Description:FIELD
The present disclosure relates to a polymer nanocomposite and a process for its preparation.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Parts per Hundred Rubber (PHR): The term “Parts per Hundred Rubber” refers to a mass proportions of the individual mixture components in a recipe for an elastomer mixture. This information is based on 100 parts (by mass) of the base polymer or base polymers (in the case of polymer blends).
Mooney viscosity: The term “Mooney viscosity” refers to measure of the viscosity of a rubber compound before curing. The viscosity value is utilized to understand the processing nature of the polymer or composite materials.
Hummer’s method: The term “Hummer’s method” refers to a chemical process that can be used to generate graphene oxide through the addition of potassium permanganate to a solution of graphite, sodium nitrate, and sulfuric acid.
Aspect ratio: Aspect ratio of thermally reduced graphene oxide is the ratio between the width of thermally reduced graphene oxide and thickness of thermally reduced graphene oxide.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Conventionally, polybutadiene rubber (PBR) is used as an essential component for manufacturing tyres. Generally, polybutadiene rubber is used (in commercial products) along with the elastomers (such as polyisoprene (NR), styrene-butadiene rubber (SBR), and the like), and the fillers (such as carbon black) to obtain enhanced properties of the product. The incorporation of the fillers in the polybutadiene rubber matrix is essential to get an optimum strength which would eventually enhance the service life of the rubber matrix. The use of carbon black (CB) as a filler in higher quantities (more than 60 PHR) in the polybutadiene rubber (PBR) is commonly adapted process in the preparation.
Due to the enforcement of CB in the PBR, the mechanical properties along with hardness, rupture energy, resistance to crack growth, tear-fatigue, and thermal aging behavior of the rubber are improved. A homogeneous dispersion of the filler inside the rubber matrix is important to form strong chemical and/or physical bonds which are known as rubber-filler interaction. Conventional rubber composites/polymer composites are associated with drawbacks such as lower tensile strength and lower tensile modulus due to poor dispersion of the fillers into the polybutadiene rubber matrix.
There is, therefore, felt a need to provide a polymer nanocomposite and a process for its preparation that mitigates the drawbacks mentioned hereinabove or at least provide a useful alternative.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a polymer nanocomposite.
Still another object of the present disclosure is to provide a polymer nanocomposite that has improved rubber-filler interactions.
Another object of the present disclosure is to provide a polymer nanocomposite that has comparatively enhanced mechanical properties.
Yet another object of the present disclosure is to provide a polymer nanocomposite wherein the intrinsic properties of the nanocomposite remain intact.
Still another object of the present disclosure is to provide a process for preparing a polymer nanocomposite.
Another object of the present disclosure is to provide a simple, effective, and environment-friendly process for the preparation of a polymer nanocomposite.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a polymer nanocomposite. The polymer nanocomposite comprises a polybutadiene rubber cement and a thermally reduced graphene oxide. The polymer nanocomposite comprises the polybutadiene rubber cement is present in an amount in the range of 99.5 wt% to 99.95 wt% with respect to the total weight of the nanocomposite and the thermally reduced graphene oxide is present in an amount in the range of 0.05 wt% to 0.5 wt% with respect to the total mass of the nanocomposite.
The present disclosure further relates to a process for the preparation of a polymer nanocomposite.
The process comprises, firstly, a predetermined amount of a polybutadiene rubber cement and a predetermined amount of a first fluid medium are homogeneously mixed to obtain a first homogeneous mixture. Thereafter, a predetermined amount an ultrasonicated thermally reduced graphene oxide is mixed into the first homogeneous mixture under stirring at a predetermined speed for a predetermined time period at a predetermined temperature to obtain a second homogeneous mixture. The second homogeneous mixture is coagulated by using a second fluid medium in the presence of an antioxidant to obtain a solid composite. Finally, the solid composite is dried at a temperature in the range of 40 °C to 70 °C for a time period in the range of 10 minutes to 600 minutes to obtain the polymer nanocomposite.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a differential scanning calorimetry (DSC) thermogram of the polybutadiene sample before compounding;
Figure 2 illustrates a differential scanning calorimetry (DSC) thermogram of the polybutadiene-thermally reduced graphene oxide (PBR-TRGO) (0.1 PHR) sample before compounding, in accordance with the present disclosure;
Figure 3 illustrates a Fourier-transform infrared spectroscopy (FTIR) spectra for graphene oxide (GO), reduced graphene oxide (RGO) and thermally reduced graphene oxide (TRGO);
Figure 4 illustrates a Raman spectrum for graphene oxide (GO), reduced graphene oxide (RGO) and thermally reduced graphene oxide (TRGO);
Figure 5 illustrates an X-ray diffraction (XRD) of thermally reduced graphene oxide (TRGO) with graphene oxide (GO) and reduced graphene oxide (RGO);
Figure 6 illustrates a High-resolution transmission electron microscopy (HRTEM) for graphene oxide (GO), thermally reduced graphene oxide (TRGO) and reduced graphene oxide (RGO);
Figure 7 illustrates a Fourier-transform infrared spectroscopy (FTIR) of conventional PBR;
Figure 8 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.05 PHR TRGO;
Figure 9 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.1 phr TRGO; and
Figure 10 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.2 phr TRGO.
DETAILED DESCRIPTION
Embodiments of the present disclosure will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Conventionally, polybutadiene rubber (PBR) is used as an essential component for manufacturing tyres. Generally, polybutadiene rubber is used (in commercial products) along with the elastomers (such as polyisoprene (NR), styrene-butadiene rubber (SBR), and the like), and the fillers (such as carbon black) to obtain enhanced properties of the product. The incorporation of the fillers in the polybutadiene rubber matrix is essential to get an optimum strength which would eventually enhance the service life of the rubber matrix. The use of carbon black (CB) as a filler in higher quantities (more than 60 PHR) in the polybutadiene rubber (PBR) is commonly adapted process in the preparation.
Due to the enforcement of CB in the PBR, the mechanical properties along with hardness, rupture energy, resistance to crack growth, tear-fatigue, and thermal aging behavior of the rubber are improved. A homogeneous dispersion of the filler inside the rubber matrix is important, to form strong chemical and/or physical bonds which are known as rubber-filler interaction. Conventional rubber composites/polymer composites are associated with drawbacks such as lower tensile strength and lower tensile modulus due to poor dispersion of the fillers into the polybutadiene rubber matrix.
The present disclosure relates to a polymer nanocomposite and a process for its preparation.
In an aspect, the present disclosure provides a polymer nanocomposite.
The polymer nanocomposite comprises a polybutadiene rubber cement and a thermally reduced graphene oxide.
In accordance with the present disclosure, the polymer nanocomposite comprises the polybutadiene rubber cement in an amount is present in the range of 99.50 wt% to 99.95 wt% and the thermally reduced graphene oxide is present in an amount in the range of 0.05 wt% to 0.5 wt% with respect to the total weight of the nanocomposite. In an exemplary embodiment, the polymer nanocomposite comprises the polybutadiene rubber cement is present in an amount of 99.95 wt% with respect to the total weight of the nanocomposite and the thermally reduced graphene oxide is present in an amount of 0.05 wt% with respect to the total mass of the nanocomposite. In another exemplary embodiment, the polymer nanocomposite comprises the polybutadiene rubber cement is present in an amount of 99.9 wt% with respect to the total mass of the nanocomposite and the thermally reduced graphene oxide is present in an amount of 0.1 wt% with respect to the total mass of the nanocomposite. In yet another exemplary embodiment, the polymer nanocomposite comprises the polybutadiene rubber cement is present in an amount of 99.8 wt% with respect to the total mass of the nanocomposite and the thermally reduced graphene oxide is present in an amount of 0.2 wt% with respect to the total mass of the nanocomposite.
In accordance with an embodiment of the present disclosure, the thermally reduced graphene oxide has a surface area in the range of 200 m2/g to 800 m2/g. In an exemplary embodiment, the thermally reduced graphene oxide has a surface area 470 m2/g.
In accordance with an embodiment of the present disclosure, the thermally reduced graphene oxide has a bulk density in the range of 0.01 g/cc to 1 g/cc. In an exemplary embodiment, the thermally reduced graphene oxide has a bulk density of 0.0180 g/cc.
In accordance with an embodiment of the present disclosure, the thermally reduced graphene oxide has the C/O ratio in the range of 8 to 10. In an exemplary embodiment, the thermally reduced graphene oxide has the C/O ratio of 9.
The C/O ratio indicated high carbon content in TRGO sample. It has less oxygen containing functional groups on its surface. Thus, exfoliation of TRGO is better and is confirmed from HR-TEM. Due to this ratio in the range of 8 to 10, the better dispersion of TRGO in the rubber matrix is observed.
In accordance with an embodiment of the present disclosure, the thermally reduced graphene oxide has a particle size distribution in the range of 5 microns to 100 microns.
In accordance with an embodiment of the present disclosure, a mean particle size (D10) of the thermally reduced graphene oxide is in the range of 5 microns to 10 microns; a mean particle size (D50) of the thermally reduced graphene oxide is in the range of 20 microns to 30 microns; and a mean particle size (D90) of the thermally reduced graphene oxide is in the range of 50 microns to 60 microns. In an exemplary embodiment, a mean particle size (D10) of the thermally reduced graphene oxide is 8.55 microns, a mean particle size (D50) of the thermally reduced graphene oxide is 23.7 microns, and a mean particle size (D90) of the thermally reduced graphene oxide is 56.7 microns.
Lower particle size of the thermally reduced graphene oxide results in better dispersion of nanoparticles in the rubber matrix.
In accordance with an embodiment of the present disclosure, the thermally reduced graphene oxide has an aspect ratio in the range of 0.05:1 to 50:1.
In another aspect, the present disclosure provides a process for the preparation of a polymer nanocomposite.
The process of the present disclosure is described in detail as given below:
In a first step, a predetermined amount of a polybutadiene rubber cement and a predetermined amount of a first fluid medium are homogeneously mixed to obtain a first homogeneous mixture.
In accordance with an embodiment of the present disclosure, the first fluid medium is at least one selected from the group consisting of benzene, toluene, hexane, chloroform, dichloromethane, pentane, cyclohexane, heptane and paraffin. In an exemplary embodiment, the first fluid medium is a mixture of benzene and toluene.
In accordance with an embodiment of the present disclosure, the ratio of the polybutadiene rubber cement to the first fluid medium is 0.67:1 w/v.
In a second step, a predetermined amount an ultrasonicated thermally reduced graphene oxide (TRGO) is mixed into the first homogeneous mixture under stirring at a predetermined speed for a predetermined time period at a predetermined temperature to obtain a second homogeneous mixture.
Ultrasonication of TRGO helps to enhance the distance among the TRGO sheets and leads to better dispersion of TRGO in PBR matrix. Thus, better homogeneous distribution of TRGO leads to better mechanical properties. Nanocomposites prepared without ultrasonication of TRGO, may leads to aggregation of TRGO in PBR matrix that result into lower mechanical strength of the composite.
The ultrasonicated thermally reduced graphene oxide (TRGO) is prepared by adding a predetermined amount of thermally reduced graphene oxide (TRGO) in toluene under sonication for a predetermined time period. In an embodiment, the predetermined time period of the sonication is in the range of 20 minutes to 60 minutes. In an exemplary embodiment, the predetermined time period is 30 minutes.
In accordance with an embodiment of the present disclosure, the predetermined speed is in the range of 10 rpm to 1000 rpm. In an exemplary embodiment, the predetermined speed is 800 rpm.
In accordance with an embodiment of the present disclosure, the predetermined time period is in the range of 30 minutes to 200 minutes. In an exemplary embodiment, the predetermined time period is 60 minutes.
The predetermined time period (mixing time period) is dependent on the speed of propeller rotation. If propeller is highly efficient in mixing, then shorter time is required and vice-versa. Therefore, the predetermined time period is completely dependent on nature of the instrument, reaction vessel volume, shape of propeller and the like.
In accordance with an embodiment of the present disclosure, the predetermined temperature is in the range of 20 °C to 50 °C. In an exemplary embodiment, the predetermined temperature is 25 °C.
In accordance with the present disclosure, thermally reduced graphene oxide is characterized by having:
• a surface area in the range of 200 m2/g to 800 m2/g;
• a bulk density in the range of 0.01 g/cc to 1 g/cc;
• C/O ratio in the range of 8 to 10;
• a mean particle size (D10) of said thermally reduced graphene oxide is in the range of 5 microns to 10 microns; mean particle size (D50) of said thermally reduced graphene oxide is in the range of 20 microns to 30 microns; and mean particle size (D90) of said thermally reduced graphene oxide is in the range of 50 microns to 60 microns; and
• an aspect ratio in the range of 0.05:1 to 50:1.
The dispersion of the thermally reduced graphene oxide (TRGO) into the polybutadiene rubber matrix is homogeneous due to highly exfoliated structure of TRGO.
Use of filler such as TRGO even at lower concentration act as a reinforcement agent for the polymer matrix. In some cases, the reinforcing fillers are normally added to the polymer matrix by melt mixing. However, generally, a solid-state mixing where two solid phases are mixed by mechanical and shear force. The fillers have a strong tendency to exist as aggregates due to their strong van der Waals and other intermolecular forces between the fillers. Therefore, poor dispersion of the fillers into the rubber matrix is a general phenomenon that often leads to producing nanocomposites with weak mechanical or tensile strength. This issue is solved by using the solution phase mixing of fillers with the PBR cement with the help of high-speed overhead stirring. Hence, better homogeneous mixing of the fillers in the rubber matrix is obtained. Such, dispersion of fillers leads to better elastomer-filler interactions which are observed from the higher mechanical strength of the polymer nanocomposite compared to the polymer nanocomposites without filler.
In a third step, the second homogeneous mixture is coagulated by using a second fluid medium in the presence of an antioxidant to obtain a solid composite.
In accordance with an embodiment of the present disclosure, the second fluid medium is at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, glycol, water, acetone, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF) and ethyl acetate. In an exemplary embodiment, the second fluid medium is methanol.
In accordance with an embodiment of the present disclosure, the antioxidant is at least one selected from the group consisting of 2,6-di-tert-butyl-p-cresol (DTBPC), monophenols, bisphenols, thiobisphenols, polyphenols, hydroquinones, phosphites, thioesters, napthylamines, diphenylamines, para-phenylenediamines, and quinolones. In an exemplary embodiment, the antioxidant is 2,6-di-tert-butyl-p-cresol (DTBPC). The antioxidant provides stability to PBR from oxidation through air or oxygen.
In a fourth step, the solid composite is dried at a temperature in the range of 40 °C to 70 °C for a time period in the range of 10 minutes to 600 minutes to obtain the polymer nanocomposite. In an exemplary embodiment, the solid composite is dried at 55 °C for 360 minutes to obtain the polymer nanocomposite.
Drying for long time does not effect on the properties of the polymer nanocomposite.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Example 1: Preparation of a thermally reduced graphene oxide (TRGO), in accordance with the present disclosure
TRGO used in the process of the present disclosure was synthesized by using a high-temperature reduction of graphene oxide (GO) which was obtained by chemical oxidation of graphite using the modified Hummers method. GO was taken in 60 cm long quartz tube under an inert atmosphere and kept in a tubular furnace which was heated at 750 °C for 60 seconds to obtain TRGO. The so obtained TRGO showed a highly exfoliated morphology which was confirmed by BET surface area (470 m2/g for TRGO whereas GO was having 55 m2/g) analysis. Further, the thermally reduced graphene oxide has a bulk density of 0.0180 g/cc, C/O ratio of 9, a mean particle size (D10) is 8.55 microns, a mean particle size (D50) is 23.7 microns, and a mean particle size (D90) is 56.7 microns
The so obtained TRGO was characterized by FTIR, XRD, Raman spectroscopy, SEM, and HRTEM techniques to see the structural and morphological characteristics of TRGO.
Figure 3 illustrates a Fourier-transform infrared spectroscopy (FTIR) spectra for graphene oxide (GO), reduced graphene oxide (RGO) and thermally reduced graphene oxide (TRGO). From Figure 3, it is evident that GO showed all the characteristic peaks corresponds to >C=C< (1620 cm-1), carboxylic –OH group (3182 cm-1), aromatic –C-H stretching (2850 and 2920 cm-1) and a carbonyl peak (1722 cm-1). RGO showed peaks around 1560 cm-1 for >C=C<, at 1101 cm-1 for C-O-H stretching and also traces of >C=O. It was expected that TRGO would give similar spectra corresponding to RGO but in case of TRGO 500/20 where GO was reduced at 500?C for 20 sec, the FTIR spectra showed broad carboxylic –OH stretching peak around 2500-3400 cm-1 which corresponds to GO and also it showed the characteristic peaks of reduced GO. The reduction time was increased from 20 to 40 and 60 seconds. The TRGO produced with longer time i.e. TRGO 500/40 and TRGO 500/60 showed complete reduction of GO.
Figure 4 illustrates a Raman spectrum for graphene oxide (GO), reduced graphene oxide (RGO) and thermally reduced graphene oxide (TRGO). From Figure 4, it is evident that the peak position and the peak-width of Raman active vibrations are sensitive towards presence of defects, molecular stresses and interaction between different phases. GO showed D-band at 1364 cm-1 which corresponds to distortion in structure and related to sp3 hybridized state carbon and G-band at 1600 cm-1 related to characteristic sp2 hybridized state of carbon. RGO and TRGO also showed peak at approximately same position except the intensity of the peaks and a ratio of intensity of D band (ID) to intensity of G band (IG) decreased. Lower intensities of the D-band and G-band were clear indication of reducing the size of the graphene sheet and widening of the band due to exfoliation of graphene sheet.
Figure 5 illustrates an X-ray diffraction (XRD) of thermally reduced graphene oxide (TRGO) with graphene oxide (GO) and reduced graphene oxide (RGO). From Figure 5, it is evident that the XRD pattern of TRGO 500/20 clearly showed low intensity peak at 2? = ~10? and a broad peak around 2? = 24.3? corresponding to GO and reduced graphene which confirmed the incomplete oxidation of graphene oxide at temperature 500?C for 20 sec. whereas when the reduction time and temperature was increased, the disappearance of peak at 2? = ~10? was observed as in case of TRGO 500/40, TRGO 600/40 and TRGO 750/40.
Figure 6 illustrates a High-resolution transmission electron microscopy (HRTEM) for graphene oxide (GO), thermally reduced graphene oxide (TRGO) and reduced graphene oxide (RGO). From Figure 6, it is evident that in GO samples, number of the layers of GO present in nano structures varied in the range of 5 to 12 layers. The number of layers of RGO present in nanostructure varied in the range of 5 to 6 layers whereas the number of layers of TRGO was varied in the range of 3 to 4 layers. This indicated lower bulk density of TRGO samples compared to GO or RGO. Thus, better dispersion of TRGO in Polybutadiene rubber matrix is obtained.
Example 2: Preparation of a polymer nanocomposite having 0.05 phr TRGO, in accordance with the present disclosure
800 gm of a polybutadiene rubber cement and 1200 ml of a mixture of benzene and toluene (first fluid medium) were homogeneously mixed to obtain a first homogeneous mixture. Thereafter, 0.058 gm of 0.05 PHR of an ultrasonicated thermally reduced graphene oxide (obtained in Example 1) was mixed into the first homogeneous mixture under stirring at 800 rpm for 1 hour at 25 °C to obtain a second homogeneous mixture. Then, the second homogeneous mixture was coagulated by using 1200 ml of methanol (second fluid medium) and 0.5 wt% of 2,6-di-tert-butyl-p-cresol (DTBPC) (antioxidant) to obtain a solid composite. Finally, the solid composite was dried at 55 °C for 6 hours to obtain the polymer nanocomposite.
Example 3: Preparation of a polymer nanocomposite having 0.1 phr TRGO, in accordance with the present disclosure
The same experimental procedure was used as mentioned in Example 2, except the TRGO used was 0.1 phr.
Example 4: Preparation of a polymer nanocomposite having 0.2 phr TRGO, in accordance with the present disclosure
The same experimental procedure was used as mentioned in Example 2, except the TRGO used was 0.2 phr.

Comparative Example 1: Preparation of a polymer nanocomposite
The same experimental procedure was used as mentioned in Example 2, except the polymer nanocomposite was prepared in absence of TRGO.
The polymer nanocomposite obtained in examples 2-4 and comparative example 1 were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), Mooney viscosity, and ash content. The thermal techniques TGA and DSC exhibited an exact similar thermogram pattern for the polymer nanocomposite prepared in accordance with the present disclosure as compared to the polymer nanocomposite prepared in accordance with the comparative example 1 (without TRGO).
Figure 7 illustrates a Fourier-transform infrared spectroscopy (FTIR) of conventional (comparative) PBR, Figure 8 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.05 PHR TRGO, Figure 9 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.1 PHR TRGO; and Figure 10 illustrates a Fourier-transform infrared spectroscopy (FTIR) of PBR-0.2 PHR TRGO. Conventional polybutadiene rubber (commercial polybutadiene rubber) was characterized from few typical peaks of its vibrational band of the chemical bonds of the functional groups. Generally, FTIR vibrational bands appeared at ~ 733 cm-1 for cis type >C=C< bond, at ~ 969 cm-1 for trans type >C=C< bond and at ~ 912 cm-1 for vinyl type >C=C< bond. All these FTIR vibrational bands were seen before and after incorporation of TRGO in Polybutadiene rubber samples. This indicated, the intrinsic properties or microstructures remained same for the rubber matrix even after preparation of nanocomposites. This did not alter on changing the filler (e.g. TRGO) contents as well.
Table 1: Microstructure configuration of the double bonds, Mooney viscosity, % volatile content, and % Ash content of the polymer nanocomposite obtained in the comparative example 1 (without TRGO) and example 3 (prepared in accordance with the present disclosure)
Examples Cis/trans/vinyl (%) Mooney Viscosity (MU), ML (1+4) minutes at 100 °C % Volatile content % Ash content
comparative example 1 (without TRGO)
95/2/3
44
0.05
0.052
Example 3 (0.1 phr TRGO) 94/4/2
44
0.04
0.14

From Table 1, it is evident that the nature of the unsaturation, i.e., the microstructure was one of the important intrinsic properties of polybutadiene rubber (PBR) which was found identical for both the polymer nanocomposite prepared in accordance with the present disclosure and the polymer nanocomposite prepared in accordance with the comparative example 1 (without TRGO). Further, from Table 1, it is evident that the Mooney Viscosity values were measured for the comparative example 1 (without TRGO), as well as Example 3 (0.1 phr TRGO) polymer nanocomposite, and no significant change was found in Mooney viscosity values after the preparation of the polymer nanocomposite in accordance with the present disclosure. Measurement of the volatile content was performed from PBR QC laboratory by following the conventional plant method and no significant change was found in terms of volatile content. However, ash content was found to be higher for the polymer nanocomposite of example 3 which was prepared in accordance with the present disclosure due to the presence of unburnt residue of TRGO.
The change of the torque was measured in Mooney Units (MU), which were defined in ISO 289 and ASTM D 1646. The Mooney units were 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 Mooney Viscometer 2000 from Alpha Technology.
The nanocomposite was used for the preparation of tyres according to the following table 2.
Table 2: Compounding formulation for PBR-TRGO (0.1 phr) and PBR (without TRGO) (30 gm batch)
Ingredients In phr Amount
(gm) 0.1 phr TRGO (gm)
PBR 100 15.93 0
PBR/TRGO nanocomposite 0 0 15.93
Aromatic oil 16 2.55 2.55
60 phr of N330 (Carbon black) 60 9.56 9.56
Stearic acid 2.5 0.4 0.4
Zinc oxide 3.5 0.56 0.56
MC wax 2 0.32 0.32
Antioxidant (6-PDD) 1.75 0.28 0.28
Sulfur 1.6 0.25 0.25
TBBS 1 0.16 0.16
TRGO in rubber 0 0.016

After compounding as per tyre formulation, the rheological property was measured following conventional protocol for vulcanization.
Table 3: Rheology (160 °C for 30 min) data for PBR-TRGO (0.1 phr) and PBR samples
Components PBR PBR- TRGO
mL (dN-M) 2.35 2.26
MH (dN-M) 14.42 14.2
ts1 (min) 3.02 2.89
ts2 (min) 3.7 3.27
ts10 (min) 3.22 2.99
ts25 (min) 4.05 3.56
ts40 (min) 4.55 4.05
ts50 (min) 4.93 4.4
ts90 (min) 8 7.17
Delta Tq. (dN-M) 12.07 11.94
Final Tq. (dN-M) 12.85 12.74

Vulcanization was performed for ts90 with addition of 2 minutes. All of the vulcanized samples were subjected to mechanical testing (tensile strength and tensile modulus) after preparation of standard samples under standard condition, i.e. gauge length 25 mm and cross-head speed 500 mm/min.
Figure 1 illustrates a differential scanning calorimetry (DSC) thermogram of the polybutadiene sample before compounding and Figure 2 illustrates a differential scanning calorimetry (DSC) thermogram of the polybutadiene-thermally reduced graphene oxide (PBR-TRGO) (0.1 PHR) sample before compounding, in accordance with the present disclosure. From Figures 1 and 2, it is evident that the pattern of the DSC traces of the pristine PBR and PBR-TRGO nanocomposite samples are found similar. The melting temperature and crystallization temperature of nanocomposite samples were found to be very similar with the conventional sample. Such studies also concluded that there is no significant change in intrinsic property of PBR after incorporation of fillers like TRGO.
Table 4: Mechanical properties of PBR (without TRGO) samples
A total of 6 dumb-bell specimens were made for PBR samples and a total of 7 specimens were made for PBR-TRGO (0.1 phr) sample. Tensile Strength (TS) was measured in Instron UTM machine following the ASTM D412 standard method.
Samples TS (kgf/cm2) TM (kgf/cm2)
S1 122.5 18.9
S2 115.8 19.4
S3 113.5 19.1
S4 110 20.4
S5 117.3 20.4
S6 123.3 20.4
Average 117.06 19.7

Table 5: Mechanical properties of PBR-TRGO samples (0.1 phr) (1st batch)
Samples TS (kgf/cm2) TM (kgf/cm2)
S1 138.4 21.9
S2 143.31 21.0
S3 128.71 21.8
S4 126.4 21.2
S5 142.9 20.5
S6 126.3 20.5
S7 135.5 21.1
Average 134.4 21.1

Table 6: Mechanical properties of PBR-TRGO samples (0.1 phr) (2nd batch)
In the 2nd batch, 3 specimens were prepared for PBR-TRGO (0.1 phr) sample. Tensile Strength (TS) was measured in Instron UTM machine following the ASTM D412 standard method.
Sample Name TS (kgf/cm2) TM (kgf/cm2)
S1 136.9 22.6
S2 125.5 21.9
S3 124.1 22.6
Average 129.1 22.4

From table 4, table 5, and table 6, it is evident that PBR-TRGO (1st batch) sample exhibited 14.95% higher TS, and 7.1% higher TM whereas for the 2nd batch exhibited 10.2 % higher TS and 13.7 % higher TM than samples prepared with commercial PBR (without TRGO). The mechanical property values for the PBR-TRGO sample was found to be higher compared with similar samples prepared without any TRGO fillers. High dispersion was indirectly proven by the increment of tensile strength and tensile modulus of the PBR-TRGO (0.1 phr) sample even in the repeated experiments.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a polymer nanocomposite that:
• has higher tensile strength and higher tensile modulus;
• has low bulk density;
• has homogeneous dispersion due to high exfoliation of TRGO in PBR cement; and
• the intrinsic properties such as microstructures, Mooney viscosity, TGA, DSC, and volatile content of PBR remained unaltered;
and
the process for preparing the polymer nanocomposite that is:
• simple and economical; and
• user friendly and sophisticated skills are not required.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising, will be understood to imply the inclusion of a stated element, integer or step,” or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure 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. A polymer nanocomposite comprising:
• a polybutadiene rubber cement; and
• a thermally reduced graphene oxide.
2. The nanocomposite as claimed in claim 1, wherein
• said polybutadiene rubber cement is present in an amount in the range of 99.5 wt% to 99.95 wt% with respect to the total weight of the nanocomposite; and
• said thermally reduced graphene oxide is present in an amount in the range of 0.05 wt% to 0.5 wt% with respect to the total weight of the nanocomposite.
3. The nanocomposite as claimed in claim 1, wherein said thermally reduced graphene oxide has a surface area in the range of 200 m2/g to 800 m2/g.
4. The nanocomposite as claimed in claim 1, wherein said thermally reduced graphene oxide has a bulk density in the range of 0.01 g/cc to 1 g/cc.
5. The nanocomposite as claimed in claim 1, wherein said thermally reduced graphene oxide has a C/O ratio in the range of 8 to 10.
6. The nanocomposite as claimed in claim 1, wherein said thermally reduced graphene oxide has a particle size distribution in the range of 5 microns to 100 microns.
7. The nanocomposite as claimed in claim 6, wherein a mean particle size (D10) of said thermally reduced graphene oxide is in the range of 5 microns to 10 microns; a mean particle size (D50) of said thermally reduced graphene oxide is in the range of 20 microns to 30 microns; and a mean particle size (D90) of said thermally reduced graphene oxide is in the range of 50 microns to 60 microns.
8. The nanocomposite as claimed in claim 1, wherein said thermally reduced graphene oxide has an aspect ratio in the range of 0.05:1 to 50:1.
9. A process for the preparation of a polymer nanocomposite, said process comprising the following steps:
a) homogeneously mixing a predetermined amount of a polybutadiene rubber cement and a predetermined amount of a first fluid medium to obtain a first homogeneous mixture;
b) mixing a predetermined amount an ultrasonicated thermally reduced graphene oxide into said first homogeneous mixture under stirring at a predetermined speed for a predetermined time period at a predetermined temperature to obtain a second homogeneous mixture;
c) coagulating said second homogeneous mixture in a second fluid medium in the presence of an antioxidant to obtain a solid composite; and
d) drying said solid composite at a temperature in the range of 40 °C to 70 °C for a time period in the range of 10 minutes to 600 minutes to obtain said polymer nanocomposite.
10. The process as claimed in claim 9, wherein said first fluid medium is at least one selected from the group consisting of benzene, toluene, hexane, chloroform, dichloromethane, pentane, cyclohexane, heptane and paraffin.
11. The process as claimed in claim 9, wherein said predetermined speed is in the range of 10 rpm to 1000 rpm; said predetermined time period is in the range of 30 minutes to 200 minutes and said predetermined temperature is in the range of 20 °C to 50 °C.
12. The process as claimed in claim 9, wherein said second fluid medium is at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, glycol, water, acetone, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF) and ethyl acetate.
13. The process as claimed in claim 9, wherein said antioxidant is at least one selected from the group consisting of 2,6-di-tert-butyl-p-cresol (DTBPC), monophenols, bisphenols, thiobisphenols, polyphenols, hydroquinones, phosphites, thioesters, napthylamines, diphenylamines, para-phenylenediamines and quinolones.
14. The process as claimed in claim 9, wherein said thermally reduced graphene oxide is characterized by having:
• a surface area in the range of 200 m2/g to 800 m2/g;
• a bulk density in the range of 0.01 g/cc to 1 g/cc;
• C/O ratio in the range of 8 to 10;
• mean particle size (D10) of said thermally reduced graphene oxide is in the range of 5 microns to 10 microns; mean particle size (D50) of said thermally reduced graphene oxide is in the range of 20 microns to 30 microns; and mean particle size (D90) of said thermally reduced graphene oxide is in the range of 50 microns to 60 microns; and
• an aspect ratio in the range of 0.05:1 to 50:1.

Dated this 17th day of August, 2022

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI