Fiber for tribological applications

Abstract

Fiber for tribological applications, with the exception of mineral fibers, comprising at least one solid lubricant, with the exception of graphite, or boated with at least one solid lubricant, with the exception of graphite.

Claims

1. A fiber for tribological applications wherein said fiber is surface-treated with at least one solid lubricant, said fiber being a metal fiber, a ceramic fiber, a natural fiber, a polymeric fiber, a cellulose fiber, an aramid fiber, a plastic fiber, a glass fiber, a nanofiber, or a carbon fiber, and the solid lubricant being formed of one or more of SnS, SnS.sub.2, MoS.sub.2, Bi.sub.2S.sub.3, ZnS, WS.sub.2, CuFeS.sub.2, FeS, CuS, Cu.sub.2S, MnS, Sb.sub.2S.sub.3, TiS.sub.2, sulfides of Cr/Co/Ni, Sn.sub.2S.sub.3, MoS.sub.3, WS.sub.3, Fe.sub.1-xS, MnS.sub.2, Sb.sub.2S.sub.5, ZrS.sub.2, CaS, MgS, sulfides of La, multi-phased metal sulfides, or mixtures thereof; wherein said solid lubricant is chemically bound to said fiber through sulfidization; wherein the amount of the at least one solid lubricant is at least 3% by weight.

2. The fiber according to claim 1, wherein said coated fiber is one of natural origin, or is synthetically produced, or is obtained through recycling of natural and/or synthetic products.

3. The fiber according to claim 1, wherein said fiber comprises metal sulfide.

4. The fiber according to claim 1, wherein said fiber comprising a solid lubricant is produced by laser sintering, melting extraction, machined fiber production, section rolling or spinning methods.

5. The fiber according to claim 1, wherein the one or more of the solid lubricants are in the form of multi-phased metal sulfides.

6. The fiber according to claim 1, wherein the amount of the at least one solid lubricant is at least 10% by weight.

7. A friction lining mixture having at least one fiber according to claim 1.

8. The friction lining mixture according to claim 7, further comprising a filler formed of one or more of barium sulfate, calcium carbonate, calcium hydroxide, calcium fluoride, iron oxide, silica, vermiculite, magnesium oxide, talc, zirconium silicate, zirconium oxide, mica, metal powder, molybdenum oxide, alumina, other metal oxides, silicon carbide, wollastonite, potassium titanate, chromite, calcium sulfate-whiskers, pet coke, rubber dust, nitrile rubber, acrylic rubber, friction dust.

Description

EXAMPLES

(1) Here, exemplary application-specific results of various sulfidized fibers are shown compared to each of the similar, but non-sulfidized fibers (blank) in brake linings.

(2) The sulfidized fibers were incorporated into a common low-met formulation, and brake linings were crimped. Application-specific lining characteristics were tested using the AK-Master test according to the SAE J2522 on a dynamometer. The inertia used is listed in the results that are given below. The braking system used was a Golf I type system.

(3) TABLE-US-00001 TABLE 1 AK-Master test results in coppery low-met formulation. Braking system: Golf 1, inertia: 60 kg m.sup.2 Fade 2 Results Average friction (Cu-containing Wear friction value formulation, lining Improvement value Improvement 100- Improvement Inertia: 60 kg m.sup.2) [g] [%] [%] >5 km/h [%] Blank 13.3 0.33 0.24 Sulfidized steel fiber; trial 1 10.6 20 0.33 0 0.28 17 Suifidized steel fiber; trial 2 12.2 8 0.34 3 0.30 25 Suifidized steel fiber; trial 3 8.4 37 0.35 6 0.27 13 Sulfidized steel fiber; trial 4 8.3 38 0.36 9 0.29 21 Blank 14.9 0.32 0.28 Sulfidized stainless steel fiber, 11.5 23 0.33 3 0.30 7 trial 1 Sulfidized stainless steel fiber, 12.1 19 0.33 3 0.28 0 trial 2 Blank 13.3 0.33 0.24 Sulfidized rock wool, trial 1 11.6 13 0.33 0 0.28 17 Sulfidized rock wool, trial 2 9.0 32 0.34 3 0.28 17 Blank 17.4 0.33 0.21 Sulfidized glass fiber, trial 1 8.8 49 0.35 6 0.30 43 Sulfidized glass fiber, trial 2 13.2 24 0.33 0 0.30 43 Blank 13.3 0.33 0.24 Sulfidized aramid fiber, trial 1 11.7 12 0.36 9 0.28 17 Suifidized aramid fiber trial 2 13.1 2 0.34 3 0.31 29

(4) In table 1, improvements for areas such as lining wear and average friction value as well as for the minimal friction value from the AK-Master block Fade 2 are shown. Across the exemplary testing series, improvements in lining wear of up to 49% could be achieved, compared to the corresponding blank, for the average friction value acc. to the AK-Master test, an improvement of up to 9% could be achieved, and for the minimal friction value, an improvement of up to 43% could be seen.

(5) The tests were repeated in a copper-free base mixture. In this formulation, improvements in lining wear of up to 29%, an increase of friction value of up to 13%, and an improvement of Fading 2 of up to 43% could be achieved.

(6) The results are shown in the table below.

(7) TABLE-US-00002 TABLE 2 AK-Master test results in Cu-free low-met formulation. Braking system: Golf 1, inertia: 40.6 kg m.sup.2 Fade 2 Results Average friction (Cu-free Wear friction value formulation, lining Improvement value Improvement 100- Improvement Inertia: 40.6 kg m.sup.2) [g] [%] [%] >5 km/h [%] Blank 7.0 0.31 0.24 Sulfidized steel fiber; trial 1 6.5 7 0.32 3 0.28 17 Sulfidized steel fiber; trial 2 6.2 11 0.33 6 0.30 25 Sulfidized steel fiber; trial 3 6.5 7 0.33 6 0.25 4 Sulfidized steel fiber; trial 4 6.3 10 0.34 10 0.24 0 Blank 6.9 0.32 0.28 Sulfidized stainless steel fiber, trial 1 6.4 7 0.33 3 0.30 7 Sulfidized stainless steel fiber, trial 2 6.3 9 0.33 3 0.28 0 Blank 7.0 0.31 0.24 Sulfidized rock wool, trial 1 5.7 19 0.32 3 0.28 17 Sulfidized rock wool, trial 2 5.9 16 0.31 0 0.28 17 Blank 6.6 0.33 0.21 Sulfidized glass fiber, trial 1 4.7 29 0.35 6 0.30 43 Sulfidized glass fiber, trial 2 5.7 14 0.33 0 0.30 43 Blank 7.0 0.31 0.24 Sulfidized aramid fiber, trial 1 5.9 16 0.35 13 0.28 17 Sulfidized aramid fiber trial 2 5.5 21 0.34 10 0.31 29

(8) The friction lining formulations for testing the benefits of the functional fiber are shown below. In the application-specific comparison, steel fibers and stainless steel fibers and rock wool or aramid fibers, respectively, were each replaced by the corresponding sulfidized type.

(9) Formulation, Cu-Containing [% by Weight] Binder 6 Organic fillers 7 Aramid fiber 3 Rock wool 7 Steel fibers/Stainless steel fibers 11 Copper/brass 16 Inorganic fillers 27 Abrasive agents 10 Graphite/Coke 13 Formulation, Cu-free [% by weight] Binder 6 Organic fillers 8 Aramid fibers 4 Rock wool 8 Steel fibers/Stainless steel fibers 13 Inorganic fillers 32 Abrasive agents 12 Graphite/Coke 17 FIG. 1 shows an example of a sulfidized steel fiber. The steel fibers which were used have the following characteristics; Fiber length: min. 100 m; max. 2000 m; average: 900 m Fiber diameter: min. 20 m; max. 100 m; average: 50 m Sulfide concentration in sulfidized steel fibers:

(10) TABLE-US-00003 Description SnS [wt %] FeS [wt %] MoS.sub.2 [wt %] Steel fiber trial 1 7 35 Steel fiber trial 2 10 10 Steel fiber trial 3 35 7 Steel fiber trial 4 10 10 Stainless steel fiber trial 1 7 35 Stainless steel fiber trial 2 10 10 Summary of various materials which could possibly be used in the friction lining formulation (individual group summary):

(11) Examples of binders: thermosetting polymer, typically phenol resin or melamine resin, epoxy resin, modified phenol resins, synthetic rubber.

(12) Examples of fillers: barium sulfate, calcium carbonate, calcium hydroxide, calcium fluoride, iron oxide, silica, vermiculite, magnesium oxide, talc, zirconium silicate, zirconium oxide, mica, metal powder, molybdenum oxide, alumina, other metal oxides, silicon carbide, wollastonite, potassium titanate, chromite, calcium sulfate-whiskers, pet coke, rubber dust, nitrile rubber, acrylic rubber, friction dust. Exemplary use of friction linings:

(13) Friction linings, e.g., disk brake linings, serve to slow moving objects, e.g., vehicles (cars). To achieve this, a friction lining is pressed against a moving counterbody with as much of its surface area as possible, and the counterbody is slowed down/braked in relation to the friction lining by the arising friction. Typically, this process leads to abrasion (wear) and frictional heat.

(14) Further examples of fibers of the invention are provided as follows; Solid lubricant surface concentration of coated steel fibers:

(15) TABLE-US-00004 Description SnS [wt %] FeS [wt %] CaF.sub.2 [wt %] Steel fiber trial 5 5 30 7 Steel fiber trial 6 10 10 10 Stainless steel fiber trial 3 5 30 7 Stainless steel fiber trial 4 10 10 10 Summary of sulfides comprised in metal sulfide fibers:

(16) TABLE-US-00005 Description CuS [wt %] SnS [wt %] FeS [wt %] MoS.sub.2 [wt %] Solid fiber 1 20 80 Solid fiber 2 6.5 13.5 80 Solid fiber 3 13.5 80 6.5 Solid lubricant fibers:

(17) Direct production, e.g., through melt spinning processes, for solid lubricants, e.g., metal sulfides or multi-phased metal sulfides from a melt which was specifically produced for this purpose. One example of this would be a SnS fiber. For friction linings, the entire fiber content or a fraction of the produced fiber, respectively, will be used.

(18) It was shown during implementation that the solid lubricant, bound to the fiber or comprising same, respectively, is distributed differently within the friction lining, meaning that it could be placed at another site where it would be needed, and thus supports tribological contact and shows its benefits of minimizing wear and stabilizing frictional values. Furthermore, the fiber-bound solid lubricant within the friction lining mixture can no longer sediment before pressing and after pre-mixing, and will continue to be present in a homogenous distribution even within the finished composite.

(19) It has been shown that the invention also provides an ecological benefit in that the amount of non-ferrous metal, especially copper, in friction linings is reduced, which would otherwise be disseminated into the environment and have ecotoxic effects on same, through the resulting wear of the lining.