Claims:WE CLAIM:

1. A solid state grafting of functional group onto polybutadiene rubber (PBR) for functionalizing the polybutadiene rubber, comprising steps of:
mixing the polybutadiene rubber, a radical initiator and the functional group to obtain a grafted polybutadiene; and
mixing the grafted polybutadiene and a ring opening agent to obtain the functionalized PBR.

2. The solid state grafting as claimed in claim 1, wherein the step of mixing the polybutadiene rubber, the radical initiator and the functional group comprises-
masticating the polybutadiene rubber at a speed ranging from about 20RPM to 60RPM at a temperature ranging from about 20ºC to 30ºC for a duration ranging from about 1 minute to 2 minutes; and
adding the radical initiator and the functional group and continuing the mastication at a speed ranging from about 20RPM to 60RPM at a temperature ranging from about 60ºC to 100ºC under an inert atmosphere for a duration ranging from about 1minute to 5 min to obtain the grafted polybutadiene .

3. The solid state grafting as claimed in claim 1, wherein the grafted polybutadiene is optionally treated with antioxidant prior to mixing with ring opening agent.

4. The solid state grafting as claimed in claim 3, wherein treating the graft mixture with antioxidant comprises adding the antioxidant and mixing for a duration ranging from about 1 minute to 5 minutes at a temperature ranging from about 60?C to 120?C to obtain the grafted polybutadiene.

5. The solid state grafting as claimed in any one of claims 1 to 4, wherein the grafted polybutadiene is subjected to internal melt mixture at a temperature ranging from about 60?C to 150?C at a pressure ranging from about 60 kg/cm2 to 200 kg/cm2 to obtain thin film.

6. The solid state grafting as claimed in any one of claims 1 to 5, wherein the grafted polybutadiene is subjected to solvent extraction to remove unreacted functional group.

7. The solid state grafting as claimed in claim 1, wherein the step of mixing the grafted polybutadiene and the ring opening agent comprises:
mixing the grafted polybutadiene and the ring opening agent at a temperature ranging from about 20ºC to 30ºC for a duration ranging from about 1 minute to 5 minutes; and
continuing the mixing at a temperature ranging from about 100?C to 160?C for a duration ranging from about 1 minute to 5minutes under inert atmosphere to obtain the functionalized PBR.

8. The solid state grafting as claimed in claim 1, wherein the radical initiator is selected from a group comprising dicumyl peroxide, Benzoyl Peroxide, azobisisobutyronitrile (AIBN), Bis (2,4-dichloro)benzoylperoxide, Di-tert.butylperoxide, tert butylcumylperoxide, 1,4-bis(tert.butylperoxyisopropyl) benzene, 2,5-bis-( tert.butylperoxy)-2,5-dimethylhexane, 4,4 di- tert.butylperoxy-n-butylvalerate or any other peroxides

9. The solid state grafting as claimed in claim 1, wherein the functional group is selected from a group comprising Maleic anhydride, ?, ß-unsaturated ketones, ?, ß-unsaturated aldehydes, ?, ß-unsaturated acids, ?, ß-unsaturated esters, ?, ß-unsaturated amides, 2H-Pyran-2,6(3H)-dione, 2[5H]-furanone, furanone, 5,6-Dihydro-2H-pyran-2-one, 3,6-dihydro-2H-Pyran-2-one, 1H-pyrrol-2(5H)-one, 1,3-Dihydro-2H-pyrrol-2-one, 5,6-Dihydro-2(1H)-pyridinone, 3,6-Dihydro-2(1H)-pyridinone, 3,4-Dihydro-2(1H)-pyridinone, 1,5,6,7-Tetrahydro-2H-azepin-2-one, 1,3,4,5-Tetrahydro-2H-azepin-2-one, itaconic anhydride, Maleimide, 6-Hydroxypyridin-2(3H)-one, Oxirene, 2H-oxete, 2,5-Dihydrofuran, dihydrofuran, 3,4-Dihydro-2H-pyran, 3,6-Dihydro-2H-pyran, 2,3,4,5-Tetrahydrooxepine and 2,3,6,7-Tetrahydrooxepine, Thiophene-2,5-dione, 2(5H)-Thiophenone, 2(3H)-Thiophenone, 3,6-Dihydro-2H-thiopyran-2-one and a combination thereof.

10. The solid state grafting as claimed in claim 1, wherein the ring opening agent is selected from a group comprising 3-amino-1,2,4-triazole, Thiourea, 2, 6-diaminopyridine, aniline, nitro-aniline, hydroxyaniline, ethylene diamine, triethylenetetramine, triethanolamine, diphenyl guanidine, 1-phenyl-1,2-ethanediol, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 4-amino-1,2,3-triazole, 5-amino-1,2,3-triazole, 5-aminotetrazole, 3-aminopyrazole, 4-aminopyrazole, 5-aminopyrazole, 3-amino-5-thiol-1,2,4-triazole, urea, Diethylene triamine (DETA), melamine, cyclodextrin, 2-hydrazino-4-(trifluoromethyl)pyridimine, PEG-6000, 1-phenyl-ethane-1,2-diol, L-Alanine benzyl ester p-toluenesulfonate salt, L-Cysteine ethyl ester hydrochloride, L-Methionine ethyl ester hydrochloride, L-Phenylalanine methyl ester hydrochloride, N-(3-indolylacetyl)-L-alanine and a combination thereof.

11. The solid state grafting as claimed in claim 3, wherein the antioxidant is selected from a group comprising Di-tert-buty-p-cresol (DTBPC), Para phenylenediamines (PPDs), N,N’-Bis (1,4-dimethylpentyl)-pphenylenediamine, N-(1,3-Dimethylbutyl)-N'-phenyl-pphenylenediamine, N-phenyl-N’ isopropyl-pphenylenediamine, Polymerized 2,2,4-Trimethyl-1,2-dihydroquinoline, 6-Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, Styrenated phenol, 2.2’-methylenebis (6-t-butyl-4methyl, phenol), 4,4’-thiobis-6-(t-butyl) metacresol, tetrakis [Methylene 3-(3,5 di-t-butyl - 4 hydroxyphenyl) propionate] methane, p-oriented styrenated diphenyl amine, 4,4, bis (a,a-domethylbenzyl)diphenylamine, Octylated diphenyl amine, Acetone diphenyl amine condensates and Didodecyl 3.3’ thiodipropionate

12. The solid state grafting as claimed in claim 1, wherein the proportion of the polybutadiene rubber to the functional group is ranging from about 1: 0.001 weight ratio to 1:0.2 weight ratio.

13. The solid state grafting as claimed in claim 1, wherein the proportion of the polybutadiene rubber to the radical initiator is ranging from about 1: 0.0001 weight ratio to 1: 0.05 weight ratio.

14. The solid state grafting as claimed in claim 1, wherein the proportion of the graft mixture to the ring opening agent is ranging from about 1:0.001 weight ratio to 1:0.2 weight ratio.

15. The solid state grafting as claimed in claim 3, wherein the proportion of the antioxidant to the radical initiator is ranging from about 1:0.005 weight ratio to 1:0.05 weight ratio.

Dated this 24th day of March, 2020

Durgesh Mukharya
IN-PA-1541
Of K & S Partners
Agent for the Applicant
To
The Controller of Patents
The Patent Office Branch
Chennai
, Description:
TECHNICAL FIELD
The present disclosure relates to polymer sciences. Particularly, the present disclosure relates to functionalization of polybutadiene rubber through solid state grafting of functional group onto polybutadiene rubber. Functionalization of polybutadiene rubber by the said solid state grafting retains the intrinsic properties of the polybutadiene rubber, particularly the supramolecular non-covalent cross-linking of cooperative H-bonding between the elastomer chains within the polybutadiene rubber.

BACKGROUND OF THE DISCLOSURE
Polybutadiene rubber (PBR) is the second most important synthetic general purpose rubber produced worldwide. Polybutadiene rubber is a homopolymer produced by polymerization of 1,3-butadiene (BD). Polybutadiene rubber finds major application in manufacturing of tyres where it is blended with other elastomers and cross-linked with the sulfur vulcanization system.

Production of next generation of tyres employing polybutadiene rubber requires target modification of the polybutadiene rubber. High cis-1, 4-polybutadiene rubber (high molecular weight PBR) is one of the important synthetic elastomers which find inevitable applications in tyre and automobile applications. PBR possesses higher concentration of unsaturated double bonds which offers a unique opportunity for converting the conventional PBR to advanced elastomers by using various functionalization techniques. However, in contrast to the low molecular weight PBR, the commercial grade-high molecular weight PBR chains exist in a coiled form which restricts the availability of unsaturated functional sites for further functionalization.

Grafting of functional group on a polymer is an established technique for modification of a given polymer. Solution based grafting of polybutadiene rubber is practiced widely for functionalization of polybutadiene rubber. However, solution based grafting of functional group onto the polybutadiene rubber chains under different reaction conditions have their limitations in terms of scaling up at commercial level due to the requirement of solvent extraction processes. Thus, making the existing process for grafting of PBR, i.e., the solution based grafting not economical and not environmentally friendly.

Thus, there is a need to develop a grafting process that is economical and environmentally friendly that can be subjected to scaling up to a commercial level conveniently and that there is a need for grafting of functional group onto a polymer (polybutadiene rubber) wherein there is no application of solvent to graft a functional moiety/functional group onto a polymer.

SUMMARY OF THE DISCLOSURE
Accordingly, the present disclosure describes a solid state grafting process for grafting of functional group onto polybutadiene rubber for functionalization of polybutadiene rubber which is economical and environmentally friendly that can be subjected to scaling up to commercial level without any limitations or adverse effect.

The solid state grafting process described in the present disclosure does not employ solvent for grafting of the functional group onto the polymer chains of the polybutadiene rubber, which is crucial for conveniently scaling up the functionalization of the polybutadiene rubber to a commercial level without any adverse effect or limitation.

The solid state grafting process described in the present disclosure retains the intrinsic properties of the polybutadiene rubber, particularly the supramolecular non-covalent cross-linking of cooperative H-bonding between the elastomer chains within the polybutadiene rubber.

BRIEF DESCRIPTION OF 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, in accordance with the present disclosure where:

Figure 1 depicts the schematic representation of reaction of maleic anhydride and triazole with PBR and creation of cooperative H-bonding into PBR matrix.

Figure 2 depicts ATR-FTIR spectra of PBR, MAH-g-PBR (graft mixture) and MAH-g-PBR (Tz) (functionalized PBR).

Figure 3 depicts DSC thermogram of virgin PBR polymer (unmodified PBR).
Figure 4 depicts DSC thermogram of MAH-g-PBR (graft mixture).

Figure 5 depicts DSC thermogram of MAH-g-PBR (Tz) (functionalized PBR).
Figure 6 depicts TGA thermogram of virgin PBR polymer (unmodified PBR).

Figure 7 depicts TGA thermogram of MAH-g-PBR (graft mixture).

Figure 8 depicts TGA thermogram of MAH-g-PBR (Tz) (functionalized PBR).

Figure 9 depicts the mechanical properties of virgin PBR and MAH-g-PBR (Tz) (functionalized PBR).

Figure 10 depicts schematic representation of modified PBR functionalization at molecular level with supramolecular H-bonding.

Figure 11 depicts schematic representation of supramolecular H-bonding in functionalized PBR under thermal stimuli

Figure 12 depicts effect of antioxidant (DTBPC) to restrict crosslinking mechanism on PBR chain.

Figure 13 depicts effect of antioxidant to restrict the Mooney viscosity of functionalized PBR.

Figure 14 depicts effect of FTIR spectra of (a) MAH-g-PBR and (b) functionalized PBR (in presence of antioxidant- 2Eqv. of DTBPC.

DETAILED DESCRIPTION
The present disclosure relates to solid state grafting process for functionalization of polybutadiene rubber.

In an embodiment of the present disclosure, the solid state grafting process produces functionalized polybutadiene rubber, wherein the polybutadiene rubber retains all the intrinsic properties by creating supramolecular non-covalent cross-linking by co-operative H-bonding between elastomer chains of the polybutadiene rubber.

In an embodiment of the present disclosure, the solid state grafting process involves grafting of functional group onto polybutadiene rubber to produce functionalized polybutadiene rubber.

In an embodiment of the present disclosure, the solid state grafting process for producing functionalized polybutadiene rubber comprises-
mixing the polybutadiene rubber (PBR), a radical initiator and a functional group to obtain a grafted polybutadiene; and
mixing the grafted polybutadiene and a ring opening agent to obtain the functionalized PBR.

In an embodiment of the present disclosure, the polybutadiene rubber is masticated at a speed ranging from about 20 RPM to 60 RPM at a temperature ranging from about 20ºC to 30ºC for a duration ranging from about 1 minute to 5 minutes.

In another embodiment of the present disclosure, the polybutadiene rubber is masticated at a speed of about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM at a temperature of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC or about 30ºC for a duration of about 1minute, about 2minutes, about 3minutes, about 4minutes or about 5 minutes.

In an embodiment of the present disclosure, the masticated polybutadiene rubber is mixed with the radical initiator and the functional group, followed by mastication at a rotor speed ranging from about 20 RPM to 60 RPM at a temperature ranging from about 60ºC to 120ºC under an inert or non-inert atmosphere for a duration ranging from about 1 minute to 5 minutes to obtain grafted polybutadiene rubber.

In another embodiment of the present disclosure, the masticated polybutadiene rubber is mixed with the radical initiator and the functional group, followed by mastication at a rotor speed of about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM at a temperature of about 60ºC, about 65ºC, about 70ºC, about 75ºC, about 80ºC, about 85ºC, about 90ºC, about 95ºC, about 100ºC, about 105ºC, about 110ºC, about 115ºC or about 120ºC under inert or non-inert atmosphere for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes to obtain grafted polybutadiene rubber.

In an embodiment of the present disclosure, the grafted polybutadiene is subjected to internal melt mixture at a temperature ranging from about 120ºC to 160?C under rotor speed ranging from about 20 RPM to 60 RPM for a duration ranging from about 1 minute to 5 minutes to obtain the final functionalized polybutadiene in a form selected from a group comprising thin film, lumps, crumb form and chunk form.
In another embodiment of the present disclosure, the grafted polybutadiene is subjected to internal melt mixture at a temperature of about 120ºC, about 125ºC, about 130ºC, about 135ºC, about 140ºC, about 145ºC, about 150ºC, about 155ºC or about 160ºC under rotor speed of about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM for a duration of about 1minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes to obtain the functionalized polybutadiene in a form selected from a group comprising thin film, lumps, crumb from and chunk form.

In an embodiment of the present disclosure, the moulded grafted polybutadiene is subjected to solvent extraction by techniques selected from a group consisting of soxhlet extraction, re-precipitation and sublimation, to remove unreacted functional groups.

In an embodiment of the present disclosure, the mixing of the grafted polybutadiene rubber and the ring opening agent comprises-
mixing the grafted polybutadiene rubber and the ring opening agent at a temperature ranging from about 20ºC to 30ºC, at a rotor speed ranging from about 10RPM to 60RPM for a duration ranging from about 1minute to 5minutes; and
continuing the mixing at a temperature ranging from about 50?C to 160?C for a duration ranging from about 1 minute to 5 minutes under inert or non-inert atmosphere to obtain functionalized PBR.

In another embodiment of the present disclosure, the mixing of the grafted polybutadiene rubber and the ring opening agent comprises-
mixing the grafted polybutadiene rubber and the ring opening agent at a temperature of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC, about 30ºC at a rotor speed of about 10RPM, about 15RPM, about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM, for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes; and
continuing the mixing at a temperature of about 50ºC, about 55ºC,about 60ºC, about 65ºC, about 70ºC, about 75ºC, about 80ºC, about 85ºC, about 90ºC, about 95ºC, about 100ºC, about 105ºC, about 110ºC, about 115ºC about 120ºC, about 125ºC, about 130ºC, about 135ºC, about 140ºC, about 145ºC, about 150ºC, about 155ºC or about 160ºC, for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes under inert or non-inert atmosphere to obtain functionalized PBR.
In an embodiment of the present disclosure, the radical initiator is selected from a group comprising dicumyl peroxide, Benzoyl Peroxide, azobisisobutyronitrile (AIBN), Bis (2,4-dichloro)benzoylperoxide, Di-tert.butylperoxide, Tert.butylcumylperoxide, 1,4-bis(tert.butylperoxyisopropyl) benzene, 2,5-bis-(tert.butylperoxy)-2,5-dimethylhexane, 4,4 di- tert.butylperoxy-n-butylvalerate or any other peroxides.

In an exemplary embodiment of the present disclosure, the radical initiator is dicumyl peroxide.

In an embodiment of the present disclosure, the functional group is selected from a group comprising Maleic anhydride, ?, ß-unsaturated ketones, ?, ß-unsaturated aldehydes, ?, ß-unsaturated acids, ?, ß-unsaturated esters, ?, ß-unsaturated amides, 2H-Pyran-2,6(3H)-dione, 2[5H]-furanone, furanone, 5,6-Dihydro-2H-pyran-2-one, 3,6-dihydro-2H-Pyran-2-one, 1H-pyrrol-2(5H)-one, 1,3-Dihydro-2H-pyrrol-2-one, 5,6-Dihydro-2(1H)-pyridinone, 3,6-Dihydro-2(1H)-pyridinone, 3,4-Dihydro-2(1H)-pyridinone, 1,5,6,7-Tetrahydro-2H-azepin-2-one, 1,3,4,5-Tetrahydro-2H-azepin-2-one, itaconic anhydride, Maleimide, 6-Hydroxypyridin-2(3H)-one, Oxirene, 2H-oxete, 2,5-Dihydrofuran, dihydrofuran, 3,4-Dihydro-2H-pyran, 3,6-Dihydro-2H-pyran, 2,3,4,5-Tetrahydrooxepine and 2,3,6,7-Tetrahydrooxepine, Thiophene-2,5-dione, 2(5H)-Thiophenone, 2(3H)-Thiophenone, 3,6-Dihydro-2H-thiopyran-2-one and any combination thereof.

In an exemplary embodiment of the present disclosure, the functional group is maleic anhydride.

In an embodiment of the present disclosure, the ring opening agent is selected from a group comprising 3-amino-1,2,4-triazole, Thiourea, 2, 6-diaminopyridine, aniline, nitro-aniline, hydroxyaniline, ethylene diamine, triethylenetetramine, triethanolamine, diphenyl guanidine, 1-phenyl-1,2-ethanediol, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 4-amino-1,2,3-triazole, 5-amino-1,2,3-triazole, 5-aminotetrazole, 3-aminopyrazole, 4-aminopyrazole, 5-aminopyrazole, 3-amino-5-thiol-1,2,4-triazole, urea, Diethylene triamine (DETA), melamine, cyclodextrin, 2-hydrazino-4-(trifluoromethyl)pyridimine, PEG-6000, 1-phenyl-ethane-1,2-diol, L-Alanine benzyl ester p-toluenesulfonate salt, L-Cysteine ethyl ester hydrochloride, L-Methionine ethyl ester hydrochloride, L-Phenylalanine methyl ester hydrochloride, N-(3-indolylacetyl)-L-alanine and a combination thereof.

In an exemplary embodiment of the present disclosure, the ring opening agent is 3-amino-1, 2, 4-triazole.

In an embodiment of the present disclosure, the proportion of the polybutadiene rubber to the functional group is ranging from about 1:0.001 weight ratio to 1:0.2 weight ratio.

In an embodiment of the present disclosure, the proportion of the polybutadiene rubber to the radical initiator is ranging from about 1:0.0001 weight ratio _to 1:0.05 weight ratio.

In an embodiment of the present disclosure, the proportion of the graft mixture to the ring opening agent is ranging from about 1:0.001 weight ratio to 1:0.2 weight ratio.

In another embodiment of the present disclosure, the solid state grafting process of polybutadiene rubber for producing functionalized polybutadiene rubber comprises-
mixing the polybutadiene rubber, a radical initiator and the functional group to obtain grafted polybutadiene;
adding antioxidant to the grafted polybutadiene; and
mixing the antioxidant treated grafted polybutadiene and a ring opening agent to obtain the functionalized PBR.

In another embodiment of the present disclosure, mixing the polybutadiene rubber, the radical initiator and the functional group comprises-
masticating the polybutadiene rubber at a speed ranging from about 20 RPM to 60 RPM at a temperature ranging from about 20ºC to 30ºC for a duration ranging from about 1 minute to 5 minutes; and
adding the radical initiator and the functional group and continuing the mastication at a speed ranging from about 20RPM to 60 RPM at a temperature ranging from about 60ºC to 100ºC under an inert atmosphere for a duration ranging from about 1 minute to 5 minutes to obtain grafted polybutadiene.

In another embodiment of the present disclosure, mixing the polybutadiene rubber, the radical initiator and the functional group comprises-
masticating the polybutadiene rubber at a speed of about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM at a temperature of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC, about 30ºC for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes; and
adding the radical initiator and the functional group and continuing the mastication at a speed of about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM at a temperature of about 60ºC, about 65ºC, about 70ºC, about 75ºC, about 80ºC, about 85ºC, about 90ºC, about 95ºC, about 100ºC under an inert atmosphere for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes to obtain grafted polybutadiene.

In another embodiment of the present disclosure, upon adding the antioxidant to the grafted Polybutadiene, the mixture is mixed for a duration ranging from about 1 minute to 5 minutes at a temperature ranging from about 60?C to 100?C to obtain antioxidant treated grafted polybutadiene .

In another embodiment of the present disclosure, upon adding the antioxidant to the grafted polybutadiene, the mixture is mixed for a duration of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes at a temperature of about 60ºC, about 65ºC, about 70ºC, about 75ºC, about 80ºC, about 85ºC, about 90ºC, about 95ºC, about 100ºC to obtain antioxidant treated grafted polybutadiene.

In another embodiment of the present disclosure, the antioxidant treated grafted polybutadiene is subjected to internal melt mixture at a temperature ranging from about 120?C to 160?C under a rotor speed ranging from about 20 RPM to 60 RPM for a duration ranging from about 1 minute to 5 minutes to obtain antioxidant treated grafted polybutadiene in a form selected from a group comprising thin film, crumb form and chunk form.

In another embodiment of the present disclosure, the antioxidant treated grafted polybutadiene is subjected to internal melt mixture at a temperature of about 120ºC, about 125ºC, about 130ºC, about 135ºC, about 140ºC, about 145ºC, about 150ºC, about 155ºC or about 160ºC under a rotor speed of about from about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM for a duration of about 1minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes to obtain antioxidant treated grafted polybutadiene in a form selected from a group comprising thin film, crumb form and chunk form.
In another embodiment of the present disclosure, the moulded graft mixture is subjected to solvent extraction by techniques selected from a group comprising of sohxlet extraction, reprecipitation and sublimation to remove unreacted functional group.

In another embodiment of the present disclosure, the mixing of the antioxidant treated grafted polybutadiene and the ring opening agent comprises-
mixing the antioxidant treated grafted polybutadiene and the ring opening agent at a temperature ranging from about 20ºC to 30ºC at rotor speed ranging from about 20RPM to 60RMP for a duration ranging from about 1 minute to 5 minutes; and
continuing the mixing at a temperature ranging from about to 120?C to 160?C for a duration ranging from about 1 minute to 5 minutes under inert or non-inert atmosphere to obtain functionalized PBR.

In another embodiment of the present disclosure, the mixing of the antioxidant treated grafted polybutadiene and the ring opening agent comprises-
mixing the antioxidant treated grafted polybutadiene and the ring opening agent at a temperature ranging of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC, about 30ºC at a rotor speed of about 10RPM, about 15RPM, about 20RPM, about 25RPM, about 30RPM, about 35RPM, about 40RPM, about 45RPM, about 50RPM, about 55RPM or about 60RPM for a duration of about 1minutes, 2 minutes, 3 minutes, 4 minutes or about 5minutes; and
continuing the mixing at a temperature of about 120?C, about 125?C, about 130?C, about 135?C, about 140?C, about 145?C, about 150?C, about 155?C or about 160?C for a duration of about about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes or about 5 minutes under inert or non-inert atmosphere to obtain functionalized PBR.

In another embodiment of the present disclosure, the radical initiator is selected from a group comprising dicumyl peroxide, Benzoyl Peroxide, azobisisobutyronitrile (AIBN), Bis (2,4-dichloro)benzoylperoxide, Di-tert.butylperoxide, Tert.butylcumylperoxide, 1,4-bis(tert butylperoxyisopropyl) benzene, 2,5-bis-(tert.butylperoxy)-2,5-dimethylhexane, 4,4 di- tert.butylperoxy-n-butylvalerate or any other peroxides.

In another exemplary embodiment of the present disclosure, the radical initiator is dicumyl peroxide.

In another embodiment of the present disclosure, the functional group is selected from a group comprising Maleic anhydride, ?, ß-unsaturated ketones, ?, ß-unsaturated aldehydes, ?, ß-unsaturated acids, ?, ß-unsaturated esters, ?, ß-unsaturated amides, 2H-Pyran-2,6(3H)-dione, 2[5H]-furanone, furanone, 5,6-Dihydro-2H-pyran-2-one, 3,6-dihydro-2H-Pyran-2-one, 1H-pyrrol-2(5H)-one, 1,3-Dihydro-2H-pyrrol-2-one, 5,6-Dihydro-2(1H)-pyridinone, 3,6-Dihydro-2(1H)-pyridinone, 3,4-Dihydro-2(1H)-pyridinone, 1,5,6,7-Tetrahydro-2H-azepin-2-one, 1,3,4,5-Tetrahydro-2H-azepin-2-one, itaconic anhydride, Maleimide, 6-Hydroxypyridin-2(3H)-one, Oxirene, 2H-oxete, 2,5-Dihydrofuran, dihydrofuran, 3,4-Dihydro-2H-pyran, 3,6-Dihydro-2H-pyran, 2,3,4,5-Tetrahydrooxepine and 2,3,6,7-Tetrahydrooxepine, Thiophene-2,5-dione, 2(5H)-Thiophenone, 2(3H)-Thiophenone, 3,6-Dihydro-2H-thiopyran-2-one and any combination thereof.

In another exemplary embodiment of the present disclosure, the functional group is maleic anhydride.

In another embodiment of the present disclosure, the ring opening agent is selected from a group comprising 3-amino-1,2,4-triazole, Thiourea, 2, 6-diaminopyridine, aniline, nitro-aniline, hydroxyaniline, ethylene diamine, triethylenetetramine, triethanolamine, diphenyl guanidine, 1-phenyl-1,2-ethanediol, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 4-amino-1,2,3-triazole, 5-amino-1,2,3-triazole, 5-aminotetrazole, 3-aminopyrazole, 4-aminopyrazole, 5-aminopyrazole, 3-amino-5-thiol-1,2,4-triazole, urea, Diethylene triamine (DETA), melamine, cyclodextrin, 2-hydrazino-4-(trifluoromethyl)pyridimine, PEG-6000, 1-phenyl-ethane-1,2-diol, L-Alanine benzyl ester p-toluenesulfonate salt, L-Cysteine ethyl ester hydrochloride, L-Methionine ethyl ester hydrochloride, L-Phenylalanine methyl ester hydrochloride, N-(3-indolylacetyl)-L-alanine and a combination thereof.

In another exemplary embodiment of the present disclosure, the ring opening agent is 3-amino-1,2,4-triazole.

In another embodiment of the present disclosure, the antioxidant is selected from a group comprising Di-tert-buty-p-cresol (DTPC), Para phenylenediamines (PPDs), N,N’-Bis (1,4-dimethylpentyl)-pphenylenediamine, N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-phenyl-N’ isopropyl-pphenylenediamine, Polymerized 2,2,4-Trimethyl-1,2-dihydroquinoline, 6-Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, Styrenated phenol, 2.2’-methylenebis (6-t-butyl-4methyl, phenol), 4,4’-thiobis-6-(t-butyl) metacresol, tetrakis [Methylene 3-(3,5 di-t-butyl - 4 hydroxyphenyl) propionate] methane, p-oriented styrenated diphenyl amine, 4,4, bis (a,a-domethylbenzyl) Diphenylamine, Octylated diphenyl amine, Acetone diphenyl amine condensates, Didodecyl 3.3’ thiodipropionate.

In another embodiment of the present disclosure, the proportion of the polybutadiene rubber to the functional group is ranging from about1:0.001 weight ratio to 1:0.2 weight ratio.

In another embodiment of the present disclosure, the proportion of the polybutadiene rubber to the radical initiator is ranging from about 1:0.0001weight ratio 1:0.05 weight ratio.

In another embodiment of the present disclosure, the proportion of the antioxidant treated graft mixture to the ring opening agent is ranging from about 1:0.001 weight ratio to 1:0.2 weight ratio.

In another embodiment of the present disclosure, the proportion of the antioxidant to the radical initiator is ranging from about 1: 0.005 weight ratio to 1:0.05 weight ratio.

In an embodiment of the present disclosure, the polybutadiene rubber was subjected to direct solid state grafting process to create supramolecular non-covalent cross-linking of cooperative H-bonding between elastomer chains without adversely affecting the intrinsic properties of PBR, as a result obtain functionalized PBR. The creation of non-covalent cross-linking of co-operative H-bonding yielded significant improvement in mechanical properties, such as tensile strength, tensile modulus and strength at break of the functionalized PBR over unmodified PBR/virgin PBR.

In an embodiment of the present disclosure, treating with antioxidant in the above described solid state grafting process minimizes cross linking of the functionalized PBR and prevents rise in Mooney Viscosity. The antioxidant minimizes cross-linking by reacting with unreacted free radicals without obstructing the grafting of the functional group onto the polymer backbone.

In the modified/functionalized PBR existing in the art, it is observed that there is a rapid increase in Mooney Viscosity (MV) even after storing under refrigerator conditions. The increment of MV is the result of cross-linking of PBR chains, such cross-linking has adverse impact on self-healing property of tyre formulation employing modified/functionalized PBR. However, in the functionalized PBR obtained by the solid state grafting process described in the present disclosure there is no increase in the Mooney viscosity of the functionalized PBR even after longer period of storage.

In an embodiment of the present disclosure, the antioxidant employed in the said solid state grafting process described above arrests the crosslinking of the unreacted radicals on the PBR backbone by quenching. Scheme 2 in Figure 12 demonstrates the quenching of the unreacted radical by the antioxidant (DTBC) and prevention of crosslinking mechanism during the solid state grafting described above, wherein it is demonstrated that the bulky group at two ortho-positions of the phenolic-OH group of DTBC caused the hydrogen atom radical extremely labile for quenching the radicals on polymer backbone. The phenoxide radicals however stabilized by delocalization and followed by re-coupling with other accessible radicals or oxygen to be inactive.

In an embodiment of the present disclosure, Mooney viscosity of the functionalized/modified PBR obtained by the above described solid state grafting process is similar to the Mooney viscosity of virgin/unmodified PBR.

In an embodiment of the present disclosure, the functionalized PBR obtained by the solid state grafting process described above has a tensile strength at least about 3.5 times higher when compared to the unmodified /virgin PBR.

In an embodiment of the present disclosure, the functionalized PBR obtained by the solid state grafting process described above has a tensile modulus at least about 7.5 times higher when compared to the unmodified /virgin PBR.

In an embodiment of the present disclosure, the functionalized PBR obtained by the solid state graft described above has a strength at break at least about 4.6 times higher when compared to the unmodified /virgin PBR.

In an embodiment of the present disclosure, functionalization of PBR by incorporation of a functional group (for e.g. maleic anhydride) using radical initiator (for e.g. DCP), followed by anhydride ring opening with ring opening agent (for e.g. 3-amino-1, 2, 4-triazole) causes a supramolecular co-operative supramolecular hydrogen bonding adduct. Such modification in PBR chain provides an additional co-operative supramolecular hydrogen bonding. Presence of such secondary crosslinking between PBR chains provides an additional strength to the functionalized PBR (modified PBR) (illustrated in figure 10). The flexible units with hydrogen bonding capability provides in the functionalized PBR obtained by the solid state grafting process described above provides a supplementary advantage (i.e., presence of hydrogen bonding which provides additional strength) to the functionalized PBR. Further, due to the dynamic thermo-reversible character of H-bonds, the donor and acceptor part of the functionalized PBR has the ability to exchange their bonding partner on heating (illustrated in figure 11). Thus, cracked or fatigued functionalized PBR has self healing properties due to interchanging of partners upon thermal stimulation.

In an embodiment of the present disclosure, the solid state grafting process described above does not require additional steps of purification, it is cost effect and environmental friendly.

In an embodiment of the present disclosure, in the solid state grafting process described above, there is no blending of additional polymer to the polybutadiene. However, only the polybutadiene is functionalized by grafting a functional group in order to achieved effective H-bonding properties.

In the instant description, the expression graft mixture or grafted polybutadiene are used interchangeably, wherein the graft mixture or grafted polybutadiene refers to polybutadiene rubber (backbone) comprising the functional group, which is obtained prior to reaction with ring opening agent.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon the description provided. The embodiments provide various features and advantageous details thereof in the description. Description of well-known/conventional process and techniques are omitted so as to not unnecessarily obscure the embodiments. The examples provided herein are intended merely to facilitate an understanding of ways in which the embodiments provided may be practiced and to further enable those of skilled in the art to practice the embodiments provided. Accordingly, the following examples should not be construed as limiting the scope of the embodiments.

EXAMPLES

Methods
a. Fourier Transform Infrared Spectroscopy (FTIR)
Stretching, bending vibrational frequency of different covalent bonds in solid elastomeric samples were determined by conventional ATR methodology using Ze-Se crystals. The frequencies were determined in terms of their wavenumbers. All the characterizations were performed as per international standard such as ASTM D3677 and ISO 4650. The used instrument was Thermo scientific instrument, Model No: Nicolet 6700 FTIR.

b. Mooney Viscosity
Mooney Viscosity is an expedient to measure the viscosity of a rubber compound before curing. The viscosity value obviously utilized to understand the processing nature of the polymer or composite materials. The viscometer consists of a sealed pressurized chamber which has serrated cavity and a serrated rotating propeller in the middle. The uncured rubber sample is placed in the temperature controller cavity between the rotor and the chamber wall. The specimen is physically deformed by rotating platen which will determine the change in viscosity at a particular temperature. The rotor turns at a constant rate of two revolutions per minute which creates shearing between the sample and the rotor. When the test is completed, the dies will automatically reset and allow for removal of specimen.

The change of the torque is measured in Mooney Units (MU), which are defined in ISO 289 and ASTM D 1646. The Mooney units are expressed as e.g. ML (1+4) 100?. In the expression of Mooney viscosity unit; M refers to Mooney, L indicates that the large rotor was used (S for small rotor), 1 is the preheating time in minutes, 4 refer to the time in minutes after which the reading is taken counting from the rotor starts and 100? is the test temperature. The Mooney viscosities of all samples were measured directly after milling by using of MV 2000 from Alpha Technology.

Example 1: Solid State grafting of maleic anhydride onto polybutadiene rubber.
Step: 1
About 32g (0.59 mol, butadiene unit) of PBR was cut into small pieces and masticated for about 30 seconds at a speed of about 60 RPM at room temperature (ranging from about 20ºC to 30 ºC) to which about 0.032g (0.1 wt%, 1.18x10-4 mol) of DCP and about 1.12g (3.5 wt%, 0.0114mol) of maleic anhydride were added to obtain a mixture. The whole mixture was masticated for about 270 seconds at a speed of about 60 RPM under nitrogen (inert atmosphere) under a temperature of about 60 ºC, about 80 ºC and about 100 ºC, independently to obtain graft mixtures or grafted polybutadiene (MAH-g-PBR).

About 1g of the graft mixture was placed in a mould at a temperature of about 150ºC under pressure of about 150 kg/cm2 compression for about 5minutes to obtain transparent thin films. These thin films were subjected to Soxhlet extraction in acetone for about 5 hours to remove unreacted maleic anhydride. After Soxhlet extraction the films were dried in vacuum oven. Figure 2 illustrates the FTIR spectra of the graft mixture, figure 4 illustrates the DSC thermogram of the graft mixture and figure 7 illustrates the TGA thermogram of the graft mixture.

Step 2:
About 30g (MAH: 0.0102 mol.) of the graft mixture obtained in step 1 was mixed with about 0.86g (0.0102 mol) of triazole (Tz) to obtain a mixture. The mixture was masticated at room temperature (ranging from about 20ºC to 30 ºC) in an internal mixture for about 3 minutes at a speed ranging from about 60RPM, subsequently the mixed rubber mass was removed from the internal mixer. Then the temperature of the mixing chamber was increased to about 150ºC and the mixed rubber was fed into the internal mixer maintained at a temperature of about 150ºC and mixed for about 2 minutes under nitrogen (inert atmosphere) to obtain functionalized/modified PBR (MAH-g-PBR(Tz)).

About 1 g of functionalized PBR was placed in a mould at a temperature of about 150ºC under pressure of about 150 kg/cm2 compression for about 5 minutes to obtain transparent thin films. Figure 2 illustrates the FTIR spectra of the graft mixture, Figure 5 illustrates the Differential scanning calorimetric (DSC) thermogram of the graft mixture and Figure 8 illustrates the Thermo-gravimetric Analysis (TGA) thermogram of the graft mixture.

ATR-FTIR analysis:
The purified & Soxhlet extracted films of MAH-g-PBR (graft mixture) showed a new peak at about 1780 cm-1 due to symmetric stretching of carbonyl group from MAH (maleic anhydride) unit. In some cases, an additional FTIR absorption peak was also appeared at about 1856 cm-1 due to asymmetric stretching of -C=O group of MAH indicating the incorporation of MAH functional group onto PBR chains. FTIR analysis of PBR-g-MAH (Tz) (functionalized PBR) product showed that the peak at ~1780 cm-1 observed in PBR-g-MAH was completely disappeared and a new peak at ~1690-1695 cm-1 appeared due to formation of carboxylic acid functional group by ring opening reaction of maleic anhydride between amino triazole (Tz). Simultaneously, the formation of new peak at about 1540 cm-1 and broadening of the peak at about 1620 cm-1 were also observed due to the -NH (amide, bending) and –CONH- (amide) functional group, respectively. The characteristics FTIR peaks of PBR (virgin/unmodified), PBR-g-MAH (graft mixture) and PBR-g-MAH (Tz) (functionalized/modified PBR) are summarized in Table 1.

Sample Mixing Temperature (ºC) Characteristic new FTIR peaks 1,4-cis (%) 1,4- trans (%) 1,2-vinyl (%)
PBR Room temperature 94 3 3
PBR-g-MAH 60 1782.3cm-1 (-C=O, MAH)
1781.2 cm-1 (-C=O, MAH) 94 3 3
PBR-g-MAH 80 1781.6 cm-1 (-C=O, MAH)
1781.6 cm-1 (-C=O, MAH) 94 3 3
PBR-g-MAH 100 1781.8, 1858.4 cm-1 (-C=O, MAH)
1781.5, 1856.5 cm-1 (-C=O, MAH) 94 3 3
PBR-g-MAH (Tz) 150 1689.5 cm-1 (-COOH), 1530.8 cm-1 (-NH bending) 94 3 3
Table 1: Characteristic new FTIR peaks appeared in PBR, MAH-g-PBR and MAH-g-PBR (Tz)

Differential Scanning Calorimetry (DSC) analysis:
Differential scanning calorimetric (DSC) analysis was carried out for both virgin PBR, MAH-g-PBR and PBR-g-MAH (Tz) using DSC Q 2000 instrument. The ramp temperature was 10ºC/min under N2 atmosphere. DSC thermograms showed glass transition (Tg) temperature at -102ºC for virgin PBR. The endothermic hump for melting temperature (Tm) was observed at -7.0ºC whereas on cooling the sample with same rate showed an exothermic peak for crystallization temperature (Tc) at -50.45ºC for the well-ordered high 1, 4-cis crystalline units. Similar values of Tg, Tm and Tc values were also observed for MAH-g-PBR and MAH-g-PBR (Tz) graft copolymers (illustrated in Figures 3, 4 and 5, respectively). The Tc values of virgin PBR at -50.45ºC increased to -48.56ºC & -48.07ºC in PBR-g-MAH & PBR-g-MAH (Tz) graft copolymers. These results indicate that inherent PBR characteristics remained unaltered after functionalization/modification by the solid state grafting described in the present disclosure.

Thermo-gravimetric Analysis (TGA) analysis:
The thermo gravimetric analysis (TGA) was performed for virgin PBR, PBR-g-MAH and PBR-g-MAH (Tz) using TGA Q500. Virgin PBR, PBR-g-MAH and PBR-g-MAH (Tz), respectively were heated under Nitrogen atmosphere from room temperature (about 20ºC to 30ºC) up to 600ºC with a heating rate 10ºC/min. The decomposition temperatures were determined from the intersection of the tangents drawn to the lines before and after the major initial weight loss. The TGA values observed for all the specimens showed identical single step degradation pattern. The TGA curve of all the samples- virgin PBR, PBR-g-MAH and PBR-g-MAH (Tz) showed almost similar decomposition patterns; starting of single step decomposition at 299.34ºC which underwent to almost complete decomposition at 524.86 ºC (illustrated in Figures 6, 7 and 8, respectively).

Mechanical Property analysis:
Mechanical properties of MAH-g-PBR (Tz) and virgin PBR polymers were determined using Instron 3366 instrument at a speed of about 500 mm/min and gauge length of about 25 mm. The dumbbell shaped PBR and MAH-g-PBR (Tz) sample specimens were prepared by compression moulding to measure their strength.

It was observed that mechanical properties were significantly increased in functionalized PBR [PBR-g-MAH (Tz)] compared to virgin PBR polymer. The tensile strength, tensile modulus and strength at break of PBR-g-MAH (Tz) increased by at least about 3.5, about 7.5 and about 4.6 times, respectively than those observed for virgin PBR (illustrated in Figure 9). On the other hand, elongation of PBR-g-MAH (Tz) reduced by at least about 4.4 times than virgin PBR due to presence of inter-chain cross-linking in PBR-g-MAH (Tz). All these results clearly indicate the formation of cooperative H-bonding in PBR chains of functionalized PBR-g-MAH (Tz) which were absent in the virgin PBR polymer in their respective gum-rubber state.

Example 2: Solid State grafting of maleic anhydride onto polybutadiene rubber in presence of antioxidant.
Step: 1
About 32g (0.59 mol, butadiene unit) of PBR was cut into small pieces and masticated for about 30 seconds at a speed of about 60 RPM at room temperature (ranging from about 20ºC to 30 ºC) to which about 0.032g (0.1 wt%, 1.18x10-4 mol) of DCP and about 1.12g (3.5 wt%, 0.0114mol) of maleic anhydride were added to obtain a mixture. The whole mixture was masticated for about 270 seconds at a speed of about 60 RPM under nitrogen at a temperature of about 60 ºC, about 80 ºC and about 100 ºC, independently to obtain graft mixtures (MAH-g-PBR). About 0.104 gm of DTBPC was added to the graft mixture and mixed for about 1minute at a temperature of about 100ºC (antioxidant treatment).

The graft functionalized polybutadiene crumb was subjected to Soxhlet extraction in acetone for about 5 hours to remove unreacted maleic anhydride. After Soxhlet extraction the crumbs were dried in vacuum oven.

Step 2:
About 30g (MAH: 0.0102 mol.) of the graft functionalized polybutadiene (after antioxidant treatment) obtained in Step 1 was mixed with about 0.86g (0.0102 mol) of triazole (Tz) to obtain a mixture. The mixture was masticated at room temperature (ranging from about 20ºC to 30 ºC) in an internal mixture for about 3 minutes at a speed ranging from about 60RPM, subsequently the mixed rubber mass was removed from the internal mixer. Then the temperature of the mixing chamber was increased to about 150ºC and the mixed rubber was fed into the internal mixer maintained at a temperature of about 150ºC and mixed for about 2 minutes under nitrogen to obtain functionalized/modified PBR (MAH-g-PBR(Tz)).

About 1 g of functionalized PBR was placed in a mould at a temperature of about 150ºC under pressure of about 150 kg/cm2 compression for about 5minutes to obtain transparent thin films.

Example 3: Mooney Viscosity Analysis
1. Mooney viscosity of the functionalized/modified PBR obtained under Example 1 above is provided in Table 2

Table 2:

According to the data illustrated in the Table 2, the unmodified PBR showed MV of 44. This MV value remained unchanged over a period of time. However, during modification of PBR with MAH, initial lowering of MV was observed. This initial dropping of MV was due to PBR chain scissoring during solid state mastication process. However, a rapid enhancement of MV were observed in most of the cases e.g. sample in Sr.no. 5 showed an increase in MV by about 5 units in 5 days while the sample in Sr.no. 6 showed an increase in MV by about 8 units in 4 days.

2. Experiment 1:
PBR was cut into small pieces and masticated for about 30 seconds at a speed of about 60 RPM at room temperature (ranging from about 20ºC to 30 ºC).
About 32g (0.59 mol, butadiene unit) of masticated PBR was mixed with about 0.032g (0.1 wt%, 1.18x10-4 mol) of DCP to obtain a mixture. The whole mixture was masticated for about 270 seconds at a speed of about 60 RPM under nitrogen at a temperature of about 100ºC. Further, the mixture was heated under mixing at a temperature of about 150ºC for about 3.5 minutes at a speed of about 60 RPM.
Table 3 describes the Mooney Viscosity (MV) of unmodified PBR, masticated PBR and mixture of masticated PBR and DCP.

Table 3:
According to the data obtained in Table 3, MV of unmodified PBR was 45. However, a drop in MV of the masticated PBR was due to chain scissoring phenomenon during mastication and heating. However, treatment with DCP lead to increase in the MV value up to about 50 under similar time period. The increase in the MV of the sample of PBR was due to the crosslinking reactions among of PBR chains generated by the free radicals of DCP.

3. Experiment 2:
About 32g (0.59 mol, butadiene unit) of masticated PBR was mixed with about 0.032g (0.1 wt%, 1.18x10-4 mol) of DCP to obtain a mixture. The whole mixture was masticated for about 270 seconds at a speed of about 60 RPM under nitrogen at a temperature of about 100ºC. The mixture was subject to antioxidant treatment with 2 equivalents of DTBPC and 4 equivalents of DTBPC, respectively.

The antioxidant treated mixture was heated under mixing at a temperature of about 150ºC and about 140ºC, respectively for about 3.5 minutes at a speed of about 60 RPM.

Table 4 describes effect of DTBPC on variation of MV with 2 equivalents of DTBPC and 4 equivalents of DTBPC at 150ºC, respectively.

Table 4:
According to the data observed in Table 4, it can be identified that there was an increment of about 4.1 units of MV after 18 days of the experiment with use of 2 equivalents of DTBPC. Further, the increment was about 3.5 units of MV with use of 4 equivalents of DTBPC after 18 days of the experiment. These results revealed that there was a radical quenching effect by the antioxidant, upon antioxidant treatment.

Table 5 describes effect of DTBPC on variation of MV with 2 equivalents of DTBPC and 4 equivalents of DTBPC at 140ºC, respectively.
Mooney Viscosity (MV)
Days 2 Equivalent of DTBPC 4 Equivalent of DTBPC
1 32 31
4 33 33
7 33 33
10 33 33
14 33 33

Table 5:
According to the data observed in Table 5, it can be identified that there was an increment of about 1.2 unit of MV after 13 days with 2 equivalents of DTBPC. Further, the increment was about 2.3 units of MV with use of 4 equivalent of DTBPC after 14 days. It can be observed that the MV became constant after 4 days in both the cases. These results revealed that there was a radical quenching effect by the antioxidant, upon antioxidant treatment.

4. Experiment 3:
About 32g (0.59 mol, butadiene unit) of masticated PBR was mixed with about 0.032g (0.1 wt%, 1.18x10-4 mol) of DCP to obtain a mixture. The whole mixture was masticated for about 270 seconds at a speed of about 60 RPM under nitrogen under a temperature of about 100ºC. The mixture was subject to antioxidant treatment with 2 equivalents of DTBPC.

The antioxidant treated mixture was mixed with about 0.86g of triazole and subjected to heating under mixing at a temperature of about 150ºC for about 3.5 minutes at a speed of about 60 RPM.

The data in Tables 4 and 5 shows reduced MV when compared to MV of unmodified PBR and mixture of PBR and DCP, respectively.

Table 6 describes effect of DTBPC on variation of MV with 2 equivalents of DTBPC.
Sample Days Mooney Viscosity
Unmodified PBR 0 45
Functionalized PBR (as per Exp.3) 1 42
4 46
5 45
8 44
9 45
10 45
Table 6:
According to the data in Table 6, there was an initial increment of about 4 units of MV after 4 days. However, MV was constant even after 10 days (45 unit) which was same as the MV value of the unmodified PBR (illustrated in figure 13).

FTIR Analysis:
The FTIR experiments (ATR mode) were performed on the functionalized PBR (without antioxidant treatment and with antioxidant treatment, respectively) to establish that incorporation of DTBPC in the optimized recipe of the functionalized PBR process has no effect on the chemical reaction at the molecular level.
FTIR analysis of functionalized PBR with no antioxidant treatment:
The >C=O functional group peak of closed ring MAH appeared at about 1780 cm-1 whereas that of opened ring peak appeared at about 1707 cm-1 (-COOH) in FTIR. Similarly, after the reaction with Tz (triazole), the >C=O group peak of the acid group appeared at about 1695 cm-1 whereas the –NH group peak of the amide (-CONH2) appeared at about 1540 cm-1.

FTIR analysis of functional PBR with antioxidant (DTBPC) treatment:
MAH (>C=O) and –COOH peaks were observed at about 1776 cm-1 and 1704 cm-1, respectively (illustrated in Figure 14(a)). After treatment with Tz in presence of DTBPC, the relative peaks appeared at 1698 cm-1 and 1536 cm-1 (illustrated in Figure 14 (b)), similar to the peaks observed without antioxidant treatment. Hence, from this IR data it could be actually established that the antioxidant does not interfere in the grafting reaction.