WO2025096319A1

WO2025096319A1 - Polymer composites formed from agglomerated carbon nanotube bundles

Info

Publication number: WO2025096319A1
Application number: PCT/US2024/053163
Authority: WO
Inventors: Krishnan ANANTHA NARAYANA IYER; Bharath Natarajan; Carlos R. Lopez-Barron; Sergey Yakovlev; Ali H. SLIM; Young Jun Yoon
Original assignee: ExxonMobil Technology and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 2023-11-01
Filing date: 2024-10-28
Publication date: 2025-05-08
Anticipated expiration: 2026-05-01

Abstract

Polymer composites containing carbon nanotubes may be produced without de-agglomerating the carbon nanotubes prior to blending the carbon nanotubes with a polymer matrix. The polymer composites may comprise a polymer matrix comprising at least one polymer, and a plurality of carbon nanotubes dispersed in the polymer matrix, in which the carbon nanotubes comprise a plurality of carbon nanotube bundles that have not been de-agglomerated prior to dispersal in the polymer matrix. The carbon nanotubes may be produced by a floating catalyst chemical vapor deposition process. The polymer matrix may be a polyolefin matrix comprising at least one polyolefin.

Description

POLYMER COMPOSITES FORMED FROM AGGLOMERATED CARBON NANOTUBE BUNDLES

FIELD

[0001] The present disclosure relates to polymer composites and, more particularly, polymer composites containing carbon nanotubes.

BACKGROUND

[0002] Carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), are an allotrope of carbon comprising cylindrical nanoscale carbon structures.

[0003] Many applications have been proposed for carbon nanotubes due to their combination of excellent mechanical, electrical, and thermal properties. Costs of carbon nanotubes have dropped considerably in recent years, thereby rendering their incorporation in a diverse range of applications much more feasible. Among the numerous desirable mechanical properties of carbon nanotubes are high values for tensile strength, strain to failure, and tensile modulus. Additionally, carbon nanotubes are highly resistant to fatigue, radiation damage, and heat, thus facilitating their use under harsh conditions.

[0004] Polymer composites containing carbon nanotubes have been explored for many of their proposed applications. For example, incorporating carbon nanotubes in a polymer composite may increase tensile strength and stiffness of the composite, as well as afford increased electrical conductivity, while maintaining desirable characteristics of the polymer itself, such as light weight and affordability. Despite the potential benefits of incorporating carbon nanotubes into polymer composites, performance gains approaching theoretical values have not yet been realized, primarily due to inadequate dispersion of the carbon nanotubes in the polymer matrix. Poor dispersion can be especially problematic for carbon nanotubes having a high aspect ratio (average length/diameter of individual tubes) (e.g., greater than about 1000).

SUMMARY

[0005] In various aspects, the present disclosure provides polymer composites comprising: a polymer matrix comprising at least one polymer; and a plurality of carbon nanotubes dispersed in the polymer matrix, wherein the carbon nanotubes comprise a plurality of carbon nanotube bundles that have not been de-agglomerated prior to dispersal in the polymer matrix.

[0006] In other various aspects, the present disclosure provides methods for making polymer composites. The methods comprise: providing a plurality of carbon nanotubes comprising a plurality of carbon nanotube bundles that have not been de-agglomerated; and dispersing the plurality of carbon nanotubes in a polymer matrix comprising at least one polymer to form a polymer composite.

[0007] These and other features and attributes of the disclosed compositions and methods of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings. The following figures are included to illustrate certain aspects of the disclosure and should not be viewed as exclusive configurations. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[0009] FIG. 1 is a representative TEM image of carbon nanotubes produced using a FCCVD process.

[0010] FIG. 2 is a graph of volume resistivity' as a function of carbon nanotube content in polypropylene composites.

[0011] FIG. 3 is a graph of Young’s Modulus as a function of carbon nanotube content in polypropylene composites.

[0012] FIG. 4 is a differential scanning calorimetry' thermogram for Samples Al and Cl (polypropylene control).

[0013] FIGS. 5 A and 5B are representative TEM images of carbon nanotubes dispersed in a polypropylene composite.

[0014] FIGS. 6A and 6B are graphs showing modulus and impact resistance of polypropylene composites with various additives as a function of loading.

[0015] FIGS. 7A and 7B are representative TEM images of polypropylene composites with carbon black and CNTs, respectively.

[0016] FIGS. 8 is a graph of surface resistivity as a function of carbon nanotube content in PA66.

[0017] FIG. 9 is a graph of tensile modulus as a function of carbon nanotube content in PA66. [0018] FIG. 10 is a graph of tensile strength as a function of carbon nanotube content in PA66. [0019] FIG. 11 is a graph of flexural modulus as a function of carbon nanotube content in PA66. DETAILED DESCRIPTION

[0020] The present disclosure relates to polymer composites and, more particularly, polymer composites containing carbon nanotubes.

[0021] Advantageously, the present disclosure provides polymer composites and methods for production thereof that may afford high tensile strength values and thorough dispersion of carbon nanotubes in the polymer matrix, but without the need for de-agglomeration of the carbon nanotubes prior to forming the polymer composites. Conventional methods for producing polymer composites containing carbon nanotubes may require various steps to deagglomerate carbon nanotubes, thereby producing individualized carbon nanotubes from carbon nanotube bundles. Additional purification of the carbon nanotubes may also sometimes be needed to achieve a satisfactory' dispersion of the carbon nanotubes when forming a polymer composite and/or to achieve desired properties within the polymer composite. Without deagglomeration taking place, tangling of the carbon nanotubes within the polymer matrix may lead to an uneven distribution of the carbon nanotubes, thereby decreasing mechanical strength and electrical conductivity⁷ of the polymer composite. However, de-agglomeration and other purification steps may add complexity⁷ and cost to processes for producing polymer composites containing carbon nanotubes. In addition, the carbon nanotubes may undergo damage during de-agglomeration as well. The present disclosure avoids these difficulties to provide polymer composites having properties including, for example, increased strength, increased electrical conductivity, and other beneficial properties. Surprisingly, these properties may be maintained even when carbon nanotubes having a high aspect ratio are used.

[0022] To accomplish the foregoing, the present disclosure utilizes carbon nanotubes in the form of a carbon nanotube powder. The carbon nanotube poyvder may be produced directly by floating catalyst chemical vapor deposition (FCCVD) or by chopping or otherwise mechanically processing carbon nanotubes obtained from FCCVD or an alternative carbon nanotube production process to provide a low-density carbon nanotube construct. The carbon nanotubes within the carbon nanotube powder may⁷ comprise carbon nanotube bundles that are entangled with one another, yet may undergo ready dispersion within the polymer matrix once blended therewith. The term "‘bundle” refers to a structure where carbon nanotubes are tightly assembled wall-to-wall, and depending on the number and diameter of the carbon nanotubes, exhibit a bundle diameter up to about 200 nm. Advantageously, FCCVD processes may readily produce the carbon nanotube bundles with a very low impurity⁷ content. As discussed further herein, carbon nanotube bundles within a carbon nanotube powder may still undergo effective dispersion in a polymer matrix. [0023] The polymer composites of the present disclosure may include a polymer matrix and carbon nanotubes, wherein the carbon nanotubes are introduced into the polymer matrix as carbon nanotube bundles. Preferably, the polymer matrix may comprise or consist essentially of at least one polyolefin due to the ready compatibility of polyolefin matrices with carbon nanotubes in the form of a plurality of carbon nanotube bundles. Accordingly, polymer composites of the present disclosure may comprise a polyolefin matrix comprising at least one polyolefin, and a plurality of carbon nanotubes dispersed in the polyolefin matrix, wherein the carbon nanotubes comprise a plurality of carbon nanotube bundles that have not been deagglomerated prior to dispersal in the polyolefin matrix. Preferably, the carbon nanotube bundles may further be in a form of a carbon nanotube powder, which may represent an especially low-density carbon nanotube construct. The carbon nanotubes within the carbon nanotube powder may comprise carbon nanotube bundles and optionally a variable fraction of individualized carbon nanotubes that are mutually entangled with each other and/or with the carbon nanotube bundles.

[0024] Example polymers suitable for use in the polymer composites of the present disclosure include, but are not limited to, polyolefin homopolymers and copolymers, or blends thereof. In some examples, the polyolefins may comprise at least one polyolefin such as polyethylene, polypropylene, a copolymer thereof (including impact copolymers), or any combination thereof. Other polymers that may be suitably present in the polymer composites include homopolymers or copolymers of polystyrenes, polyesters, polyurethanes, polysiloxanes, polyacrylates, polyamides, the like, or any combination thereof. Any of the foregoing may be blended with a polypropylene or polyethylene in the polymer composites disclosed herein. The polymers may be synthesized prior to formation of the polymer composites and provided in a form suitable to produce the polymer composites through blending with the carbon nanotubes. In non-limiting examples, the polymers may be provided in a form including, but not limited to, pellets, particles, the like, or any combination thereof. Alternately, the polymer may be formed in situ from a polymer precursor having the carbon nanotubes dispersed therein.

[0025] The polymer composites of the present disclosure may have a carbon nanotube content, by mass of the polymer composite, of about 0.01 wt.% or above, such as within a range from about 0.05 wt.% to about 10 wt.%, or about 0.05 wt.% to about 7 wt.%. or about 0.05 wt.% to about 6 wt.%, or about 0.05 wt.% to about 2.5 wt.%, or about 0.05 wt.% to about 1.5 wt.%, or about 0.05 wt.% to about 0.75 wt.%, or about 0.05 wt.% to about 0.5 wt.%, or about 0.05 wt.% to about 0.1 wt.%, or about 0.1 wt.% to about 10 wt.%, or about 0.1 wt.% to about 7 wt.%, or about 0.1 wt.% to about 6 wt.%. or about 0.1 wt.% to about 2.5 wt.%. or about 0.1 wt.% to about 1.5 wt.%, or about 0.1 wt.% to about 0.75 wt.%, or about 0.1 wt.% to about 0.5 wt.%, or about 1 wt.% to about 5 wt.%, or about 1 wt.% to about 2.5 wt.%, or about 1 wt.% to about 1.5 wt.%.

[0026] In addition, the polymer composites of the present disclosure may have a polymer content, by mass of the polymer composite, of about 80 wt.% or greater, or about 85 wt.% or greater, or about 90 wt.% or greater, or about 95 wt.% or greater, or about 97 wt.% or greater, or about 98 wt.% or greater, or about 99 wt.% or greater, such as within a range of about 95 wt.% to about 99.99 wt.%, or about 96 wt.% to about 99.99 wt.%, or about 97 wt.% to about 99.99 wt.%, or about 98 wt.% to about 99.99 wt .%, or about 99 wt.% to about 99.99 wt .%. The polymer may comprise any suitable polymer including, but not limited to, at least one polyolefin.

[0027] Accordingly, in more specific examples, the polymer composites of the present disclosure may comprise about 0.05 wt.% to about 10 wt.% carbon nanotubes, and 90 wt.% or greater polyolefin, each based on a total mass of the polymer composite.

[0028] Any carbon nanotubes containing carbon nanotube bundles that may be used without de-agglomeration and preferably with minimal or no further purification may be suitably used in the polymer composites disclosed herein. In more specific examples, the carbon nanotubes may be produced using a floating catalyst chemical vapor deposition (FCCVD) process. Illustrative FCCVD processes are disclosed in more detail in U.S. Patent 8,999,285 and International Patent Application Publication WO 2005/007926, each of which is incorporated herein by reference. Illustrative FCCVD processes may synthesize carbon nanotubes from a vaporized carbon source in a heated chamber. Example carbon sources suitable for use in the present disclosure may include hydrocarbons such as, but not limited to, acetylene, ethylene, methane, the like, or any combination thereof. Alcohols such as methanol or ethanol may also be suitably used, optionally in combination with the foregoing hydrocarbons. The heated chamber utilized in FCCVD may have any suitable temperature under w hich carbon nanotube formation takes place such as, for example, a temperature from about 500°C to about 1500°C or about 600°C to about 1300°C. In some examples, the FCCVD process may take place at or near atmospheric pressure (1 bar at sea level).

[0029] Suitable FCCVD processes may take place in the presence of a catalyst effective to convert the carbon vapor into carbon nanotubes. The catalyst may be introduced to the carbon source within the heated chamber and/or prior to entry⁷ of the carbon source into the heated chamber. Example catalysts suitable for use in the present disclosure may include, but are not limited to, an iron-based catalyst, a cobalt-based catalyst, a nickel-based catalyst, a molybdenum-based catalyst, the like, or any combination thereof. One of ordinary skill in the art will be able to implement an FCCVD system and suitable catalyst therefor for production of carbon nanotubes suitable for use herein.

[0030] The carbon nanotubes used herein may comprise single-walled carbon nanotubes, multi-walled carbon nanotubes, or any combination thereof. Any of the carbon nanotubes may contain a discontinuous wall structure along the carbon nanotube length, which may introduce discontinuities ranging from about 1 nm up to about 10 microns, about 100 microns, or about 1000 microns in length. When present, the discontinuous wall structure does not extend all the way around the circumference of the carbon nanotube, as this would result in the carbon nanotube being divided into two sections. Branched/bifurcated carbon nanotubes and bamboolike carbon nanotubes are also possible and may be suitably used. The carbon nanotubes may be further characterized in terms of suitable dimensions and/or properties, as specified hereinafter. It should be noted that the dimensions and/or properties of suitable carbon nanotubes may be dependent on factors including, but not limited to, the polymer type used, the type(s) of carbon nanotubes present, the ty pe of article being manufactured, the desired end use application, the like, or any combination thereof.

[0031] In non-limiting examples, the carbon nanotubes may have a diameter of about 1 nanometer (nm) to about 500 nm, or about 5 nm to about 500 nm, or about 5 nm to about 100 nm, or about 1 nmto about 50 nm. The carbon nanotubes may have a length of about 0.001 millimeter (mm) (z.e., 1 micron) to about 20 mm. or about 0.001 mm to about 10 mm. The carbon nanotubes may have a bulk density of about 0.5 g/cm³ to about 2.5 g/cm³, or about 0.5 g/cm³ to about 2.0 g/cm³, or about 0.7 g/cm³ to about 1.9 g/cm³. The carbon nanotubes may have an aspect ratio of about 500 or greater, or about 1000 or greater, such as about 500 to about 2000, or about 500 to about 10,000, or about 1000 to about 10,000, or about 10,000 to about 50,000, or even greater than 50,000. The carbon nanotubes may have a strain to failure ratio of about 0.5% to about 20.0%, or about 0.5% to about 15.0%, or about 1.0% to about 20.0%, or about 1.0% to about 15.0%, or about 1.0% to about 10.0%, or about 1.0% to about 8.0%. The carbon nanotubes may have a surface area, as determined by BET, of about 20 m²/g to about 2000 m²/g, or about 50 m²/g to about 1000 m²/g, or about 50 m²/g to about 500 m²/g, or about 500 m²/g to about 1000 m²/g. The carbon nanotubes may have a tensile strength of about 0. 1 GPa to about 4.0 GPa, or about 0.2 GPa to about 3.2 GPa, or about 0.3 GPa to about 3 GPa, or about 0.3 GPa to about 2.8 GPa. The carbon nanotubes may have a specific strength of about 1800 kN m/kg to about 2900 kN m/kg, or about 2000 kN-m kg to about 2700 kN m/kg, or about 2200 kN m/kg to about 2600 kN m/kg. The carbon nanotubes may have a strength modulus of about 1 GPa to about 400 GPa, or about 5 GPa to about 300 GPa, or about 5 GPa to about 250 GPa, or about 5 GPa to about 150 GPa. It should be understood that carbon nanotube properties outside the aforementioned ranges are additionally contemplated and furthermore it should be understood that selected individual carbon nanotubes within a plurality of carbon nanotubes may fall outside the aforementioned ranges. [0032] In turn, the polymer composites described herein may be characterized by having high values for Young's Modulus (tensile modulus) and volume resistivity. In non-limiting examples, the polymer composites may have a Y oung’s Modulus of about 2000 MPa or above, or about 2500 MPa or above, or about 3000 MPa or above, or about 4000 MPa or above, or about 5000 MPa or above, or about 6000 MPa or above, such as within a range of about 2000 MPa to about 3500 MPa, or about 2000 MPa to about 3000 MPa, or about 3000 MPa to about 5000 MPa, or about 4000 MPa to about 6000 MPa. or about 5000 MPa to about 7000 MPa. In some or other examples, the polymer composites may have a volume resistivity of about IxlO⁹ Ohm»cm to about 9xl0¹² Ohrmcm and/or a surface resistivity of about IxlO³ Ohm/sq to about 5xl0ⁿ Ohm/sq.

[0033] Carbon nanotubes of the present disclosure may be treated with an organic acid following synthesis thereof so as to remove all or at least a portion of any metal impurities that may be present within the plurality of carbon nanotubes. The level of metal impurities may be reduced to about 5 wt.% or less, or about 2 wt.% or less, or about 1 wt.% or less, or about 0.5 wt.% or less, or about 0.1 wt.% or less, based on the total mass of the carbon nanotubes. Preferably, after treatment with the organic acid, the content of metal impurities may be about 200 ppm or below, or about 100 ppm or below, or about 50 ppm or below, or about 5 ppm or below. Any suitable organic acid may be used to promote purification including, but not limited to, glycolic acid, ascorbic acid, malonic acid, the like, or any combination thereof. Stronger organic acids such as methanesulfonic acid, chlorosulfonic acid, and the like may also be suitably used. Inorganic acid such as hydrochloric acid may also be suitable. When used, the organic acid may be used neat or dissolved in water, an aqueous fluid, or an inert organic solvent at any suitable strength such as, for example, about 0. 1 mol/L (M) to about 5 M, or about 0.1 M to about 1 M. The carbon nanotubes may be treated at room temperature or below with the acid or heated at any temperature up to reflux, preferably with mechanical agitation such as stirring or sonication, during the treatment process. A carbon nanotube powder may be formed before or after conducting purification with an acid.

[0034] In addition to carbon nanotubes, the polymer composites of the present disclosure may comprise additional additives. Additional additives may be added at a concentration within the polymer composites to perform an intended function. Additional additives may be added to the polymer composite through any suitable means and at any suitable point during production of the polymer composites including, but not limited to, prior addition of the additive to the polymer before blending with the carbon nanotubes, addition of the additive during blending with the carbon nanotubes, after blending with the carbon nanotubes, or any combination thereof. One of ordinary' skill in the art will be able to select and appropriately add additional additives to the polymer composites of the present disclosure. Examples of additional additives include, but are not limited to, plasticizers, block additives, antiblock additives, antioxidants, pigments, fillers, processing aids, UV stabilizers, neutralizers, lubricants, surfactants, nucleating agents, the like, or any combination thereof.

[0035] Once suitable carbon nanotubes and optional additives have been provided according to the foregoing description, the carbon nanotubes and the optional additives may be dispersed in a polymer matrix, preferably a polyolefin matrix or a blend of a polyolefin with another type of polymer material, to form the polymer composite. The carbon nanotubes may comprise carbon nanotube bundles that have not been de-agglomerated and may be produced using a FCCVD process. To further prepare the carbon nanotubes for incorporation in the polymer matrix, the methods of the present disclosure may further comprise dissociating and/or chopping the carbon nanotubes prior to formation of the polymer composite by forming a carbon nanotube powder. Powder formation may take place by one or any combination of chopping (e.g., in a blender), grinding, milling, mulling, homogenizing in a high-pressure homogenizer or shear mixer, sonication, tensile dissociation, and the like.

[0036] Additionally, or alternately, the carbon nanotubes may be formed into a liquid dispersion and then wet compounded into the polymer matrix to form the polymer composite. The liquid dispersion may include a solvent and a plurality of carbon nanotubes dispersed in the solvent. An anionic, cationic, or polymeric surfactant may also be present to facilitate the dispersion of the carbon nanotubes. The carbon nanotubes may be produced by FCCVD and be in the form of readily dispersible bundles, as discussed above. The carbon nanotubes may be dissolved, dispersed as solids, or any combination thereof in the solvent. Preferably, the carbon nanotube bundles may further be in the form of a carbon nanotube powder prior to dispersion in the solvent.

[0037] Blending the carbon nanotubes with the polymer matrix may take place by any method suitable to disperse the carbon nanotubes in the polymer matrix without de-agglomerating the carbon nano tubes and/or breaking up the carbon nanotube bundles prior to incorporation in the polymer matrix. Example techniques for promoting dispersion of the carbon nanotubes in the polymer matrix may include shearing techniques including, but are not limited to melt mixing, extrusion, compounding (e.g. , wet compounding) or any combination thereof. As a nonlimiting example, the carbon nanotubes and the polymer may be combined using a melt mixing process taking place at or above the melting point or softening temperature of the polymer matrix. Melt mixing may occur at any suitable temperature at or above the melting point or softening temperature of the polymer matrix, including, for example, temperatures ranging from about 100°C to about 250°C or about 110°C to about 230°C. The temperature may be held constant or varied during the melt mixing process.

[0038] The present disclosure may include forming a master batch polymer composite comprising the carbon nanotubes and polymer at a high carbon nanotube loading, such that a polymer composite having a carbon nanotube loading of about 0.05 wt.% to about 10 wt.% may be produced by blending a portion of the master batch with additional polymer lacking the carbon nanotubes. One of ordinary skill in the art will be able to make such a master batch and polymer composite therefrom with the benefit of the present disclosure.

Additional Embodiments

[0039] The present disclosure is further directed to the following non-limiting embodiments.

[0040] Embodiment 1. A polymer composite comprising: a polymer matrix comprising at least one polymer; and a plurality⁷ of carbon nanotubes dispersed in the polymer matrix, wherein the carbon nanotubes comprise a plurality' of carbon nanotube bundles that have not been de-agglomerated prior to dispersal in the polymer matrix.

[0041] Embodiment 2. The polymer composite of Embodiment 1, wherein the polymer matrix is a polyolefin comprising at least one polyolefin.

[0042] Embodiment 3. The polymer composite of Embodiment 2, wherein the polymer composite comprises about 0.05 wt.% to about 10 wt.% carbon nanotubes and about 90 wt.% or greater polyolefin, each based on a total mass of the polymer composite.

[0043] Embodiment 4. The polymer composite of Embodiment 2 or Embodiment 3, wherein the at least one polyolefin comprises a polypropylene, a polyethylene, a copolymer thereof, or any combination thereof.

[0044] Embodiment 5. The polymer composite of any one of Embodiments 1-4. wherein the carbon nanotubes have a diameter of about 1 nm to about 1000 nm.

[0045] Embodiment 6. The polymer composite of any one of Embodiments 1-5, wherein the carbon nanotubes have a length of about 1 pm to about 2000 pm. [0046] Embodiment 7. The polymer composite of any one of Embodiments 1-6, wherein the carbon nanotubes have an aspect ratio of about 1000 or greater.

[0047] Embodiment 8. The polymer composite of any one of Embodiments 1-7, wherein the carbon nanotubes have one or more of the following properties: a bulk density of about 0.5 g/cm³ to about 2.5 g/cm³, a strain to failure ratio of about 0.5% to about 20.0%, a surface area of about 25 m²/g to about 1500 m²/g, a tensile strength of about 0.1 GPa to about 4.0 GPa, a specific strength of about 1800 kN m/kg to about 2900 kN m/kg, or a strength modulus of about 1 GPa to about 400 GPa.

[0048] Embodiment 9. The polymer composite of any one of Embodiments 1-8, wherein the plurality' of carbon nanotubes were produced by a floating catalyst chemical vapor deposition (FCCVD) process.

[0049] Embodiment 10. The polymer composite of Embodiment 9, wherein the FCCVD process uses an iron-based catalyst.

[0050] Embodiment 11. A method comprising: providing a plurality of carbon nanotubes comprising a plurality of carbon nanotube bundles that have not been de-agglomerated; and dispersing the plurality of carbon nanotubes in a polymer matrix comprising at least one polymer to form a polymer composite.

[0051] Embodiment 12. The method of Embodiment 11, wherein the polymer matrix is a polyolefin matrix comprising at least one polyolefin.

[0052] Embodiment 13. The method of Embodiment 12, wherein the polymer composite comprises about 0.05 wt.% to about 10 wt.% carbon nanotubes and about 90 wt .% or greater polyolefin, each based on a total mass of the polymer composite.

[0053] Embodiment 14. The method of Embodiment 12 or Embodiment 13, wherein the polyolefin matrix comprises a polypropylene, a polyethylene, a copolymer thereof, or any combination thereof.

[0054] Embodiment 15. The method of any one of Embodiments 11-14, further comprising: powdering the plurality of carbon nanotubes prior to forming the polymer composite.

[0055] Embodiment 16. The method of any one of Embodiments 11-15. wherein dispersing comprises melt mixing.

[0056] Embodiment 17. The method of any one of Embodiments 11-16, wherein the carbon nanotubes have a diameter of about 1 nm to about 1000 nm.

[0057] Embodiment 18. The method of any one of Embodiments 11-17, wherein the carbon nanotubes have a length of about 1 pm to about 2000 pm. [0058] Embodiment 19. The method of any one of Embodiments 11-18, wherein the carbon nanotubes have an aspect ratio of about 1000 or greater.

[0059] Embodiment 20. The method of any one of Embodiments 11-19, wherein the carbon nanotubes have one or more of the following properties: a bulk density of about 0.5 g/cm³ to about 2.5 g/cm³, a strain to failure ratio of about 0.5% to about 20.0%, a surface area of about 25 m²/g to about 1500 m²/g, a tensile strength of about 0.1 GPa to about 4.0 GPa, a specific strength of about 1800 kN m/kg to about 2900 kN m/kg, or a strength modulus of about 1 GPa to about 400 GPa.

[0060] Embodiment 21. The method of any one of Embodiments 11-20, wherein the plurality of carbon nanotubes were produced using a FCCVD process.

[0061] Embodiment 22. The method of Embodiment 21. wherein the FCCVD process uses an iron-based catalyst.

[0062] Embodiment 23. A polymer composite formed by the method of any one of Embodiments 11 -22.

[0063] To facilitate a better understanding of the embodiments of the present disclosure, the following examples of preferred or representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES

Polypropylene Composites

[0064] Carbon nanotubes were produced according to a FCCVD process, such as that described in International Patent Application Publication WO 2005/007926. FIG. 1 is a transmission electron microscope (TEM) image of illustrative carbon nanotubes produced using a FCCVD process. The carbon nanotubes largely comprised bundles of carbon nanotubes having 2-8 walls and having a diameter ranging from 10-50 nm and a length of greater than 10 microns. The carbon nanotube was subsequently processed into a carbon nanotube powder.

[0065] The resulting carbon nanotubes were formed into a polymer composite master batch (Sample A0) comprising 5.26 wt.% carbon nanotubes in polypropylene. The polymer composite master batch was formed by melt mixing the carbon nanotubes with the polypropylene at a feed rate of 50 g/h and ramped to 230°C. Subsequently, the master batch polymer composite was combined with additional polypropylene (PP3155, ExxonMobil) in various amounts by melt mixing to form polymer composites having a lower loading of carbon nanotubes (Samples A1-A4). All samples additionally included IRGANOX® 1010 (BASF) as a stabilizer. A comparative sample of the polypropylene alone was also prepared (Sample Cl). Compositional data for the polypropylene composites is summarized in Table 1. Table 1

[0066] Selected physical properties for samples A0-A4 and Cl were determined according to the testing procedures provided hereinafter, and results are compiled in Table 2 below. Notched Izod Impact was determined by a method based on ASTM D256. Tensile testing was performed by a method based on ASTM D638, yielding Young’s Modulus and strain at break values. Volume resistivity was determined by a method based on ASTM D257.

Table 2

[0067] Volume resistivity and Young’s Modulus were plotted as a function of carbon nanotube loading, as shown in FIGS. 2 and 3. respectively. As demonstrated, volume resistivity decreased rapidly with increased carbon nanotube loading, and Young’s Modulus increased rapidly with increased carbon nanotube loading. Heat flow properties were also analyzed for samples Al and Cl by differential scanning calorimetry' (DSC), as shown in FIG. 4. As shown, peak heat flow occurred at a higher temperature (127.82°C) for sample Al than for sample Cl (1 18.98°C), and faster crystallization kinetics were realized in the presence of carbon nanotubes. [0068] Samples were also imaged to determine the extent of dispersion of the carbon nanotubes in the polypropylene matrix. FIGS. 5A and 5B are transmission electron microscope (TEM) images of a representative sample. As shown, the carbon nanotubes were well dispersed in the polypropylene matrix.

Polypropylene Composites 2

[0069] In a separate trial, FCCVD carbon nanotubes, carbon black 1, carbon black 2, and talc were each extruded with polypropylene at different concentrations. FIGS. 6A and 6B show the modulus and impact resistance at various additive loadings. The trend shows that the polypropylene composites with the CNT additive achieve higher modulus and impact resistance especially at the lower additive loadings compared to the polypropylene composites with the other additives.

Samples were also imaged to verily homogenous dispersion of the different additives inside the polypropylene matrix. FIGS. 7A and 7B are TEM images of a representative sample. As shown, both carbon black and carbon nanotubes were well dispersed in the polypropylene matrix.

Polyamide Composites

[0070] Carbon nanotubes from two different sources were blended with PA66 (ZYTEL, Celanese) by melt mixing in a similar manner to polypropylene. Blending was conducted with a Thermo Scientific™ Process 11 Parallel Twin-Screw Extruder at a feed rate of 20 g/min, a rotation rate of 300 rpm, and a temperature ramp to 270°C. Compositional data for the polyamide composites is summarized in Table 4.

Table 3

[0071] Specimens for mechanical testing were prepared by injection molding on an Xplore MC 15 HT micro-compounder having an IM 12 injection molder. The extruder for the injection molder was operated at 50 rpm and 290°C. Selected physical properties for injected molded samples based on D1-D6 and the control were determined according to the testing procedures provided hereinafter, and results are compiled in Table 5 below. Notched Izod Impact was determined by a method based on ASTM D256. Tensile testing was performed according to a method based on ASTM D638. yielding Young’s Modulus and strain at break values. Surface resistivity was determined according to a method based on ASTM D257. Table 4

[0072] FIGS. 8. 9, 10, and 11 are plots of surface resistivity, tensile modulus, tensile strength and flexural modulus, respectively, as a function of carbon nanotube loading in PA66. As shown, surface resistivity decreased rapidly with increased carbon nanotube loading, and tensile modulus and strength increased rapidly with increased carbon nanotube loading.

[0073] All documents described herein are incorporated by reference herein for purposes of all jurisdictions where such practice is allowed, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the disclosure be limited thereby. For example, the compositions described herein may be free of any component, or composition not expressly recited or disclosed herein. Any method may lack any step not recited or disclosed herein. Likewise, the term “comprising” is considered synonymous with the term “including.” Whenever a method, composition, element or group of elements is preceded with the transitional phrase “comprising.” it is understood that we also contemplate the same composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

[0074] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by one or more embodiments described herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. [0075] Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces.

[0076] One or more illustrative embodiments are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment of the present disclosure, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer's efforts might be time-consuming, such efforts would be, nevertheless, a routine undertaking for one of ordinary skill in the art and having benefit of this disclosure.

[0077] Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to one having ordinary skill in the art and having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present disclosure. The embodiments illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.

Claims

CLAIMS The invention claimed is:

1. A polymer composite comprising: a polymer matrix comprising at least one polymer; and a plurality of carbon nanotubes dispersed in the polymer matrix, wherein the carbon nanotubes comprise a plurality of carbon nanotube bundles that have not been de-agglomerated prior to dispersal in the polymer matrix.

2. The polymer composite of claim 1, wherein the polymer matrix is a polyolefin matrix comprising at least one polyolefin.

3. The polymer composite of claim 2, wherein the polymer composite comprises about 0.05 wt.% to about 10 wt.% carbon nanotubes and about 90 wt.% or greater polyolefin, each based on a total mass of the polymer composite.

4. The polymer composite of claim 2, wherein the at least one polyolefin comprises a polypropylene, a polyethylene, a copolymer thereof, or any combination thereof.

5. The polymer composite of claim 1, wherein the carbon nanotubes have a diameter of about 1 nm to about 1000 nm.

6. The polymer composite of claim 1 , wherein the carbon nanotubes have a length of about 1 pm to about 2000 pm.

7. The polymer composite of claim 1, wherein the carbon nanotubes have an aspect ratio of about 1000 or greater.

8. The polymer composite of claim 1, wherein the carbon nanotubes have one or more of the following properties: a bulk density of about 0.5 g/cm³ to about 2.5 g/cm³, a strain to failure ratio of about 0.5% to about 20.0%, a surface area of about 25 m²/g to about 1500 m²/g, a tensile strength of about 0. 1 GPa to about 4.0 GPa, a specific strength of about 1800 kN m/kg to about 2900 kN m/kg, or a strength modulus of about 1 GPa to about 400 GPa.

9. The polymer composite of claim 1, wherein the plurality of carbon nanotubes were produced by a floating catalyst chemical vapor deposition (FCCVD) process.

10. The polymer composite of claim 9, wherein the FCCVD process uses an iron-based catalyst.

11. A method comprising: providing a plurality of carbon nanotubes comprising a plurality of carbon nanotube bundles that have not been de-agglomerated; and dispersing the plurality of carbon nanotubes in a polymer matrix comprising at least one polymer to form a polymer composite.

12. The method of claim 11, wherein the polymer matrix is a polyolefin matrix comprising at least one polyolefin.

13. The method of claim 12, wherein the poly mer composite comprises about 0.05 wt.% to about 10 wt.% carbon nanotubes and about 90 wt.% or greater polyolefin, each based on a total mass of the polymer composite.

14. The method of claim 12, wherein the polyolefin matrix comprises a polypropylene, a polyethylene, a copolymer thereof, or any combination thereof.

15. The method of claim 11, further comprising: powdering the plurality of carbon nanotubes prior to forming the polymer composite.

16. The method of claim 11, wherein dispersing comprises melt mixing.

17. The method of claim 11, wherein the carbon nanotubes have a diameter of about 1 nm to about 1000 nm.

18. The method of claim 11, wherein the carbon nanotubes have a length of about 1 pm to about 2000 pm.

19. The method of claim 11, wherein the carbon nanotubes have an aspect ratio of about 1000 or greater.

20. The method of claim 11, wherein the carbon nanotubes have one or more of the following properties: a bulk density of about 0.5 g/cm³ to about 2.5 g/cm³, a strain to failure ratio of about 0.5% to about 20.0%, a surface area of about 25 m²/g to about 1500 m²/g, a tensile strength of about 0. 1 GPa to about 4.0 GPa, a specific strength of about 1800 kN m/kg to about 2900 kN m/kg, or a strength modulus of about 1 GPa to about 400 GPa.

21. The method of claim 11. w herein the plurality of carbon nanotubes were produced using a FCCVD process.

22. The method of claim 21, wherein the FCCVD processes uses an iron-based catalyst.

23. A polymer composite formed by the method of claim 11.