTFE slider material with an ultra-low coefficient of friction according to claim 6, characterized in that, In the pretreatment step, the drying temperature is 80-120℃ and the drying time is 2-4 hours. In the dispersion and stirring step, the stirring temperature is 15℃, the stirring speed is 300-800 r / min, and the stirring time is 30-90 minutes.

8. The method for preparing a modified PTFE slider material with an ultra-low coefficient of friction according to claim 6, characterized in that, In the molding step, the molding pressure is 15-30 MPa, and the holding time is 10-30 minutes.

9. The method for preparing a modified PTFE slider material with an ultra-low coefficient of friction according to claim 6, characterized in that, In the sintering step, the heating rate is 5-10℃ / min, the sintering temperature is 360-380℃, the holding time is 2-4 hours, and then it is naturally cooled to room temperature.

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