RUBBER COMPOSITION FOR DYNAMIC USES, PRODUCTION METHOD THEREOF, PRODUCTS CONTAINING SAME, AND USES THEREOF

Abstract

The invention relates to a rubber composition for a mechanical member with a dynamic function, to a process for preparing this composition, to such a member and to a use of a polymer bearing urethane functions.

The composition is based on at least one elastomer and comprises a reinforcing filler and said polymer dispersed in the elastomer, the composition comprising the product of an in situ thermomechanical blending reaction of the elastomer with the filler, precursors of the polymer and a chain extender.

According to the invention, the composition has a ratio G′ 0.5%/G′ 20% of storage moduli G′ relative to the complex shear moduli G* satisfying at least one of the following conditions (i) to (v), G′ 0.5% and G′ 20% being measured according to the standard ISO 4664 at respective dynamic strain amplitudes of 0.5% and 20%, on double shear test specimens subjected to shear strains of from 0.02% to 50% at the same frequency of 5 Hz and at the same temperature T:

G′ 0.5%/G′ 20% ≤1.15 for T=100° C.,   (i)

G′ 0.5%/G′ 20% ≤1.40 for T=65° C.,   (ii)

G′ 0.5%/G′ 20% ≤1.50 for T=25° C.,   (iii)

G′ 0.5%/G′ 20% ≤1.60 for T=0° C.,   (iv)

G′ 0.5%/G′ 20% ≤2.50 for T=−30° C.   (v)

Claims

1-27. (canceled)

28. A rubber composition usable in a mechanical member with a dynamic function chosen from antivibration supports and elastic articulations for motorized vehicles or industrial devices, the composition being based on at least one elastomer and comprising: a reinforcing filler, and a polymer bearing urethane groups dispersed in said at least one elastomer, p1 the composition comprising the product of an in situ thermomechanical blending reaction of said at least one elastomer with said reinforcing filler, precursors of said polymer bearing urethane groups and a chain extender, in which the composition has a ratio G′ 0.5%/G′ 20% of storage moduli G′ relative to the complex shear moduli G* satisfying at least one of the following conditions (i) to (v), G′ 0.5% and G′ 20% being measured according to the standard ISO 4664 at respective dynamic strain amplitudes of 0.5% and 20%, on double shear test specimens subjected to shear strains of from 0.02% to 50% at the same frequency of 5 Hz and at the same temperature T:
G′ 0.5%/G′ 20%≤1.15 for T=100° C.,   (i)
G′ 0.5%/G′ 20%≤1.40 for T=65° C.,   (ii)
G′ 0.5%/G′ 20%≤1.50 for T=25° C.,   (iii)
G′ 0.5%/G′ 20%≤1.60 for T=0° C.,   (iv)
G′ 0.5%/G′ 20%≤2.50 for T=−30° C.   (v)

29. The rubber composition as claimed in claim 28, in which the composition satisfies at least condition (i), and in which said test specimens are subjected to preliminary mechanical conditioning of 0±4 mm, 50 mm/minute over 8 cycles.

30. The rubber composition as claimed in claim 29, in which the composition satisfies also conditions (ii), (iii), (iv) and (v).

31. The rubber composition as claimed in claim 28, in which the composition comprises (phr: parts by weight per 100 parts of elastomer(s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer bearing urethane groups.

32. The rubber composition as claimed in claim 31, in which the composition also satisfies the following condition (i-a):
G′ 0.5%/G′ 20%≤1.12 for T=100° C.   (i-a)

33. The rubber composition as claimed in claim 31, in which the composition comprises from 15 to 30 phr of said carbon black and from 15 to 30 phr of said polymer bearing urethane groups.

34. The rubber composition as claimed in claim 28, in which said polymer bearing urethane groups is dispersed in said at least one elastomer in the form of nodules with a largest number-average transverse dimension of between 1 nm and 5 μm.

35. The rubber composition as claimed in claim 34, in which said polymer bearing urethane groups is dispersed in said at least one elastomer in the form of nodules with a largest number-average transverse dimension of between 50 nm and 2 μm.

36. The rubber composition as claimed in claim 28, in which the composition has: at least one of the following secant moduli M100, M300 and M400 at 100%, 300% and 400% strain, respectively, measured in uniaxial tension according to the standard ASTM D 412: M100≥1.5 MPa, M300≥5.5 MPa, and M400≥9.5 MPa; and/or a tensile strength R/r measured in uniaxial tension according to the standard ASTM D 412 of at least 26 MPa.

37. The rubber composition as claimed in claim 28, in which the composition has a Shore A hardness, measured according to the standard ASTM D 2240, of at least 48.

38. The rubber composition as claimed in claim 28, in which said at least one elastomer is a rubber chosen from diene or non-diene elastomers, with the exception of silicone rubbers, the composition comprising a crosslinking system which is capable of reacting with said product of said in situ thermomechanical blending reaction to co-crosslink said at least one elastomer with said polymer bearing urethane groups.

39. The rubber composition as claimed in claim 38, in which the crosslinking system is with sulfur.

40. The rubber composition as claimed in claim 38, in which said at least one elastomer is an apolar diene elastomer.

41. The rubber composition as claimed in claim 40, in which said at least one elastomer is chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR).

42. The rubber composition as claimed in claim 28, in which said polymer bearing urethane groups is segmented with: rigid segments which are present in said polymer in a mass fraction of between 20% and 40%, and which comprise said chain extender and a first said precursor, and with flexible segments comprising a second said precursor which is a diene polymer bearing functionalized chain ends, said polymer bearing urethane groups being co-crosslinked, via double bonds of said second precursor, with said at least one elastomer, forming a three-dimensional network connected via covalent bonds to said at least one elastomer.

43. The rubber composition as claimed in claim 42, in which said rigid segments are present in said polymer in a mass fraction of between 25% and 35%, and wherein in said flexible segments said second precursor is a functionalized polybutadiene.

44. The rubber composition as claimed in claim 42, in which said first precursor and second precursor form two separate reagents for said in situ thermomechanical blending reaction with said at least one elastomer, said reinforcing filler and said chain extender, said precursors not forming a prepolymer of precursors.

45. The rubber composition as claimed in claim 42, in which said chain extender has a molar mass of less than or equal to 700 g/mol.

46. The rubber composition as claimed in claim 42, in which said polymer bearing urethane groups belongs to the family of polyurethanes obtained from an isocyanate compound, excluding polyurethane-ureas.

47. The rubber composition as claimed in claim 46, in which: said first precursor is a polyisocyanate with a functionality of greater than 2, said second precursor is a diol-functionalized diene polymer with a functionality of greater than 2, and said chain extender is a polyol chosen from diols and triols which has a molar mass of less than or equal to 300 g/mol.

48. The rubber composition as claimed in claim 47, in which: said first precursor is chosen from monomers or prepolymers based on 4,4′-methylenebis(phenyl isocyanate), isophorone diisocyanate, hexamethylene diisocyanate and 4,4′-diphenylmethylene diisocyanate, said second precursor is a non-hydrogenated hydroxytelechelic polybutadiene with a number-average molecular mass of between 1000 and 3000 g/mol and a functionality of greater than or equal to 2.2, and said chain extender is chosen from cyclohexanedimethanol, isosorbide and glycerol.

49. The rubber composition as claimed in claim 46, in which: said at least one elastomer is an apolar diene elastomer chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR), said reinforcing filler comprises a carbon black, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer(s)), said polymer bearing urethane groups is present in the composition in an amount of between 15 and 30 phr, and the total amount of said carbon black and of said polymer bearing urethane groups in the composition is between 35 and 55 phr.

50. The rubber composition as claimed in claim 49, in which the composition satisfies the following condition (i-a):
G′ 0.5%/G′ 20%≤1.12 for T=100° C.   (i-a)

51. The rubber composition as claimed in claim 42, in which said polymer bearing urethane groups belongs to the family of polyhydroxyurethanes obtained without an isocyanate.

52. The rubber composition as claimed in claim 51, in which: said first precursor is a polyamine chosen from diamines and triamines, said second precursor is a diene polymer functionalized with cyclocarbonate chain ends, and said chain extender is a cyclic carbonate which has a molar mass of less than or equal to 500 g/mol.

53. The rubber composition as claimed in claim 52, in which: said first precursor is chosen from 1,3-cyclohexanebis(methylamine), xylylenediamine, 2,2′-(ethylenedioxy)bis(ethylamine) and tris(2-aminoethyl)amine, said second precursor is a polybutadiene functionalized with two carbonate end rings which are each 5- or 6-membered, and said chain extender is chosen from cyclohexane bis carbonate, resorcinol bis carbonate, glycerol tricarbonate and phloroglucinol tricarbonate.

54. The rubber composition as claimed in claim 51, in which: said at least one elastomer is an apolar diene elastomer chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR), said reinforcing filler comprises a carbon black, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer(s)), said polymer bearing urethane groups is present in the composition in an amount of between 15 and 30 phr, and the total amount of said carbon black and of said polymer bearing urethane groups in the composition is between 35 and 55 phr.

55. The rubber composition as claimed in claim 54, in which the composition satisfies at least one of the following conditions (i-a) to (v-a):
G′ 0.5%/G′ 20%≤1.12 for T=100° C.   (i-a)
G′ 0.5%/G′ 20%≤1.20 for T=65° C.,   (ii-a)
G′ 0.5%/G′ 20%≤1.30 for T=25° C.,   (iii-a)
G′ 0.5%/G′ 20%≤1.40 for T=0° C.,   (iv-a)
G′ 0.5%/G′ 20%≤1.50 for T=−30° C.   (v-a)

56. The rubber composition as claimed in claim 55, in which the composition also satisfies at least one of the following conditions (i-b) to (v-b):
G′ 0.5%/G′ 20%≤1.10 for T=100° C.,   (i-b)
G′ 0.5%/G′ 20%≤1.15 for T=65° C.,   (ii-b)
G′ 0.5%/G′ 20%≤1.20 for T=25° C.,   (iii-b)
G′ 0.5%/G′ 20%≤1.25 for T=0° C.,   (iv-b)
G′ 0.5%/G′ 20%≤1.40 for T=−30° C.   (v-b)

57. A mechanical member with a dynamic function chosen from antivibration supports and elastic articulations for motorized vehicles or industrial devices, said member comprising at least one elastic part which consists of a rubber composition and which is configured to be subjected to dynamic stresses, in which said composition is as defined in claim 28.

58. A process for preparing a rubber composition as claimed in claim 28, in which the process comprises the following steps: a) the formation of a noncrosslinked mixture comprising a dispersion, in said at least one elastomer, of said polymer bearing urethane groups via said thermomechanical blending reaction of said at least one elastomer with said reinforcing filler, said precursors and said chain extender, b) addition to the mixture of a crosslinking system with mechanical working of the crosslinkable mixture thus obtained, and then c) crosslinking of the crosslinkable mixture by vulcanization in a press at a temperature of between 130° C. and 180° C., said polymer bearing urethane groups being chemically co-crosslinked with said at least one elastomer, forming covalent bonds therewith.

59. The process for preparing a rubber composition as claimed in claim 58, in which: in step a), said reaction is performed in an internal mixer at a maximum temperature of between 130° C. and 180° C.; in step b), the mechanical working of the crosslinkable mixture is performed in an open mill at a maximum temperature below 80° C.; and in step c), the crosslinking of the crosslinkable mixture is performed by compression molding.

60. The process as claimed in claim 58, in which said precursors form a first precursor and a second precursor which are added separately in step a) after said at least one elastomer, said polymer bearing urethane groups being segmented with rigid segments comprising said chain extender and said first precursor and with flexible segments comprising said second precursor.

61. The process as claimed in claim 60, in which the total mass fraction of said first precursor and of said chain extender in said polymer bearing urethane groups formed in step a) is between 20% and 40%.

62. A method to reduce the Payne effect in a rubber composition being based on at least one elastomer, at a temperature T inclusively between −30° C. and 100° C., the Payne effect being quantified by said ratio G′ 0.5%/G′ 20% of storage moduli G′ relative to the complex shear moduli G* of the composition, in comparison with a rubber mixture based on said at least one elastomer, free of said polymer bearing urethane groups and comprising said reinforcing filler in an amount in phr equal to the sum of the phrs, in the composition, of said reinforcing filler and of said polymer bearing urethane groups, wherein the method comprises preparing the rubber composition as claimed in claim 58.

63. The method to reduce the Payne effect in a rubber composition as claimed in claim 35, wherein the method comprises using in the composition (phr: parts by weight per 100 parts of elastomer(s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer bearing urethane groups, to reduce said ratio G′ 0.5%/G′ 20% by more than 40% in comparison with said rubber mixture free of said polymer bearing urethane groups and comprising said carbon black in an amount in phr equal to the sum of the phrs, in the composition, of said carbon black and of said polymer bearing urethane groups.

Description

FOR THE FIRST EMBODIMENT OF THE INVENTION (PU)

[0088] FIG. 1 is a graph illustrating the secant moduli M100, M300 and M400, the Shore A hardness and the ratio G′ 0.5%/G′ 20% at 100° C. of a non-reinforced control rubber mixture, of a mixture of the prior art reinforced with 40 phr of carbon black, of a rubber mixture not in accordance with the invention which is not reinforced and comprises 40 phr of a PU without chain extender (i.e. without rigid segments, referred to as RS hereinbelow) and of a rubber composition not in accordance with the invention which comprises 20 phr of carbon black and 20 phr of PU without RS,

[0089] FIG. 2 is a graph illustrating the influence of adding a glycerol chain extender on M100, M300 and M400, the tensile strength R/r, the Shore A hardness and the G′ 0.5%/G′ 20% at 100° C., for said mixture of the prior art reinforced with 40 phr of carbon black, another mixture of the prior art reinforced with 20 phr of carbon black, said composition not in accordance with the invention and a composition I1 according to the invention with 20 phr of carbon black and 20 phr of a PU comprising 30% by mass of RS,

[0090] FIG. 2a is a graph illustrating the influence of the functionality and the unsaturations of the second precursor on M100, M300 and M400, and R/r, for a mixture of the prior art with 40 phr of carbon black, two mixtures not in accordance with the invention with 20 phr of carbon black and 20 phr of a PU derived from a first precursor according to the invention but from a second precursor not in accordance with the invention, and a composition I1′ according to the invention with 20 phr of carbon black and 20 phr of a PU derived from the same first precursor but from a second precursor according to the invention,

[0091] FIG. 3 is a graph illustrating the influence, for the same polyisocyanate (Suprasec 2015) and polyol (polyBd R20 LM) precursors as for composition I1, of various chain extenders on M100, M300 and M400, R/r, Shore A and G′ 0.5%/G′ 20% at 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black and three compositions according to the invention I2, I3 and I1 with 20 phr of carbon black and 20 phr of three PUs comprising 30% by mass of RS and obtained, respectively, with CHDM, isosorbide and glycerol chain extenders (see the illustrated formulae),

[0092] FIG. 4 is a graph illustrating, for the same CHDM chain extender and polyol precursor (polyBd R20 LM), the influence of various polyisocyanate precursors on M100, M300 and M400, R/r, Shore A and G′ 0.5%/G′ 20% at 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black, composition I2 with the polyisocyanate Suprasec 2015 and three other compositions according to the invention I4, I5 and I6 with 20 phr of carbon black and 20 phr of three other PUs comprising 30% by mass of RS but obtained, respectively, with IPDI, HDI and 4,4′-MDI polyisocyanates (see the illustrated formulae),

[0093] FIG. 5 is a graph illustrating the ratios G′ 0.5%/G′ 20% obtained at various temperatures ranging from −30° C. to 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black and compositions I1, I2, I3, I4, I5 and I6,

[0094] FIGS. 6, 7, 8, 9 and 10 are atomic force microscopy (AFM) images in “tapping” mode obtained, respectively, for compositions I2, I3, I1, I4 and I5, with, for each composition, the left-hand image as a topographic image and the right-hand image as a phase image,

FOR THE SECOND EMBODIMENT OF THE INVENTION (NIPU)

[0095] FIG. 11 is a graph illustrating the influence, for the same first polyamine precursor (1,3-cyclohexanebis(methylamine), abbreviated as CHMA) and the same second polycyclocarbonate precursor (cyclocarbonate-terminated polybutadiene), of various cyclic carbonate (abbreviated as CC hereinbelow) chain extenders on M100, M300 and M400, R/r, Shore A and G′ 0.5%/G′ 20% at 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black, and four compositions according to the invention I7, I8, I9 and I10 with 20 phr of carbon black and 20 phr of four NIPUs obtained, respectively, with the cyclohexane bis CC, resorcinol bis CC, glycerol tri CC and phloroglucinol tri CC extenders (see the illustrated formulae),

[0096] FIG. 12 is a graph illustrating the influence, for the same phloroglucinol tri CC chain extender and the same polycyclocarbonate second precursor (cyclocarbonate-terminated polybutadiene), of various first polyamine precursors on M100, M300 and M400, R/r, Shore A and G′ 0.5%/G′ 20% at 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black, composition I10 with the CHMA extender and three other compositions according to the invention I11, I12 and I13 with 20 phr of carbon black and 20 phr of three NIPUs obtained, respectively, with the polyamines xylylenediamine, EDEA and TAEA (see the illustrated formulae),

[0097] FIG. 13 is a graph illustrating the ratios G′ 0.5%/G′ 20% obtained at various temperatures ranging from −30° C. to 100° C., for the mixture of the prior art reinforced with 40 phr of carbon black and compositions I7, I8, I9, I10, I11, I12 and I13, and

[0098] FIGS. 14, 15, 16, 17, 18, 19 and 20 are atomic force microscopy (AFM) images in “tapping” mode obtained, respectively, for compositions I7, I8, I9, I10, I11, I12 and I13, with, for each composition, the left-hand image as a topographic image and the right-hand image as a phase image.

[0099] In all these examples of mixtures and of compositions thus illustrated, the elastomer matrix used is the same synthetic polyisoprene known as IR Nipol 2200, with N330 carbon black as reinforcing filler and the ingredients identified in the tables below (expressed in phr: parts by weight per 100 parts of IR).

[0100] For the first embodiment of the invention illustrated in FIGS. 1 to 10, the PUs were obtained in situ with the following first and second precursors for compositions I1, I2 and I3 according to the invention:

##STR00002##

The PUs for compositions I4, I5 and I6 according to the invention were obtained with the same second precursor PolyBd R20 LM but with the other first precursors IPDI, HDI and 4,4′-MDI having the formulae illustrated in FIG. 4.

[0101] For the second embodiment of the invention illustrated in FIGS. 11 to 20, the NIPUs were obtained in situ with the following first and second precursors for compositions I7, I8, I9, and I10 according to the invention:

[0102] 1,3-cyclohexanebis(methylamine) (cf. cyclohexamine in the tables below or abbreviated as CHMA), and

[0103] cyclocarbonate-terminated polybutadiene (abbreviated as PolyBd-CC).

[0104] The NIPUs for compositions I11, I12 and I13 were obtained with the same second precursor but with the other first precursors xylylenediamine, EDEA and TAEA having the formulae illustrated in FIG. 12.

[0105] As regards the process used for obtaining all of the compositions I1 to I13 according to the invention, the experimental protocol below was followed.

[0106] The mixtures of polyisoprene/polymer bearing urethane groups (PU or NIPU) were prepared using a Haake internal mixer for the thermomechanical blending step, and then a Polymix open roll mill for the incorporation of the crosslinking system into the mixture obtained.

[0107] The elastomer was introduced first into the internal mixer to enable it to plasticize and to facilitate the incorporation of the other ingredients. The nominal temperature was then 55° C. and the rotor speed was 45 rpm. After blending for 1.5 minutes, the activator complex consisting of stearic acid and ZnO (Silox 3C), the oil (Plaxolene 50) and the N330 carbon black were added. One minute later, the first and second precursors were introduced into the internal mixer. Since these two precursors are liquid, the mechanical blending torque fell considerably on incorporating them, and it was necessary to await the formation of the PU or the NIPU in order for this mechanical torque to increase again. The material was then heated by increasing the speed of the rotors present in the Haake mixer, and the mixture was then recovered when it reached 150° C.

[0108] The crosslinking system was then added to the Polymix open mill, the temperature of the rollers having been set at 40° C. Vulcanization of the crosslinkable compositions obtained was then performed by compression-molding under a hydraulic press at 150° C.

[0109] For the measurement of the static properties of the compositions including the secant modules M100, M300 and M400, the tensile strength R/r (successively presented from left to right for each material in the attached graphs) and the Shore A hardness, uniaxial tensile tests were performed according to the standard ISO 37: at 23° C. on an Instron 5565 dynamometer with a 10 kN force cell and with a throughput speed of 500 mm/minute. The dumbbell test specimens used were of H2 type (working length=25 mm, width=4 mm, thickness=2 mm).

[0110] For the measurement of the dynamic properties of the compositions and notably of said ratio G′ 0.5%/G′ 20% representative of the Payne effect of the various rubber mixtures and compositions, the process was performed at various temperatures (−30, 0, 25, 65 and 100° C.) on a Metravib DMA+1000 machine. To do this, use was made of ½ QC double shear test specimens, which were subjected to a shear strain ranging from 0.02% to 50% at a frequency of 5 Hz. Preliminary mechanical conditioning (0±4 mm, 50 mm/min, 8 cycles) was performed. The standard IS04664 of 2005 (confirmed in 2011) was followed for the measurements of these storage moduli G′.

First Embodiment of the Invention (PU)

[0111]

TABLE-US-00001 TABLE 1 Non-reinforced control rubber mixture Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 228.48 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 11.42 Stearic acid 141500 1.00 0.85 1.18 2.28 Plaxolene 50 oil 3.00 0.9 3.33 6.85 Acc CBS 80% 140130 1.40 1.22 1.15 3.20 Rhenogran CLD/80 143910 0.6 1.199 0.50 1.37 Sulfur M300 1.4 2.07 0.68 3.20 Total 112.40 0.97 116.42 256.81

TABLE-US-00002 TABLE 2 Mixture of the prior art reinforced with 40 phr of carbon black Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 192.20 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 9.61 Stearic acid 141500 1.00 0.85 1.18 1.92 N330 155004 40 1.82 21.98 76.88 Plaxolene 50 oil 3.00 0.90 3.33 5.77 Acc CBS 80% 140130 1.4 1.22 1.15 2.69 Rhenogran CLD/80 143910 0.60 1.20 0.50 1.15 Sulfur M300 1.4 2.07 0.68 2.69 Total 152.40 1.10 138.40 292.91

TABLE-US-00003 TABLE 3 Mixture of the prior art with 20 phr of carbon black Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 208.77 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 10.44 Stearic acid 141500 1.00 0.85 1.18 2.09 N330 155004 20 1.82 10.99 41.75 Plaxolene 50 oil 3.00 0.90 3.33 6.26 Acc CBS 80% 140130 1.4 1.22 1.15 2.92 Rhenogran CLD/80 143910 0.60 1.20 0.50 1.25 Sulfur M300 1.4 2.07 0.68 2.92 Total 132.40 1.04 127.41 276.41

TABLE-US-00004 TABLE 4 Rubber mixture not in accordance with the invention (non- reinforced, with 40 phr of a PU derived from PolyBd R20 LM and Suprasec 2015, without chain extender): Masse volumique Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 165.66 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.28 Stearic acid 141500 1.00 0.85 1.18 1.66 N330 155004 0 1.82 0.00 0.00 PolyBd R20 LM 31.22 0.90 34.69 51.72 MDI Suprasec 2015 8.78 1.23 7.14 14.54 CHDM 0.00 1.04 0.00 0.00 Plaxolene 50 oil 3.00 0.9 3.33 4.97 Acc CBS 80% 140130 2.80 1.22 2.30 4.64 Rhenogran CLD/80 143910 1.2 1.199 1.00 1.99 Sulfur M300 2.8 2.07 1.35 4.64 Total 155.80 0.97 160.57 258.09

TABLE-US-00005 TABLE 5 Rubber composition not in accordance with the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and Suprasec 2015, without chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.67 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.88 Stearic acid 141500 1.00 0.85 1.18 1.78 N330 155004 20 1.82 10.99 35.53 PolyBd R20 LM 15.61 0.90 17.34 27.73 MDI Suprasec 2015 4.39 1.23 3.57 7.80 CHDM 0.00 1.04 0.00 0.00 Plaxolene 50 oil 3.00 0.9 3.33 5.33 Acc CBS 80% 140130 2.24 1.22 1.84 3.98 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.71 Sulfur M300 2.24 2.07 1.08 3.98 Total 154.44 1.03 149.72 274.39

TABLE-US-00006 TABLE 6 Rubber composition I2 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and Suprasec 2015, with CHDM chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 178.99 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.95 Stearic acid 141500 1.00 0.85 1.18 1.79 N330 155004 20 1.82 10.99 35.80 PolyBd R20 LM 10.93 0.90 12.14 19.56 MDI Suprasec 2015 7.15 1.23 5.82 12.80 CHDM 1.92 1.04 1.85 3.43 Plaxolene 50 oil 3.00 0.9 3.33 5.37 Acc CBS 80% 140130 2.24 1.22 1.84 4.01 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.72 Sulfur M300 2.24 2.07 1.08 4.01 Total 154.44 1.04 148.61 276.44

TABLE-US-00007 TABLE 7 Rubber composition I6 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and 4,4′-MDI, with CHDM chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 178.51 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.93 Stearic acid 141500 1.00 0.85 1.18 1.79 N330 155004 20 1.82 10.99 35.70 PolyBd R20 LM 11.39 0.90 12.65 20.33 MDI Aldrich 6.42 1.18 5.44 11.45 CHDM 2.19 1.04 2.11 3.92 Plaxolene 50 oil 3.00 0.9 3.33 5.36 Acc CBS 80% 140130 2.24 1.22 1.84 4.00 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.71 Sulfur M300 2.24 2.07 1.08 4.00 Total 154.44 1.04 149.01 275.70

TABLE-US-00008 TABLE 8 Rubber composition I4 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and IPDI, with CHDM chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.73 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.89 Stearic acid 141500 1.00 0.85 1.18 1.78 N330 155004 20 1.82 10.99 35.55 PolyBd R20 LM 11.63 0.90 12.92 20.67 IPDI 6.01 1.06 5.67 10.68 CHDM 2.36 1.04 2.27 4.20 Plaxolene 50 oil 3.00 0.9 3.33 5.33 Acc CBS 80% 140130 2.24 1.22 1.84 3.98 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.71 Sulfur M300 2.24 2.07 1.08 3.98 Total 154.44 1.03 149.67 274.48

TABLE-US-00009 TABLE 9 Rubber composition I5 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and HDI, with CHDM chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.56 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.88 Stearic acid 141500 1.00 0.85 1.18 1.78 N330 155004 20 1.82 10.99 35.51 PolyBd R20 LM 12.13 0.90 13.48 21.54 HDI 5.10 1.05 4.86 9.06 CHDM 2.77 1.04 2.66 4.92 Plaxolene 50 oil 3.00 0.9 3.33 5.33 Acc CBS 80% 140130 2.24 1.22 1.84 3.98 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.98 Total 154.44 1.03 149.80 274.23

TABLE-US-00010 TABLE 10 Rubber composition I3 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and Suprasec 2015, with isosorbide chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 179.44 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.97 Stearic acid 141500 1.00 0.85 1.18 1.79 N330 155004 20 1.82 10.99 35.89 PolyBd R20 LM 10.93 0.90 12.14 19.61 MDI Suprasec 2015 7.14 1.23 5.80 12.80 Isosorbide 1.94 1.30 1.49 3.47 Plaxolene 50 oil 3.00 0.9 3.33 5.38 Acc CBS 80% 140130 2.24 1.22 1.84 4.02 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.72 Sulfur M300 2.24 2.07 1.08 4.02 Total 154.44 1.04 148.24 277.13

TABLE-US-00011 TABLE 11 Rubber composition I1 according to the invention (with 20 phr of carbon black and 20 phr of PU derived from PolyBd R20 LM and Suprasec 2015, with glycerol chain extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 179.36 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.97 Stearic acid 141500 1.00 0.85 1.18 1.79 N330 155004 20 1.82 10.99 35.87 PolyBd R20 LM 10.93 0.90 12.14 19.60 MDI Suprasec 2015 8.07 1.23 6.56 14.48 Glycerol 1.00 1.26 0.79 1.79 Plaxolene 50 oil 3.00 0.9 3.33 5.38 Acc CBS 80% 140130 2.24 1.22 1.84 4.02 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.72 Sulfur M300 2.24 2.07 1.08 4.02 Total 154.44 1.04 148.30 277.00

[0112] As may be seen in FIG. 1, the non-reinforced mixture with 40 phr of PU synthesized in situ has improved moduli in comparison with the non-reinforced PU-free mixture, without, however, reaching the modulus level of the mixture with 40 phr of carbon black. The Payne effect of this non-reinforced mixture with 40 phr of PU is, however, very much reduced compared with that of the mixture with 40 phr of carbon black instead of PU. The composition not in accordance with the invention with a “mixed reinforcement” of carbon black+PU synthesized in situ without RS makes it possible to obtain better static properties while at the same time having a Payne effect equivalent to that of the non-reinforced mixture with 40 phr of PU (cf. ratio G′ 0.5%/G′ 20% of 1.05, very much less than that equal to 1.94 for the mixture with 40 phr of carbon black).

[0113] As may be seen in FIG. 2, the addition of a chain extender makes it possible to further improve the static properties via the formation of rigid segments (RS) within the PU synthesized in situ, by notably increasing the moduli and the hardness of the compositions. With an RS mass content of 30%, composition I1 shows that the same level of hardness is achieved as for the reference mixture (loaded with 40 phr of carbon black), with in addition a Payne effect that is greatly reduced relative to this reference mixture (cf. ratio G′ 0.5%/G′ 20% of 1.08).

[0114] As may be seen in FIG. 3, the choice of the structure of the chain extender chosen, and thus of the nature of the rigid segments obtained in the elastomer matrix, makes it possible to modify the mechanical properties of compositions I1, I2 and I3, for the same polyisocyanate (Suprasec 2015) and the same RS content of 30%, while at the same time having hardnesses close or equivalent to that of said reference mixture and also low Payne effects (cf. the ratios G′ 0.5%/G′ 20% at 100° C. which are always less than 1.12, or even less than or equal to 1.10).

[0115] As may be seen in FIG. 4, the choice of the structure of the polyisocyanate (for the same CHDM chain extender) also makes it possible to modify the mechanical properties of compositions I2, I4, I5 and I6. The Payne effect at 100° C. remains low for I2, I4, I5 and I6 (cf. ratio G′ 0.5%/G′ 20% less than or equal to 1.12) and very much less than that of said reference mixture.

[0116] As may be seen in FIG. 5 which shows the dynamic properties of compositions I1 to I6 measured at various temperatures (at −30° C., 0° C., 25° C., 65° C. and 100° C.), the Payne effect is considerably reduced for these compositions I1 to I6 in comparison with said reference mixture.

[0117] In conclusion, the abovementioned results demonstrate that the dynamic properties of the compositions according to this first embodiment of the invention are markedly improved relative to the prior art represented by said reference mixture (with 40 phr of carbon black and without PU), which advantageously makes it possible to use these compositions in dynamic applications and over a wide temperature range extending from −30° C. to 100° C.

[0118] FIGS. 6 to 10 show that the PUs thus obtained in situ are very finely dispersed relatively homogeneously in the polyisoprene in the form of nodules with a larger number-average transverse dimension of between 50 nm and 2 μm, or even between 100 nm and 1 μm. This dispersion contributes toward obtaining the abovementioned mechanical properties of the compositions of the invention, notably including their minimized Payne effect.

[0119] In summary, chemical reinforcement of the elastomer matrix with PU networks thus entangled makes it possible to maintain the mechanical properties (moduli and hardness) of compositions I1 to I6 relative to said reference mixture, and while minimizing the nonlinearity (dynamic stiffness) relative to said reference mixture.

[0120] The influence of the functionality and of the ethylenic unsaturations of the second precursor on the mechanical properties obtained for the compositions was moreover studied, using the same given masterbatch, the formulation of which is that of the non-reinforced control rubber mixture detailed in table 1 above, by preparing:

[0121] A control rubber mixture of the prior art reinforced with 40 phr of N330 carbon black added to the masterbatch;

[0122] A composition I1′ according to the invention with, in addition to the masterbatch, 20 phr of N330 carbon black and 20 phr of a PU derived from the first MDI precursor “Suprasec 2015”, a hydroxytelechelic polybutadiene known as “PolyBd-OH R45 HTLO” as second precursor (Mn=2800 g/mol, functionality=2.5) and the abovementioned CHDM as chain extender;

[0123] A rubber mixture No. 1 not in accordance with the invention, with, in addition to the masterbatch, 20 phr of N330 carbon black and 20 phr of a PU derived from the first MDI precursor “Suprasec 2015”, CHDM as chain extender and hydroxytelechelic polybutadiene “Krasol LBH 2000” (of Mn=2100 g/mol and a functionality equal to 1.9) as second precursor; and

[0124] A rubber mixture No. 2 not in accordance with the invention, with, in addition to the masterbatch, 20 phr of N330 carbon black and 20 phr of a PU derived from the first MDI precursor “Suprasec 2015”, CHDM as chain extender and hydrogenated hydroxytelechelic polybutadiene “Krasol HLBH-P 2000” (of Mn=2100 g/mol and a functionality equal to 1.9) as second precursor.

[0125] Composition I1′ and the three abovementioned mixtures were prepared as indicated above with 1.6 equivalents of vulcanization agents as crosslinking system (see table 1) and with a PU comprising 30% of rigid segments RS, as explained above for compositions I1 to I6. Table 12 below summarizes the formulations used starting with the masterbatch for I1′ and the mixtures No. 1 and No. 2.

TABLE-US-00012 TABLE 12 Composition I1′ according to the invention and mixtures No. 1 and 2 (with 20 phr of carbon black and 20 phr of PU derived from Suprasec 2015 and various polybutadienes-OH, with CHDM chain extender): Compounds Composition I1′ Mixture 1 Mixture 2 Masterbatch 134.44 134.44 134.44 PolyBd R45 HTLO 12.31 — — Krasol LBH 2000 — 12.29 — Krasol HLBH-P — — 12.29 2000 MDI Suprasec 5.78 5.80 5.80 2015 CHDM 1.91 1.91 1.91

[0126] As may be seen in FIG. 2a, the second precursor Krasol LBH 2000 gives the mixture No. 1 tensile moduli that are markedly lower than those of composition I1′, the second polyol precursor of which (just like the first precursor) has a functionality of greater than 2, whereas the molecular mass Mn of Krasol LBH 2000 is less than that of PolyBd R45 HTLO. Despite having shorter flexible segments, poorer mechanical properties were in fact obtained for this mixture No. 1 in which the PU formed is linear, which demonstrates the positive effect of the functionality of 2.5 of the second polyol precursor which makes it possible, via the double bonds thereof, to chemically co-crosslink the PU formed with the elastomer matrix of composition I1′, giving this PU a three-dimensional structure which better reinforces the composition.

[0127] It is also seen in FIG. 2a that the second hydrogenated precursor Krasol HLBH-P 2000, free of double bonds, gives the mixture No. 2 mechanical properties that are even poorer than those of the mixture No. 1. Specifically, the absence of double bonds in this second precursor counters the co-vulcanization of the PU with the polyisoprene (the PU formed in the mixture No. 2 also being linear) and thus does not generate any covalent bonds between the PU and the elastomer matrix of the mixture, which leads to poorer reinforcement thereof.

[0128] The Payne effect obtained for the mixture of the prior art with 40 phr of N330 was measured at 100° C. as indicated above, for the mixtures No. 1 and No. 2 and for composition I1′ (see table 13 below).

TABLE-US-00013 TABLE 13 Control Composition mixture I1′ Mixture 1 Mixture 2 G′ 0.5% (kPa) 1928 850 894 786 G′ 0.5%/G′ 20% 1.81 1.07 1.25 1.20

[0129] As may be seen in table 13, the Payne effect is higher with mixtures No. 1 and No. 2 each incorporating a linear PU. It is in fact easier to break, during a dynamic stress, the low-energy bonds between the chains of the linear PU of mixtures No. 1 and No. 2 than to break the three-dimensional network of the co-crosslinked PU of composition I1′.

[0130] The intrinsic properties of the second precursor (notably its functionality and its double bonds) are thus determining factors for the production of the targeted mechanical properties of the composition.

Second Embodiment of the Invention (NIPU)

[0131]

TABLE-US-00014 TABLE 14 Rubber composition I7 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and 1,3- cyclohexanebis(methylamine), with cyclohexane bis CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.08 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.85 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.42 PolyBd-CC 10.87 0.90 12.08 19.25 Cyclohexamine 3.45 0.945 3.65 6.11 Cyclohexane bis CC 5.68 1.00 5.68 10.06 Plaxolene 50 oil 3.00 0.9 3.33 5.31 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.44 1.03 150.21 273.48

TABLE-US-00015 TABLE 15 Rubber composition I8 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and 1,3- cyclohexanebis(methylamine), with resorcinol bis CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.07 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.85 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.41 PolyBd-CC 10.87 0.90 12.08 19.25 Cyclohexamine 3.56 0.945 3.77 6.30 Resorcinol bis CC 5.57 1.00 5.57 9.86 Plaxolene 50 oil 3.00 0.9 3.33 5.31 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.44 1.03 150.22 273.47

TABLE-US-00016 TABLE 16 Rubber composition I9 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and 1,3- cyclohexanebis(methylamine), with glycerol tri CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.07 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.85 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.41 PolyBd-CC 10.87 0.90 12.08 19.25 Cyclohexamine 3.72 0.945 3.94 6.59 Glycerol tri CC 5.40 1.00 5.40 9.56 Plaxolene 50 oil 3.00 0.9 3.33 5.31 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.43 1.03 150.22 273.45

TABLE-US-00017 TABLE 17 Rubber composition I10 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and 1,3-cyclohexanebis(methylamine), with phloroglucinol tri CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.08 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.85 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.42 PolyBd-CC 10.87 0.90 12.08 19.25 Cyclohexamine 3.50 0.945 3.70 6.20 Phloroglucinol tri CC 5.63 1.00 5.63 9.97 Plaxolene 50 oil 3.00 0.9 3.33 5.31 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.44 1.03 150.22 273.48

TABLE-US-00018 TABLE 18 Rubber composition I11 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and xylylenediamine, with phloroglucinol tri CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.42 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.87 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.48 PolyBd-CC 10.92 0.90 12.13 19.37 Xylylenediamine 3.39 1.032 3.28 6.01 Phloroglucinol tri CC 5.70 1.00 5.70 10.11 Plaxolene 50 oil 3.00 0.9 3.33 5.32 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.45 1.03 149.92 274.03

TABLE-US-00019 TABLE 19 Rubber composition I12 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and EDEA, with phloroglucinol tri CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.31 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.87 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.46 PolyBd-CC 10.85 0.90 12.06 19.24 EDEA 3.59 0.998 3.60 6.37 Phloroglucinol tri CC 5.56 1.00 5.56 9.86 Plaxolene 50 oil 3.00 0.9 3.33 5.32 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.44 1.03 150.02 273.84

TABLE-US-00020 TABLE 20 Rubber composition I13 according to the invention (with 20 phr of carbon black and 20 phr of NIPU derived from PolyBd-CC and TAEA, with phloroglucinol tri CC extender): Density Volume Mass Compound Parts (g/mL) (mL) (g) IR Nipol 2200 100.00 0.92 108.70 177.20 ZnO 2(silox 3C) 141000 5.00 5.6 0.89 8.86 Stearic acid 141500 1.00 0.85 1.18 1.77 N330 155004 20 1.82 10.99 35.44 PolyBd-CC 11.22 0.90 12.47 19.88 TAEA 2.55 0.977 2.61 4.52 Phloroglucinol tri CC 6.23 1.00 6.23 11.04 Plaxolene 50 oil 3.00 0.9 3.33 5.32 Acc CBS 80% 140130 2.24 1.22 1.84 3.97 Rhenogran CLD/80 143910 0.96 1.199 0.80 1.70 Sulfur M300 2.24 2.07 1.08 3.97 Total 154.44 1.03 150.11 273.67

[0132] As may be seen in FIG. 11, the addition of a NIPU synthesized in situ also makes it possible to reinforce the elastomer matrix, as shown notably by the moduli of the IR/NIPU mixtures which are greater than those of the mixture reinforced with only 20 phr of carbon black.

[0133] Furthermore, the choice of the structure of the chain extender (with a first polyamine precursor 1,3-cyclohexanebis(methylamine)) makes it possible to modify the mechanical properties of compositions I7 to I10 so as to obtain hardnesses close to that of said reference mixture (with 40 phr of carbon black and without NIPU).

[0134] The Payne effect at 100° C. of each of the compositions I7 to I10 is very low (see said ratio of less than or equal to 1.05), irrespective of the chain extender used.

[0135] As may be seen in FIG. 12, the choice of the polyamine used (for the same phloroglucinol tri CC chain extender) also has an impact on the mechanical properties of compositions I10 to I13 and makes it possible to give them variable hardnesses (48 to 52 Shore A). In all the cases, the Payne effect at 100° C. is always greatly reduced in comparison with said reference mixture (see said ratio of less than or equal to 1.09, or even 1.06).

[0136] As may be seen in FIG. 13 which shows the dynamic properties of compositions I7 to I13 measured at various temperatures (at −30° C., 0° C., 25° C., 65° C. and 100° C.), the Payne effect is considerably reduced for these compositions I7 to I13 in comparison with said reference mixture.

[0137] In conclusion, the abovementioned results demonstrate that the dynamic properties of the compositions according to this second embodiment of the invention are markedly improved relative to the prior art represented by said reference mixture (with 40 phr of carbon black and without NIPU), which advantageously makes it possible to use these compositions in dynamic applications and over a wide temperature range extending from −30° C. to 100° C.

[0138] FIGS. 14 to 20 show that the NIPUs thus obtained in situ are very finely dispersed relatively homogeneously in the polyisoprene in the form of nodules with a larger number-average transverse dimension of between 50 nm and 2 μm, or even between 100 nm and 1 μm. This dispersion contributes toward obtaining the abovementioned mechanical properties of the compositions of the invention, notably including their minimized Payne effect.

[0139] In summary, chemical reinforcement of the elastomer matrix with NIPU networks thus entangled makes it possible to maintain the mechanical properties (moduli and hardness) of compositions I7 to I13 relative to said reference mixture, and while minimizing the nonlinearity (dynamic stiffness) relative to said reference mixture.