PTFE POLYMER-BASED SLIDING MATERIAL HAVING FILLERS WHICH IMPROVE THE TRIBOLOGICAL PROPERTIES

Abstract

The invention relates to a PTFE polymer-based sliding material having fillers which improve the tribological properties, wherein the fillers comprise at least one phosphate, in particular calcium phosphate, calcium pyrophosphate, magnesium phosphate, magnesium pyrophosphate, lithium phosphate, hydroxyapatite or combinations thereof, and at least one metal sulfide, wherein the fraction of the metal sulfide is >2% by volume. The invention also relates to uses of said sliding material.

Claims

1. PTFE polymer-based sliding material having fillers which improve the tribological properties, characterized in that the fillers comprise at least one phosphate and at least one metal sulfide as a primary filler and wherein the proportion of the at least one metal sulfides is at least >2% by volume.

2. The PTFE polymer-based material according to claim 1, characterized in that the at least one phosphate calcium phosphate, calcium pyrophosphate, magnesium phosphate, magnesium pyrophosphate, lithium phosphate, hydroxyapatite or combinations thereof.

3. The PTFE polymer-based siding material according to claim 1, characterized in that the at least one metal sulfide comprises SnS.sub.2, MoS.sub.5, Bi.sub.2S.sub.3, WS.sub.2, ZnS or CuS and combinations thereof.

4. The PTFE polymer-based sliding material according to claim 1, characterized in that the PTFE polymer-base sliding material comprises a PTFE polymer-base having at least 70% by volume, including at least 80% by volume, at least 90% by volume and 100% by volume of PTFE, and also including proportions of up to 30% by volume of a polymer fraction, including up to 20% by volume, and or up to 10% by volume, of the PTFE polymer-base is replaced by other polymers and combinations thereof, including PVDF, PFA, FEP, ECTFE, ETFE.

5. The PTFE polymer-based sliding material according to claim 1, characterized in that the proportion of the at least one phosphates in total is 1 to 30% by volume, or 1 to 25% by volume, or 1 to 20% by volume of the PTFE polymer-based sliding material.

6. The PTFE polymer-based sliding material according to claim 1, characterized in that the proportion of the at least one metal sulfides as fillers in total is more than 3% by volume, or more than 5% by volume, or more than 7% by volume, or more than 9% by volume, or 10% by volume, or more than 10% by volume, or at most 30% by volume, or at most 20% by volume, or at most 15% by volume of the PTFE polymer-based sliding material.

7. The PTFE polymer-based sliding material according to claim 1, characterized in that the ratio of volumes of the at least one phosphate to the at least one metal sulfide is 6:1 to 1:2, including 4:1 to 1:1.

8. The PTFE polymer-based sliding material according to claim 1, characterized in that the PTFE polymer-based sliding material comprises further secondary fillers, including further solid lubricants, or, BaSO.sub.4, Lithophones and/or fluorides, or calcium fluoride, and/or pigments and combinations of the further secondary fillers.

9. The PTFE polymer-based sliding material according to claim 7, characterized in that the proportion of the further secondary fillers is 0 to 30% by volume, or 1 to 20% by volume, or 1 to 10% by volume of the PTFE polymer-based sliding material.

10. The PTFE polymer-based sliding material according to claim 1, characterized in that further tertiary fillers are carbon fibers, glass fibers, polymer fibers (in particular aramid fibers); and/or solid lubricants, including graphite, carbon black, BN and/or plastic particles, such as PFPE, aramid (PPTA), PPSO.sub.2, PI and PAI particles, polyacrylate particles (PAR), PBA particles, PBI particles; and/or metal oxides, including Fe.sub.2O.sub.3, Al.sub.2O.sub.3, SiO.sub.2, CrO.sub.2, TiO.sub.2, CuO, MgO, ZnO; and/or hard material particles, including ceramic particles, such as SiC, Si.sub.3N.sub.4, BC, cubic BN; and/or fluorides, such as in particular NaF, AlF.sub.3; and/or sheet silicates, including kaolin, mica, wollastonite, talc, silicic acid; and/or metallic fine powders, in particular bronze and bismuth; and/or pigments or mixed phase oxide pigments, including Co—Al, Cr-13 Sb—Ti, Co—Ti, Fe—Al, Mn—Fe or Co—Cr.

11. The PTFE polymer-based siding material according to claim 9, characterized in that the proportion of further tertiary fillers substances is 0 to 15% by volume, including 0 to 10% by volume of the PTFE polymer-based sliding material.

12. The PTFE polymer-based sliding material according to claim 1, characterized in that the PTFE polymer-based sliding material comprises a PTFE polymer base that constitutes 50 to 95% by volume, including 60 to 95% by volume, or 70 to 90% by volume of the PTFE polymer-based sliding material.

13. A PTFE polymer-based sliding bearing composite material with a metallic support layer, including steel or bronze, including with a porous support layer, including being made of bronze, and with a sliding material filling, pores of the metallic support layer according to claim 1.

14. A sliding bearing element made of the PTFE polymer-based sliding bearing composite material according to claim 13.

15. The sliding bearing element according to claim 14, characterized in that the sliding bearing element is a sliding strip, a sliding shoe or sliding pad or a sliding bearing shell, a slide bearing bush or slide collar bush.

16. The PTFE polymer-based sliding material according to claim 2, characterized in that the at least one metal sulfide comprises SnS.sub.2, MoS.sub.s, Bi.sub.2S.sub.3, WS.sub.2, ZnS or CuS and combinations thereof.

17. The PTFE polymer-based sliding material according to claim 2, characterized in that the PTFE polymer-base sliding material comprises a PTFE polymer-base having at least 70% by volume, including at least 80% by volume, at least 90% by volume and 100% by volume of PTFE, and also including proportions of up to 30% by volume of a polymer fraction, including up to 20% by volume, and or up to 10% by volume of the PTFE polymer-base is replaced by other polymers and combinations thereof, including PVDF, PFA, FEP, ECTFE, ETFE.

18. The PTFE polymer-based sliding material according to claim 2, characterized in that the proportion of the at least one phosphates in total is 1 to 30% by volume, or 1 to 25% by volume, or 1 to 20% by volume of the PTFE polymer-based sliding material.

19. The PTFE polymer-based sliding material according to claim 2, characterized in that the proportion of the at least one metal sulfides as fillers in total is more than 3% by volume, or more than 5% by volume, or more than 7% by volume, or more than 9% by volume, or 10% by volume, or more than 10% by volume, or at most 30% by volume, or at most 20% by volume, or at most 15% by volume of the PTFE polymer-based sliding material.

20. The PTFE polymer-based sliding material according to claim 2, characterized in that the ratio of volumes of the at least one phosphate to the at least one metal sulfide is 6:1 to 1:2, including 4:1 to 1:1.

Description

[0031] In the drawings:

[0032] FIG. 1 shows a schematic sectional view of a metal/plastic sliding bearing composite material according to the invention;

[0033] FIG. 2 shows measurement results of wear values of sliding bearing members made of the above sliding materials;

[0034] FIG. 3 shows measurement results of friction coefficients of sliding bearing members made of the above sliding materials.

[0035] FIG. 1 shows a schematic sectional view of a sliding bearing composite material 2 according to the invention with a metallic support layer 4, typically of steel, and with a porous carrier layer 6. The porous carrier layer 6 is formed by a sintered layer of bronze-based metallic particles 7. The particles of the carrier layer 6 form coherent macroscopic cavities (which are not shown to scale), in which a polymer-based sliding material 8 according to the invention is impregnated. The sliding material 8 fills the pores of the support layer 6 substantially completely. The matrix-forming polymer component of the sliding layer material 8 is based on PTFE in the sense defined above. The polymer component is advantageously made of PTFE. The sliding layer material 8 further comprises fillers incorporated in the matrix-forming polymer component, namely one or more phosphates and one or more metal sulfides. Other fillers in addition to phosphates and metal sulfides may prove to be advantageous and are also not shown. In particular, the above-mentioned secondary and/or tertiary fillers are suitable.

[0036] FIG. 2 shows the result of wear measurements and FIG. 3 of friction coefficient measurements on sliding bearing elements, which were measured with sliding bearing composite materials using sliding materials of the above examples 1 to 9. The sliding bearing composites comprise a metallic support layer of steel, a porous support layer of the type described above, and a polymer-based sliding material filling the pores of the support layer. The examined sliding bearing elements differ only with regard to the composition of the sliding material.

[0037] The wear resistance and friction coefficients were determined in a rotation test with a sliding speed of 2 m/s under a load of 0.75 MPa. The test parameters are given in the table below.

TABLE-US-00002 Test Test parameters parameters Lubrication Dry run condition Counter body 100Cr6 Load 0.75 MPA Sliding speed 2 m/s Test time 15 h

[0038] For this purpose, a bush was produced as a sliding bearing element having an inner diameter of 20 mm and an outer diameter of 23 mm and 15 mm width, comprising the sliding material according to the above examples 1 to 9.

[0039] Example 2, which contains only calcium phosphate as a filler, serves as reference example, to the measured values of which the other examples are related. Examples 1 and 3 to 5 are not comparative examples according to the invention. Examples 6 to 9 show sliding materials according to the invention.

[0040] The sliding materials to which calcium phosphate and a metal sulfide have been added as fillers and which thus correspond to the invention show a significantly and surprisingly lower wear than the comparative examples and the reference example.

[0041] The wear resistance can be further improved by targeted combinations of calcium phosphate with metal sulfides as further solid lubricants (primary fillers), such as Bi.sub.2S.sub.3 (Example 6), SnS.sub.2 (Example 7) or WS.sub.2 (Example 8). Furthermore, a mixture of phosphate and primary fillers (here Bi.sub.2S.sub.3) and secondary fillers, here BaSO.sub.4 as a solid lubricant, were investigated, which further improves the wear values (s. Example 9). Especially the examples 8 and 9 show a more than 50% lower wear than the references with consistently good friction coefficients.