Claims:WE CLAIM:

1. A composite comprising:
a) disentangled ultra-high molecular weight polyethylene (DUHMWPE);
b) functionalized multi walled carbon nanotubes (f-MWCNT); and
c) a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO), and graphite (Gr).
2. The composite as claimed in claim 1, wherein said functionalized multi walled carbon nanotubes (f-MWCNT) and said nanofiller, are each in an amount in the range of 500 to 25000 ppm of the DUHMWPE.
3. The composite as claimed in claim 1, wherein the weight ratio of said functionalized multi walled carbon nanotubes (f-MWCNT) to said nanofiller is 1:1.
4. The composite as claimed in claim 1, wherein said disentangled ultra-high molecular weight polyethylene (DUHMWPE) has a bulk density in the range of 0.04 to 0.2 g/cc, molecular weight in the range of 2 ×106 to 15 ×106 g/mole, percent crystallinity in the range of 96 to 99, with a heat of fusion > 200 J/g and reduced specific viscosity (RSV) in the range of 25 to 30 dL/g.
5. The composite as claimed in claim 1, wherein said functionalized multi walled carbon nanotubes (f-MWCNT) are selected from the group consisting of multi walled carbon nanotubes functionalized with COOH (MWCNT-COOH).
6. The composite as claimed in claim 1, wherein said nanofiller being graphene oxide (GO) has crystallite size in the range of 120 to 130 Å.
7. The composite as claimed in claim 1, wherein said nanofiller being reduced graphene oxide (RGO) has crystallite size in the range of 10 to 15 Å.
8. A process for preparation of a composite, said process comprising the following steps:
i. sonicating a mixture of functionalized multi walled carbon nanotubes (f-MWCNT), and a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO) and graphite (Gr), in a first fluid medium to obtain a first dispersion;
ii. sonicating disentangled ultra-high molecular weight polyethylene (DUHMWPE) in a second fluid medium to obtain a second dispersion;
iii. mixing said first dispersion with said second dispersion to obtain a homogenized dispersion; and
iv. drying said homogenized dispersion to form a cake, and then particulating said cake to obtain said composite in powder form.
9. The process as claimed in claim 8, wherein said first fluid medium and said second fluid medium are acetone.
10. The process as claimed in claim 8, wherein in the step of drying, said first fluid medium and second fluid medium are evaporated in hot air oven at a temperature in the range of 25 to 70 °C for a time period in the range of 3 to 6 hours.
11. The process as claimed in claim 8, wherein the sonication is carried out for 20 to 40 minutes, at a power of 100 watts.
12. The process as claimed in claim 8, wherein the mixing is carried out at a stirring speed in the range of 100 to 800 rpm, at a temperature of 25 to 60 C, for a time period in the range of 1 hour to 6 hours.
13. A process for preparing an article using the composite as claimed in claim 1, wherein said process comprises the following steps:
a) melt mixing said composite at a temperature in the range of 130 to 220 oC, at a screw speed in the range of 50 to 250 rpm, and for a mixing time in the range of 5 to 30 minutes to obtain a melt mixed composite; and
b) extruding said melt mixed composite, followed by injection moulding said extrudates into said article at temperature in the range of 150 to 240 oC and a mould temperature in the range of 25 to 100 oC, at a pressure in the range of 6 to 10 bar to obtain said article,
wherein said article has tensile modulus in the range of 340 to 430 MPa and tensile strength of 45 to 51 MPa.
14. The process as claimed in claim 13, wherein in the step of melt mixing of said composite, final torque generated is in the range of 2800 to 3200 N.
, Description:FIELD
The present disclosure relates to a composite comprising disentangled ultra-high molecular weight polyethylene and hybrid nanofillers.
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 indicate otherwise.
Disentangled ultra-high molecular weight polyethylene (DUHMWPE): The term “disentangled ultrahigh molecular weight polyethylene” refers to a homo-polymer or copolymer of ethylene having molar mass in the range of 2 million to 15 million g/mole, wherein the polyethylene chains are have low entanglement or are completely disentangled.
Nanofiller: The term “nanofiller” refers to a doping agent distributed in the matrix of a composite, whose individual elements have at least one of their dimensions in the nanoscale.
Hybrid Nanofiller: The term “Hybrid Nanofiller” refers to nanofillers obtained by combining at least two different types of nanofillers.
Graphene: The term “Graphene” refers to single layer form of graphite having a one atom-thick planar sheet of sp2-bonded carbon atoms arranged in a hexagonal lattice.
Graphene Oxide (GO): The term “Graphene Oxide” refers to the oxide form of graphene with the presence of many oxygen-containing functional groups such as epoxide, hydroxyl, carbonyl and carboxyl groups formed as a result of oxidation of carbon atoms.
Reduced Graphene Oxide (RGO): The term “Reduced Graphene Oxide” refers to a form of graphene oxide formed as a result of thermal or chemical reduction of graphene oxide, and contains lesser amount of oxygen functionalized groups as compared to GO.
Multi-walled carbon nanotubes (MWCNTs): The term “Multi-walled carbon nanotubes” (MWCNTs) refers to multiple layers (concentric tubes) of graphene rolled in the form of a cylindrical nanostructures.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Disentangled ultrahigh molecular weight polyethylene (DUHMWPE) is a thermoplastic polyethylene. Disentangled ultrahigh molecular weight polyethylene (DUHMWPE) has long chains with molecular mass usually between 2 million and 15 million g/mole). As a result of very high molecular mass, DUHMWPE has high viscosity. Melt processing of disentangled ultra-high molecular weight polyethylene (DUHMWPE) by conventional processing methods is tough because of its high melt viscosity and very high molecular weight. Prior art describes preparation of DUHMWPE composites using a single type of nanofiller and processing these composites by compression moulding. However, these DUHMWPE composites comprising a single type of nanofiller are difficult to process and mould into moulded articles, using conventional methods.
Therefore, there is felt a need to provide a DUHMWPE composite and a process for its preparation which is easy to process and mould into moulded articles, using conventional methods.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure 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 composite comprising disentangled ultra-high molecular weight polyethylene and hybrid nanofillers.
Still another object of the present disclosure is to provide a process for preparation of composite comprising disentangled ultra-high molecular weight polyethylene and hybrid nanofillers.
Yet another object of the present disclosure is to provide a process for preparing an article using the composite comprising the disentangled ultra-high molecular weight polyethylene and hybrid nanofiller.
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
In a first aspect, the present disclosure provides a composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and hybrid nanofillers. The composite comprises disentangled ultra-high molecular weight polyethylene (UHMWPE), functionalized multi walled carbon nanotubes (f-MWCNT) and a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO), and graphite (Gr).
In accordance with the present disclosure, the functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller are each in an amount in the range of 500 to 25000 ppm of the DUHMWPE.
In accordance with the present disclosure, the weight ratio of the functionalized multi walled carbon nanotubes (f-MWCNT) to the nanofiller is 1: 1.
In a second aspect, the present disclosure provides a process for preparation of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE), and hybrid nanofillers. The process involves sonicating a mixture of functionalized multi walled carbon nanotubes (f-MWCNT), and a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO) and graphite (Gr), in a first fluid medium to obtain a first dispersion. In the next step, disentangled ultra-high molecular weight polyethylene (DUHMWPE) is sonicated in a second fluid medium to obtain a second dispersion. The first dispersion is mixed with the second dispersion to obtain a homogenized dispersion. In the next step, the homogenized dispersion is dried to form a cake, and then the cake is particulated to obtain the composite in powder form.
In a third aspect, the present disclosure provides a process for preparing an article using the composite. The process involves melt mixing the composite at a temperature profile in the range of 130 to 220 oC, at a screw speed in the range of 50 to 250 rpm, and for a mixing time in the range of 5 to 30 minutes, to obtain a melt mixed composite. The melt mixed composite is extruded, followed by injection / compression moulding the extrudates into the article at a temperature in the range of 150 to 240 oC and a mould temperature in the range of 25 to 100oC, at a pressure in the range of 6 to 10 bar to obtain the article. The article has tensile modulus in the range of 340 to 430 MPa and tensile strength of 45 to 51 MPa.
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 the effect of amount of hybrid nanofillers on the torque generated during the homogenization of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and the hybrid nanofillers comprising graphene oxide and multi walled carbon nanotubes (GOCNT);
Figure 2 illustrates the effect of amount of hybrid nanofillers on the torque generated during the homogenization of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and the hybrid nanofillers comprising reduced graphene oxide and multi walled carbon nanotubes (RGOCNT);
Figure 3 illustrates the effect of amount of hybrid nanofillers on the torque generated during the homogenization of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and the hybrid nanofillers comprising in situ reduced graphene oxide and multi walled carbon nanotubes (iRGCNT);
Figure 4 illustrates the effect of amount of hybrid nanofillers on the torque generated during the homogenization of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and the hybrid nanofillers comprising graphite and multi walled carbon nanotubes (Gr-CNT);
Figures 5(a) and 5(b) show the thermo-gravimetric (TG) thermograms of the composites comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and various concentrations of hybrid nanofillers comprising reduced graphene oxide and multi walled carbon nanotubes (RGOCNT);
Figures 6(a) and 6(b) show the thermo-gravimetric (TG) thermograms of the composites comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and various concentrations of hybrid nanofillers comprising in situ reduced graphene oxide and multi walled carbon nanotubes (iRGCNT);
Figures 7(a) and (b) show the thermo-gravimetric (TG) thermograms of composites comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and various concentrations of hybrid nanofillers comprising graphene oxide and multi walled carbon nanotubes (GOCNT); and
DETAILED DESCRIPTION
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.
Disentangled ultra-high molecular weight polyethylene (DUHMWPE), have long chains with very high molecular mass, and are highly viscous whereas DUHMWPE composites comprising single nanofiller are difficult to process and mould into moulded articles, using conventional methods. Single component nanofiller has shown some limitations in its performance, which can be overcome by hybrid nanofillers with two different components.
The present disclosure describes a composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and hybrid nanofillers and a process for preparation of these composites. Further, the present disclosure provides conventional moulding methods, which includes a combination of melt extrusion and injection / compression moulding techniques, for moulding these composites of DUHMWPE and hybrid nanofillers into moulded articles.
In a first aspect, the present disclosure provides a composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE) and hybrid nanofillers. The composite comprises disentangled ultra-high molecular weight polyethylene (DUHMWPE), functionalized multi walled carbon nanotubes (f-MWCNT) and a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO), and graphite (Gr).
In accordance with the embodiments of the present disclosure, the disentangled ultra-high molecular weight polyethylene (DUHMWPE) has bulk density in the range of 0.04 to 0.2 g/cc, molecular weight in the range of 2 ×106 to 15 ×106 g/mole, reduced specific viscosity (RSV) in the range of 25 to 30 dL/g and percent crystallinity in the range of 96 to 99 with heat of fusion values > 200 J/g.
In accordance with one embodiment of the present disclosure, the disentangled ultra-high molecular weight polyethylene (DUHMWPE) has bulk density of 0.08 g/cc.
In accordance with one embodiment of the present disclosure, the disentangled ultra-high molecular weight polyethylene (DUHMWPE) has molecular weight of 5.1 ×106 g/mole.
In accordance with one embodiment of the present disclosure, the disentangled ultra-high molecular weight polyethylene (DUHMWPE) has percent crystallinity of 96.
In accordance with one embodiment of the present disclosure, the disentangled ultra-high molecular weight polyethylene (DUHMWPE) has reduced specific viscosity (RSV) of 27.4 dL/g.
Carbon nanotubes (CNT’s) have extraordinary thermal conductivity, and mechanical and electrical properties, as a result of which the carbon nanotubes find applications as additives to various structural materials. Carbon nanotubes (CNT’s) can be single walled (SWCNT) or multi walled (MWCNT). At certain concentration the CNTs form highly associated aggregates and/or precipitates of CNTs in polar solvents.
In accordance with the embodiments of the present disclosure, the functionalized multi walled carbon nanotubes (f-MWCNT) are multi walled carbon nanotubes functionalized with COOH (MWCNT-COOH).
Nanofiller is a reinforcing agent whose individual elements have at least one dimension in the nanoscale and the nanofiller is distributed in the matrix of a polymer to form a composite. The size of nanofillers is usually below 100 nm. However, the nanofillers have greater specific surface area as compared to the specific surface area of fillers with larger particles size. Therefore, greater surface interaction and the intensity of intermolecular interaction between the nanofillers and the polymer matrices significantly reduces the amount of filling used in synthesizing a composite having the same properties. Thus, the use nanofillers help reduce specific consumption of the nanofiller and produce higher performance materials. It is very important to make sure that the nanofillers are evenly distributed in the composite matrix.
Graphite and graphene are hydrophobic in nature, which limits its dispersibility with polymer matrices.
Graphene oxide (GO) is considered to be amphiphilic, having both hydrophobic domains and hydrophilic domains. Graphene oxide (GO) has hydrophilic nature due to the presence of a number of oxygen functionalities, which allows better interfacial interaction with polar solvents and polar polymer matrices. Whereas, due to the pi-stacking interactions of the graphene sheet in graphene oxide, GO has interfacial interaction with MWCNTs, leading to enhanced dispersion of the MWCNTs in polar solvents and polar matrices. The major benefit of combining the graphene oxide with DUHMWPE matrices is to enhance the mechanical and/or electrical properties of the composite.
In accordance with the embodiments of the present disclosure, the functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller are each in an amount in the range of 500 to 25000 ppm of the DUHMWPE.
In accordance with the embodiments of the present disclosure, the composite comprises functionalized multi walled carbon nanotubes (f-MWCNT) and a nanofiller, and the weight ratio of the functionalized multi walled carbon nanotubes (f-MWCNT) to the nanofiller is in the range of 1 : 3 to 3 : 1.
In accordance with one embodiment of the present disclosure, the weight ratio of the functionalized multi walled carbon nanotubes (f-MWCNT) to the nanofiller is 1:1.
In accordance with the embodiments of the present disclosure, the nanofiller is graphene oxide (GO), which has oxygen functionality in the range of 10 to 50%.
In accordance with one embodiment of the present disclosure, the nanofiller is graphene oxide (GO), which has oxygen functionality of 48 %.
In accordance with the embodiments of the present disclosure, the nanofiller is graphene oxide (GO), which has crystallite size in the range of 120 to 130 Å.
In accordance with one embodiment of the present disclosure, the nanofiller is graphene oxide (GO), which has crystallite size of 125 Å.
In accordance with the embodiments of the present disclosure, the nanofiller is reduced graphene oxide (RGO), which has oxygen functionality in the range of 3 to 15%.
In accordance with one embodiment of the present disclosure, the nanofiller is reduced graphene oxide (RGO), which has oxygen functionality of 8 %.
In accordance with the embodiments of the present disclosure, the nanofiller is reduced graphene oxide (RGO), which has crystallite size in the range of 10 to 15 Å.
In accordance with one embodiment of the present disclosure, the nanofiller is reduced graphene oxide (RGO), which has crystallite size of 12 Å.
In accordance with the exemplary embodiments, the composite comprises disentangled ultra-high molecular weight polyethylene (DUHMWPE) functionalized multi walled carbon nanotubes (f-MWCNT) and a nanofiller. The functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller are each in an amount in the range of 500 to 25000 ppm of the DUHMWPE. The nanofiller is selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO) and graphite (Gr).
In one embodiment of the present disclosure, the composite comprises functionalized multi walled carbon nanotubes and the nanofiller is graphene oxide. This hybrid nanofiller is graphene oxide : carbon nanotubes (GOCNT).
In accordance with the embodiments of the present disclosure, the hybrid nanofiller GOCNT is characterized by XRD peaks for GO at 2? = 10.1o and MWCNT at 2? = 25.8o, in the XRD spectra. Thus, GOCNT is a physical mixture of GO and MWCNT.
In another embodiment of the present disclosure, the composite comprises functionalized multi walled carbon nanotubes and the nanofiller is graphene oxide. This hybrid nanofiller is reduced graphene oxide: carbon nanotubes (RGOCNT).
In accordance with the embodiments of the present disclosure, the nanofiller RGOCNT is characterized by XRD peaks for RGO at 2? = 24.3o and MWCNT at 2? = 25.8o), in the XRD spectra. Thus, RGOCNT is a physical mixture of RGO and MWCNT.
In still another embodiment of the present disclosure, the composite comprises functionalized multi walled carbon nanotubes and the nanofiller is graphite. This hybrid nanofiller is graphite: carbon nanotubes (Gr-CNT).
In yet another embodiment of the present disclosure, the composite comprises functionalized multi walled carbon nanotubes and the nanofiller is in situ reduced graphene oxide. This hybrid nanofiller is in situ reduced graphene oxide: carbon nanotubes (iRGCNT).
In accordance with the embodiments of the present disclosure, in the XRD spectra, the nanofiller iRGCNT is characterized by XRD peak for iRGCNT (2? = 25.7o), which confirms the presence of covalent interaction between graphene and MWCNT surface.
In one embodiment of the present disclosure, the weight ratio of the functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller is 1:1.
In a second aspect, the present disclosure provides a process for preparation of composite comprising disentangled ultra-high molecular weight polyethylene (DUHMWPE), functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller. The process involves sonicating a mixture of functionalized multi walled carbon nanotubes (f-MWCNT), and a nanofiller selected from the group consisting of graphene oxide (GO), reduced graphene oxide (RGO) and graphite (Gr), in a first fluid medium to obtain a first dispersion. In the next step, disentangled ultra-high molecular weight polyethylene (DUHMWPE) is sonicated in a second fluid medium to obtain a second dispersion. The first dispersion is mixed with the second dispersion to obtain a homogenized dispersion. In the next step, the homogenized dispersion is dried to form a cake, and then the cake is particulated to obtain the composite in powder form.
Sonication of the functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller in a first fluid medium helps disperse these nanofillers in the first fluid medium. The sonication time in the range of 20 to 40 minute and power (100 W) is optimized to help obtain a dispersion of the functionalized multi walled carbon nanotubes (f-MWCNT) and the nanofiller in a first fluid medium, without inducing fragmentation of functionalized multi walled carbon nanotubes (f-MWCNT’s) by extended sonication or high power.
In accordance with the embodiments of the present disclosure, the first fluid medium and the second fluid medium are both acetone.
In accordance with the embodiments of the present disclosure, in the step of mixing, the first dispersion and the second dispersion are homogenized by stirring at a speed in the range of 100 to 800 rpm at a temperature in the range of 25 to 60 °C, for a time period in the range of 1 to 6 hours.
In accordance with one embodiment of the present disclosure, in the step of mixing, the first dispersion and the second dispersion are homogenized by stirring at a speed of 600 rpm, at 50 °C and for 4 hours.
In accordance with the embodiments of the present disclosure, in the step of drying, the first fluid medium and the second fluid medium in the homogenized dispersion are evaporated and dried in hot air oven at a temperature in the range of 25 to 70 °C for a time period in the range of 3 to 5 hours.
In accordance with one embodiment of the present disclosure, in the step of drying, the first fluid medium and the second fluid medium in the homogenized dispersion are evaporated and dried in hot air oven at 50 °C for 4 hours.
In a third aspect, the present disclosure provides a process for preparing an article using the composite. The process involves melt mixing the composite at a temperature profile in the range of 130 to 220 oC, at a screw speed in the range of 50 to 250 rpm, and for a mixing time in the range of 5 to 30 minutes, to obtain a melt mixed composite. The melt mixed composite is extruded, followed by moulding the extrudates into the article at a temperature in the range of 150 to 240 oC and a mould temperature in the range of 25 to 100 oC, at a pressure in the range of 6 to 10 bar to obtain the article. The article has tensile modulus in the range of 340 to 430 MPa and tensile strength of 45 to 51 MPa.
In accordance with one embodiment of the present disclosure, melt mixing of the composite is carried out at a temperature profile of 190/210/210 oC.
In accordance with one embodiment of the present disclosure, melt mixing of the composite is carried out in microcompounder at a screw speed of 220 rpm.
In accordance with one embodiment of the present disclosure, melt mixing of the composite is carried out for 15 minutes.
In accordance with one embodiment of the present disclosure, in the step of melt mixing of the composite, the final torque generated is in the range of 2800 to 3200 N.
In accordance with one embodiment of the present disclosure, extruded melt mixed composite is moulded at 220 oC using microinjection moulding machine.
In accordance with one embodiment of the present disclosure, a mould temperature is 80 oC.
In accordance with one embodiment of the present disclosure, injection pressure is 8 bars.
The foregoing description of the embodiments has been provided for purposes of illustration and 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 tested to scale up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experimental Details:
Example 1: Synthesis of Graphene Oxide (GO)
Graphite (3 g) and NaNO3 (3 g) were added to concentrated Sulphuric acid (200 mL) at 0 °C, and stirred for 20 minutes. KMnO4 (18 g) was gradually added to the mixture by keeping the reaction temp below 20 oC and the reaction mixture was kept for 6 hrs. at room temperature to form a thick paste. Deionized water (200 mL, DI water) was added to the paste and the slurry was stirred for 10 minutes. Then, additional 500 mL water was added to quench the oxidation reaction. H2O2 (15 mL, 30% solution) was added to the aqueous slurry to destroy excess of KMnO4, as indicated by change of color from dark brown to yellowish. The slurry was then treated with HCl (5%) to destroy excess of sulphate. Subsequently, the slurry was filtered and washed with DI water till neutral pH to obtain a paste of graphite oxide. The filtered paste was dispersed in 100 ml of water and the dispersion was sonicated for 1 hour to exfoliate the layers and centrifuged for 10 minutes at 8000 rpm and then dried at room temperature to obtain graphene oxide (GO) powder (5 g).
The percentage of oxygen in graphene oxide (GO) was found to be ~48% by elemental analysis and the crystallite size of graphene oxide (GO) was found to be 125 Å.
Example 2: Synthesis of Reduced Graphene Oxide (RGO)
Graphene oxide (GO) powder (0.5 g) obtained in Example 1, was dispersed in DI water (500 mL) and sonicated for 30 minutes. Hydrazine hydrate (5 mL) was added to the dispersion and the slurry was heated to 100 °C and stirred for 24 hours. Then, the slurry was filtered to obtain wet reduced graphene oxide, which was dried in hot air oven at 50 °C for 6 hours to obtain reduced graphene oxide (0.3 g).
The percentage of oxygen in reduced graphene oxide (RGO) was found to be ~8% by elemental analysis and the crystallite size of reduced graphene oxide (RGO) was found to be 12 Å.
Preparation of hybrid nanofillers:
Hybrid nanofillers were prepared by mixing graphite (Gr), graphene oxide (GO) or reduced graphene oxide (RGO) with f-MWCNT (MWCNT-COOH, which was purchased commercially).
Example 3: Preparation of hybrid nanofiller GOCNT from GO and f-MWCNT
A mixture (1:1 w/w) of graphene oxide (GO) (0.25 g) and f-MWCNT (0.25 g) in DI water (500 mL) was sonicated for 1 h, filtered to obtain a paste, which was then dried to obtain graphene oxide : f-MWCNT (0.5 g, GOCNT) powder.
These hybrid nanofillers were characterized by XRD, FTIR and Raman spectroscopy. In the XRD spectra, the XRD pattern of GOCNT shows separate peaks for GO (2? = 10.1o) and MWCNT (2? = 25.8o).
Example 4: Preparation of hybrid nanofiller RGOCNT from RGO and f-MWCNT
A mixture (1:1 w/w) of reduced graphene oxide (RGO) (0.25 g) and f-MWCNT (0.25 g) in DI water (500 mL) was sonicated for 1 h, filtered to obtain a paste, which was then dried to obtain graphene oxide: f-MWCNT (0.5 g, RGOCNT) powder.
These hybrid nanofillers were characterized by XRD, FTIR and Raman spectroscopy. In the XRD spectra, the XRD pattern of RGOCNT shows separate peaks for RGO (2? = 24.3o) and MWCNT (2? = 25.8o).

Example 5: Preparation of hybrid nanofiller Gr-CNT from Gr and f-MWCNT
A mixture (1:1 w/w) of graphite (Gr) (0.25 g) and f-MWCNT (0.25 g) in DI) water (500 mL) was sonicated for 1 h, filtered to obtain a paste, which was then dried to obtain graphite: f-MWCNT (0.5 g, Gr-CNT) powder.
Example 6: Synthesis of hybrid nanofiller iRGCNT from GO and f-MWCNT
A mixture (1:1 w/w) of graphene oxide (GO) (0.4 g) and f-MWCNT (0.25 g) in DI water (500 mL) was sonicated for 1 h. Hydrazine hydrate (4 mL) was added to the dispersion and the slurry was heated to 100 °C and stirred for 24 hours. Then, the slurry was filtered obtain wet in situ reduced graphene oxide: f-MWCNT, which was dried in an oven at 50 °C for 6 hours to obtain reduced graphene oxide: f-MWCNT in 1:1 ratio (0.5 g, iRGCNT).
These hybrid nanofillers were characterized by XRD, FTIR and Raman spectroscopy. In the XRD spectra, the XRD pattern of iRGCNT shows one peak at 2? = 25.7o, which confirms the presence of covalent interaction between graphene and f-MWCNT surfaces.
Synthesis of composites comprising DUHMWPE and hybrid nanofillers
The melt processing of DUHMWPE and hybrid nanofillers was carried out in micro-compounder (M/s. DSM Explore) to see the effect of nano-fillers on processing of composite. The graphene oxide (GO) used in this study has oxygen percentage of ~48% by elemental analysis and crystallite size of 125 Å. DUHMWPE polymer used this study has a bulk density of 0.08 g/cc, molecular weight (MW) of 5.01 million g/mole, 96% crystallinity and reduced specific viscosity (RSV) of 27.4 dL/g.
Example 7: Composite comprising DUHMWPE and GOCNT (1000 ppm)
DUHMWPE (10 g) was dispersed in acetone (100 ml) and stirred for 30 min. Separately, GOCNT (1000 ppm w.r.t. DUHMWPE, 1:1 wt/wt of GO and MWCNT, 0.01 g) was dispersed in acetone (10 ml) and sonicated for 30 min. Both these dispersions were mixed by sonicating at a power of 100 W for 30 minutes and then homogenized at a stirring speed of 600 rpm, at 50 °C, for 4 hours using solvent blending method for another 2 hours. Acetone was evaporated to obtain a wet cake of composite, which was dried in hot air oven at 50 oC for 4 hours to obtain the composite in powder form.
Example 8: Composite comprising DUHMWPE and GOCNT (2500 ppm)
A composite was prepared according to the process of Example 7, excepting that GOCNT content was 2500 ppm with respect to DUHMWPE.
Example 9: Composite comprising DUHMWPE and GOCNT (5000 ppm)
A composite was prepared according to the process of Example 7, excepting that the GOCNT was 5000 ppm with respect to DUHMWPE.
Example 10: Composite comprising DUHMWPE and RGOCNT (1000 ppm)
The composite was prepared as described in Example 7, excepting that the GOCNT was replaced by RGOCNT to the extent of 1000 ppm with respect to DUHMWPE.
Example 11: Composite comprising DUHMWPE and RGOCNT (2500 ppm)
A composite was prepared according to the process of Example 7, excepting that the RGOCNT was 2500 ppm with respect to DUHMWPE.
Example 12: Composite comprising DUHMWPE and RGOCNT (5000 ppm)
A composite was prepared according to the process of Example 7, excepting that the RGOCNT was 5000 ppm with respect to DUHMWPE.
Example 13: Composite comprising DUHMWPE and iRGCNT (1000 ppm)
The composite was prepared as described in Example 7, excepting that the GOCNT was replaced with iRGCNT to the extent of 1000 ppm with respect to DUHMWPE.

Example 14: Composite comprising DUHMWPE and iRGCNT (2500 ppm)
A composite was prepared according to the process of Example 7, excepting that the iRGCNT was 2500 ppm with respect to DUHMWPE.
Example 15: Composite comprising DUHMWPE and iRGCNT (5000 ppm)
A composite was prepared according to the process of Example 7, excepting that the iRGCNT was 5000 ppm with respect to DUHMWPE.
Example 16: Composite comprising DUHMWPE and GrCNT (1000 ppm)
The composite was prepared as described in Example 7, excepting that the GOCNT was replaced with Gr-CNT to the extent of 1000 ppm with respect to DUHMWPE.
Example 17: Composite comprising DUHMWPE and Gr-CNT (2500 ppm)
A composite was prepared according to the process of Example 7, excepting that the Gr-CNT was 2500 ppm with respect to DUHMWPE.
Example 18: Composite comprising DUHMWPE and Gr-CNT (5000 ppm)
A composite was prepared according to the process of Example 7, excepting that the Gr-CNT was 5000 ppm with respect to DUHMWPE.
In a similar way, DUHMWPE and nanofiller composites, comprising higher concentrations of the above nanofillers (e.g. 10K, 25K and 50K ppm), were prepared according to the process of Example 7.
The composites of DUHMWPE and hybrid nanofillers, obtained in above Examples 7-18 were melt processed in a Micro-compounder and moulded into different articles using microinjection moulding machine.

Example 19: Melt processing of composites comprising DUHMWPE and hybrid nanofillers
The melt mixing of each of the above composites comprising DUHMWPE and hybrid nanofillers, was carried out independently/separately in Micro-compounder (M/s DSM Xplore) at a temperature profile of 190/210/210 oC, screw speed 220 rpm and mixing time 15 min in a batch size of 6 g to develop high shear and properly mix hybrid nanofillers with DUHMWPE. The melt mixed extrudates of the composite was extruded through a die and moulded into different articles on micro-injection moulding machine at 220 oC and mould temp 80 oC with injection pressure 8 bars, in the form of sheets, rounded plaques or flexural bars.
The effect of torque generated during the homogenization of DUHMWPE and hybrid nanofiller was recorded and results are presented in Figures 1-3 and Table 1, which indicate that very high torque values (Force: 5733N) were observed for DUHMWPE resin. However, the torque values observed during the homogenization of composites comprising DUHMWPE and hybrid nanofiller were found to decrease when hybrid nanofillers were incorporated in DUHMWPE resin. Lower torque values signify ease of processing the composites.
(a) Melt processing of DUHMWPE/GOCNT composites
In case of DUHMWPE and GOCNT composite comprising 1000 ppm of GOCNT, the final torque value was found to be 2980 N (Figure 1 and Table 1). However, no significant decrease in torque values was observed with further increase in the amount of hybrid nanofiller GOCNT. Thus, the torque values were 3000 N and 3055 N for composite comprising DUHMWPE and 2500 ppm and 5000 ppm GOCNT as nanofiller, respectively (Figure 1 and Table 1).
(b) Melt processing of DUHMWPE/RGOCNT composite
The reduced graphene oxide (RGO) used in this study has oxygen percentage of ~8% by elemental analysis and crystallite size of 12 Å.
The melt mixing and moulding carried out as explained above Example 19.
In case of DUHMWPE and RGOCNT composite comprising 1000 ppm of RGOCNT, the final torque value was found to be 2901 N (Figure 2 and Table 1). However, no significant decrease in torque values was observed with further increase in the amount of hybrid nanofiller RGOCNT. Thus, the torque values were 2900 N and 2937 N for composite comprising DUHMWPE and 2500 ppm and 5000 ppm RGOCNT as nanofiller, respectively (Figure 2 and Table 1).
This decrease in the observed torque values of the GO-CNT and DUHMWPE, and RGO-CNT and DUHMWPE composites, can be attributed to the behaviour of GO and RGO like individual particulates and lubricating behaviour of MWCNT’s in the composite.
(c) Melt processing of DUHMWPE/iRGCNT composite
In case of DUHMWPE and iRGCNT composite comprising 1000 ppm of iRGCNT, the final torque value was found to be 5859 N (Figure 3 and Table 1). Thus, no significant decrease in torque values was observed with incorporation of hybrid nanofiller iRGCNT. Similarly, the torque values were 5458 N and 5470 N for composite comprising DUHMWPE and 2500 ppm and 5000 ppm iRGCNT as nanofiller, respectively (Figure 3 and Table 1). Hence, incorporation of iRGCNT hybrid Nanofillers into DUHMWPE matrix has no significant effect on the torque values as given in Figure 3 and Table 1.
(d) Melt processing of DUHMWPE/Gr-CNT composite
In case of DUHMWPE and Gr-CNT composite comprising 1000 ppm of Gr-CNT, the torque value was found to be 2930 N (Figure 4 and Table 1). However, the torque values were 5550 N and 5703 N for composite comprising DUHMWPE and 2500 ppm and 5000 ppm Gr-CNT as nanofiller, respectively (Figure 4 and Table 1). Thus, incorporation of Gr-CNT hybrid nanofillers into DUHMWPE matrix has shown that as the filler concentration increased the torque values observed for the resulting composites were also increased as given in Figure 4 and Table 1. This could be attributed to the agglomeration of graphite particles as indicated by higher crystallite size of 333 Å which resulted into increased melt viscosity hence the torque.
Table 1: Comparison of final torque values observed during melt mixing of DUHMWPE with different hybrid nanofiller composites
Composite (DUHMWPE + nanofiller) Force (N) value of resulting Torque
DUHMWPE + 0 DUHMWPE + 1000 ppm DUHMWPE + 2500 ppm DUHMWPE + 5000 ppm
Initial Final Initial Final Initial Final Initial Final
DUHMWPE + CNT 6540 5733 5833 5455 6173 5490 6290 5805
DUHMWPE + GO 6540 5733 5333 5310 5435 5378 5698 5870
DUHMWPE + GOCNT 6540 5733 3375 2980 3383 3000 3575 3055
DUHMWPE + RGO 6540 5733 5183 5170 5133 5125 5065 4980
DUHMWPE + RGOCNT 6540 5733 3475 2901 3460 2900 3470 2937
DUHMWPE + iRGCNT 6540 5733 6655 5859 6460 5458 6240 5470
DUHMWPE + Gr 6540 5733 7533 7190 7488 7509 7583 7503
DUHMWPE + Gr-CNT 6540 5733 3418 2930 6605 5550 6840 5703

Overall, the results show that among all the hybrid nanofillers, GOCNT and RGOCNT show very good interaction in terms of reinforcement with DUHMWPE matrix during melt mix processing whereas iRGCNT and Gr-CNT do not show any interaction with DUHMWPE matrix during melt mixing.

Example 20: Analysis of the physical properties of the composite
(a) Thermal Properties of the composite
Composites comprising DUHMWPE and hybrid nanofillers were evaluated for their thermal stability by differential scanning calorimetry (DSC) analysis and thermogravimetric analysis (TGA).
Differential Scanning Calorimetry (DSC)
DSC analysis of DUHMWPE and hybrid nanofiller composites was carried out using DSC Q2000 from M/s TA instruments. The DSC thermograms of DUHMWPE and hybrid nanofiller composites were recorded under heating/cooling/heating scan method at the rate of 10 oC/min in N2 atmosphere from ambient temperature to 200 oC. Results are presented in Table 2.
The results show the melting temperature (Tm1) of the composite is 134 oC. Also the melting temperature (Tm2) was unchanged in case of DUHMWPE hybrid nanofiller composites. The heat of fusion (?Hm1) for virgin DUHMWPE, and the heat of fusion (?Hm2) composites of DUHMWPE and hybrid nanofillers are found to be more or less equal, which shows almost no change in the crystallinity of the polyethylene. This can be attributed to no change in the crystallisation temperature (Tc).
Thus it can be inferred that the incorporation of these hybrid nanofiller in DUHMWPE is not affecting its melting and crystallization behaviour.

Table 2: Results of DSC analysis of DUHMWPE/hybrid nanofiller composites
Sample name Tm1 (oC) ?Hm1 (J/g) Tc (oC) ?Hc (J/g) Tm2 (oC) ?Hm2 (J/g) % Crystallinity
virgin DUHMWPE 134 150 121 145 135 142 52
DUHMWPE +
RGO-CNT (1000 ppm) 137 138 120 132 138 141 47
DUHMWPE +
RGO-CNT (2500 ppm) 136 137 121 130 136 142 47
DUHMWPE +
RGO-CNT (5000 ppm) 135 143 121 135 136 143 49
DUHMWPE +
iRGCNT (1000 ppm) 135 137 120 126 136 139 47
DUHMWPE +
iRGCNT (2500 ppm) 135 138 120 128 135 141 47
DUHMWPE +
iRGCNT (5000 ppm) 135 139 121 127 136 141 47
DUHMWPE +
GO-CNT (1000 ppm) 134 137 121 135 135 145 47
DUHMWPE +
GO-CNT (2500 ppm) 135 140 121 133 136 144 48
DUHMWPE +
GO-CNT (5000 ppm) 135 132 121 133 136 143 45
DUHMWPE +
Gr-CNT (1000 ppm) 136 149 121 140 136 149 51
DUHMWPE +
Gr-CNT (2500 ppm) 134 134 121 134 136 150 46
DUHMWPE +
Gr-CNT (5000 ppm) 134 149 121 140 136 150 51

(b) Thermogravimetric analysis (TGA)
Thermal stability of DUHMWPE and hybrid nanofiller composites was evaluated by recording their thermo-gravimetric (TG) thermograms in nitrogen atmosphere. TGA Q500 from M/s TA instruments was used for recording TG thermograms at a heating rate of 10 oC/min in the temperature range RT to 650 oC.
Figure 5 (a) shows that the TG thermograms of the DUHMWPE/RGOCNT, DUHMWPE/iRGCNT and DUHMWPE/GOCNT composites along with virgin DUHMWPE. The TG traces shows that all the three composites show similar stability like the virgin DUHMWPE. Only slight decrease in the stability was observed in case of DUHMWPE/RGOCNT composite as compared to DUHMWPE (Figure 5 (b)) which on increasing concentration of RGOCNT further increased up to virgin DUHMWPE. Similar observation was found in case of DUHMWPE/GOCNT hybrid composites where a slight decrease in the thermal stability was observed at all the concentration of GOCNT as compared to DUHMWPE.
(c) Mechanical properties
Mechanical properties of DUHMWPE/hybrid nanofiller composites were evaluated on Universal Testing Machine (UTM) of M/s Lloyd Instruments (Model No: EZ 20). For this purpose, the DUHMWPE/hybrid nanofiller composites were compression moulded into sheet of dimension 100 mm× 100 mm× 1 mm at temperature 200 oC. These sheets were cut into tensile bars (Thickness 1 mm and width 6 mm) using punch cutter of Type IV samples as per ASTM D 638 standard.
The tensile testing was carried out at a gauze length of 50 mm and cross head speed (CHS) of 50 mm/min at room temperature. Table 3 shows the results of tensile testing for some of the representative DUHMWPE/hybrid nanofiller composite samples. Higher tensile strength and tensile modulus indicates stronger composites.

Table 3: Evaluation of DUHMWPE/hybrid nanofiller composites for their tensile properties
Sample Name Tensile Strength (MPa) Tensile Modulus (MPa) Elongation at Break (%)
virgin DUHMWPE 45 346 201
DUHMWPE/RGO-CNT (5000 ppm) 46 350 192
DUHMWPE/RGO-CNT (10000 ppm) 48 386 190
DUHMWPE/RGO-CNT (25000 ppm) 48 383 180
DUHMWPE/RGO-CNT (50000 ppm) 51 424 183

DUHMWPE/GO-CNT (5000 ppm) 48 394 195
DUHMWPE/GO-CNT (10000 ppm) 46 356 181
DUHMWPE/GO-CNT (25000 ppm) 45 381 181
DUHMWPE/GO-CNT (50000 ppm) 46 397 183

DUHMWPE/Gr-CNT (5000 ppm) 51 377 214
DUHMWPE/Gr-CNT (10000 ppm) 48 407 197
DUHMWPE/Gr-CNT (50000 ppm) 43 430 130

It was found that the incorporation of hybrid nanofiller increases the tensile modulus (TM) of the DUHMWPE/hybrid nanofiller composites in case of DUHMWPE/RGOCNT hybrid composites but there were differences in the tensile strength (TS) of other composite samples. In case of DUHMWPE/GO-CNT, the TS value was found to be similar as virgin DUHMWPE whereas DUHMWPE/Gr-CNT composite shows a decreasing trend with increasing Gr-CNT concentration. DUHMWPE/RGO-CNT hybrid nanofiller composites shows ~14 % increase in TS value and 25 % in tensile modulus at RGO-CNT concentration (50K ppm) with slight decrease (10%) in the percent elongation at break. This can be attributed to the good interaction and better reinforcement effect of RGO-CNT nanofiller which helps in easy load transfer from nanofiller to DPE matrix.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to the realization of composites comprising disentangled ultra-high molecular weight polyethylene and hybrid nanofillers, that are:
i. Physically stronger;
ii. Thermally stable; and
iii. Enhanced processability.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein has been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
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 disclosure to achieve one or more of the desired object or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values ten percent higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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.