Description:TECHNICAL FIELD
The present disclosure relates to polymer chemistry. The disclosure particularly relates to rubber composition, vulcanized rubber comprising the rubber composition and pneumatic retreated tire comprising the vulcanized rubber and methods of preparation and application thereof.

BACKGROUND OF THE DISCLOSURE
Service life of vehicle tyres used in mines and building industry is very minimal as these tyres are operated in odd condition than regular road tyres. In mining areas there are several external factors such as sharp edge of stone which can initiate crack in the tyres, abnormal road condition like full of sand stone and other abrasive minerals and unusual road turning due to mines geographical condition that severely affects the tyre performance. Further, sudden start and braking of the heavy vehicle in the mines damages tread and sidewall of the tyre, thus having strong influence on the life of the tyre.

Large number of tyres are generated every year which requires retreading for further use. It is noted that tyre manufactures are employing various techniques to increase the service life of the retreaded tyres, one such technique is introduction of graphene, graphene oxide, graphene nanoplatelet in tread compound. However, it is noted that graphene has poor dispersion in the rubber matrix and it is affecting the production and commercialization of retreaded tyres or even in new tyres. The poor dispersion of the graphene in the rubber matrix is due to high Van Der Waals force of interaction and pi-pi interaction between two graphene layers.

Thus, there is a need to overcome the issues noted in production of retreaded tyres so that the performance of the retreaded tyre can be improved.

The present disclosure aims at arriving at a rubber composition/composite that overcomes the problem of graphene dispersion in the rubber matrix and improves the quality of the retreated tyres.

STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure relates to a rubber composition having improved graphene dispersion in the rubber matrix, which is achieved by particularly employing graphene nanoplatelets. The rubber composition comprises, based on parts by weight per 100 parts by weight of the elastomer (phr)- about 30 phr to 40 phr of natural rubber, about 60 phr to 70 phr of synthetic rubber, about 0.5 phr to 3 phr of graphene nanoplatelet, and about 50 phr to 60 phr of carbon black. The rubber composition provides for improved properties to the corresponding rubber compound.

The present disclosure further relates to vulcanized rubber comprising the rubber composition described above. The vulcanized rubber has improved modulus at 300%, improved tear strength, improved tensile strength and reduced abrasion loss.

The present disclosure further relates to method of preparing the vulcanized rubber, said method comprises- mixing natural rubber and synthetic rubber; mixing carbon black, oil, graphene nanoplatelets, optionally along with component selected from a group comprising fatty acid, metal oxide, antioxidant, tackifier and any combinations thereof to obtain rubber mass; and adding curative to the rubber mass, followed mixing and vulcanizing to obtain the vulcanized rubber.

The present disclosure further relates to retreaded pneumatic tyre comprising the vulcanized rubber described above. The retreaded pneumatic tyre has improved service life when compared to conventionally known retreaded pneumatic tyres.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, where:

Figure 1 illustrates a plot describing service life of reteraded pneumatic tyre of the present disclosure and new tyre upon use in Undwa mines, Udaipur, India.

Figure 2 illustrates a plot describing service life of retreaded pneumatic tyre of the present disclosure and conventional retreaded tyre upon use in Keshunda mines, Udaipur, India.

Figure 3a and 3b illustrate plots describing modulus at 300% of the vulcanized rubber of the present disclosure and the vulcanized rubber without graphene nanoplatelets (base compound).

Figure 4a and 4b illustrate plots describing tear strength of the vulcanized rubber of the present disclosure and the vulcanized rubber without graphene nanoplatelets.

Figures 5a and 5b illustrate plots describing abrasion loss of the vulcanized rubber of the present disclosure and the vulcanized rubber without graphene nanoplatelets.

DETAILED DESCRIPTION OF THE DISCLOSURE
Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ include both singular and plural referents unless the context clearly dictates otherwise.

The term ‘comprising’, ‘comprises’ or ‘comprised of’ as used herein are synonymous with ‘including’, ‘includes’, ‘containing’ or ‘contains’ and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.

Reference throughout this specification to ‘some embodiments’, ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. thus, the appearances of the phrases ‘in some embodiments’, ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification may not necessarily all refer to the same embodiment. It is appreciated that certain features of the disclosure, which are for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

As used herein ‘rubber processing oil’ or ‘rubber process oil’ refers to process oil comprising selected from a group comprising paraffin oil, naphthalene oil and a mixture thereof. The process oil comprises other related oils having varied molecular weight distribution. The rubber processing oil is used as processing aid in the preparation of the rubber composition.

As used herein ‘modulus at 300%’ refers to stress value of that particular rubber at an elongation of 300%, i.e., at four times the original length.

As used herein, ‘elongation at break’ or elongation at break%’ means ratio between changed length and initial length after breakage of the rubber. It expresses the capability of the rubber to deform or elongate before rupture.

As used herein, ‘shore A hardness’ refers hardness level of the rubber, indicating resistance to indentation. Shore A hardness is measured through shore durometer tool.

The terms ‘tyre’, ‘tyres’, ‘tire’, ‘tires’ are used interchangeable in the specification, which means covering for a wheel.

The present disclosure relates to a rubber composition having improved graphene dispersion.

The present disclosure relates to a rubber composition comprising based on parts by weight per 100 parts by weight of elastomer (phr)- about 30 phr to 40 phr of natural rubber; about 60 phr to 70 phr of synthetic rubber, about 0.5 phr to 3 phr of graphene nanoplatelet; and about 50 phr to 60 phr of carbon black.
In an embodiment of the present disclosure, the rubber composition comprises based on parts by weight per 100 parts by weight of elastomer (phr)- about 30 phr, about 31 phr, about 32 phr, about 33 phr, about 34 phr, about 35 phr, about 36 phr, about 37 phr, about 38 phr, about 39 phr or about 40 phr of synthetic rubber.

In an embodiment of the present disclosure, the rubber composition comprises based on parts by weight per 100 parts by weight of elastomer (phr)- about 60 phr, about 61 phr, about 62 phr, about 63 phr, about 64 phr, about 65 phr, about 66 phr, about 67 phr, about 68 phr, about 69 phr or about 70 phr of natural rubber.

In an embodiment of the present disclosure, the rubber composition comprises based on parts by weight per 100 parts by weight of elastomer (phr)- about 0.5 phr, about 0.6 phr, about 0.7 phr, about 0.8 phr, about 0.9 phr, about 1.0 phr, about 1.1 phr, about 1.2 phr, about 1.3 phr, about 1.4 phr, about 1.5 phr, about 1.6 phr, about 1.7 phr, about 1.8 phr, about 1.9 phr, about 2.0 phr, about 2.0 phr, about 2.1 phr, about 2.2 phr, about 2.3 phr, about 2.4 phr, about 2.5 phr, about 2.6 phr, about 2.7 phr, about 2.8 phr, about 2.9 phr or about 3.0 phr of the graphene nanoplatelet.

In an embodiment of the present disclosure, the rubber composition comprises based on parts by weight per 100 parts by weight of elastomer (phr)- about 50 phr, about 51 phr, about 52 phr, about 53 phr, about 54 phr, about 55 phr, about 56 phr, about 57 phr, about 58 phr, about 59 phr or about 60 phr of carbon black.

In some embodiments of the present disclosure, the rubber composition further comprises based on parts by weight per 100 parts by weight of elastomer (phr), component selected from a group comprising-
- about 4 phr to 6 phr of oil, including all the values in the range, for instance, 4.1 phr, 4.2 phr, 4.3 phr, 4.4 phr and so on and so forth.
- about 2 phr to 5 phr of fatty acid, including all the values in the range, for instance, 2.1 phr, 2.2 phr, 2.3 phr, 2.3 phr and so on and so forth.
- about 3 phr to 5 phr of metal oxide, including all the values in the range, for instance, 3.1 phr, 3.2 phr, 3.3 phr, 3.4 phr and so on and so forth.
- about 1 phr to 3 phr of antioxidant, including all the values in the range, for instance, 1.1 phr, 1.2 phr, 1.3 phr, 1.4 phr and so on and so forth.
- about 4 phr to 6 phr of tackifier, including all the values in the range, for instance, 4.1 phr, 4.2 phr, 4.3 phr, 4.4 phr and so on and so forth.
- about 1 phr to 3 phr sulphur, including all the values in the range, for instance, 1.1 phr, 1.2 phr, 1.3 phr, 1.4 phr and so on and so forth.
- about 1 phr to 2 phr of accelerator, including all the values in the range, for instance, 1.1 phr, 1.2 phr, 1.3 phr, 1.4 phr and so on and so forth,
and any combinations thereof.

In some embodiments of the present disclosure, the rubber composition comprises, based on parts by weight per 100 parts by weight of elastomer (phr):
- about 30 phr to 40 phr of natural rubber,
- about 60 phr to 70 phr of synthetic rubber,
- about 0.5 phr to 3 phr of graphene nanoplatelet,
- about 50 phr to 60 phr of carbon black,
- about 4 phr to 6 phr of oil,
- about 2 phr to 5 phr of fatty acid,
- about 1 phr to 3 phr of metal oxide,
- about 1 phr to 3 phr of antioxidant, and
- about 4 phr to 6 phr of tackifier,

In some embodiments of the present disclosure, based on parts by weight per 100 parts by weight of elastomer (phr), about 1 phr to 3 phr of sulphur and about 1 phr to 2 phr of accelerator are included in the rubber composition while vulcanizing the rubber composition.

In some embodiments of the present disclosure, the synthetic rubber is selected from a group comprising styrene butadiene rubber, butadiene rubber and a combination thereof.

In some embodiments of the present disclosure, the fatty acid includes but it is not limited to stearic acid.

In some embodiments of the present disclosure, the metal oxide includes but it is not limited to zinc oxide.

In some embodiments of the present disclosure, the antioxidant is selected from a group comprising poly(1,2-dihydro-2,2,4-trimethyl-quinoline), p-Phenylenediamine and a combination thereof.

In some embodiments of the present disclosure, the accelerator is selected from a group comprising 2-(4-Morpholinothio) benzothiazole (MBS), Diphenyl Guanidine (DPG), N-Cyclohexyl-2- benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), and any combinations thereof.

In some embodiments of the present disclosure, the accelerator is selected from a group comprising combination of 2-(4-Morpholinothio) benzothiazole (MBS) and Diphenyl Guanidine (DPG), combination of N-Cyclohexyl-2- benzothiazole sulfenamide (CBS) and Diphenyl Guanidine (DPG) and combination of N-tert-butyl-2-benzothiazole sulfenamide (TBBS) and Diphenyl Guanidine (DPG).

In some embodiments of the present disclosure, the tackifier is selected from a group comprising biroza resin, CI resin and a combination thereof.

In some embodiments of the present disclosure, the oil is rubber processing oil, including but it is not limited to paraffinic oil and naphthenic oil.

The inventors have identified that employing graphene nanoplatelet provides for improved dispersion of graphene in the rubber composition, as a result, the corresponding cured rubber has improved property, such as tensile strength, tear strength and modulus at 300% and reduced abrasion loss. Particularly, use of 0.5 phr to 3 phr of graphene nanoplatelet based on the parts by weight per 100 parts by weight of the elastomer (phr), provides for improved dispersion of the graphene and improved properties to the corresponding cured rubber.

The inventors identified that good dispersion of graphene nanoplatelet in the rubber composition increases interaction with rubber matrix which increases the modulus. The dispersion of the graphene nanoplatelet in the rubber matrix creates exfoliated nanocomposites, which enables to open up further surface area of the graphene so that the graphene is available for improved bonding with the rubber matrix. The inventors additionally identified that, platelet like structure of the graphene nanoplatelet used in the rubber composition resists crack propagation by creating zig-zig pathway which indeed enhances the time required for crack propagation, thus improving the properties of the corresponding cured rubber/rubber compound.

The inventors have particularly identified that using graphene nanoplatelet in a range of 0.5 phr to 3phr, including all the values in the range, for instance, 0.6 phr, 0.7 phr, 0.8 phr, 0.9 phr, based on the parts by weight per 100 parts by weight of the elastomer, increases wear resistance behaviour by decreasing abrasion loss by about 20% in the corresponding rubber compound.

The present disclosure further relates to vulcanized rubber comprising the rubber composition described above.

In an embodiment, the vulcanized rubber is in sheet form.

The vulcanized rubber of the present disclosure possesses improved properties due to the presence of graphene nanoplatelet in the rubber composition described above.

In some embodiments of the present disclosure, the vulcanized rubber has modulus at 300% ranging from about 41 Kgf/cm2 to 43 Kg/cm2, including all the values in the range, for instance, 41.1 Kgf/cm2, 41.2 Kgf/cm2, 41.3 Kgf/cm2, 41.4 Kgf/cm2 and so on and so forth. In an embodiment, the modulus at 300% of the vulcanized rubber of the present disclosure is at least 9% improvement when compared to vulcanized rubber lacking graphene nanoplatelet. In an embodiment, the improvement of modulus at 300% is ranging from about 9% to 10%. Figures 3a and 3b of the present disclosure illustrates the improved modulus at 300% of the vulcanized rubber when compared to vulcanized rubber lacking graphene nanoplatelet (base compound).

In some embodiments of the present disclosure, the vulcanized rubber has tear strength ranging from about 52 kN/M to 58 kN/M, including all the values in the range, for instance, 52.1 kN/M, 52.2 kN/M, 52.3 kN/M, 52.4 kN/M and so on and so forth. In an embodiment, the tear strength of the vulcanized rubber of the present disclosure is at least 15% improvement when compared to vulcanized rubber lacking graphene nanoplatelet. In an embodiment, the improvement in the tear strength is ranging from about 15% to 28%. Figures 4a and 4b of the present disclosure illustrates the improved tear strength of the vulcanized rubber when compared to vulcanized rubber lacking graphene nanoplatelet (base compound).

In some embodiments of the present disclosure, the vulcanized rubber has abrasion loss ranging from about 85 mm3 to 86 mm3, including all the values in the range, for instance, 85.1 mm3, 85.2 mm3, 85.3 mm3, 85.4 mm3. In an embodiment, the abrasion loss of the vulcanized rubber of the present disclosure is at least 20% reduced when compared to vulcanized rubber lacking graphene nanoplatelet. In an embodiment, reduction in abrasion loss in a range of 20% to 22%. Figures 5a and 5b of the present disclosure illustrates the reduced abrasion loss of the vulcanized rubber when compared to vulcanized rubber lacking graphene nanoplatelet (base compound).

In some embodiments of the present disclosure, the vulcanized rubber has tensile strength ranging from about 180 kgf/cm2 to 184 kgf/cm2, including all the values in the range, for instance, 180.1 kgf/cm2, 180.2 kgf/cm2, 180.3 kgf/cm2, 180.4 kgf/cm2, and so on and so forth. In an embodiment, the tensile strength of the vulcanized rubber of the present disclosure is at least 2.5% improvement when compared to vulcanized rubber lacking graphene nanoplatelet. In an embodiment, the improvement in the tensile strength is ranging from about 2.5% to 5%.

In some embodiments of the present disclosure, the vulcanized rubber has elongation at break (facture strain) ranging from about 418% to 640%, including all the values in the range, for instance, 419%, 420%, 421%, 422%, 423% and so on and so forth.

In some embodiments of the present disclosure, the vulcanized rubber has shore A hardness ranging from about 62 to 65, including all the values in the range, for instance, 62.1, 62.2, 62.3, 62.4 and so on and so forth.

The present disclosure further relates to method of preparing the vulcanized rubber.

In some embodiments of the present disclosure, the method of preparing vulcanized rubber comprises:
a) mixing the natural rubber and the synthetic rubber;
b) mixing the carbon black, the oil and the graphene nanoplatelet, optionally along with component selected from a group comprising the fatty acid, the metal oxide, the antioxidant, the tackifier and any combinations thereof to obtain rubber mass; and
c) adding curative to the rubber mass, followed by mixing and vulcanizing to obtain the vulcanized rubber.

In some embodiments of the present disclosure, the mixing of the natural rubber and the synthetic rubber is carried out by technique selected from a group comprising kneading and intermixing.

In some embodiments of the present disclosure, the mixing of the natural rubber and the synthetic rubber is carried out for a duration ranging from about 2 minutes to 3 minutes, including all the values in the range, for instance, 2.1 minutes, 2.2 minutes, 2.3 minutes, 2.4 minutes and so on and so forth.

In some embodiments of the present disclosure, the mixing of the carbon black, the oil and the graphene nanoplatelet, optionally along with component selected from a group comprising the fatty acid, the antioxidant, the tackifier, and any combinations thereof, is carried out by technique selected from a group comprising kneading and intermixing. In an embodiment, the mixing is carried out for a duration ranging from about 2 minutes to 3 minutes, including all the values in the range, for instance, 2.1 minutes, 2.2 minutes, 2.3 minutes, 2.4 minutes and so on and so forth.

In some embodiments of the present disclosure, the rubber mass is prepared by-
- mixing the natural rubber and the synthetic rubber for a duration ranging from about 2 minutes to 3 minutes;
- adding about half the amount of the carbon black and the oil from total amount of the carbon black and the oil, followed by mixing for a duration ranging from about 4 minutes to 5 minutes, including all the values in the range, for instance, 4.1 minutes, 4.2 minutes, 4.3 minutes, 4.4 minutes and so on and so forth, followed by adding the graphene nanoplatelet and mixing for a duration ranging from about 4 minutes to 5 minutes, including all the values in the range, for instance, 4.1 minutes, 4.2 minutes, 4.3 minutes, 4.4 minutes and so on and so forth, and adding remaining amount of the carbon black and the oil, followed by mixing for a duration ranging from about 3 minutes to 5 minutes, including all the values in the range, for instance, 3.1 minutes, 3.2 minutes, 3.3 minutes, 3.4 minutes and so on and so forth;
- adding the fatty acid, the metal oxide, the antioxidant, and the tackifier, followed by mixing for a duration ranging from about 2 minutes to 3 minutes, including all the values in the range, for instance, 2.1 minutes, 2.2 minutes, 2.3 minutes, 2.4 minutes and so on and so forth, to obtain the rubber mass.

In some embodiments of the present disclosure, the rubber mass is prepared by-
- mixing about 30 phr to 40 phr the natural rubber and about 60 phr to 70 phr of the synthetic rubber for a duration ranging from about 2 minutes to 3 minutes;
- adding about 25 phr to 30 phr of the carbon black and about 2 phr to 3 phr of the oil (half the amount of the carbon black and the oil from the total amount), followed by mixing for a duration ranging from about 4 minutes to 5 minutes, followed by adding 0.5 phr to 3 phr of the graphene nanoplatelet and mixing for a duration ranging from about 4 minutes to 5 minutes, and adding about 25 phr to 30 phr of the carbon black and about 2 phr to 3 phr of the oil (remaining half the amount of the carbon black and the oil), followed by mixing for a duration ranging from about 3 minutes to 5 minutes; and
- adding about 2 phr to 5 phr of the fatty acid, about 3 phr to 5 phr of the metal oxide, about 1 phr to 3 phr of the antioxidant and about 4 phr to 6 phr of the tackifier, followed by mixing for a duration ranging from about 2 minutes to 3 minutes to obtain the rubber mass.
The weights of the components employed in the preparation of the rubber mass is based on the parts by weight per 100 parts by weight of the elastomer (phr).

The inventors have particularly identified that, during the preparation of the rubber mass, adding about half the amount of the carbon black and the oil from total amount of the carbon black and the oil, followed by adding the graphene nanoplatelet and adding remaining amount of the carbon black and the oil, provides for improved dispersion of the graphene nanoplatelets into the rubber matrix. That is, it was particularly noted that, adding graphene nanoplatelets between the addition of carbon black and the oil provides for improved dispersion of the graphene nanoplatelet in the rubber matrix. Thus, imparting improved properties to the corresponding rubber compound, i.e., the vulcanized rubber.

In some embodiments of the present disclosure, the rubber mass is prepared at a temperature ranging from about 110 ? to 130 ?, including all the values in the range, for instance, 111 ?, 112 ?, 113?, 114 ? and so on and so forth.

In some embodiments of the present disclosure, the rubber mass is mixed with about 3 phr to 5 phr of the curative for a duration ranging from about ranging from about 2 minutes to 5 minutes, including all the values in the range, for instance, 2.1 minutes, 2.2 minutes, 2.3 minutes, 3.4 minutes and so on and so forth, to obtain curated rubber mass. In an embodiment, the curative is in an amount of about 3 phr, about 3.1 phr, about 3.2 phr, about 3.3 phr, about 3.4 phr, about 3.5 phr, about 3.6 phr, about 3.7 phr, about 3.8 phr, about 3.9 phr, about 4.0 phr, about 4.1 phr, about 4.2 phr, about 4.3 phr, about 4.4 phr, about 4.5 phr, about 4.6 phr, about 4.7 phr, about 4.8 phr, about 4.9 phr or about 5 phr

In some embodiments of the present disclosure, upon mixing the rubber mass with the curative, it is subjected to milling, wherein the milling is carried out in two-roll mill.

In some embodiments of the present disclosure, the curated rubber mass is subjected to vulcanization. The vulcanization is carried out by adding about 1 phr to 3 phr of the sulphur and about 1 phr to about 2 phr of the accelerator. In an embodiment, vulcanization is carried out at a temperature of about 140 ?. In another embodiment, vulcanization is carried out at a temperature of about 150 ?. In an embodiment, the vulcanization is carried out for a duration ranging from about 39 minutes to 45 minutes, including all the values in the range, for instance, 39.1 minutes, 39.2 minutes, 39.3 minutes, 39.4 minutes and so on and so forth.

The present disclosure further relates to retreaded pneumatic tire comprising the vulcanized rubber described above.

In some embodiments of the present disclosure, the retreaded pneumatic tire has service life ranging from about 3100 hours to 3800 hours, including all the values in the range, for instance, 3101 hours, 3102 hours, 3103 hours 3104 hours and so on and so forth.

The inventors have identified that the retreaded pneumatic tire of the present disclosure has least 1.5 times enhanced service life when compared to conventional retreaded tires. Figure 2 illustrates improved service life of the retreaded pneumatic tire of the present disclosure vis-à-vis the conventional retreaded tire.

The retreaded pneumatic tire of the present disclosure has service life of at least 85% vis-à-vis the service life of brand-new tires. Figure 1 describes a plot illustrating service life of the retreaded pneumatic tire of the present disclosure and the service life of brand new tire. From the plot it can be noted that the service life of the retreaded pneumatic tire has service life about 86% vis-a-vis the brand-new tire. Thus, emphasising that the retreaded pneumatic tire of the present disclosure has performance similar to the brand-new tire.

In some embodiments of the present disclosure, the vulcanized rubber described above is subjected to apparatus two-roll mill to obtain treads of specified thickness of 24 mm to 25 mm.

In some embodiments of the present disclosure, retreading of the pneumatic tire is carried out through hot retreading process, followed by curing of the retreaded pneumatic tire in curing mould to obtain retreaded pneumatic tire.

It is to be understood that the foregoing description is illustrative not a limitation. While considerable emphasis has been placed herein on particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.

Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES
Example 1: Preparation of vulcanized rubber
About 30 phr of natural rubber and about 70 phr of synthetic rubber was uniformly masticated at the same time in a twin screw kneader for a duration ranging from about 2 minutes to 3 minutes, until the torque was stabilized.
About 25 phr of the carbon black and about 2phr of the oil (half the amount of the carbon black and the half of the amount of the oil from the total amount of 50 phr of oil carbon black and 4 phr of the oil) was added and mixed for a duration of about 5 minutes, followed by adding about 1.5 phr of the graphene nanoplatelet and mixing for about 5 minutes. Further remaining amount of the carbon black and the oil was added, i.e., 25 phr of the carbon black and 2 phr of the oil was added and mixed for about 5 minutes.
About 5phr of the zinc oxide, about 3 phr of the stearic acid, about 5 phr of the tackifier, about 3 phr of the antioxidant were added and mixed for a duration of about 3 minutes, thus obtaining rubber mass. The temperature during mixing was maintained at about 120 ? to 130 ? and dumping temperature was maintained at about 150 ? to 155 ?. The rotor speed during mixing was maintained at speed of about 25 rpm to 30 rpm.
The rubber mass was processed in two-roll mill and about 5 phr of the curative was added and mixed for about 5 minutes and the rubber mass was converted into sheets. The mixing was carried out at a temperature of about 70 ? to 80 ? and rotor speed was maintained at about 30 rpm to 35 rpm.

The obtained sheets were vulcanized at a temperature of about 140 ?.

Table 1 describes the properties of the obtained vulcanized rubber and the vulcanized rubber lacking graphene nanoplatelets (conventional rubber).
Parameter Vulcanized rubber of the present disclosure Conventional rubber
300% Modulus 41.5 (9%) 38
Tensile strength (Kgf/cm2) 184 175
Elongation @break% 640 450
Tear Strength (kN/m) 52 (15%) 45
Hardness (Shore A) 65 62
Abrasion loss (mm3) 86 (21%) 110
Table 1:

The data in Table 1 demonstrates that there is about 9% improvement in modulus at 300%, about 15% improvement in tear strength and about 21% reduction in abrasion loss, i.e., 21% improvement in the wear resistance when compared to conventional rubber lacking graphene nanoplatelet. Thus, demonstrating that the corresponding rubber composition of the present disclosure having graphene nanoplatelet provides the improved properties to the rubber compound (vulcanized rubber).

Example 2: Preparation of vulcanized rubber
About 30 phr of natural rubber and about 70 phr of synthetic rubber was uniformly masticated at the same time in a intermix machine for a duration ranging from about 2 minutes to 3 minutes, until the torque was stabilized.
About 25 phr of the carbon black and about 2phr of the oil (half the amount of the carbon black and the half of the amount of the oil from the total amount of 50 phr of oil carbon black and 4 phr of the oil) was added and mixed for a duration of about 5 minutes, followed by adding about 1.2 phr of the graphene nanoplatelet and mixing for about 5 minutes. Further remaining amount of the carbon black and the oil was added, i.e., 25 phr of the carbon black and 2 phr of the oil was added and mixed for about 5 minutes.
About 5phr of the zinc oxide, about 3 phr of the stearic acid, about 5 phr of the tackifier, about 3 phr of the antioxidant were added and mixed for a duration of about 2 minutes, thus obtaining rubber mass. The temperature during mixing was maintained at about 110 ? to 120 ? and dumping temperature was maintained at about 150 ? to 155 ?. The rotor speed during mixing was maintained at speed of about 25 rpm to 30 rpm.
The rubber mass was processed in two-roll mill and about 5 phr of the curative was added and mixed for about 5 minutes and the rubber mass was converted into sheets. The mixing was carried out at a temperature of about 70 ? to 80 ? and rotor speed was maintained at about 30 rpm to 35 rpm.
The obtained sheets were vulcanized at a temperature of about 140 ?.

Table 2 describes the properties of the obtained vulcanized rubber and the vulcanized rubber lacking graphene nanoplatelets (conventional rubber).
Parameter Vulcanized rubber of the present disclosure Conventional rubber
300% Modulus 42.56 (10%) 38
Tensile strength (Kgf/cm2) 180 175
Elongation @break% 418 450
Tear Strength (kN/m) 58 (28%) 45
Hardness (Shore A) 62 62
Abrasion loss (mm3) 85 (22%) 110
Table 2:
The data in Table 2 demonstrates that there is about 10 % improvement in modulus at 300%, about 28% improvement in tear strength and about 22% reduction in abrasion loss, i.e., 22% improvement in the wear resistance when compared to conventional rubber lacking graphene nanoplatelet. Thus, demonstrating that the corresponding rubber composition of the present disclosure having graphene nanoplatelet provides improved properties to the rubber compound (vulcanized rubber).

Example 3: Preparation of retreaded pneumatic tire
The vulcanized rubber obtained in examples 1 and 2 were transferred to two-roll mill to obtain thickness of about 18mm to 20 mm to make the tread. Retreading was performed through hot retreading process and curing was performed in curing mould to obtain retreaded pneumatic tires.
The obtained retreaded pneumatic tires were subjected to field trial in mines of India for about 10 months.

The trial included 3 sets of tires.
- Set 1: 8 retreaded pneumatic tires of the present disclosure (prepared in Example 3);
- Set 2: 8 retreaded pneumatic tires lacking graphene nanoplatelets (conventional retreaded tires); and
- Set 3: 4 brand new tires.

Figures 1 and 2 provides plots demonstrating service life of the retreaded pneumatic tires of the present disclosure, conventional retreaded tires and brand-new tires, respectively.
The plot in Figure 2 demonstrates that the pneumatic tires of the present disclosure have 55% improvement in service life when compared to conventional retreaded tires.
The plot in Figure 1 demonstrates that the service life of the retreaded pneumatic tires of the present disclosure is at least 85% vis-a-vis the brand-new tyre.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

, Claims:WE CLAIM:
1. Rubber Composition comprising, based on parts by weight per 100 parts by weight of elastomer (phr):
- about 30 phr to 40 phr of natural rubber;
- about 60 phr to 70 phr of synthetic rubber;
- about 0.5 phr to 3 phr of graphene nanoplatelet; and
- about 50 phr to 60 phr of carbon black.

2. The rubber composition as claimed in claim 1, wherein the composition further comprises based on parts by weight per 100 parts by weight of elastomer (phr), component selected from a group comprising:
- about 4 phr to 6 hpr of aromatic oil;
- about 2 phr to 5 phr of fatty acid;
- about 3 phr to 5 phr of metal oxide;
- about 1 phr to 3phr of antioxidant;
- about 4 phr to 6 phr of tackifier;
- about 1 phr to 3 phr of sulphur;
- about 1 phr to 2 phr of accelerator; and any combination thereof.

3. The rubber composition as claimed in claim 1, wherein the synthetic rubber is selected from a group comprising styrene butadiene rubber, butadiene rubber and a combination thereof.

4. The rubber composition as claimed in claim 2, wherein the fatty acid is stearic acid.

5. The rubber composition as claimed in claim 2, wherein the metal oxide is zinc oxide.

6. The rubber composition as claimed in claim 2, wherein the accelerator is selected from a group comprising of 2-(4-Morpholinothio) benzothiazole (MBS), N-Cyclohexyl-2- benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), Diphenyl Guanidine (DPG) and any combination thereof.

7. The rubber composition as claimed in claim 2, wherein the tackifier is selected from a group comprising of Biroza and CI resin.

8. The rubber composition as claimed in claim 2, wherein the oil is rubber processing oil selected from a group comprising paraffinic oil, naphthenic oil and a combination thereof.

9. The rubber composition as claimed in claim 2, wherein the antioxidant is selected from a group comprising poly(1,2-dihydro-2,2,4-trimethyl-quinoline) (TMQ), p-Phenylenediamine (6PPD) and a combination thereof.
`
10. A vulcanized rubber comprising the rubber composition as claimed in claim 1.

11. The vulcanized rubber as claimed claim 10, wherein the rubber is in sheet form.

12. The vulcanized rubber as claimed in claim 10, wherein the rubber has modulus at 300% ranging from about 41 Kgf/cm2 to 42.56 Kgf/cm2.

13. The vulcanized rubber as claimed in claim 10, wherein the rubber has tear strength ranging from about 52 kN/M to 58 kN/M.

14. The vulcanized rubber as claimed in claim 10, wherein the rubber has abrasion loss ranging from about 86 mm3 to 85 mm3.

15. The vulcanized rubber as claimed in claim 10, wherein the rubber has tensile strength ranging from about 180 kgf/cm2 to 184 kgf/cm2.

16. The vulcanized rubber as claimed in claim 10, wherein the rubber has elongation at break (fracture strain) ranging from about 418% to 640%.

17. The vulcanized rubber as claimed in claim 10, wherein the rubber has Shore A hardness ranging from about 62 to 65.

18. A method of preparing the vulcanized rubber as claimed in claim 10, said method comprises-
a) mixing the natural rubber and the synthetic rubber;
b) mixing the carbon black, the oil and the graphene nanoplatelets, optionally along with component selected from a group comprising the fatty acid, the metal oxide, the antioxidant, the tackifier, and any combinations thereof to obtain rubber mass; and
c) adding the curative to the rubber mass, followed by mixing and vulcanizing to obtain the vulcanized rubber.

19. The method as claimed in claim 18, wherein the mixing of steps (a) and (b) is carried out by technique selected from a group comprising kneading and intermixing.

20. The method as claimed in claim 18, wherein the mixing of the natural rubber and the synthetic rubber is carried out for a duration ranging from about 2 minutes to 3 minutes.

21. The method as claimed in claim 18, wherein the step (b) comprises-
- adding about half the amount of the carbon black and the oil from total amount of the carbon black and the oil, followed by mixing for a duration ranging from about 4 minutes to 5 minutes;
- adding the graphene nanoplatelet, followed by mixing for a duration ranging from about 4 minutes to 5 minutes;
- adding remaining amount of the carbon black and the oil, followed by mixing for a duration ranging from about 3 minutes to 5 minutes;
- optionally adding the tackifier, the antioxidant, the fatty acid and the processing aid, followed by mixing for a duration ranging from about 2minutes to 3minutes; and

22. The method as claimed in claim 18, wherein the mixing in step (c) is carried out for a duration ranging from about 25 minutes to 30 minutes.

23. The method as claimed in claim 18, wherein the mixing in steps (a) and (b) is carried out at a temperature ranging from about 110 °C to 130 °C.

24. The method as claimed in claim 18, wherein the rubber mass is subjected to milling upon mixing with curative; wherein the milling is carried out in two-roll mill.

25. The method as claimed in claim 18, wherein the vulcanizing is carried out at a temperature ranging from about 140°C to 150°C, for a duration ranging from about 39 minutes to 45 minutes.

26. A retreaded pneumatic tire comprising the vulcanized rubber as claimed in claim 10.

27. The retreaded pneumatic tire as claimed in claim 26, wherein the retreaded pneumatic tire has service life ranging from about 3100 hours to 3800 hours.