GRAPHENE AS ADDITIVE IN SIDEWALL APPLICATIONS

Abstract

The introduction of graphene as an additive in rubber compounds is disclosed. The product shows increased barrier protection for tire sidewalls, with no tradeoffs in other characteristics.

Claims

1. A rubber composition comprising: natural rubber; polybutadiene; carbon black; peptizer; process oil; paraffinic wax; microcrystalline wax; stearic acid; zinc oxide; sulfur; accelerator; pre vulcanization inhibitor; and graphene, wherein the sidewall has no additional antioxidant or antiozonant.

2. A rubber composition comprising: natural rubber; polybutadiene; carbon black; and graphene, wherein the sidewall has no additional antiozonants.

3. The rubber composition of claim 2, wherein the sidewall has no additional antioxidants.

4. The rubber composition of claim 2, wherein the graphene is between about 0.5 PHR and about 10.0 PHR.

5. The rubber composition of claim 2, wherein the composition has no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine.

6. The rubber composition of claim 3, wherein the composition has no 2,2,4-trimethyl-1,2-dihydroquinoline.

7. The rubber composition of claim 2, wherein the graphene is a graphene plate, wherein the graphene plate is between about 0.5 PHR and about 10.0 PHR.

8. The rubber composition of claim 7, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

9. The rubber composition of claim 8, wherein the graphene plate has an oxygen content of less than about 1%.

10. The rubber composition of claim 2, wherein the graphene has a thickness less than about 1 nm and an aspect ratio of about 1000.

11. The rubber composition of claim 2, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

12. The rubber composition of claim 7, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

13. The rubber composition of claim 3, wherein the composition further comprises: peptizer; process oil; paraffinic wax; microcrystalline wax; stearic acid; zinc oxide; sulfur; accelerator; and pre vulcanization inhibitor.

14. The rubber composition of claim 13, wherein the composition contains no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline.

15. The rubber composition of claim 1, wherein the composition contains no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline.

16. The rubber composition of claim 1, wherein the rubber composition is a tire sidewall.

17. The rubber composition of claim 2, wherein the rubber composition is a tire sidewall.

18. The rubber composition of claim 12, wherein the rubber composition is a tire sidewall.

Description

III. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present teachings are described hereinafter with reference to the accompanying drawings.

[0024] FIG. 1 depicts a graph showing rapid reduction in permeability;

[0025] FIG. 2 depicts the structures of graphene, graphene oxide, and reduced graphene oxide;

[0026] FIG. 3 depicts a tire;

[0027] FIG. 3A depicts a partial cross-section of a tire;

[0028] FIG. 4 is a graphical representation of the graphene plates acting as a barrier to gas flow;

[0029] FIG. 5A depicts the structure of paraffin wax;

[0030] FIG. 5B depicts the structure of microcrystalline wax;

[0031] FIG. 5C depicts the structure of an antiozonant;

[0032] FIG. 5D depicts the structure of an antioxidant;

[0033] FIG. 6 is a chart showing sidewall components; and

[0034] FIG. 7 is a chart showing antiozonant percentage over time.

IV. DETAILED DESCRIPTION

[0035] With reference to FIGS. 1-4, in one aspect of the present teaching, a tire innerliner is a calendered halobutyl rubber sheet compounded with additives that result in low air permeability. The innerliner assures that the tire will hold high-pressure air inside, without an inner tube, minimizing diffusion through the rubber structure. Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component. Mixing is the process of applying mechanical work to the ingredients in order to blend them into a homogeneous substance. Internal mixers are often equipped with two counter-rotating rotors in a large housing that shear the rubber charge along with the additives. The mixing is done in two or three stages to incorporate the ingredients in the desired order. The shearing action generates considerable heat, so both rotors and housing are water-cooled to maintain a temperature low enough to assure that vulcanization does not begin.

[0036] With continuing reference to FIGS. 1-4, the graphene is added to the rubber and mixed as noted above. Graphene will be added to a rubber formulation, such as one based on bromobutyl, at levels from about 0.1 PHR to about 50.0 PHR, including about 0.5 PHR to about 45.0 PHR, about 0.5 PHR to about 40.0 PHR, about 0.5 PHR to about 35.0 PHR, about 0.5 PHR to about 30.0 PHR, about 0.5 PHR to about 25.0 PHR, about 0.5 PHR to about 20.0 PHR, about 0.5 PHR to about 15.0 PHR, and from 0.5 PHR to 10.0 PHR. In another aspect of the present teachings, the graphene is added at less than about 50.0 PHR, less than about 45.0 PHR, less than about 30.0 PHR, less than about 25.0 PHR, less than about 20.0 PHR, less than about 15.0 PHR, and less than about 10.0 PHR. In another aspect of the present teachings, the graphene is added at greater than about 0.5 PHR, greater than about 1.0 PHR, greater than about 5.0 PHR, greater than about 10.0 PHR, greater than about 15.0 PHR, greater than about 20.0 PHR, greater than about 25.0 PHR, greater than about 30.0 PHR, greater than about 35.0 PHR, greater than about 40.0 PHR, and greater than about 45.0 PHR. With continuing reference to FIGS. 1-4, the graphene is added to the rubber and mixed as noted above. Graphene in this aspect is described as in Table 1.

TABLE-US-00001 TABLE 1 Typical Properties of Graphene Form Powder, dark grey, odorless Carbon >95% Particle size 50 nm to 10 μm Moisture, Oxygen, Ash <0.75 wt. %, <2.0 wt. %, <4.5 wt. %, respectively Resistivity <150 ohm cm Particle (sheet) thickness) <3.2 nm Particle layers <16 Specific gravity 2. gm/cubic centimeter Surface area (specific) 180 square m.sup.2/gm

[0037] The particle size range of graphene used in the present teachings can range from about 50 nm to about 10 μm. In one aspect, the particle size range is from about 100 nm to about 5 μm. In one aspect, the particle size range is greater than about 50 nm, greater than about 100 nm, greater than about 150 nm, greater than about 200 nm, greater than about 250 nm, greater than about 300 nm, greater than about 350 nm, greater than about 400 nm, greater than about 450 nm, greater than about 500 nm, greater than about 550 nm, greater than about 600 nm, greater than about 650 nm, greater than about 700 nm, greater than about 750 nm, greater than about 800 nm, greater than about 850 nm, greater than about 900 nm, greater than about 950 nm, greater than about 1 μm, greater than about 2 μm, greater than about 3 μm, greater than about 4 μm, greater than about 5 μm, greater than about 6 μm, greater than about 7 μm, greater than about 8 μm, or greater than about 9 μm. In one aspect, the particle size range is less than about 10 μm, less than about 9 μm, less than about 8 μm, less than about 7 μm, less than about 6 μm, less than about 5 μm, less than about 4 μm, less than about 3 μm, less than about 2 μm, less than about 1 μm, less than about 950 nm, less than about 900 nm, less than about 850 nm, less than about 800 nm, less than about 750 nm, less than about 700 nm, less than about 650 nm, less than about 600 nm, less than about 550 nm, less than about 500 nm, less than about 450 nm, less than about 400 nm, less than about 350 nm, less than about 300 nm, less than about 250 nm, less than about 200 nm, less than about 150 nm, or less than about 100 nm. The form is plate-like rather that cylindrical or fibrous. To further define the material, carbon content is greater than 95%, and in one aspect greater than 99%. The carbon content can be greater than 96%, greater than 97%, or greater than 98% as well. Ash and oxygen content is less than 1% in one aspect of the present teachings. In one aspect, the average particle thickness is about 2.5 nm and the number of layers in a particle would is less than 15, thus allowing attainment of a near exfoliated condition when compounded. Specific surface area of the graphene plate will range from 100 m.sup.2/gram to 250 m.sup.2/gram and in one aspect is about 180 m.sup.2/gram. In one aspect, the surface area of the graphene plate is greater than 150 m.sup.2/gram, greater than 100 m.sup.2/gram, less than 250 m.sup.2/gram, less than 200 m.sup.2/gram, or less than 150 m.sup.2/gram.

[0038] Graphene is added to the rubber compound formulations at between about 0.0 PHR and about 50.00 PHR, including in the range of about 0.5 PHR to about 8.00 PHR. Reductions in compound permeability initially show a large decrease (as shown in FIG. 1), tapering as graphene levels increase. Gas-permeability decreases with increasing graphene loading of about 0.4 vol % in rubber composites. The percolation threshold is about 40 times lower than that for clay-based composites. According to the Nielsen model on gas permeability, the thickness of an individual graphene based sheet dispersed in the graphene styrene-butadiene rubber (SBR) composite with 2.0 vol. % of GO was predicted to be 1.47 nm.

[0039] Graphene, when added to a bromobutyl rubber compound formulation, can be in various forms and which can be part of the present teaching, such as a powder, in pastilles or pellets using wax as a carrier, aiding dust suppression, in pre-weight sealed, low-melt temperature polyethylene bags, and melt or solution blended with a compatible polymer, such as butyl rubber or halobutyl rubber and then compounded as part of the total rubber hydrocarbon content.

[0040] Graphene has an aspect ratio of near 1000, assuming the graphene plate thickness is about 1 nm. The plate length/diameter can be up to about 1 micron. The graphene can thus function as a barrier. The graphene exfoliates into sheets when added to the rubber compound, which improves the barrier properties when perpendicular alignment to the sheet direction is achieved. The graphene plates provide a barrier to oxygen and nitrogen migration, and moisture or water vapor molecules migrating through the liner compound of the tire or other product requiring such properties. Such gas molecule transport phenomenon is described as a “tortuous path” as shown in FIG. 4. With continuing reference to FIGS. 1-4, with the addition of graphene as a filler, there is no trade-off or loss in conventional processing and mechanical properties. Graphene has a very high aspect ratio. Small amounts have a large impact on reducing permeability. The nominal aspect ratio of graphene of up to 1000 compares with the typical aspect ratio of 20 for kaolin clay fillers. The clay fillers have to be added at about 40 PHR and also need a surfactant for compatibility. Due to the relatively large size of the graphene plates versus inorganic fillers, graphene can be added at about 1 PHR to about 2 PHR.

[0041] Measurement of Properties of Rubber Compositions

[0042] Mooney viscosity (ML1+4) at 100° C. measured in accordance with ASTM D1646. Vulcanization kinetics and associated properties was measured by following the procedure in ASTM D5289. Tensile strength and associated data generated through measurement of tensile strength was determined following ASTM D412. Shore-A Hardness was measured following the method in ASTM D2240. Tear strength and adhesion were measured following ASTM D624. Oxygen permeability was measured using an Ametek Mocon OX-TRAN 2/22 permeability tester and following ASTM D3985. Air permeability determined according to the method in ASTM D1434.

Example 1

[0043] In this example tire model innerliner compounds were prepared containing graphene levels, ranging from about 0.00 PHR to about 20.00 PHR. The graphene was first blended with bromobutyl rubber and then added as a master-batch to the compounds. The amount of free bromobutyl polymer added to the formulation was adjusted with the graphene master-batch to ensure the total polymer content is 100.00 PHR as described earlier. Graphene was added at 0.5 PHR, 2.0 PHR, 5.00 PHR, 8.00 PHR, and 20.0 PHR. Compounds were prepared using a laboratory internal mixer, using a two-stage mixing procedure. The first stage is referred to as non-productive, followed by the final stage or productive phase, where the vulcanization chemicals are added. The formulations are shown in Table 2. Though not necessary, in Table 1 a re-mill is illustrated which can be included in the mixing procedure should it be desired. A re-mill is a procedure where the compound is passed through a mixer for a short period of time so as to optimized final compound viscosity.

[0044] The mechanical properties illustrated in Table 3 are equivalent to innerliners with no graphene. This is the case for compounds containing graphene at levels up to about 10 PHR. It is noted that industrial levels of graphene usage will be in the range of about 0.5 PHR to about 10.0 PHR. There is no shift in tensile strength, Mooney viscosity, modulus, tack, green strength, or tear strength. However, there is direction improvement in adhesion, consistent with results from other compound classes.

Example 2

[0045] This example shows the excellent reduction in permeability achieved with small amounts of graphene in the bromobutyl innerliner compound. Permeability was measured and two sets of results are reported, (i) permeation of oxygen through the innerliner compounds and (ii) permeation of air. In both instances there is a sharp reduction in permeability with very small amounts of graphene added to the bromobutyl compounds, followed by a less steep drop than would be predicted by computational models proposed by Neilson.

[0046] Addition of graphene to the bromobutyl compound shows a very rapid drop in permeability which is required for tire innerliner applications. This drop is considered significantly greater than that possible using other plate-like additives, such as kaolin clays, other clays, or talc nanocomposites. It is noted that this reduced tire liner permeability is useful for electric vehicle tires, truck tires, bus tires, off road tires, farm equipment tires, and aircraft tires. Graphene has an aspect ratio of near 1000, assuming the graphene plate thickness is about 1 nm. The plate length/diameter can be up to about 1 micron. The graphene thus functions as a barrier or creation of the tortuous path noted above (FIG. 4). The graphene exfoliates into sheets when added to the rubber compound, which improves the barrier properties. The graphene plates provide a barrier to oxygen and nitrogen migration through the liner compound of the tire.

TABLE-US-00002 TABLE 2 Compound 3 (control) 1 2 4 5 6 Number ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- 54-03 54-01 54-02 54-04 54-05 54-06 BIIR 2222 100.00 98.67 94.67 86.67 78.67 46.70 Carbon Black N660 60.00 60.00 60.00 60.00 60.00 60.00 ERTNB10-53-MB 0.00 1.83 7.33 18.33 29.33 73.30 Naphthenic oil 8.00 8.00 8.00 8.00 8.00 8.00 Struktol 40MS 7.00 7.00 7.00 7.00 7.00 7.00 Koresin 2.00 2.00 2.00 2.00 2.00 2.00 Escorez 1102 2.00 2.00 2.00 2.00 2.00 2.00 Stearic Acid 1.00 1.00 1.00 1.00 1.00 1.00 Zinc Oxide 1.00 1.00 1.00 1.00 1.00 1.00 MBTS 1.25 1.25 1.25 1.25 1.25 1.25 Sulfur 0.50 0.50 0.50 0.50 0.50 0.50 Total 182.75 183.25 184.75 187.75 190.75 202.75 Graphene 0.00 0.50 2.00 5.00 8.00 20.00 1st Pass or Non-Productive Set-up Start Temp. 65° C., 65 RPM, & 50 Ram pressure 0′ add elastomers and ertnb10-53-MB   0.25′ add carbon black 2′ add others 3′ sweep   3.5′ adjust (increase) rotor speed, ramp temperature to 150° C. at 5′ 5′ (try to reach 150° C. at 5′) Re-mill if required Set-up Start Temp. = RT, 65 RPM, & 50 Ram pressure 0′ ADD 1st Pass MB 3′ DUMP MILL 1′ on mill with mill rolls at R.T. 5′ (try to reach 150° C. at 5′) Final Pass Productive Set-Up SANDWICH IN CURES 0′ ADD ⅔ of 2nd pass MB ADD Sulfur, Accelerator pocket, & 15″ ⅓ of 2nd pass MB 1′ SWEEP 5′ (try to reach 150° C. at 5′)

TABLE-US-00003 TABLE 3 Compound 3 1 2 4 5 6 Number ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- 54-03 54-01 54-02 54-04 54-05 54-06 BIIR 2222 PHR 100.00 100.00 100.00 100.00 100.00 100.00 Graphene PHR 0.00 0.50 2.00 5.00 8.00 20.00 Mooney Viscosity ML1 + 4 57.80 57.50 57.60 58.70 58.60 60.40 100° C. MDR Rheometer 160 C. ° Delta Torque in-lb 2.59 2.67 2.75 2.58 2.74 3.18 Ts1 min 5.08 5.15 5.04 5.10 4.78 5.52 T50 min 6.15 6.32 6.24 6.12 5.90 5.52 T90 min 12.63 12.86 12.86 12.14 11.80 12.49 Tack [Tel Tack] 3.86 2.88 3.31 3.10 3.67 5.12 Tensile Strength MPa 9.47 9.76 9.63 9.49 9.04 8.54 Elongation % 833 836 854 804 785 708  50% Modulus MPa 0.72 0.73 0.75 0.93 0.91 1.28 100% Modulus MPa 1.04 1.05 1.15 1.40 1.46 2.26 200% Modulus MPa 2.05 2.11 2.32 2.66 2.80 4.02 300% Modulus MPa 3.39 3.51 3.66 4.04 4.09 5.21 Shore A 54.00 54.00 53.00 56.00 57.00 60.00 Tear Strength KN/m 53.34 51.33 52.37 52.12 51.96 51.12 Trouser Tear Str. lbf/in 147.00 153.00 142.00 149.00 157.00 169.00 Peel Adhesion 79.00 71.00 73.00 73.00 86.00 46.00

TABLE-US-00004 TABLE 4 Compound 3 1 2 4 5 6 Number ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- ERTNB10- 54-03 54-01 54-02 54-04 54-05 54-06 BIIR 2222 PHR 100.00 100.00 100.00 100.00 100.00 100.00 Graphene PHR 0.00 0.50 2.00 5.00 8.00 20.00 Oxygen Permeability using Ametek Mocon (ASTM D3985) (40° C., 100% O.sub.2) Permeation cc*mm/(m.sup.2*day) 220 201 168 146 152 101 Permeability cc*mm/(m.sup.2*day*mmHg) 0.289 0.264 0.221 0.192 0.200 0.133 Rating (Lower is better) 100 91 76 73 69 46 Air Permeability to ASTM D1434 60 C. ° Permeability cc STP − cm/cm2 − s − atm 2.455 1.249 1.495 1.668 1.745 1.610 Rating (Lower is better) 100 51 61 68 71 66 Note: Permeation and Permeability coefficients taken from the industry reference formulation (#3) in the text Tire Engineering, CRC Press 2021

[0047] Tire sidewall performance requirements include resistance to oxidation, ozone attack, UV light degradation, light, heat, fatigue, discoloration, and low hysteresis. Protection systems include waxes, antioxidants, and antiozonants. Polymer blends of natural rubber, butyl rubber, and styrene-butadiene rubber facilitate fatigue resistance. Table 5 below shows a tire sidewall formulation (units are PHR).

TABLE-US-00005 TABLE 5 Natural Rubber (TSR10) 50.00 Polybutadiene 50.00 Carbon black (N330) 45.00 Peptizer (Renacit 11) 0.25 Process oil (TDAE) 5.00 Paraffinic wax 1.50 Microcrystalline wax 1.50 Antioxidant TMQ 1.50 Antiozonant 6PPD 3.50 Stearic acid 1.50 Zinc oxide 4.00 Sulfur 1.00 Accelerator (TBBS) 1.00 Retarder (PVI) 0.25

[0048] With reference to FIGS. 5A-5D, waxes, antiozonants, and antioxidants are used to protect the sidewall compounds. Paraffin wax provides short term protection after manufacturing and in storage. Microcrystalline wax provides three to twelve months protection in storage before installation. N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine (6PPD) provides medium protection against ozone and fatigue. 6PPD is an effective antiozonant, but blooms, which causes sidewall discoloration. 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) provides short to long term protection against heat and light, and acts as an antioxidant. TMQ and 6PPD block rubber polymer degradation via free radical termination, chain termination, and free radical removal.

[0049] With reference now to FIGS. 6 and 7, 6PPD is the primary antiozonant used in tire sidewalls. It is insoluble, which results in blooming to the surface causing discoloration. Up to 30% of 6PPD can be exhausted in 32 days. 6PPD is also consumed in protecting the sidewall from ozonolysis and oxidation. Given that 6PPD will ultimately either be consumed or bloom to the sidewall surface, additional protective components are desired. An effective material would be highly aromatic (such as 6-member cyclic carbons), high molecular weight, soluble in rubber, a free molecular scavenger, and non-migratory. In one aspect of the present teaching, graphene can be used to replace 6PPD.

[0050] The addition of graphene to tire sidewall compounds can extend the life and performance of the sidewall. Graphene is non-staining and is persistent (i.e., the graphene stays in the compound and in the tire). Graphene can function as an antioxidant and antiozonant, all while having no trade off or loss in basic mechanical properties, processing, or vulcanization kinetics.

[0051] A rubber tire sidewall compound formulation will consist of many types of materials and chemicals. Typically the sidewall compound formulation used on a passenger tire light truck tire, heavy duty truck tire mounted on a commercial truck and trailer, earthmover or OTR tire, aircraft, and farm tires will consist of natural rubber and synthetic rubber blend. The amount of natural rubber will be expressed in parts per hundred rubber (PHR) and which is familiar to those skilled in the art of rubber compounding. A sidewall compound containing 30 PHR to 100 PHR of natural rubber can be utilized but a level of 30 PHR to 50 PHR is typical. A synthetic rubber is added from about 0 PHR to about 70 PHR and the natural rubber correspondingly adjusted between about 30 PHR about 100 PHR. Synthetic rubbers may be selected from polybutadiene of which there are many types used in tire compounding, halogenated butyl rubbers, emulsion polymerized styrene butadiene rubber (SBR), or solution polymerized SBR, and ethylene propylene diene rubber ((EPDM). Blends of such synthetic rubbers may also be used as part of the total rubber hydrocarbon content. The ideal tire tread sidewall compound will have between 30 PHR and 50 PHR of natural rubber and 70 PHR to 50 PHR of polybutadiene and a preferred ratio of the two polymers of 50 PHR and 50 PHR. Carbon black may be of different grades as described in the text “Rubber Compounding Chemistry and Applications, 2.sup.nd edition, by CRC Press (2015)”. Though grades including N330, N326, N347, and N358 are often used, other examples of grades could be selected from the SAF, ISAF, or HAF, FEF groups might also be selected depending on the manufacturer, and is noted they will have no material impact on the present teaching. Carbon black can be N330 at amounts of about 40 PHR to about 55 PHR and can be about 45 PHR. In addition, a peptizer designed to improve compound mixing efficiency may be added at between about 0.0 and about 0.5 and can be about 0.25 PHR. An antioxidant is added at between about 0.0 and about 2.0 PHR. An antiozonant is added at between about 0.0 and about 5.0 PHR and between about 2.5 to about 4.5 PHR. Waxes such as paraffinic was and microcrystalline wax are added at between about 0.0 and about 3.0 PHR in total and can be about 1.5 PHR each. Process oil to facilitate compound mixing and extrusion is added at between about 0.0 and about 12.0 PHR and can be 5.0 PHR. An example of a process oil is treated distilled aromatic extract (TDAE). Other process oils may also be used such as conventional aromatic oil, residual extract aromatic (RAE), naphthenic oil, or MES. Stearic acid is added at between about 0.0 and about 2.0 PHR and can be about 1.5 PHR. Zinc oxide is added at between about 0.0 and about 6.0 PHR and can be about 4.0 PHR to about 5.0 PHR.

[0052] Tire sidewalls may also have a white appearance, applied as stripes in addition to letters molded onto the sidewall, and to which this invention equally applies. White sidewall compounds will contain blends of all four polymers, natural rubber, chlorobutyl rubber, polybutadiene and EPDM or blends chosen form this selection. Rather than carbon black the filler system will consist of titanium dioxide, calcium carbonate, clays and silica. In such instances, no antiozonant such as 6PPD would be used.

[0053] The vulcanization system contains sulfur, accelerators, and may also use a retarder to optimize compound induction time. Sulfur is used between about 0.5 and about 2.0 PHR and between about 0.8 and about 1.0 PHR. The accelerator may be sulfonamides including cyclohexyl benzothiazole disulfide (CBS) and tertiary butyl benzothiazole disulfide (TBBS). The amount is added at between about 0.25 and about 2.0 PHR and can be about 1.0 PHR. In some instances, a secondary accelerator is added, such as a thiuram such as, though not limited to, tetramethyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD), tetra t-butyl thiuram disulfide (TBTD or tetrabenzyl thiuram disulfide (TBzTD). The amount is added at between about 0.0 and about 2.0 PHR and between about 0.25 PHR to about 0.5 PHR. Alternatively a guanidine secondary accelerator such as DOPG or DPG could be used at between about 0.0 and about 2.5 PHR. A retarder or pre-vulcanization inhibitor (PVI) is also added at between about 0.0 and about 2.0 PHR and between about 0.15 to about 0.25 PHR.

[0054] Clause 1—A rubber composition including natural rubber, polybutadiene, carbon black, peptizer, process oil, paraffinic wax, microcrystalline wax, stearic acid, zinc oxide, sulfur, accelerator, pre vulcanization inhibitor, and graphene, wherein the sidewall has no additional antioxidant or antiozonant.

[0055] Clause 2—A rubber composition including natural rubber, polybutadiene, carbon black, and graphene, wherein the sidewall has no additional antiozonants.

[0056] Clause 3—The rubber composition of clause 2, wherein the sidewall has no additional antioxidants.

[0057] Clause 4—The rubber composition of clauses 2 or 3, wherein the graphene is between about 0.5 PHR and about 10.0 PHR.

[0058] Clause 5—The rubber composition of clauses 2-4, wherein the composition has no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine.

[0059] Clause 6—The rubber composition of clauses 2-5, wherein the composition has no 2,2,4-trimethyl-1,2-dihydroquinoline.

[0060] Clause 7—The rubber composition of clauses 2-6, wherein the graphene is a graphene plate, wherein the graphene plate is between about 0.5 PHR and about 10.0 PHR.

[0061] Clause 8—The rubber composition of clauses 2-7, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

[0062] Clause 9—The rubber composition of clauses 2-8, wherein the graphene plate has an oxygen content of less than about 1%.

[0063] Clause 10—The rubber composition of clauses 2-9, wherein the graphene has a thickness less than about 1 nm and an aspect ratio of about 1000.

[0064] Clause 11—The rubber composition of clauses 2-9, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

[0065] Clause 12—The rubber composition of clauses 2-11, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

[0066] Clause 13—The rubber composition of clauses 2-12, wherein the composition further includes peptizer, process oil, paraffinic wax, microcrystalline wax, stearic acid, zinc oxide, sulfur, accelerator, and pre vulcanization inhibitor.

[0067] Clause 14—The rubber composition of clauses 2-4 or 7-13, wherein the composition contains no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline.

[0068] Clause 15—The rubber composition of clause 1, wherein the composition contains no N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline.

[0069] Clause 16—The rubber composition of clauses 1-15, wherein the rubber composition is a tire sidewall.

[0070] Non-limiting aspects have been described, hereinabove. It will be apparent to those skilled in the art that the above methods and apparatuses may incorporate changes and modifications without departing from the general scope of the present subject matter. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.

[0071] Having thus described the present teachings, it is now claimed: