Composite bearing comprising a polyimide matrix

Abstract

Warehouse, comprehensive: a. a substrate; and b. a first layer arranged on the substrate, wherein the layer comprises i. a polyimide matrix, wherein the polyimide matrix comprises a cross-linked and imidized polyamic acid or polyamic acid salt; and ii. a filler material dispersed in the polyimide matrix, wherein the filler material comprises a thermoplastic material, the thermoplastic material being present in the first layer in an amount of at least 25 wt.% and not more than 50 wt.%, based on the combined weight of thermoplastic material and polyimide matrix; iii. wherein the bearing has a coefficient of friction, determined according to ASTM G-77, of less than 1, and a wear resistance, determined according to ASTM G-77, of less than 2.9 mm 3 exhibits.

Description

Disclosure field

[0001] This disclosure relates to composite materials, and in particular to composite materials used to manufacture bearings and seals. Technical field

[0002] Assembly components comprising bearings and seals are widely used in industry as the interface between a moving surface and a stationary surface. Traditionally, it is desirable to increase a bearing's resistance to wear while simultaneously achieving the lowest possible coefficient of friction. However, most attempts to increase wear resistance have, in most cases, a negative effect on the coefficient of friction, and vice versa. Therefore, there is a need to develop a novel bearing-seal assembly in which the combination exhibits both improved wear resistance and an improved coefficient of friction.

[0003] Furthermore, the process for manufacturing composite bearings, and in particular composite bearings comprising a polyimide matrix, has disadvantages. Specifically, a process for in-situ or continuous forming of the polyimide matrix is ​​desirable. Such in-situ imidization and forming of polyimide matrices with dispersed fillers or thermoplastics into composite materials, bearings, and seals has neither been disclosed nor proposed to date.

[0004] The present invention provides an arrangement of composite materials that meets these and other requirements, as will be explained in detail below.

[0005] US 2012 / 0 128 280 A1 discloses a bushing comprising a load-bearing substrate, an adhesive film and a friction-reducing layer.

[0006] US 2011 / 0317955A1 discloses a plastic polymer-based bearing material and a method for its production. Brief description of the drawings

[0007] The embodiments are shown in the accompanying drawings in an exemplary manner and are not limiting. Fig. Figure 1 includes a drawing of a composite material according to an embodiment of the disclosure. Fig. 2 includes a drawing of a composite material according to another embodiment of the disclosure. Fig. Figure 3 includes a drawing of a test setup for wear rates and coefficients of friction according to ASTM G-77. Fig. Figure 4 illustrates the recording of wear and temperature as a function of time for sample 1. Fig. Figure 5 illustrates the recording of the coefficient of friction as a function of time for sample 1. Fig. Figure 6 illustrates a recording of wear and temperature as a function of time for sample 2. Fig.Figure 7 illustrates the recording of the coefficient of friction as a function of time for sample 2. Fig. Figure 8 illustrates the recording of abrasion and temperature as a function of time for sample 3. Fig. Figure 9 illustrates the recording of the coefficient of friction as a function of time for sample 3. Fig. 10 and Fig. Figure 11 illustrates the SEM of Sample 1. Fig. 12 and Fig. Figure 13 illustrates the SEM of Sample 2. Fig. 14 and Fig. Figure 15 illustrates the SEM of Sample 3. Fig. Figure 16 illustrates the dry friction coefficient data from Example 3. Fig. Figure 17 illustrates the data for the wet coefficient of friction from Example 3. Fig. Figure 18 illustrates a pre-composite material for a bearing according to one embodiment. Fig.Figure 19 illustrates a pre-composite material for a bearing according to another embodiment. Fig. 20 illustrates the camp before the composition of Fig. 19, wherein the release layer was removed according to one embodiment.

[0008] Those skilled in the art understand that elements in the drawings are depicted for clarity and comprehensibility and are not necessarily drawn to scale. For example, the dimensions of elements in the drawings may be disproportionately large compared to other elements to improve the understanding of the embodiments of the invention. Detailed description

[0009] The following description, in combination with the drawings, is provided to enhance understanding of the teaching. The subsequent discussion will focus on specific implementations and embodiments of the teaching. This focus is intended to support the description of the teaching and should not be interpreted as limiting its scope or applicability. Thus, embodiments other than those disclosed in this application may also be used for teaching purposes.

[0010] The terms “comprises”, “encompassing”, “includes”, “including”, “has”, “having”, or other variations thereof are used to signify non-exclusive inclusion. For example, a method, article, or device comprising a list of features is not necessarily limited to those features alone, but may also include other features not expressly mentioned or inherent in such method, article, or device. Furthermore, unless expressly stated otherwise, the term “or” refers to an inclusive “or” and not an exclusive “or”.For example, a condition A or B is already fulfilled in one of the following cases: A is the case (or present) and B is not the case (or not present), A is not the case (or not present) and B is the case (or present), and both A and B are the case (or present).

[0011] The use of the term "a" or "one" has also been made to describe elements and components within it. This was done essentially for convenience and to provide a general understanding of the scope of the invention. This description should be read as including one, at least one, or both the singular and the plural, or vice versa, insofar as it is clear that the opposite is not intended. For example, if a single item is described herein, more than one item may be used instead of the single item. Correspondingly, if more than one item is described, these may be replaced by one item.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those understood by a person skilled in the art in this invention. The materials, methods, and examples are for illustrative purposes only and are not intended to be limiting. Many details relating to specific materials and procedures are conventional and can be found in textbooks and other sources in the field of composites, bearings, and seals, and extend to areas not described here.

[0013] The following disclosure describes composite materials, and in particular composite bearings, comprising a polyimide matrix dispersed with materials such as thermoplastics within the polyimide matrix. A process for producing the composite material is also described, wherein a mixture comprising a polyimide precursor or imide monomers is deposited on a substrate and imidized on the substrate. Such in-situ imidization and formation of a polyimide matrix with dispersed fillers or thermoplastics in composite materials, bearings, and seals has not been previously disclosed or proposed. The concepts are more readily understood in light of the exemplary embodiments described below, which illustrate, rather than limit, the scope of the present invention.

[0014] The present invention relates to a bearing according to claim 1. The bearing according to the invention comprises a substrate and a first layer arranged on the substrate. The first layer comprises a polyimide matrix, wherein the polyimide matrix comprises a cross-linked and imidized polyamic acid or polyamic acid salt, and a filler material dispersed in the polyimide matrix, wherein the filler material comprises a thermoplastic material. The thermoplastic material is present in the first layer in an amount of at least 25 wt.% and not more than 50 wt.%, based on the combined weight of the thermoplastic material and the polyimide matrix. The bearing has a coefficient of friction, determined according to ASTM G-77, of less than 1, and a wear resistance, determined according to ASTM G-77, of less than 2.9 mm. 3 The dependent claims relate to particular embodiments of the bearing according to the invention.

[0015] Fig.Figure 1 illustrates a composite material 100 comprising a substrate 20 and a first layer 30 deposited on the substrate 20. As shown, the first layer 30 can be deposited directly adjacent to the substrate 20, so that the first layer 30 is in direct contact with the substrate 20. However, as will be discussed in detail below, the composite material can include one or more intermediate layers arranged between the substrate and the first layer 30.

[0016] Substrate 20 can be made from any material that can be formed into a bearing or seal. In certain embodiments, the substrate can contain a metal, such as steel, aluminum, bronze, copper, or combinations thereof.

[0017] The surface 22 of the substrate 20, which borders the layer 30, can be mechanically treated to improve the adhesion between the substrate and the first layer 30. For example, the mechanical treatment of layer 22 of the substrate 20 can include sandblasting or mechanical etching of the surface 22 of the substrate 20. The surface 22 of the substrate 20 can be mechanically treated so that it has a desirable surface roughness.

[0018] Regarding Fig. 1. Adjacent to substrate 20, a first layer 30 can be formed. The first layer 30 can be made from a combination of materials. The first layer 30 contains a polyimide matrix and a filler dispersed within the polyimide matrix.

[0019] “Polyimide matrix”, as used herein, refers to a cross-linked network of polyimides wherein the polyimide constitutes at least 25 wt% of the first layer, based on the total weight of the first layer 30.

[0020] As will be discussed in more detail below, the polyimide matrix can be formed by imidizing a polyimide precursor after deposition on a substrate. A suitable polyimide precursor can be, for example, poly(amide) acid (PAA). The poly(amide) acid (PAA) can be a reaction product of a monomer mixture containing at least two different monomers. In certain embodiments, the at least two different monomers can be selected from a group consisting of: pyromellitic dianhydride (PMDA), 3,3'-4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxiphenyl)hexafluoropropane dianhydride (6FDA), 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), benzophenone tetracarboxylic dianhydride (BTDA), and 4,4'-oxydianiline (ODA), or m-phenyldiamine (m-PDA), 4,4'-diaminophenylsulfone (4,4'-DDS), p-phenylenediamine (p-PDA), and methylenedianiline (MDA).In specific embodiments, the polyimide matrix can be cross-linked and, as such, a reaction product of at least two different monomers listed above. In specific embodiments, the polyimide matrix can be a pure polyimide matrix. As used here, the formulation "pure polyimide matrix" can be a polyimide matrix that is substantially free of copolymers with imide monomers. In other words, in various embodiments, the polyimide matrix can be substantially free of non-imide monomers.

[0021] Furthermore, the polyamino acid can be derived from a first monomer and a second monomer in various embodiments. The first monomer can be selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3'-4,4'-bifenyltetracarboxide ianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane ianhydride (6FDA), 2,2'-bis[4-(3,4-dicarboxyphenoxy)[phenyl]propane ianhydride (BPADA), benzophenone tetracarboxide ianhydride (BTDA), and any combination thereof. The second monomer can be selected from the group consisting of 4,4'-oxydianiline (ODA), m-phenyldiamine (m-PDA), 4,4'-diamonophenylsulfone (4,4'-DDS), p-phenyldiamine (p-PDA), methylenedianiline (MDA), and any combination thereof.

[0022] In specific embodiments, the polyimide matrix can be derived from a polyamino acid salt. For example, the dipolyamino acid can be dissolved in a solvent such as n-methylpyrolidone and reacted with a tertiary amine to obtain a water-soluble polyamino acid salt solution. This polyamino acid salt solution can then be mixed with an aqueous dispersion of the filler, and because the polyamino acid salt solution is in water, a relatively uniform dispersion of the filler with the polyimide matrix is ​​produced. After application to the substrate and curing, volatile materials present in the first layer, including the functional salt group of the polyamino acid salt, such as the imide bond, are formed during curing.

[0023] As discussed above, the first layer 30 also contains a filler dispersed in the polyimide matrix. Fillers can, but are not limited to, contain carbon graphite, graphene, carbon nanotubes, Ekonol, glass fibers, a polymeric component such as thermoplastics, an organic component, an inorganic component, or combinations thereof.

[0024] According to the invention, the filler comprises a thermoplastic material. In certain embodiments, the thermoplastic can be a fluoropolymer, for example, a perfluoropolymer. In even more specific embodiments, the thermoplastic can be PTFE, PVF, PVDF, PCTFE, PFA, FEP, ETFE, or combinations thereof. In particularly specific embodiments, the thermoplastic can contain PTFE or even consist essentially of PTFE. Furthermore, the thermoplastic, such as PTFE, can be a thermoplastic regrind.

[0025] In specific embodiments, the filler material may further comprise an organic filler material. For example, in specific embodiments, the organic filler material may contain an aromatic polyester, or a recycled polyimide, polyamidetherimide, polyamideimide, PEEK, PEEK-like polymers from the polyaryl family, liquid crystal polymers (LCP), polybenzimidazoles, or combinations thereof.

[0026] The thermoplastic material is present in the mixture in a proportion of at least 25 wt.% and not more than 50 wt.%, based on the combined weight of the thermoplastic material and the polyamide precursor. For example, in certain embodiments, the thermoplastic material may be present in the mixture in an amount of at least 26 wt.%, at least 28 wt.%, or even at least 30 wt.%, based on the combined weight of the thermoplastic material, the polyimide precursor, and the filler material.

[0027] This means that the mixture can include all combinations of filler material as described above. In specific embodiments, the mixture can include a thermoplastic filler and an organic filler.

[0028] The first layer 30 can also contain any desired additive. For example, some additives may contain a thickener or stabilizer. Stabilizers, for instance, may include surfactants such as perfluoroalkoxy components or viscosity improvers. Thickeners may contain, for example, Algocel and glycols, or combinations thereof. The additives can be added in any desired quantity to achieve their intended effect.

[0029] In specific embodiments, the first layer 30 can have a thickness of no more than 1 mm, no more than 800 µm, no more than 500 µm, no more than 300 µm, no more than 250 µm, no more than 200 µm, or even no more than 175 µm. Furthermore, in certain embodiments, the first layer 30 can have a thickness of at least approximately 0.01 µm, at least approximately 1 µm, at least approximately 50 µm, or even at least approximately 100 µm. It is to be understood that the first layer 30 can contain one or more layers. In specific embodiments, the first layer 30 can contain more than one layer formed by multiple passes through a coating process.

[0030] The first layer 30 can have a specific porosity. For example, in certain embodiments, the first layer 30 can have a porosity of at least approximately 0.01%, at least approximately 0.05%, or at least approximately 0.1%.

[0031] In certain embodiments, as shown in particular in Fig.2. One or more additional intermediate layers 40 can be inserted between the substrate 20 and the first layer 30. An intermediate layer 40 can be provided, for example, to improve the adhesion between the first layer 30 and the substrate 20. As can be confirmed by a person skilled in the art, the specific selection of the intermediate layer 40 will depend on the substrate 20 and the composition of the first layer 30. In specific embodiments, the intermediate layer 40 can contain zinc or zinc-containing components. The additional intermediate layer can be provided as an alternative to, or in addition to, the mechanical treatment of the surface 22 of the substrate 20 described above.

[0032] A particular advantage of the present disclosure is the achievement of certain performance characteristics, such as an average coefficient of friction, average wear resistance, and the ability to pass the laminar adhesion test (Erichsen). Until now, it was not known how these performance characteristics could be achieved, and especially not the combinations of performance characteristics described herein.

[0033] One characteristic that quantifies the performance of a bearing can be the coefficient of friction (COF). The average coefficient of friction (COF) is an industry standard term and can be measured according to ASTM G-77.

[0034] According to the invention, a bearing as disclosed herein has an average coefficient of friction (COF) of less than 1, not greater than approximately 0.8, not greater than approximately 0.7, not greater than approximately 0.6, not greater than approximately 0.5, not greater than approximately 0.4, not greater than approximately 0.3, not greater than approximately 0.25, not greater than approximately 0.2, not greater than approximately 0.18, not greater than approximately 0.15, or even not greater than approximately 0.12, as measured according to ASTM G-77. Furthermore, in certain embodiments, the bearings as disclosed may have an average coefficient of friction (COF) of not less than approximately 0.001, not less than approximately 0.01, or even not less than approximately 0.05, as measured according to ASTM G-77.Furthermore, in certain embodiments, a bearing according to the disclosure herein may have an average coefficient of friction within a range between one of the minimum and one of the maximum values ​​as described above, such as in the range from 0.001 to less than 1, or from 0.01 to 0.7.

[0035] Another characteristic that quantifies a bearing's performance is its average wear resistance. Wear resistance is a measurement of the amount of material removed from the bearing during a wear test performed according to ASTM G-77.

[0036] According to the invention, a bearing as disclosed herein has an average wear resistance of less than 2.9 mm. 3 , not larger than approximately 2 mm 3 , not larger than approximately 1.5 mm 3 , not larger than approximately 1.3 mm 3 , not larger than approximately 1.1 mm3 , not larger than approximately 1 mm 3 , not larger than approximately 0.8 mm 3 , not larger than approximately 0.6 mm 3 , not larger than approximately 0.5 mm 3 , not larger than approximately 0.3 mm 3 , or not larger than approximately 0.2 mm 3 , measured according to ASTM G-77. Furthermore, in certain embodiments, a bearing according to this disclosure can have a mean wear resistance of not less than approximately 0.001 mm. 3 , not less than approximately 0.01 mm 3 , or no less than approximately 0.05 mm 3 have, measured according to ASTM G-77. Furthermore, in certain embodiments, a bearing according to the disclosure herein may have a mean wear resistance in a range of one of the minimum and one of the maximum values ​​specified above, such as, for example, in the range of 0.001 mm. 3 to less than 2.9 mm 3, or also from 0.01 mm 3 to less than 2.9 mm 3 .

[0037] A third characteristic that can quantify the performance of a bearing is its ability to pass the laminar adhesion test (Erichsen). The laminar adhesion test measures the adhesion of the first layer to the second layer within the bearing and is a well-established engineering practice.

[0038] In certain embodiments, a bearing according to the disclosure herein can pass the laminar adhesion test (Erichsen).

[0039] According to another aspect of the disclosure, methods for forming a composite layer and for forming a composite bearing are described. For example, the method may include: providing a polyimide precursor or imide monomer; providing a filler material; providing a solvent; mixing the filler material, the solvent, and the polyimide precursor or imide monomer to produce a mixture; depositing the mixture onto a substrate; and thermally curing the substrate and the deposited mixture. To produce a composite bearing, the method may further include creating a composite bearing from the composite layer.

[0040] As described herein, the formation of the composite material can be a continuous process. For example, imidation can be carried out in situ, so that the mixture can be blended with a polyimide precursor or monomer and a filler material, deposited onto the substrate, and then imidized in situ after application to the substrate.

[0041] The process can produce a bearing with a coefficient of friction and wear resistance as described above. For example, the method can form a bearing with a coefficient of friction of less than approximately 1 and a wear resistance of less than 2.9 mm. 3 .

[0042] The polyimide precursor can contain non-crosslinked polyimides or imide monomers. For example, the polyimide precursor can contain a polyamino acid. The polyamino acid can be derived from the reaction of at least two different monomers. In specific examples, the at least two different monomers may be selected from the group consisting of: pyromellitic dianhydride (PMDA), 3,3'-5,4'-biphenyltetracarboxide ianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane ianhydride (6FDA), 2,2'-bis[4-3,4-dicarboxyphenoxy)phenyl]propane ianhydride (BPADA), benzophenone tetracarboxide ianhydride (BTDA), and 4,4'-oxydianiline (ODA), or m-phenyldiamine (m-PDA), 4,4'-diaminophenylsulfone (4,4'-DDS), p-phenylenediamine (p-PDA), and methylenedianiline (MDA).

[0043] In further examples, the first monomer may be a monomer selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3'-4,4'-biphenyltetracarboxide ianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane ianhydride (6FDA), 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane ianhydride (BPADA), benzophenone tetracarboxide ianhydride (BTDA), and any combination thereof; and the second monomer may be a monomer selected from the group consisting of 4,4'-oxydianiline (ODA), or m-phenyldiamine (m-PDA), 4,4'-diaminophenylsulfone (4,4'-DDS), p-phenylenediamine (p-PDA), methylenedianiline (MDA), and any combination thereof.

[0044] The polyamino acid can be present in the form of a salt, as described above. Furthermore, the method can include the preparation or formation of a polyamino acid salt. For example, the polyamino acid can be combined with a tertiary amine in a solvent, reacting to produce a water-soluble polyamino acid salt mixture. An aqueous dispersion containing the filler material can then be added to the polyamino acid salt mixture. Because the polyamino acid salt mixture is water-soluble, the filler material can also be uniformly dispersed in the polyamino acid salt and maintain this uniform dispersion after imidization during curing.

[0045] In specific examples, the polyimide precursor may be present in the mixture at a proportion of 25 to 50 wt.%, based on the combined weight of the thermoplastic and the polyimide precursor. For example, the polyimide precursor may be present in the mixture at a proportion of at least 26 wt.%, at least 28 wt.%, at least 30 wt.%, at least 32 wt.%, at least 34 wt.%, at least 36 wt.%, at least 38 wt.%, or at least 40 wt.%, based on the combined weight of the thermoplastic and the polyimide precursor.

[0046] As discussed above, the method can include providing a filler material and incorporating the filler material into the mixture, as well as retaining the polyimide matrix after imidation and curing.

[0047] As discussed above, the filler material can be a number of different materials; in particular, the examples include a thermoplastic and can include an organic filler material, other filler materials, or combinations thereof.

[0048] In various examples, when a combination of filler materials is used, such as thermoplastics and / or organic filler materials, the filler materials can be combined with each other before being combined with other components.

[0049] In specific examples, the filler material may be in particle form before being mixed into the solvent. In such embodiments, the filler material, and in particular a thermoplastic filler material, and even more specifically PTFE, may have an average particle size (D 50) of at least approximately 1 µm, at least approximately 3 µm, at least approximately 5 µm, at least approximately 10 µm, at least approximately 15 µm, or even at least approximately 20 µm. Furthermore, the filler material can have a mean particle size (D) in various examples. 50 ) of no more than approximately 1000 µm, no larger than approximately 500 µm, no larger than approximately 50 µm, no larger than approximately 30 µm, no larger than approximately 20 µm, or even no larger than approximately 10 µm. Furthermore, the filling material can have an average particle size (D 50 ) exhibit in a range between one of the maximum and one of the minimum values ​​described herein, such as in a range from approximately 1 µm to 50 µm, from approximately 3 µm to approximately 30 µm, or from approximately 5 µm to 20 µm.

[0050] Furthermore, the filler material, before being combined with the polyimide precursor or the imide monomer, can be in powder form, for example, or, in other examples, in a dispersed phase in a solvent such as water. In other examples, the mixture can be prepared using either a powdered filler material or a filler material dispersed in a solvent.

[0051] In other examples, the filler material, such as a thermoplastic filler, may be present in the mixture in a proportion greater than 25 to 50 wt%, based on the combined weight of the filler material and the polyimide precursor. For example, the thermoplastic material may be present in the mixture in an amount of at least 26 wt%, at least 28 wt%, or even at least 30 wt%, based on the combined weight of the thermoplastic material and the polyimide precursor. In various examples, a solvent may be provided together with the filler material, polyimide precursor, or imide monomers, or it may be added individually to the components or after the filler material and the polyimide precursor or the imide monomers have been combined. In various examples, the solvent may be mixed with the filler material before being mixed with the polyimide precursor or the imide monomer.Furthermore, a solvent may be added to the mixture. In specific examples, the solvent may contain N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, diglyme, dimethyl sulfoxide, xylene, or a combination thereof.

[0052] In specific examples, the solvent may contain an aqueous component. In very specific examples, the solvent may contain, at a minimum, water and NMP.

[0053] As discussed above, the process may involve mixing the polyimide precursor or imide monomer, the filler material and any solvent to form a mixture.

[0054] In various examples, the components can be mixed for a period of at least 1 minute, at least 5 minutes, or at least 15 minutes.

[0055] As discussed above, the process can involve applying the mixture to a substrate. The substrate can be any of the materials discussed above, particularly a metal such as steel, aluminum, bronze, copper, or combinations thereof.

[0056] The mixture can be deposited onto the substrate using any available method. For example, in specific embodiments, the mixture can be deposited onto the substrate by dip coating, spray coating, doctor blade coating, or any other suitable method. In particular, the mixture can be deposited onto the substrate by dip coating. It is possible that the first layer contains more than one layer, for example, due to multiple coating passes. The mixture can be thermally cured between layers.

[0057] A particular advantage of certain examples of the present disclosure is the ability to form the first layer 30 by coating processes instead of, for example, peeling or extrusion. Previously common sliding layers formed by coating processes were unable to achieve the performance characteristics described herein. Furthermore, when using a coating process, the filler material, for example, a thermoplastic material, can retain its morphology, unlike extrusion or peeling processes, which affect the morphology of the filler material.

[0058] The mixture can be deposited such that the first layer 30 has the desired thickness. For example, the thickness of the first layer 30 can be any of the thicknesses described above. Furthermore, the process can additionally include adjusting the viscosity of the mixture to achieve the desired thickness when coating the substrate. For example, the viscosity of the mixture can be adjusted as desired by varying the percentage of the components and / or by adding a viscosity-influencing agent.

[0059] Following deposition on the first layer, the process can include thermal curing of the applied mixture of polyimide precursor or imide monomers, thermoplastics, and solvent. Thermal curing results in the formation of polyimides (in the case of imide monomers) and cross-linking of the polyimide precursor upon solvent removal. In specific examples, thermal curing can include stepwise thermal curing. For instance, stepwise thermal curing can involve multiple steps lasting between 6 and 10 hours, with each step representing a temperature increase of approximately 10 degrees Celsius to 50 degrees Celsius. In specific examples, the temperature during one and / or all steps can range from approximately 80 degrees Celsius to not exceeding approximately 450 degrees Celsius.

[0060] Thermal curing can be carried out in such a way that the desired porosity of the first layer 30 is achieved. For example, thermal curing can be carried out in such a way that the porosity of the first layer 30 is at least approximately 0.1%.

[0061] In various examples, the process may further involve the application of an intermediate layer 90 between the substrate and the first layer 30. For instance, an intermediate layer 90 may be provided to improve the adhesion between the first layer 30 and the substrate. As a person skilled in the art can estimate, the specific choice of the intermediate layer 90 depends on the substrate and the composition of the first layer 30. In specific examples, the intermediate layer 90 may contain zinc or a zinc-containing component.

[0062] In various examples, the method can involve the mechanical treatment of the surface of the first layer 30 adjacent to the substrate to improve the adhesion between the first layer 30 and the substrate. In such examples, the substrate can directly contact the first layer 30. Mechanical treatment of the substrate surface can include, for example, blasting or mechanical etching of the substrate surface. Indeed, a particular advantage of the various examples of this disclosure is the excellent adhesion between a substrate and the first layer, as described herein, especially with metal substrates such as steel. For example, it was previously assumed that adhesion would be difficult due to the difference in thermal expansion between the first layer and the substrate.However, without being bound to any theory, the inventors were able to carefully control the curing conditions and produce a composite material with excellent adhesion between the substrate and the first layer through an in-situ, continuous, composite forming process.

[0063] In various examples, the method can further include providing a catalyst and mixing the catalyst with the other components in the mixture. In specific examples, the catalyst can first be combined with the thermoplastic, and this combination can then be mixed with the other components of the mixture. The catalyst can accelerate the imidation of the polyamino acid.

[0064] In specific examples, the catalyst can include a strong tertiary aliphatic base, such as 1,4-diazabicyclo[2.2.2]octane (DABCO); 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); a nitrogen-containing base; phenol; or an amphoteric material.

[0065] The method may also include providing and mixing a desired additive into the mixture. For example, some additives may include a thickener or stabilizer.

[0066] In various examples, and especially with regard to Fig. 18. The polyimide layer can be formed and cured separately from the substrate and then laminated onto the substrate, for example, using a laminating adhesive. For example, as shown in Fig.18, the composite precursor 100 can enclose a first substrate 105, as well as a release layer, and the cured polyimide-based layer 110 can be applied adjacent to the first substrate 105. Subsequently, and with respect to Fig. 19. The composite precursor 101 can include an adhesive layer 120 applied adjacent to the polyimide-based layer 100, and then a second substrate 130, for example a metallic substrate, and more specifically a steel substrate, can be deposited adjacent to the adhesive layer 120. The release layer can then be removed from the composite, leaving the polyimide-based layer 110 as an outer large surface area of ​​the composite 100, as shown in Fig. 20, trains.

[0067] In specific cases, the release layer can be a film, such as a Kapton film. The release layer can be treated, for example, by ionizing it with UV light.

[0068] The polyimide precursor solution can then be applied to the release layer, for example by spray coating, dip coating, doctor blade application, roller coating, or combinations thereof.

[0069] The coated release layer can then be cured to imidify the polyimide precursor and filler mixture.

[0070] An adhesive layer can then be applied to the exposed polyimide layer, or to the substrate, and the cured coated release layer can be laminated onto the substrate. The adhesive layer can, for example, contain a modified ETFE film, epoxy, or combinations thereof.

[0071] In specific examples, the adhesive layer can enclose a film, such as a modified ETFE film, and can be bonded to the composite, for example by lamination, such as hot pressing.

[0072] A particular advantage of various examples of the present disclosure is the formation of a composite material that has a substantially crack-free polyimide layer. For example, some methods for forming composite bearings involve applying the uncured solution directly onto the substrate and curing it on the substrate. However, polyimide has a coefficient of thermal expansion that is significantly different from that of typical metallic substrates, causing the polyimide layer to shrink and crack during curing when applied directly to and cured on the metallic substrate. In contrast, the fabrication of a composite material by forming and curing the polyimide onto a release liner and subsequently laminating it to the metallic substrate has produced a composite that is substantially free of stress-induced microcracks and does not delaminate.

[0073] To form a composite bearing from the composite layer material, the layer material can be at least partially cut and rolled to form a bearing with an inner layer (substrate) and an outer layer (first layer 30).

[0074] The present disclosure represents a departure from the prior art. In particular, it was previously unknown how to manufacture a composite bearing that possesses the performance characteristics, and especially the combination of performance characteristics, described herein. For example, the present disclosure illustrates various bearings, seals, and similar components that have a cross-linked polyimide matrix with various filler materials, such as a thermoplastic or organic filler dispersed in the polyimide matrix. Surprisingly, such designs, as described in detail herein, have exhibited significantly improved coefficients of friction and wear rates, which were previously unattainable.

[0075] These and other unexpected and outstanding features are illustrated in the examples below, which are exemplary and not limiting, as are the embodiments described therein. Example 1

[0076] A two-liter reactor, equipped with a mechanical stirrer, a thermocouple, a Dean-Stark adapter, and a reflux condenser, was loaded with packing material F4PN40 and xylene (425 g). The mixture was stirred at 60 °C and 150 rpm to achieve a uniform dispersion of PTFE in the xylene solvent. Oxydianilin (ODA, 70 g, 0.350 mol) and N-methylpyrolidone (NMP, 433 g) were then added. The solution mixture was stirred (150 rpm) and heated under nitrogen to 160 °C to remove residual water as a xylene azeotrope using the Dean-Stark adapter. The mixture was cooled to 60 degrees Celsius and pyromellitic dianhydride (PMDA, 76.9 g, 0.353 mol) was added to the mixture under reaction conditions in a ratio of 1.0000:1.0085 ODA to PMDA. After the addition, the reaction mixture was heated to approximately 89 degrees Celsius and became extremely viscous.The temperature increase confirms the exothermic nature of the polyamino acid formation. The reaction mixture was stirred and heated to 70°C for 2 hours. Stirring was then reduced to 60 rpm and the solution was cooled to room temperature. A 15% polyamino acid solution was obtained. The solution was stored in a clean, pre-dried glass bottle.

[0077] The polyamino acid solution was heated to 60 degrees Celsius and stirred at 12 rpm. The solution was then poured onto an aluminum substrate. The coated substrate was thermally cured at 70 degrees Celsius for 1 hour, 100 degrees Celsius for 1 hour, 120 degrees Celsius for 1 hour, 140 degrees Celsius for 1 hour, 160 degrees Celsius for 30 minutes, and at 250 degrees Celsius overnight in a vacuum oven under nitrogen purge. The composite layer was gradually cooled over approximately 6 hours and removed from the oven.

[0078] Three samples were prepared and tested for their coefficients of friction and wear rate. Sample 1 was prepared as described above, with a 30 wt% PTFE charge and a coating thickness of approximately 175 µm. Sample 2 was prepared in the same manner as Sample 1, except for a 50 wt% PTFE charge and a coating thickness of approximately 70 µm. Sample 3 was prepared like Sample 2, with a coating thickness of approximately 285 µm. Reference samples 4-6, acquired from Saint-Gobain Corporation, were also provided and tested.

[0079] Each sample was tested for its coefficient of friction and wear rate according to ASTM G-77. A schematic diagram of the test configuration is shown in Fig.3. During the test, a block-on-ring setup was used to determine the sliding wear of the plastic material. A stationary block sample was pressed with a constant force against a rotating ring sample at 90 degrees to the ring's axis of rotation. Friction between the sliding surface of the block and the ring resulted in material loss for both samples. Wear was calculated from the volume loss of the block and the weight loss of the ring. The temperature of each sample was also measured to illustrate the heat generated during the test. The test results are shown below and in Fig. 4-9. Fig. Figure 4 illustrates the recording of wear and temperature as a function of time for sample 1; and Fig. Figure 5 illustrates a recording of the coefficient of friction as a function of time for sample 1. Fig.Figure 6 illustrates a recording of wear and temperature as a function of time for sample 2; and Fig. Figure 7 illustrates a recording of the coefficient of wear as a function of time for sample 2. Fig. Figure 8 illustrates a recording of wear and temperature as a function of time for sample 3; and Fig. Figure 9 illustrates a recording of the coefficient of wear as a function of time for sample 3.

[0080] Samples 1-3 were also observed under a microscope and their microstructure was analyzed using SEM. The results are presented in Fig. 10-15 shown in which Fig. 10 and Fig. 11. Represent the SEM of sample 1; Fig. 12 and Fig. 13. Represent the SEM of sample 2; and Fig. 14 and Fig. Figure 15 shows the SEM of sample 3. The SEM images illustrate an inhomogeneous distribution of the PTFE filling material in all three samples. Table 1 sample Wear volume (mm³) 3 ) coefficient of friction Temperature (°C) 1 1,3 0,17 46 2 0,3 0,22 46 3 0,3 0,21 46 C4 7,8 0,3 60 C5 4,8 0,17 48 C6 2,9 0,16 45

[0081] As shown by the results in Table 1, samples 1-3 exhibited an unexpected and surprising significant improvement in the combination of wear volume and coefficient of friction. Until then, it was unknown how to manufacture a bearing that possesses the combined outstanding wear volume and coefficient of friction of the samples 1-3 shown. Sample 2 - Polyamino acid salt

[0082] Three samples were prepared and tested with respect to the coefficient of friction in dry and moistened conditions and compared to the commercially available Norglide material from Saint Gobain Performance Plastics. The three samples, according to the various embodiments of the present disclosure, were prepared as follows:

[0083] ODA was dissolved in a mixture of NMP and xylene. While stirring, the same molar amount of PMDA was added to the ODA solution at 60°C, and a polyamino acid solution was obtained after two hours. The same molar amount of triethylamine was slowly added to the above polyamino acid solution to obtain a homogeneous, viscous polyamino acid salt solution. Specific amounts of PTFE suspensions were mixed with the above polyamino salt solution and used to form a substrate.

[0084] The coefficient of friction (COF) test was performed on a plint tester, also known as a ball-on-flat sliding test. The test was conducted under two different conditions: moistened and dry. For the moistened test, the sample was immersed in an oil bath at room temperature throughout the test. For the dry test, the ball was in direct contact with the sample without any moistening other than that provided by the coating itself. The three samples according to the embodiments of the disclosure were differentiated as follows: • 25% PTFE and a coating thickness of approximately 50 µm, prepared with the following composition: Mass (g) % Solids DI Water 2,3 100 PAA Salt 2,0 17 PTFE 0,27 50 • 35% PTFE and a coating thickness of approximately 90 µm, prepared with the following composition: Mass (g) % Solids DI Water 2,3 100 PAA Salt 2,0 17 PTFE 0,43 50 • 45% PTFE and a coating thickness of approximately 130 µm, prepared with the following composition: Mass (g) % Solids DI Water 2,3 100 PAA salt (12 µm particles) 2,0 17 PTFE 0,66 50

[0085] The ball's oscillation frequency was 0.11 Hz, the distance traveled in one period was 3 cm (round trip), the load was 25 N, and the test duration was 5 minutes. The pressure applied to the coating during the test was 53 MPa to meet the same conditions as those listed for Test 1. The contact area between the coating and the ball was approximately 5.10 -5 m 2 , thus the pressure (with a 25 N load) was close to 50 MPa.

[0086] In the moistened test, all PTFE / PI samples had approximately the same COF as shown in Table 8 below. They are all lower than the COF of Norglide. Table 8 Results of the plint test under humidified conditions Coating composition (in solids %) Norglide 25% PTFE 35% PTFE 45% PTFE COF humidified (+ / - 10%) 0,022 0,017 0,018 0,018

[0087] In the dry test, the COF values ​​showed greater differences and a decrease with an increase in the weight percent PTFE in the coating (Table 9). Again, all PTFE / PI samples performed better than the Norglide material. Table 9 Results of the plint test for dry conditions Coating composition (in solids %) Norglide 25% PTFE 35% PTFE 45% PTFE COF dry (+ / - 10%) 0,028 0,023 0,018 0,016 Example 3 Lamination

[0088] Samples were prepared according to the various embodiments of the present disclosure by coating a corona-pretreated Kapton® release film with the 25% PTFE mixture described in Example 2 and curing it. The coating had a thickness of approximately 70 to 130 µm. The composite was then laminated onto a zinc-coated steel substrate instead of directly onto the blasting substrate, as in Example 2. In one example, a layer of modified ETFE film was used between the steel substrate and the cured composite, with the cured coating being in indirect contact with the modified ETFE film. In another example, a layer of epoxy was used between the steel substrate and the cured composite. The stock samples were then hot-pressed to cure the modified ETFE or epoxy layers.The COF was then measured in dry conditions, as described above, in the plint test, with the following parameters:. The ball's oscillation frequency was 5 Hz, the distance traveled per period was 3 cm (circular track), the load was 82 N, and the test duration was 18 minutes. The pressure exerted on the coating during the test was 53 MPa to represent the same conditions as listed for Test 1. The contact area between the coating and the ball was approximately 5.10 -5 m 2 , so that the pressure (with an 82 N load) was close to 53 MPa.

[0089] The result of the dry test of the two samples described above is in Fig. Figure 16 is reproduced. As shown, similarly excellent COF values ​​were obtained for both samples.

[0090] The sample containing modified ETFE was then measured against commercially available Norglide material, and a JBT sample was obtained from Saint-Gobain Pampus, Germany, under the trade name Norglide T. The results are presented in Fig. Figure 17 shows that, as shown, the sample according to various embodiments of the present disclosure significantly outperformed the Norglide sample and was essentially equivalent to the JBT sample.

[0091] Example 3 above illustrates, at least, that samples can be prepared and cured by coating them onto a release film and then laminated onto a substrate without suffering shrinkage due to differences in thermal expansion between the steel substrate and the coating. Accordingly, a superior and longer-lasting bearing can be obtained.

Claims

[1] Camp, encompassing: a. a substrate; and b. a first layer arranged on the substrate, wherein the layer comprises i. a polyimide matrix, wherein the polyimide matrix comprises a cross-linked and imidized polyamic acid or polyamic acid salt; and ii. a filler material dispersed in the polyimide matrix, wherein the filler material comprises a thermoplastic material, the thermoplastic material being present in the first layer in an amount of at least 25 wt.% and not more than 50 wt.%, based on the combined weight of thermoplastic material and polyimide matrix; iii. wherein the bearing has a coefficient of friction, determined according to ASTM G-77, of less than 1, and a wear resistance, determined according to ASTM G-77, of less than 2.9 mm 3 exhibits. [2] Bearing according to claim 1, wherein the substrate comprises a metallic substrate. [3] Bearing according to claim 1, wherein the substrate comprises steel, aluminium, bronze or copper. [4] Bearing according to claim 1, wherein the cross-linked and imidized polyamic acid or polyamic acid salt comprises a reaction product of two different monomers selected from the group consisting of: pyromellitic dianhydride (PMDA), 3,3'-4,4'-biphenyltetracarboxide ianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane ianhydride (6FDA), 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]-propane ianhydride (BPADA), benzophenone tetracarboxide ianhydride (BTDA), and 4,4'-oxydianiline (ODA), or m-phenylenediamine (m-PDA), 4,4'-diaminophenylsulfone (4,4'-DDS), p-phenylenediamine (p-PDA), and methylenedianiline (MDA). [5] Bearing according to claim 1, wherein the filling material comprises a thermoplastic fluoropolymer. [6] Bearing according to claim 1, wherein the filling material comprises a thermoplastic perfluoropolymer. [7] Bearing according to claim 1, wherein the filling material comprises PTFE. [8] The bearing according to claim 1, wherein the filling material further comprises an organic filling material. [9] Bearing according to claim 1, wherein the filler material is present in the first layer in an amount greater than 25 to 80 wt.%, based on the combined weight of filler material and polyimide matrix. [10] Bearing according to claim 1, a. wherein the substrate comprises steel; and b. wherein the filling material comprises PTFE. [11] Bearing according to claim 2, wherein the bearing further comprises an adhesive layer arranged between the metal substrate and the first layer. [12] Bearing according to claim 10, wherein the bearing further comprises a release layer adjacent to the first layer, whereby the first layer and the adhesive layer are arranged between the release layer and the metal substrate.

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