DESC:

FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
and
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention – A PTFE BASED COMPOSITION FOR REDUCED FRICTION COEFFICIENT AND METHOD OF PREPARATION THEREOF

2. Applicant(s)
(a) NAME: HARSHA ENGINEERS INTERNATIONAL LTD.
(b) NATIONALITY: INDIAN
(c) ADDRESS: SARKEJ-BAVLA ROAD, PO CHANGODAR,
AHMEDABAD- 382213, GUJARAT – INDIA

3. PREAMBLE TO THE DESCRIPTION

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

A PTFE - BASED COMPOSITION FOR REDUCED FRICTION COEFFICIENT AND METHOD OF PREPARATION THEREOF

FIELD OF INVENTION:

The present invention relates to a PTFE - based composition for reduced friction coefficient and method of preparation thereof. Particularly it relates to Polytetrafluoroethylene (PTFE) based composition capable of reducing the friction coefficient with steel surfaces that are under loading conditions and also the method of preparation different compositions.

BACKGROUND OF INVENTION:

Polytetrafluoroethylene (PTFE) has long been valued for its unique combination of properties, including exceptional chemical inertness, low surface energy, and outstanding non-stick and low-friction characteristics. These attributes have led to widespread use of PTFE in diverse applications.

Despite its many advantages, traditional PTFE composition have exhibited limitations, particularly when subjected to high loads or extreme environmental conditions. Under such circumstances, the coefficient of friction of conventional PTFE materials against steel may increase with increase in load and time, leading to diminished performance, increased wear, and reduced operational efficiency of mechanical systems.

Recognizing this challenge, there has been a growing demand for PTFE composition capable of maintaining low friction coefficient even under significant loading conditions.

Moreover, the method of preparing PTFE composition plays a crucial role in determining their performance and effectiveness in reducing the friction with the contacting surfaces. Conventional blending techniques may not always ensure uniform dispersion of additives/secondary phases within the PTFE matrix, leading to inconsistencies in material properties and suboptimal friction-reducing capabilities.

Some inventions use PTFE compositions. The invention disclosed in patent “KR100650819B1” relates to an earthquake isolation support using advanced composite materials. It features a concave spherical surface with a lower curvature radius than traditional designs, formed by convex spheres with matching curvature radii. This design ensures close contact, preventing abrasion and providing damping force. The invention enhances rotational and moving functions required for bridge bearings, improving upon existing steel-based sliding seismic isolation bearings. It leverages the strength differences and light weight of composite materials to improve seismic performance, durability, and usability, while also reducing construction costs by minimizing the cross-section of main structural members.

Another such invention is disclosed in patent “US9790358B2” involves blended fluoropolymer compositions. It describes a method where a liquid dispersion of low molecular weight polytetrafluoroethylene (LPTFE) is blended with a liquid dispersion of a melt-processable fluoropolymer (MPF), such as fluorinated ethylene propylene (FEP). Both polymers are in aqueous dispersions with mean particle sizes of less than 1.0 microns. The blending allows for submicron interaction, forming a true alloy with unique melt characteristics. This blended composition, when dried, results in a coating that offers improved impermeability, stain resistance, abrasion resistance, smoothness, and higher contact angles compared to the individual fluoropolymers.

While numerous prior art references detail various PTFE composition designed to reduce friction coefficient, these existing solutions often fall short when subjected to heavy load applications. Traditional PTFE-based materials typically suffer from increased wear and degradation under substantial pressure, leading to a significant rise in the coefficient of friction and diminished performance over time. For instance, many prior compositions rely on basic PTFE blends that lack the mechanical robustness and durability required to withstand prolonged exposure to high loads. Additionally, conventional preparation methods often fail to ensure the uniform dispersion of reinforcing additives, resulting in composites with inconsistent properties and limited efficacy in demanding environments. As a result, these prior art solutions are unable to maintain their friction-reducing capabilities and structural integrity under heavy load conditions, highlighting the need for a more advanced and reliable PTFE composition and method of preparation.

In response to these challenges, the present invention introduces PTFE composition for reduced friction coefficient, even under high loads and harsh operating conditions. By incorporating carefully selected substances into the PTFE, the composition effectively improves frictional resistance while retaining the desirable attributes of PTFE.

OBJECT OF INVENTION

The principle object of the present invention is to overcome all the mentioned and existed drawbacks of the prior arts by providing PTFE - based composition for reduced friction coefficient and method of preparation thereof.

Another objective of the present invention is to provide a PTFE-based composite material for sliding bearing liners that achieves an optimal balance between low friction characteristics and mechanical strength, enabling reliable performance under demanding operational conditions while maintaining structural integrity under high loads.

Another objective of the present invention is to provide PTFE - based composition to achieve significantly reduced friction coefficients, even when subjected to substantial loading conditions.

Yet another objective of the present invention is to provide PTFE - based composition that maintain their low friction coefficients and structural integrity over prolonged periods of use under high pressure and heavy loads.

Yet another objective of the present invention is to provide PTFE - based composition being capable of providing significantly lesser friction even under high loads.

Yet another objective of the present invention is to provide PTFE - based composition which can be used in the sliding isolation devices for earthquake protection of structures.

Yet another objective is to develop a material composition that incorporates graphene to enhance thermal conductivity and modify tribological properties, improving heat dissipation from the sliding interface and contributing to stable friction performance with reduced thermal degradation during operation.

SUMMARY OF THE INVENTION:

This summary is provided to introduce a selection of concepts in a simplified form that are further disclosed in the detailed description of the invention. This summary is not intended to identify key or essential inventive concepts of the claimed subject matter, nor is it intended for determining the scope of the claimed subject matter.

The present invention is all about PTFE - based composition for reduced friction coefficient and method of preparation thereof.

The main aspect of the present invention is to provide a PTFE-based composite material, wherein the composite material comprises 74.90-97.90% by weight of polytetrafluoroethylene (PTFE), 0.1-25% by weight of glass fibers, and 1-10% by weight of graphene. This composition provides an optimal balance between low friction characteristics and mechanical strength, enabling reliable performance under demanding sliding bearing applications while maintaining structural integrity under high loads.

According to an embodiment, the PTFE-based composite material comprises 95.90-97.90% by weight of PTFE, 0.1-4.10% by weight of glass fibers, and 2-4% by weight of graphene. This high PTFE content formulation achieves superior low-friction performance with minimal reinforcement, resulting in excellent sliding characteristics particularly suitable for high-velocity applications.
According to an embodiment, the composite material exhibits a coefficient of friction of approximately 0.10 at high sliding velocities under axial pressures in the range of 20-30 MPa. This low friction coefficient significantly reduces energy losses and wear during operation, extending bearing service life and improving overall system efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS:

The foregoing summary, as well as the following detailed description of the invention, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, exemplary constructions of the invention are shown in the drawings.

FIG. 1 represents the sectional view of the assembly view of the Single Surface Sliding Bearing with Adaptive Stiffening and Damping Restrainer System with PTFE - based composition for reduced friction coefficient

Fig. 2a and 2b represents the sectional view when the Single Surface Sliding Bearing with Adaptive Stiffening and Damping Restrainer System with PTFE - based composition for reduced friction coefficient is in motion due to an earthquake.

Fig 3 represents the sectional view of the Single Surface Sliding Bearing with Adaptive Stiffening and Damping Restrainer System with PTFE - based composition for reduced friction coefficient as per optional embodiment of the present invention.

Figure A-1 shows force-displacement curves for composite A at 0.24 Hz frequency under cyclic loading conditions.

Figure A-2 shows variation of average coefficient of friction with maximum sliding velocity for composite A at 0.24 Hz frequency.

Figure A-3 shows wear debris of composite A deposited on the concave surface at the end of 90 kN test.

Figure A-4 shows articulated slider of composite A at the end of different stages of progressive loading.

Figure B-1 shows force-displacement curves for composite B at 0.24 Hz frequency under cyclic loading conditions.

Figure B-2 shows variation of average coefficient of friction with maximum sliding velocity for composite B at 0.24 Hz frequency.

Figure B-3 shows wear debris of composite B deposited on the concave surface at the end of 90 kN test.

Figure B-4 shows articulated slider of composite B at the end of different stages of progressive loading.

Figure C-1 shows force-displacement curves for composite D at 0.24 Hz frequency under cyclic loading conditions.

Figure C-2 shows variation of average coefficient of friction with maximum sliding velocity for composite D at 0.24 Hz frequency.

Figure C-3 shows wear debris of composite D deposited on the concave surface at the end of 90 kN test.

Figure C-4 shows articulated slider of composite D at the end of 90 kN test.
Figure D-1 shows force-displacement curves for composite E at 0.24 Hz frequency under cyclic loading conditions.

Figure D-2 shows variation of average coefficient of friction with maximum sliding velocity for composite E at 0.24 Hz frequency.

Figure D-3 shows wear debris of composite E deposited on the concave surface at the end of 90 kN test.

Figure D-4 shows articulated slider of composite E at the end of different stages of progressive loading.

Figure E-1 shows force-displacement curves for composite M at 0.24 Hz frequency under cyclic loading conditions.

Figure E-2 shows variation of average coefficient of friction with maximum sliding velocity for composite M at 0.24 Hz frequency.

Figure E-3 shows articulated slider of composite M at the end of different loading stages.

Figure F-1 shows force-displacement curves for composite N at 0.24 Hz frequency under cyclic loading conditions.

Figure F-2 shows variation of average coefficient of friction with maximum sliding velocity for composite N at 0.24 Hz frequency.

Figure F-3 shows articulated slider of composite N at the end of different progressive loading stages.

Figure G-1 shows force-displacement plots for composite O at 0.24 Hz frequency under cyclic loading conditions.

Figure G-2 shows variation of average coefficient of friction with maximum sliding velocity for composite O at 0.24 Hz frequency.

Figure G-3 shows articulated slider of composite O at the end of different loading stages.

Figure H-1 shows force-displacement plots for composite P at 0.24 Hz frequency under cyclic loading conditions.

Figure H-2 shows variation of average coefficient of friction with maximum sliding velocity for composite P at 0.24 Hz frequency.

Figure H-3 shows articulated slider of composite P at the end of different progressive loading stages.

DETAILED DESCRIPTION OF THE INVENTION:

Detailed method of the present invention are disclosed herein, however, it is to be understood that the disclosed method are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

The objects, features, and advantages of the present invention will now be described in greater detail. Also, the following description includes various specific details and is to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that: without departing from the scope of the present disclosure and its various embodiments there may be any number of changes and modifications described herein.

It must also be noted that as used herein and in the appended claims, the singular forms "a", "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred, systems are now described.

The main embodiment of the present invention is to provide PTFE - based composition for reduced friction coefficient with steel and method of preparation thereof.

Throughout the invention, abbreviate “PTFE” represents Polytetrafluoroethylene.

Throughout the invention, “Article” can be of any shape or size or form, which can be made from the composition of the present invention. The article can be used to reduce the friction between two or more surfaces.

According to the main embodiment of the present invention, PTFE - based composites for reduced friction coefficient comprising 74.90- 97.90% wt. of polytetrafluoroethylene (PTFE), 0.1 – 25% wt. of glass fibers, and 1 - 10% wt. of graphene.

As per detailed embodiment of the present invention, the PTFE - based composition for reduced friction coefficient being capable of having a range of load bearing capacity of 10 MPa – 100 MPa.

As per detailed embodiment of the present invention, said composite material exhibits a coefficient of friction of approximately 0.10 at high sliding velocities under axial pressures in the range of 20-30 MPa.

As per detailed embodiment of the present invention, the composite material maintains stable performance under cyclic loading conditions up to 80 kN loading corresponding to 57.8 MPa pressure.

As per detailed embodiment of the present invention, the composite material exhibits hysteretic behavior characteristic of viscoelastic materials under cyclic loading at 0.24 Hz frequency.

As per detailed embodiment of the present invention, the glass fibers are uniformly distributed throughout the PTFE matrix to enhance mechanical properties and performance.

As per detailed embodiment of the present invention, the graphene provides enhanced thermal conductivity and modified tribological properties.

As per detailed embodiment of the present invention, the PTFE - based composition for reduced friction coefficient can be modified to achieve a specific desired load bearing capacity.

As per detailed embodiment of the present invention, the PTFE - based composition for reduced friction coefficient being capable of reducing sliding friction in isolation devices for earthquake protection of structures.

As per detailed embodiment of the present invention, the PTFE is used as a base material or a matrix material due to its properties of withstanding significant levels of axial loads.

As per detailed embodiment of the present invention, the glass fiber is used to improve the wear and tear properties of the article.

As per detailed embodiment of the present invention, the PTFE - based composition for the reduced friction coefficient, the glass fiber can also be used to increase the friction coefficient if intended.

As per detailed embodiment of the present invention, the PTFE - based composition for the reduced friction coefficient, the graphene is used as a solid lubricant to reduce the coefficient of friction.

As per another embodiment of the present invention, the PTFE – based composition for the reduced friction coefficient, can be but not limited to a solid substance, a sprayable substance or coatings.

As per another embodiment of the present invention, the PTFE - based composition for the reduced friction coefficient, can be used in isolation devices for earthquake protection of structures.

As per another main embodiment of the present invention, the method of preparation the PTFE - based composition for reduced friction coefficient, said method comprising following steps:-

a. screening PTFE powder through a coarse wire mesh with a size of 2 mm;
b. mixing the PTFE powder of step a with glass fibers and graphene using a mixer grinder to ensure uniform distribution;
c. gradually adding the PTFE mixture of step b to a steel die and compacting using a tamping rod to remove excess air;
d. compacting the mixture of step c in a hydraulic press;
e. removing molded samples from the die; and
f. sintering the samples of step e in a hot air oven.

As per another embodiment of the present invention, said method steps further comprising machining the sintered specimens using a CNC turning machine to achieve required dimensional tolerances and surface finish.

As per another embodiment of the present invention, said cold pressing-hot sintering technique consolidates the PTFE particles and creates a cohesive composite structure.

As per detailed embodiment of the present invention, said PTFE based composition can be used to prepare an articles.

As per another embodiment of the present invention, the article can be used in a single surface sliding bearing with adaptive stiffening and damping restrainer system (100).

As per another embodiment of the present invention, the method of preparing said article comprising the following steps,
a) screening PTFE powder through a coarse wire mesh with a size of 2 mm;
b) mixing the PTFE powder of step a with glass fibers and graphene using a mixer grinder to ensure uniform distribution;
c) gradually adding the PTFE mixture of step b to a steel die and compacting using a tamping rod to remove excess air;
d) compacting the mixture of step c in a hydraulic press;
e) removing molded samples from the die; and
f) sintering the samples of step e in a hot air oven.
g) preparing the article with formulation of step f.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising a sliding surface (1), a slider (2), a housing plate (3), a plurality of article (4a, 4b), a ring restrainer (5) and a plurality of restrainer (6).

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising sliding surface (1) is a concave shaped surface. The raised surface assist in reducing the vibrations of the structure.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the slider (2) being capable of sliding on the sliding surface (1). The article (4a) being secured in between the sliding surface (1) and the slider (2).

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the housing plate (3) being capable of maintaining the horizontal plane by adjusting the change in angle due to sliding of the slider (2) in the event of an earthquake.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the article (4b) being secured in between the sliding surface (1) and the slider (2).

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the ring restrainer (5) being capable of limiting the movement of slider (2) within the sliding surface (1). The ring restrainer (5) is a protrusion in the sliding surface (1) along the circumference.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the plurality of restrainer (6) being capable of providing stiffening and damping by restricting the movement of the housing plate (3).

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) comprising the plurality of restrainer (6) with varying cross section and curvature to provide the adaptive stiffening and damping.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100), the housing plate (3) is optimized such that its shape that comes in contact with the plurality of restrainer further enhances the adaptive stiffening and damping.

As per another embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100), the curvatures of the sliding surface (1), the slider (2) and the housing plate (3) can be varied to further isolate the frequency of the vibrations from an earthquake.

As per optional embodiment of the present invention, the single surface sliding bearing with adaptive stiffening and damping restrainer system (100). The adaptive stiffening and damping is achieved by plurality of springs (9). The plurality of springs (9) is mounted between an inner ring (7) and outer ring (8). The plurality of springs (9) deform upon oscillation due to earthquake to damp the natural frequency of the structure.

The embodiments and its arrangement of the present invention is further explained through the reference of drawings.

Referring to figure 1 of the present invention, it shows the section view of the single surface sliding bearing with adaptive stiffening and damping restrainer system (100), having a sliding surface (1), a slider (2), a housing plate (3), a plurality of article (4a, 4b), a ring restrainer (5) and a plurality of restrainer (6).

Referring to figures 2a and 2b of the present invention, it shows the section view of the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) in two different positions of the slider (2) and also how the restrainer (6) interacts with the surface of the housing plate (3) to adaptive stiffening and damping. The varying cross section and the curvature of the restrainer (6) is displayed.

Referring to figure 3 of the present invention, it shows the section view of the single surface sliding bearing with adaptive stiffening and damping restrainer system (100) as an optional embodiment, having a sliding surface (1), a slider (2), a housing plate (3), a plurality of article (4a, 4b), a ring restrainer (5), an inner rim (7), an outer rim (8) and a plurality of springs (9)

The present invention has been further exemplified by the following test data, which demonstrate the performance and advantages of the invention. It is to be understood that the test data are provided solely for illustrative purposes and should not be construed as limiting the scope of the invention in any manner. The results obtained confirm the efficacy and utility of the invention as described herein, and substantiate the technical effect achieved. Variations in test conditions, materials, or methodologies may lead to different values, but such variations are within the scope of the present invention.

The manufacturing process involves a cold pressing-hot sintering technique. The PTFE powder is first screened through a coarse wire mesh with a size of 2 mm. The PTFE powder is then mixed with glass fibers and graphene using a mixer grinder to ensure uniform distribution of the reinforcing materials throughout the matrix.

The PTFE mixture is gradually added to a steel die and compacted using a tamping rod to remove excess air. After each compaction step, additional powder is added until the die is completely filled. The die is then placed in a hydraulic press, and the mixture is compacted.

The molded samples (green compacts) are carefully removed from the die by gradually loosening the pressure release mechanism. The green compacts are then placed in a hot air oven for the sintering process, which consolidates the PTFE particles and creates a cohesive composite structure.

After sintering, the cylindrical specimens are machined using a CNC turning machine to achieve the required dimensional tolerances and surface finish. The machined liners are then integrated into sliding bearings for testing and application.

SI. No.
Composite PTFE Glass fibre Graphene Total
% w/w quantity
(grams) % w/w quantity
(grams) %
w/w quantity
(grams) quantity
(grams)
1 A 74.90 580 15.10 116 10 78 774
2 B 82.90 640 15.10 116 2 16 772
3 D 73.90 580 20.10 157 6 47 784
4 E 73.90 580 25.10 196 1 8 784
5 M 97.90 760 0.10 0.75 2 16 776.75
6 N 95.90 740 0.10 0.75 4 31 771.75
7 O 93.90 725 4.10 31 2 16 772
8 P 91.90 710 4.10 31 4 31 772

Testing has demonstrated that certain compositions exhibit particularly favorable performance characteristics. Under axial pressures in the range of 20-30 MPa, compositions with high PTFE content (such as materials M, N, and O) achieve coefficients of friction of approximately 0.10 at high sliding velocities, making them suitable for demanding applications requiring low friction and reliable performance. Specifically, composite M (97.90% PTFE, 0.10% glass fiber, 2% graphene) demonstrated stable performance up to 80 kN loading (57.8 MPa), while composite N (95.90% PTFE, 0.10% glass fiber, 4% graphene) and composite O (93.90% PTFE, 4.10% glass fiber, 2% graphene) showed progressive loading capabilities through 50 kN (36.1 MPa), 60 kN (43.3 MPa), 70 kN (50.5 MPa), and 80 kN (57.8 MPa) stages. The force-displacement curves obtained at 0.24 Hz frequency reveal hysteretic behavior characteristic of viscoelastic materials, with the area enclosed by the curves indicating energy dissipation during cyclic loading. Wear debris analysis shows that higher PTFE content compositions produce finer, more uniform debris patterns, indicating controlled wear mechanisms that contribute to the low friction performance.

The invention will now be described in more detail with reference to the accompanying figures, in which:

Figure A-1 shows force-displacement curves for composite A (74.90% PTFE, 15.10% glass fiber, 10% graphene) at 0.24 Hz frequency under cyclic loading conditions. The hysteresis loops demonstrate the viscoelastic behavior of the PTFE-based composite material, with the enclosed area representing energy dissipation during each loading cycle. The curves reveal progressive changes in stiffness and damping characteristics as the loading amplitude increases, indicating the material's response to dynamic stress conditions typical in sliding bearing applications.

Figure A-2 depicts the variation of average coefficient of friction with maximum sliding velocity for composite A at 0.24 Hz frequency. The graph demonstrates how the friction coefficient changes as a function of sliding speed, showing the transition from static to kinetic friction regimes. The data reveals the velocity-dependent friction behavior critical for predicting bearing performance under varying operational speeds, with particular emphasis on the low-friction characteristics achieved at higher sliding velocities.

Figure A-3 presents wear debris of composite A deposited on the concave surface at the end of the 90 kN (65.0 MPa) test, providing visual evidence of the wear mechanisms and debris formation patterns. The morphology and distribution of wear particles indicate the tribological behavior of the composite, showing how the PTFE matrix and reinforcing materials interact during sliding contact. The debris characteristics are indicative of controlled wear processes that contribute to the formation of a transfer film essential for low-friction operation.

Figure A-4 illustrates the articulated slider of composite A at the end of different stages of progressive loading, revealing the evolution of surface wear and deformation behavior. The images show the progressive changes in surface topography and material removal patterns as the applied load increases through various test stages, demonstrating the material's ability to maintain structural integrity under increasing mechanical stress while developing the characteristic wear patterns associated with PTFE-based sliding bearings.

Figures B-1 to B-4 show corresponding results for composite B (82.90% PTFE, 15.10% glass fiber, 2% graphene), including force-displacement curves at 0.24 Hz frequency, coefficient of friction variation with sliding velocity, wear debris patterns at 90 kN loading, and slider condition at different loading stages. The higher PTFE content in composite B results in modified hysteresis behavior compared to composite A, with generally lower energy dissipation and different friction characteristics. The reduced graphene content affects the wear debris morphology and the overall tribological performance of the bearing liner.

Figures C-1 to C-4 present similar comprehensive analysis for composite D (73.90% PTFE, 20.10% glass fiber, 6% graphene), demonstrating the performance characteristics of the higher glass fiber content formulation. The increased glass fiber reinforcement results in enhanced mechanical properties and modified wear behavior, as evidenced by the force-displacement curves showing increased stiffness and altered hysteresis characteristics. The friction coefficient variation and wear debris patterns reflect the influence of the higher fiber content on the tribological performance.

Figures D-1 to D-4 illustrate the behavior of composite E with maximum glass fiber content (25.10% by weight, with 73.90% PTFE and 1% graphene). The high fiber loading significantly affects the mechanical response, as shown in the force-displacement curves with increased stiffness and reduced hysteresis loop area. The friction characteristics and wear patterns demonstrate how maximum fiber reinforcement influences the sliding bearing performance, particularly under high-load conditions up to 90 kN.

Figures E-1 to E-3 show results for composite M with high PTFE content (97.90% by weight, 0.10% glass fiber, 2% graphene), including force-displacement curves at 0.24 Hz and slider condition at 50 kN (36.1 MPa) and 80 kN (57.8 MPa) loading stages. The minimal fiber content and high PTFE proportion result in distinctive mechanical behavior characterized by lower stiffness but excellent friction performance. The coefficient of friction variation demonstrates the superior low-friction characteristics achievable with high PTFE content, making this composition particularly suitable for applications requiring minimal friction resistance.

Figures F-1 to F-3 present performance data for composite N (95.90% PTFE, 0.10% glass fiber, 4% graphene), showing progressive loading stages from 50 kN (36.1 MPa) through 60 kN (43.3 MPa), 70 kN (50.5 MPa), to 80 kN (57.8 MPa) and the corresponding slider conditions. The increased graphene content compared to composite M provides enhanced thermal conductivity and modified tribological properties while maintaining the benefits of high PTFE content. The force-displacement curves and friction coefficient data demonstrate the material's capability to handle progressive loading with consistent performance characteristics.

Figures G-1 to G-3 illustrate the behavior of composite O (93.90% PTFE, 4.10% glass fiber, 2% graphene) under various loading conditions from 50 kN to 70 kN (50.5 MPa), demonstrating its performance characteristics with balanced PTFE and glass fiber content. The moderate glass fiber reinforcement provides improved mechanical properties while maintaining the low-friction benefits of high PTFE content. The progressive loading data shows excellent performance stability across the tested load range, with consistent friction coefficients and controlled wear behavior.

Figures H-1 to H-3 show the performance of composite P (91.90% PTFE, 4.10% glass fiber, 4% graphene) across different loading stages from 50 kN through 60 kN, 70 kN, to 80 kN (57.8 MPa), providing comparative data for the complete range of tested compositions. The balanced composition with moderate glass fiber and higher graphene content demonstrates versatile performance characteristics suitable for various operating conditions. The comprehensive test data allows for direct comparison with other compositions to optimize material selection for specific sliding bearing applications based on load requirements and performance criteria.

The experimental results demonstrate that the PTFE-based composite materials of the present invention successfully achieve the desired balance between low friction characteristics and mechanical durability for sliding bearing applications. Among the tested compositions, materials M, N, and O represent the optimal formulations that best embody the objectives of the present invention. Composite M (97.90% PTFE, 0.10% glass fiber, 2% graphene) achieved exceptional performance with stable operation up to 80 kN loading (57.8 MPa) while maintaining coefficients of friction of approximately 0.10 at high sliding velocities. Composite N (95.90% PTFE, 0.10% glass fiber, 4% graphene) and composite O (93.90% PTFE, 4.10% glass fiber, 2% graphene) similarly demonstrated superior performance characteristics through progressive loading stages, confirming their suitability for demanding sliding bearing applications. These optimal compositions successfully address the technical challenges identified in conventional PTFE-based bearing materials by providing enhanced mechanical strength without compromising the inherent low-friction benefits of PTFE. The cold pressing-hot sintering manufacturing process ensures uniform material distribution and consistent performance characteristics throughout the bearing liner. The viscoelastic behavior observed under cyclic loading at 0.24 Hz frequency provides beneficial energy dissipation and vibration damping properties. The incorporation of graphene enhances thermal conductivity and modifies tribological properties, contributing to stable friction performance and reduced thermal degradation during operation. The present invention thus provides sliding bearing liners that meet the stringent requirements of modern industrial applications requiring reliable low-friction performance under demanding operational conditions, with materials M, N, and O representing the preferred embodiments that achieve optimal performance characteristics.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the illustrative examples, make and utilize the present invention and practice the claimed methods. It should be understood that the foregoing discussion and examples merely present a detailed description of certain preferred embodiments. It will be apparent to those of ordinary skill in the art that various modifications and equivalents can be made without departing from the spirit and scope of the invention.

LIST OF REFERENCE NUMERALS
Single Surface Sliding Bearing with Adaptive Stiffening and Damping Restrainer System (100)
Sliding Surface (1)
Slider (2)
Housing Plate (3)
Article (4a, 4b)
Ring Restrainer (5)
Restrainer (6)
Inner Rim (7)
Outer Rim (8)
Springs (9)
,CLAIMS:CLAIMS:
We Claim:
1. A PTFE - based composition for reduced friction coefficient, wherein the composite material comprises:-
a. 74.90-97.90% by weight of polytetrafluoroethylene (PTFE); and
b. 0.1-25% by weight of glass fibers; and
c. 1-10% by weight of graphene.

2. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the PTFE-based composite material comprises:
a. 93.90-97.90% by weight of PTFE; and
b. 0.1-4.10% by weight of glass fibers; and
c. 2-4% by weight of graphene.

3. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the composite material exhibits a coefficient of friction of approximately 0.10 at high sliding velocities under axial pressures in the range of 20-30 MPa.

4. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the composite material maintains stable performance under cyclic loading conditions up to 80 kN loading corresponding to 57.8 MPa pressure.

5. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the composite material exhibits hysteretic behavior characteristic of viscoelastic materials under cyclic loading at 0.24 Hz frequency.

6. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the glass fibers are uniformly distributed throughout the PTFE matrix to enhance mechanical properties and performance.

7. The PTFE - based composition for reduced friction coefficient as claimed in claim 1, wherein the graphene provides enhanced thermal conductivity and modified tribological properties.

8. A method of preparation the PTFE - based composition for reduced friction coefficient, said method comprising following steps:-
a. screening PTFE powder through a coarse wire mesh with a size of 2 mm;
b. mixing the PTFE powder of step a with glass fibers and graphene using a mixer grinder to ensure uniform distribution;
c. gradually adding the PTFE mixture of step b to a steel die and compacting using a tamping rod to remove excess air;
d. compacting the mixture of step c in a hydraulic press;
e. removing molded samples from the die; and
f. sintering the samples of step e in a hot air oven.

9. The method of preparation the PTFE - based composition for reduced friction coefficient claim 8, further comprising machining the sintered specimens using a CNC turning machine to achieve required dimensional tolerances and surface finish.

10. The method of preparation the PTFE - based composition for reduced friction coefficient claim 8, wherein the cold pressing-hot sintering technique consolidates the PTFE particles and creates a cohesive composite structure.
Dated this on 13th Oct 2025