RUBBER COMPOSITION, METHOD FOR PREPARING SAME, FUEL HOSE AND FUEL FEED CIRCUIT INCORPORATING SAME

Abstract

The invention in relates in particular to a rubber composition able to be extruded to form an inner layer of a fuel hose for a motor vehicle, a method for preparing this composition, this hose and a fuel feed circuit of a motor vehicle incorporating it. This composition is based on at least one fluoroelastomer (FKM) and includes a filler and a micronised powder of at least one fluorinated thermoplastic polymer which are dispersed in said at least one fluoroelastomer. According to the invention, the composition includes said micronised powder according to a quantity greater than 20 phr (phr: parts by weight per 100 parts of elastomer(s)), and the filler includes at least one inorganic filler having lamellas which has an aspect ratio greater than 30 and which is based on a phyllosilicate chosen from kaolinite and micas, or is based on a talc.

Claims

1. Crosslinkable rubber composition able to be extruded to form an inner layer of a fuel hose for a motor vehicle, the composition being based on at least one fluoroelastomer (FKM) and comprising a filler and a micronised powder of at least one fluorinated thermoplastic polymer which are dispersed in said at least one fluoroelastomer, wherein the composition comprises said micronised powder according to a quantity greater than 20 phr (phr: parts by weight per 100 parts of elastomer(s)) and wherein the filler comprises at least one inorganic filler having lamellas which has an aspect ratio greater than 30 and which is based on a phyllosilicate chosen from kaolinite and micas, or is based on a talc, said aspect ratio being defined as being the ratio of an average largest dimension over an average smallest dimension of the lamellas, said ratio being measured by the scanning electron microscopy technique.

2. Crosslinkable composition according to claim 1, in which said at least one inorganic filler has an average transversal smaller dimension which defines an average thickness of lamellas comprised between 100 nm and 500 nm and an average larger dimension which defines an average width of lamellas comprised between 1 m and 50 m.

3. Crosslinkable composition according to claim 1, in which the composition comprises said micronised powder of at least one fluorinated polymer according to a quantity greater than or equal to 30 phr.

4. Composition according to claim 1, in which said micronised powder is based on at least one polytetrafluoroethylene (PTFE) modified or not in terms of said at least one fluorinated thermoplastic polymer, and has an average particle diameter D50 measured according to the standard ASTM D 4464 which is comprised between 2 m and 20 m.

5. Composition according to claim 4, in which said micronised powder has an average particle diameter D50 measured according to the standard ASTM D 4464 which is comprised between 5 m and 15 m.

6. Crosslinkable composition according to claim 1, in which the filler comprises said at least one inorganic filler according to a mass fraction of at least 40%.

7. Crosslinkable composition according to claim 6, in which the filler comprises said at least one inorganic filler according to a mass fraction greater than 50%.

8. Crosslinkable composition according to claim 1, in which the composition comprises said micronised powder according to a quantity comprised between 45 and 65 phr and said at least one inorganic filler according to a quantity comprised between 5 and 25 phr.

9. Crosslinkable composition according to claim 8, in which the filler further comprises an organic filler based on a carbon black and/or a graphite.

10. Crosslinkable composition according to claim 9, in which the filler comprises less than 5 phr of carbon black and less 10 phr of graphite.

11. Crosslinkable composition according to claim 1, in which the composition comprises a crosslinking system comprising a peroxide or a bisphenol.

12. Crosslinkable composition according to claim 11, in which the composition comprises the crosslinking system according to a quantity comprised between 2 and 6 phr.

13. Crosslinkable composition according to claim 1, in which the composition has, after passing through a Garvey extrusion die, a pressure applied to the composition measured at the outlet of the die that is continuously comprised between 25.Math.10.sup.5 Pa and 70.Math.10.sup.5 Pa, with the extruder having the following characteristics: a conveying screw of diameter D equal to 25 mm and of length equal to 12D, a feed belt 2 to 3 cm wide, a feed roller cooled with a water circulation system, a screw body heated to 85 C. by a regulator by means of water, the die being heated to 95 C. or 110 C. by a heating ring, said pressure applied to the composition at the outlet of the die being measured by a sensor at a head of the screw, a speed of the screw varying between 4 and 20 rpm regulated according to the aspect of the extruded composition at the outlet of the die, and a conveyor belt on which the composition is disposed for the driving thereof.

14. Crosslinkable composition according to claim 1, in which said at least one fluoroelastomer is an FKM chosen from terpolymers of vinylidene fluoride (VDF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) with a fluorine mass rate greater than or equal to 70%, the composition having a Mooney viscosity ML(1+4) at 100 C. measured according to the standard ASTM D 1646 comprised between 50 and 75.

15. Crosslinkable composition according to claim 14, in which the composition comprises at least two of said fluoroelastomers (FKM), comprising a first FKM and a second FKM with respective Mooney viscosities ML(1+10) at 121 C., measured according to the standard ASTM D 1646, comprised between 17 and 21 and between 22 and 26, with the first FKM present in the composition according to a quantity of at least 50 phr, and the second FKM present in the composition according to a quantity of at most 50 phr.

16. Crosslinkable composition according to claim 1, in which said at least one inorganic filler is based on said phyllosilicate, of which the aspect ratio is at least 35.

17. Crosslinkable composition according to claim 16, in which the aspect ratio of said phyllosilicate is at least 80.

18. Crosslinkable composition according to claim 16, in which said at least one inorganic filler comprises kaolinite, being based on a kaolin.

19. Crosslinkable composition according to claim 18, in which an average transversal smaller dimension of said kaolin defines an average thickness of lamellas comprised between 120 nm and 280 nm and an average larger dimension of said kaolin defines an average width of lamellas comprised between 4 m and 12 m.

20. Crosslinkable composition according to claim 16, in which said at least one inorganic filler is based on a mica of the muscovite or phlogopite type.

21. Crosslinkable composition according to claim 20, in which the aspect ratio of said mica is at least 120.

22. Crosslinkable composition according to claim 20, in which an average transversal smaller dimension of said mica defines an average thickness of lamellas comprised between 110 nm and 470 nm and an average larger dimension of said mica defines an average width of lamellas comprised between 13 m and 40 m.

23. Crosslinkable composition according to claim 1, in which said at least one inorganic filler is based on a talc of which the aspect ratio is at least 35.

24. Crosslinkable composition according to claim 23, in which an average transversal smaller dimension of said talc defines an average thickness of lamellas comprised between 120 nm and 180 nm and an average larger dimension of said talc defines an average width of lamellas comprised between 4 m and 8 m.

25. Crosslinked rubber composition able to form an extruded inner layer of a fuel hose for a motor vehicle, wherein the crosslinked composition is the product of a chemical crosslinking by a peroxide or a bisphenol of the crosslinkable composition according to claim 1.

26. Crosslinked composition according to claim 25, in which the composition has an average permeation flux Q with an alcohol essence of the FAM B type such as described in the standard DIN 51604, said permeation flux being measured through a plate formed from the composition over 18 days at 40 C. according to the standard D 451652 of PSA of June 2010, which is less than 0.30 g.Math.h.sup.1.Math.m.sup.2.

27. Crosslinked composition according to claim 25, in which the composition satisfies at least one of the conditions (i) to (iii) hereinafter: (i) at least one of the following secant moduli M50, M100 and M200 respectively at 50%, 100% and 200% deformation, measured in uni-axial tensile force according to the standard ASTM D 412: M50 greater than 3 MPa, M100 greater than 4 MPa, M200 greater than 6 MPa; (ii) a resistance to breaking R/r, measured in uni-axial tensile force according to the standard ASTM D 412, greater than 8 MPa; and (iii) a Shore A hardness measured after 3 seconds according to the standard ASTM D2240 which is greater than 70.

28. Method for preparing a crosslinkable composition according to claim 1, wherein the method comprises the following steps: a) thermomechanical mixing of said at least one fluoroelastomer (FKM), of said filler and of said micronised powder of at least one fluorinated thermoplastic polymer and of other ingredients of the composition with the exception of a crosslinking system, the mixing being implemented at a falling temperature between 90 and 100 C. with a peak temperature between 105 and 115 C.; b) mechanical mixing of the mixture obtained in step a) on cylinders with the adding of the crosslinking system comprising a peroxide or a bisphenol, for the obtaining of the crosslinkable composition.

29. Tubular extrudate able to form after crosslinking an inner layer of a fuel hose for a motor vehicle, wherein the extrudate is formed from a crosslinkable composition according to claim 1.

30. Fuel hose for a motor vehicle with a combustion or hybrid engine, in particular for a fuel of the petrol type, including a radially internal layer and at least one radially external layer, wherein the radially internal layer is formed from a crosslinked composition according to claim 25, with the hose further including, between the radially internal and external layers, at least one radially intermediate layer and a textile reinforcement.

31. Fuel feed circuit of a motor vehicle with a combustion or hybrid engine comprising lines between a fuel tank and a fuel injection rail, wherein at least one of the lines comprises a hose according to claim 30.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Other characteristics, advantages and details of this invention shall appear when reading the following description of several embodiments of the invention, given for the purposes of information and in a non-limiting way in relation with the accompanying drawings, among which:

[0066] FIG. 1a is a scanning electron microscope snapshot (SEM hereinafter) of an inorganic filler with a high aspect ratio Barrisurf HX (kaolin) tested according to the invention showing thicknesses and widths of lamellas.

[0067] FIG. 1b is another SEM snapshot of the inorganic filler of FIG. 1a showing the thickness of a lamella.

[0068] FIG. 2a is a SEM snapshot of another inorganic filler with a high aspect ratio Chinafill 800 (kaolin) tested according to the invention showing widths of lamellas.

[0069] FIG. 2b is another SEM snapshot of the inorganic filler of FIG. 2a showing thicknesses of lamellas.

[0070] FIG. 3a is an SEM snapshot of an inorganic filler with a high aspect ratio Mistron HAR (talc) tested according to the invention showing widths of lamellas.

[0071] FIG. 3b is another SEM snapshot of the inorganic filler of FIG. 3a showing thicknesses of lamellas.

[0072] FIG. 4a is an SEM snapshot of an inorganic filler with a high aspect ratio Mica F (mica) tested according to the invention showing widths of lamellas.

[0073] FIG. 4b is another SEM snapshot of the inorganic filler of FIG. 4a showing thicknesses of lamellas.

[0074] FIG. 5a is an SEM snapshot of an inorganic filler with a high aspect ratio Suzorite 325 HK (mica) tested according to the invention showing widths of lamellas.

[0075] FIG. 5b is another SEM snapshot of the inorganic filler of FIG. 5a showing thicknesses of lamellas.

[0076] FIG. 6 is a photograph showing in perspective a Garvey extrusion die used in the invention to test the aptitude for use by extrusion of the crosslinkable compositions of the invention.

[0077] FIG. 7a comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a control composition A, obtained by the die of FIG. 6.

[0078] FIG. 7b comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition B according to the invention incorporating the filler Chinafill 800, obtained by the die of FIG. 6.

[0079] FIG. 7c comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition C according to the invention incorporating the filler Chinafill 800, obtained by the die of FIG. 6.

[0080] FIG. 7d comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition D according to the invention incorporating the filler Chinafill 800, obtained by the die of FIG. 6.

[0081] FIG. 7e comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition E according to the invention incorporating the filler Chinafill 800 and graphite, obtained by the die of FIG. 6.

[0082] FIG. 7f comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition F that is not in accordance with the invention incorporating an insufficient quantity of fluorinated micronised powder and of carbon black in place of the inorganic filler, obtained by the die of FIG. 6.

[0083] FIG. 7g comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition G according to the invention incorporating the filler Chinafill 800 and graphite, obtained by the die of FIG. 6.

[0084] FIG. 8a is a SEM snapshot of the control composition A showing in particular the morphology of the dispersion of the fluorinated micronised powder and of the carbon black.

[0085] FIG. 8b is a SEM snapshot of the composition B according to the invention showing in particular the morphology of the dispersion of the fluorinated powder and of its inorganic filler Chinafill 800.

[0086] FIG. 8c is a SEM snapshot of the composition C according to the invention showing in particular the morphology of the dispersion of the fluorinated powder and of its inorganic filler Chinafill 800.

[0087] FIG. 8d is a SEM snapshot of the composition D according to the invention showing in particular the morphology of the dispersion of the fluorinated powder and of its inorganic filler Chinafill 800.

[0088] FIG. 8e is a SEM snapshot of the composition E according to the invention showing in particular the morphology of the dispersion of the fluorinated powder, of its inorganic filler Chinafill 800 and of a graphite.

[0089] FIG. 8f is a SEM snapshot of the composition F that is not in accordance with the invention showing in particular the morphology of the dispersion of the fluorinated powder and of the carbon black that it contains.

[0090] FIG. 8g is a SEM snapshot of the composition G according to the invention showing in particular the morphology of the dispersion of the fluorinated powder, of its inorganic filler Chinafill 800 and of a graphite.

[0091] FIG. 8h is a SEM snapshot of the control composition H showing in particular the morphology of the dispersion of its fluorinated powder and of the carbon black.

[0092] FIG. 8i is a SEM snapshot of the composition I according to the invention showing in particular the morphology of the dispersion of its fluorinated powder and of its inorganic filler Barrisurf HX.

[0093] FIG. 8j is a SEM snapshot of the control composition J showing in particular the morphology of the dispersion of its fluorinated powder and of the carbon black.

[0094] FIG. 9 is a graph showing the change in the stress (Pa) according to the shear rate (s.sup.1), measured by capillary rheometry for the control crosslinkable composition H and for the crosslinkable composition I according to the invention, at each time on a smooth wall of the extrusion die and on a rough wall of the extrusion die.

[0095] FIG. 10 is an exploded front diagrammatical view, slightly in perspective, of a device for measuring the average permeation flux Q of a plate formed from a rubber composition by an essence over 18 days at 40 C. according to the standard D 451652 of PSA of June 2010.

[0096] FIG. 11a comprises two upper and lower photographs showing respectively the top and an end of an extrudate of another control composition M, obtained by the die of FIG. 6.

[0097] FIG. 11b comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition N according to the invention incorporating the filler Barrisurf HX, obtained by the die of FIG. 6.

[0098] FIG. 11c comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition O according to the invention incorporating the filler Chinafill 800, obtained by the die of FIG. 6.

[0099] FIG. 11d comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition P according to the invention incorporating the filler Mistron HAR, obtained by the die of FIG. 6.

[0100] FIG. 11e comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition Q according to the invention incorporating the filler Suzorite 325 HK, obtained by the die of FIG. 6.

[0101] FIG. 11f comprises two upper and lower photographs showing respectively the top and an end of an extrudate of a composition R according to the invention incorporating the filler Mica F, obtained by the die of FIG. 6.

[0102] FIG. 12 is a partial view in perspective with partial pull-outs of a fuel hose according to an embodiment of the invention, of which the inner layer is formed from a crosslinked composition according to the invention.

EMBODIMENTS OF THE INVENTION

[0103] In all of the following examples, the crosslinkable compositions based on one or two FKMs have been prepared by implementing the following method.

[0104] a) Step of Thermomechanical Mixing in an Internal Mixer: [0105] adjustment to 35 C., [0106] beginning of the cycle at a rotating speed of the blades of the rotor of 40 rpm, [0107] initial instant t0: introduction of the gum (i.e. of the FKM(s)), [0108] t=1 min.: introduction of the other ingredients of the composition except the crosslinking system with peroxide, and pressure of the piston at 10.sup.5 Pa then 3.Math.10.sup.5 Pa, [0109] t=2 min. 30 s: pressure of the piston at 3.Math.10.sup.5 Pa and speed of the blades of 50 rpm., [0110] t=3 min.: scanning, [0111] t=3 min. 30 s: change in the speed of the blades to 80 rpm., [0112] t=6 min. or 95 C. displayed: falling, the temperature at the peak being about 110 C.

[0113] b) Mechanical Mixing in an Open Mixer (on Cylinders): [0114] adding of the crosslinking system with peroxide, then [0115] 7 passages at the end of the crosslinkable composition.

[0116] All of the compositions tested at instant t95 at 180 C. were crosslinked, without a post-curing step.

[0117] The following table 1 lists the characteristics of the powders of PTFE used in the compositions tested (D50 being measured according to ASTM D 4464).

TABLE-US-00001 TABLE 1 Commercial name Supplier Nature Characteristics Algoflon Solvay PTFE BET > 7.5 m.sup.2/g D50 = 5 m L203 powder Polymist Solvay PTFE BET = 3 m.sup.2/g D50 = 12 m F5A EX powder

[0118] The following table 2 lists the characteristics of the inorganic fillers with high aspect ratios used in the compositions tested.

TABLE-US-00002 TABLE 2 Commercial name Supplier Nature Characteristics Chinafill 800 AKW Kaolin Average thickness = 250 nm Average width = 10 m Aspect ratio = 40 Barrisurf HX Imerys Kaolin Average thickness = 150 nm Average width = 5 m Aspect ratio = 35 Mistron HAR Imerys Talc Average thickness = 150 nm Average width = 6 m Aspect ratio = 40 Mica F Aspanger Mica Average thickness = 130 nm Average width = 16 m Aspect ratio = 125 Suzorite 325 Imerys Mica Average thickness = 450 nm HK Average width = 35 m Aspect ratio = 80

[0119] The aspect ratios of these fillers were determined by preparing samples by Au/Pd metallisation, then by the scanning electron microscopy technique (SEM) by means of a Centaurus (backscattered electrons) or SE2 (secondary electrons) sensor. In light of the definition of the aspect ratio by the ratio of the average largest dimension (width of the lamellas) over the average smallest dimension (thickness of the lamellas), these average dimensions were measured by observation under SEM, as can be seen in FIGS. 1a-1b, 2a-2b, 3a-3b, 4a-4b and 5a-5b and details in table 2.

First Series of Tests:

[0120] This first series shows in particular the effect of adding the filler Chinafill 800 in control compositions A and according to the invention B, C, D, E, G, which are all based on a single and same FKM of denomination DAIEL G-902 (DAIKIN) and which all include 50 phr of powder of PTFE of denomination Algoflon L203, while the composition F that is not in accordance with the invention based on FKM DAIEL G-902 comprises only 15 phr of this powder of PTFE.

The filler Chinafill 800 was added according to 13 phr to the composition B and according to 20 phr to the compositions C-D, and a blend of 7 and 12 phr of Chinafill 800 and of 6 and 8 phr graphite Timrex C-Therm 002 to the compositions E and G, respectively. The composition F is devoid of Chinafill 800 and of any other inorganic filler, comprising only 10 phr of a carbon black as a filler.
The crosslinking system used was formed from DHBP 45 (crosslinking agent: organic peroxide) and from coagent TAIC (liquid), and only for compositions D, F and G an implementation assistance agent (VPA 2) was furthermore added.

[0121] Garvey extrusion tests were conducted on the various crosslinkable compositions so as to evaluate the extrudability thereof, i.e. aptitude for use by extrusion, by following the prescriptions of the standard NF T43-016. Recall that the Garvey test is a usual appreciation method of the aptitude for socking of the non-crosslinked rubber compositions. According to this test the various compositions were extruded with a Garvey die such as the one that can be seen in the photograph of FIG. 6 (die with a substantially prismatic shape with a globally trapezoidal section).

[0122] The classification system A was used which ranks on a scale from 1 (poor) to 4 (good) the following parameters: [0123] swelling and porosity, [0124] sharpness of the edge (angle of 30 C.), [0125] uniformity of the surface, and [0126] continuity of the three other angles.

[0127] The following protocol was followed for the extrusion test.

The extrusion was carried out on a laboratory extruder with a conveying screw of diameter D=25 mm and of length 12D. The feeding with a belt 2 to 3 cm wide was carried out, and the feed roller was cooled with a water circulation system. The screw body was heated to 85 C. by a regulator (water). The die was heated to 95 C. or 110 C. (according to the tests) using a heating ring.
During the test, the pressure was measured by a sensor located at the screw head. The speed of the screw was made to vary between 4 and 20 rpm., with the speed having been adjusted according to the aspect of the extrudate at the die outlet.
The extrudate was placed on a conveyor belt which drove it all throughout the test.

[0128] Table 3 hereinafter provides details on the formulations of the compositions A to G (quantities in phr), and table 4 hereinafter the results obtained during the extrusion tests in the Garvey die (screw heated to 85 C., die to 95 C., speed of the screw of 8 rpm.).

TABLE-US-00003 TABLE 3 A B C D E F G DAIEL G-902 100 100 100 100 100 100 100 Black MT N 991 5 2 2 2 2 10 2 VPA 2 1 1 1 TAIC liq 2.1 2.1 2.1 2.1 2.1 2.1 2.1 Algoflon L203 50 50 50 50 50 15 50 Timrex C-Therm 002 6 8 Chinafill 800 13 20 20 7 12 DHBP 45 2 2 2 2 2 2 2

TABLE-US-00004 TABLE 4 A B C D E F G Initiation of the Difficult Good Good Good Good Good Good in feed part Backflow at the Yes No No No No No No feed roller Pressure at die Varies 45 40 45 45 35 45 outlet (in 10.sup.5 Pa) from 40 to 4 Aspect 4.4.3.4 4.4.3.4 4.4.3.4 4.4.4.4 4.4.3.4 4.4.3.4 4.4.4.4 (classification system A)

[0129] FIGS. 7a to 7g show the aspect of the surfaces and of the end profiles respectively obtained for these compositions A to G, following these Garvey extrusion tests.

[0130] The control composition A is therefore not correctly extrudable, see the priming of the feed, the undesirable backflow at the feed and the fluctuation in the extrusion pressure obtained for the composition A without filler Chinafill 800. On the contrary, the compositions B to E and G that incorporate the filler Chinafill 800, in particular when it is used alone (see compositions B, C, D), show a clear improvement in the extrusion conditions with a resolution of the material sliding problems at the feed and a stabilisation in the extrusion pressure, without degrading the Garvey score on the extrudates obtained, as well as for the composition F that is not in accordance with the invention despite a pressure at the die outlet that is less than that relative to the compositions B to E and G.

[0131] FIGS. 8a to 8g show the morphologies respectively obtained for the crosslinked compositions A to G, following the aforementioned crosslinking with peroxide (at t95 at 180 C., without post-curing), with the homogeneous dispersion of the fluorinated powder of PTFE and, for the compositions B to G, of the filler Chinafill 800.

[0132] Table 5 hereinafter shows the properties measured for these compositions A to G, in the non-crosslinked state (Mooney viscosity measured according to the standard ASTM D 1646) as well as in the crosslinked state: [0133] properties in uni-axial tensile force at the initial state according to the standard ASTM D 412, [0134] Delft resistance to tearing, [0135] Shore A hardness at 3 s measured at the initial state according to the standard ASTM D2240, [0136] CSR compression set resistance of type B measured at 22 hours, 135 C. and 25% compression rate, and [0137] FAM B permeability at 40 C. (average permeation rate Q avg over 18 days) measured on a plate according to the standard D 451652 of PSA (June 2010).

TABLE-US-00005 TABLE 5 unit A B C D E F G Non-crosslinked composition ML (1 + 4) 100 C. MU 56 56 60 55 54 46 59 Crosslinked composition Initial state traction Resistance to break. MPa 9.4 12.3 11.8 11.4 11.1 11.2 10.0 Elongation at break. % 358 346 310 333 364 403 319 Modulus 50% MPa 1.9 3.4 4.2 4.2 4.0 1.4 4.8 Modulus 100% MPa 2.5 5.0 6.2 5.7 5.0 2.1 5.7 Modulus 200% MPa 4.0 7.6 8.8 7.8 6.4 3.7 7.1 Delft tearing Resistance N/mm 19.2 18.9 27.1 17.4 20.6 22.8 Shore A hardness at 3 s Initial state Sh A 70 77 80 80 79 62 82 CSR type B after 22 h at 135 C. and 25% compression CSR % 14 14 15 16 15 14 19 Permeability - FAM B, at 40 C. (average permeation rate over 18 days) Average Q g .Math. h.sup.1 .Math. m.sup.2 0.32 0.16 0.23 0.18 0.65 0.19

[0138] FIG. 10 shows the device used to measure the average permeation rate of the plate 1 formed from each composition tested by the FAM B fuel housed in a tank 2 of the device, which is formed in the lower portion thereof by means of a screw passing through a closing grid 4. In a known manner, the permeation flux Q, expressed in g.Math.h.sup.1.Math.m.sup.2, is brought to a nominal plate thickness of 2 mm and is given by the formula:

Q=(M.sub.iM.sub.i+1).sub.max/24.Math.S.Math.e/2, where

(M.sub.iM.sub.i+1).sub.max is the maximum difference in mass, in g, between two successive weighings separated by 24 hours,
S is the surface in m.sup.2 of the plate-test piece in contact with the fuel on one side and on the other with the open air, and
e is the thickness in mm of the plate-test piece.

[0139] Table 5 shows that the modification according to the invention of the formula FKM-PTFE by adding the filler with a high aspect ratio Chinafill 800 does not penalise the mechanical properties of the compositions B to E and G according to the invention in the crosslinked state in relation to the control composition A devoid of this filler, even by improving some of them (see in particular the resistance to breaking, the increased moduli and Shore hardness), and that this adding of the filler with a high aspect ratio even makes it possible to reduce the permeability to the fuel of the compositions B, D, E, G in relation to this control composition A. Table 5 also shows that using 15 phr of micronised powder of fluoropolymer gives the crosslinked composition F that is not in accordance with the invention a permeability to fuel and mechanical properties that are clearly penalised (see moduli), compared to those of compositions B, D, E and G according to the invention.

Second Series of Tests.

[0140] This second series shows in particular the effect of the adding of the filler Barrisurf HX in compositions according to the invention I, L in relation to control compositions H, J, K without a filler with a high aspect ratio, which are all based on a blend of two DAIEL G-902 FKMs (50 phr) and Tecnoflon P-459 (Solvay: 50 phr) and which include 50 phr (for the compositions H, I, J) or 62.5 phr (for the compositions K, L) of powder of PTFE of denomination Polymist F5AEX.

[0141] The adding of 20 phr of the filler Barrisurf HX to the compositions I and L of the invention with the adding of 20 phr of a carbon black to the composition J. The crosslinking system and the agent VPA 2 were the same as hereinabove.

[0142] Table 6 hereinafter provides details on the formulations of the compositions H to L (quantities in phr), and table 7 hereinafter the results obtained during extrusion tests in the same Garvey die as hereinabove (screw heated to 85 C., die at 95 C., speed of the screw of 8 rpm.).

TABLE-US-00006 TABLE 6 H I J K L DAIEL G-902 50 50 50 50 50 Technoflon P-459 50 50 50 50 50 Noir MT N 991 2 2 20 2 2 VPA 2 1 1 1 1 1 TAIC liq 2.1 2.1 2.1 2.1 2.1 Polymist F5AEX 50 50 50 62.5 62.5 Barrisurf HX 20 20 DHBP 45 2 2 2 2 2

TABLE-US-00007 TABLE 7 H I J K L Initiation of the feed Good Good Good Good Good Pressure at die Varies 30 to Varies Varies 45 outlet (in 10.sup.5 Pa) from 70 35 from 70 from 70 to 0 to 0 to 0 Aspect (classification 4.2.3.3 4.2.3.3 4.2.2.3 4.2.3.3 4.2.3.3 system A)

[0143] The control compositions H, J, K therefore are not correctly extrudable, see the fluctuation in the extrusion pressure obtained without a filler with a high aspect ratio. On the contrary, the compositions I and L of the invention that incorporate 20 phr of the filler Barrisurf HX show a very clear improvement in the extrusion conditions with a stabilisation in the extrusion pressure (in particular thanks to the suppression of the sliding in the screw, as explained hereinafter), without degrading the Garvey score on the extrudates obtained, in comparison with compositions with little filler H, K and with the composition I loaded with 20 phr of carbon black.

[0144] FIGS. 8h to 8j show the morphologies respectively obtained for the crosslinked compositions H, I, J, following the crosslinking thereof with peroxide (at t95 at 180 C., without post-curing), with the homogeneous dispersion of the fluorinated powder of PTFE and, for the composition I of the invention, of the filler Barrisurf HX.

[0145] Table 8 hereinafter shows the properties measured as hereinabove for these compositions H to L, in the non-crosslinked as well as crosslinked state.

TABLE-US-00008 TABLE 8 unit H I J K L Non-crosslinked composition ML (1 + 4) MU 56 63 67 62 72 100 C. Crosslinked composition Initial state traction Resistance MPa 9.1 10.7 9.7 9.8 10.1 to break. Elongation % 337 298 282 270 215 at break. Modulus 50% MPa 2.3 5.0 3.8 3.9 5.9 Modulus 100% MPa 2.7 6.2 4.8 4.7 7.3 Modulus 200% MPa 3.9 8.1 7.4 6.8 9.8 Delft tearing Resistance N/mm 15.7 19.3 15.3 13.3 15.6 Shore A hardness at 3 s Initial state Sh A 72 81 80 76 74 CSR type B after 22 h at 135 C. and 25% compression CSR % 22 24 24 24 25 Permeability - FAM B, at 40 C. (average permeation rate over 18 days) Average Q g .Math. h.sup.1 .Math. m.sup.2 0.44 0.24 0.48 0.35 0.18

[0146] Table 8 shows that the modification according to the invention of the formula FKM-PTFE by adding the filler with a high aspect ratio Barrisurf HX does not penalise the mechanical properties of the compositions I and L according to the invention in the crosslinked state in relation to the control compositions H, J, K devoid of this filler, even by improving some of them (see in particular the resistance to breaking, the increased moduli and Shore hardness), and that this adding of the filler with a high aspect ratio even makes it possible to reduce the permeability to the fuel of the compositions I, L, in relation to these control compositions H, J, K.

[0147] Sliding measurements were taken on extrusion die walls that were respectively smooth and rough, concerning the control composition H and the composition of the invention I, by means of a capillary rheometer in order to reveal the difference in behaviour between these two compositions H and I (respectively without and with the clear filler Barrisurf HX), via comparative measurements on a smooth die wall and on a rough die wall. The protocol hereinafter was followed for these capillary rheometer tests.

[0148] The compositions H and I were characterised using the capillary rheometer Gttfert 6000 in order to observe the sliding at the wall. Capillary extrusions at 70 C. were carried out through the following dies with a diameter equal to 1 mm: [0149] rough die with a length of 5 mm in order to evaluate the sliding at the wall, [0150] smooth die with a length of 5 mm in order to evaluate the sliding at the wall, [0151] dies with a quasi-zero length in order to perform the Bagley correction of the inlet pressure.

[0152] A 10.sup.8 Pa sensor was used to measure the pressures at the different programmed extrusion speeds, for shear rates ranging from 0.3 s.sup.1 to 30,000 s.sup.1. The selected die and the selected pressure sensor were installed, then a waiting time of about one half hour was respected in order for the test temperature to stabilise. The sheath was filled with the material to be tested (in the form of granules) and this was packed using a brass pestle. The piston was lowered until engaging in the sheath and observing the presence of an extrudate. The extrusion started after the programmed preheating to condition the material. The programmed speeds followed each other automatically. The test was stopped when the piston was fully descended, or when the pressure exceeded that of the sensor.

[0153] The results obtained can be seen in the graph of FIG. 9. For the composition H, it can be seen that the stress levels according to the shear rate are very different between the smooth die and the rough die, sign of a phenomenon of substantial sliding for this control composition H. On the contrary, for the composition I according to the invention, the smooth die/rough die curves are practically confounded starting at a shear rate of 10 s.sup.1, sign of low sliding at the wall.

Third Series of Tests:

[0154] This third series shows in particular the effect of the adding of the five aforementioned fillers with high aspect ratios in relation with FIGS. 1a to 5b in a control composition M without a filler with a high aspect ratio and of compositions according to the invention N, O, P, Q, R, which are all based on a blend of the two DAIEL G-902 (DAIKIN: 75 phr) and Tecnoflon P-459 (Solvay: 25 phr) FKMs and which all include 50 phr of powder of PTFE of denomination Algoflon L203.

Each filler with a high aspect ratio was added according to 20 phr. The crosslinking system and the implementation assistance agent VPA 2 were the same as hereinabove.

[0155] Table 9 hereinafter provides details on the formulations of the compositions M to R (quantities in phr), and table 10 hereinafter the results obtained during extrusion tests in the same Garvey die as hereinabove (screw heated to 85 C., die at 95 C., speed of the screw of 8 rpm.).

TABLE-US-00009 TABLE 9 M N O P Q R DAIEL G-902 75 75 75 75 75 75 Tecnoflon P-459 25 25 25 25 25 25 Noir MT N 991 2 2 2 2 2 2 VPA 2 1 1 1 1 1 1 TAIC liq 2.1 2.1 2.1 2.1 2.1 2.1 Algoflon L203 50 50 50 50 50 50 Barrisurf HX 20 Chinafill 800 20 Mistron HAR 20 Suzorite 325 HK 20 Mica F 20 DHBP 45 2 2 2 2 2 2

TABLE-US-00010 TABLE 10 M N O P Q R Initiation of Jamming Good Good Good Good Good the feed Pressure at 50 55 50 65 45 40 die outlet (in 10.sup.5 Pa) Aspect 4.4.4.4 4.4.4.4 4.4.4.4 4.4.3, 4.4.4.4 4.4.3.4 (classification 5.4 system A)

[0156] FIGS. 11a to 11g show the aspect of the surfaces and of the end profiles respectively obtained for these compositions M to R, following these Garvey extrusion tests.

[0157] The control composition M is therefore not correctly extrudable, see the priming of the feed. On the contrary, the compositions N to R that incorporate 20 phr of fillers with corresponding high aspect ratios show a clear improvement in the extrusion conditions with a resolution of the material sliding problems at the feed and a stabilisation in the extrusion pressure, without degrading the Garvey score on the extrudates obtained.

[0158] Table 11 hereinafter shows the properties measured as hereinabove for these compositions M to R, in the non-crosslinked as well as crosslinked state.

TABLE-US-00011 TABLE 11 unit M N O P Q R Non-crosslinked composition ML (1 + 4) MU 54 56 56 61 57 54 100 C. Crosslinked composition Initial state traction Resistance to MPa 10.5 9.6 8.7 9.7 9.3 9.4 break. Elongation at % 393 274 262 304 295 319 break. Modulus 50% MPa 1.8 4.5 4.0 4.3 4.2 3.7 Modulus 100% MPa 2.4 6.0 5.4 5.5 5.4 4.8 Modulus 200% MPa 3.5 8.1 7.5 7.2 7.2 6.6 Delft tearing Resistance N/mm 10.8 19.6 12.6 19.4 12.6 19.4 Shore A hardness at 3 s Initial state Sh A 69 81 80 81 80 79 CSR type B after 22 h at 135 C. and 25% compression CSR % 17 19 21 21 17 16 Permeability - FAM B, at 40 C. (average permeation rate over 18 days) Average Q g .Math. h.sup.1 .Math. m.sup.2 0.35 0.18 0.17 0.21 0.23 0.23

[0159] Table 11 shows that the modification according to the invention of the formula FKM-PTFE by the adding of each filler with a high aspect ratio tested does not penalise the mechanical properties of the compositions N to R according to the invention in the crosslinked state in relation to the control composition M devoid of this filler, even by improving some of them (see in particular the resistance to breaking, the increased moduli and Shore hardness), and that this adding of each filler with a high aspect ratio even makes it possible to reduce the permeability to the fuel of the compositions N to R in relation to this control composition M.

[0160] FIG. 12 shows an example of a structure that can be used for a fuel hose according to the invention, comprising a radially internal layer 10 (or sheath) formed from a rubber composition according to the invention, an intermediate layer of rubber 12 for example based on an epichlorhydrin rubber (ECO), a textile reinforcement, 14 and a radially external layer 16 for example also based on an ECO, although other structures and rubber compositions can be used for the layers other than the sheath.