阅读说明：本技术 使用具有目标氧化水平的离散碳纳米管的屏蔽配制剂及其配制剂 (Shielding formulations using discrete carbon nanotubes with targeted oxidation levels and formulations thereof ) 是由 克莱夫·P·波斯尼亚 库尔特·W·斯沃格尔 于 2018-10-11 设计创作，主要内容包括：要求保护离散的个体化碳纳米管,其在管壁的内部和外部具有目标或选择性的氧化水平和/或含量。这种碳纳米管可以几乎没有或没有内管表面氧化,或者在管的内表面和外表面之间的氧化的量和/或类型不同。这些新的离散碳纳米管可用于电磁和射频屏蔽应用,尤其是在相对宽的频率范围内屏蔽基本上恒定的情况下。在弹性体、热塑性和热固性复合材料的配混和配制中可以使用添加剂如增塑剂以改善机械、电和热性能。(Discrete individualized carbon nanotubes are claimed having targeted or selective oxidation levels and/or levels both inside and outside the tube wall. Such carbon nanotubes may have little or no oxidation of the inner tube surface, or a difference in the amount and/or type of oxidation between the inner and outer surfaces of the tube. These new discrete carbon nanotubes are useful for electromagnetic and radio frequency shielding applications, especially where the shielding is substantially constant over a relatively wide frequency range. Additives such as plasticizers may be used in the compounding and formulation of elastomeric, thermoplastic and thermoset composites to improve mechanical, electrical and thermal properties.)

1. An electromagnetic shielding composition comprising a plurality of discrete carbon nanotubes and at least one magnetic metal and/or alloy thereof, wherein the discrete carbon nanotubes comprise an inner surface and an outer surface, the inner surface comprising an inner surface oxidizing species content and the outer surface comprising an outer surface oxidizing species content, wherein the inner surface oxidizing species content differs from the outer surface oxidizing species content by at least 20% and up to 100%.

2. The electromagnetic shielding composition of claim 1, wherein the inner surface oxidizing species content comprises from about 0.01 to less than about 0.8% by weight of the carbon nanotubes and the outer surface oxidizing species content comprises from greater than about 1.2% to about 3% by weight of the carbon nanotubes.

3. The electromagnetic shielding composition of claim 1, wherein the magnetic metal and/or alloy thereof is selected from the group consisting of iron, chromium, aluminum, uranium, platinum, copper, cobalt, lithium, nickel, neodymium, and samarium.

4. The electromagnetic shielding composition of claim 1, wherein the magnetic metal and/or alloy thereof comprises a metal and/or alloy oxide.

5. The composition of claim 1, wherein the discrete carbon nanotubes comprise a plurality of open ended tubes.

6. The composition of claim 1, wherein the plurality of discrete carbon nanotubes comprises a plurality of open-ended tubes.

7. The composition of claim 1, wherein the inner surface oxidizing species content is less than the outer surface oxidizing species content.

8. The composition of claim 1, wherein the inner surface oxidizing species content is at most 3 wt% relative to the weight of the carbon nanotubes.

9. The composition of claim 1, wherein the outer surface oxidizing species is present in an amount of about 1 to about 6 weight percent relative to the weight of the carbon nanotubes.

10. The composition of claim 1, wherein the inner surface oxidizing species content and the outer surface oxidizing species content total about 1 to about 9 weight percent relative to the weight of the carbon nanotubes.

11. The composition of claim 1, wherein the difference in oxidation of the inner and outer surfaces is at least about 0.2 wt.%.

12. The composition of claim 1, wherein the oxidizing species is selected from the group consisting of carboxylic acids, phenols, aldehydes, ketones, ether linkages, and combinations thereof.

13. The composition of claim 1, wherein the total oxidized species content of the inner and outer surfaces comprises about 1 to 15 weight percent of the carbon nanotubes.

14. The composition of claim 1, in the form of free-flowing particles.

15. The composition of claim 1, wherein the composition is further compounded with at least one rubber.

16. The composition of claim 1 or 2, wherein the composition further comprises at least one thermoplastic polymer, at least one thermoplastic elastomer, or a combination thereof.

17. The composition of claim 1, wherein the composition further comprises at least one thermoset polymer selected from the group consisting of epoxy, polyurethane, and combinations thereof.

18. A composition useful for treating contaminated groundwater comprising a plurality of discrete carbon nanotubes and at least one magnetic metal and/or alloy thereof, and at least one degrading molecule attached to an inner surface or an outer surface of at least a portion of the plurality of discrete carbon nanotubes, wherein the discrete carbon nanotubes comprise an inner surface and an outer surface, the inner surface comprising an inner surface oxidizing species content and the outer surface comprising an outer surface oxidizing species content.

19. A method of making the composition of claim 1, comprising the steps of:

a) selecting a plurality of discrete carbon nanotubes having an average aspect ratio of about 10 to about 500 and a total level of oxygenated species content of about 1 to about 15 weight percent,

b) suspending the discrete carbon nanotubes in an aqueous medium at a nanotube concentration of about 1 wt% to about 10 wt% to form an aqueous medium/nanotube slurry,

c) mixing the carbon nanotube/aqueous media slurry with at least one magnetic metal and/or alloy thereof at a temperature of about 30 ℃ to about 100 ℃ for a time sufficient to adhere the carbon nanotubes to the at least one magnetic metal and/or alloy thereof to form a wet nanotube/magnetic metal and/or alloy thereof mixture,

d) separating the aqueous medium from the wet carbon nanotube/magnetic metal and/or alloy mixture thereof to form a dry nanotube/magnetic metal and/or alloy mixture thereof, and

e) removing residual aqueous medium from the dried nanotube/magnetic metal and/or alloy mixture thereof by drying from about 40 ℃ to about 120 ℃ to form an anhydrous nanotube/magnetic metal and/or alloy mixture thereof.

20. The composition of claim 1, wherein the at least one magnetic metal and/or alloy thereof is bonded or attached to the plurality of discrete carbon nanotubes.

21. The composition of claim 1, wherein the plurality of discrete carbon nanotubes comprises multi-walled carbon nanotubes.

Technical Field

The present invention relates to shielding formulations using novel compositions of discrete carbon nanotubes having targeted oxidation levels and/or content, and formulations thereof such as with metal oxides and/or plasticizers. Shielding formulations include electromagnetic and radio frequency shielding applications.

Background

Carbon nanotubes can be classified by the number of walls in the tube: single wall, double wall and multi-wall. Currently, carbon nanotubes are manufactured as agglomerated nanotube spheres, bundles, or clumps that are attached to a substrate. The use of carbon nanotubes as reinforcing agents in elastomeric, thermoplastic or thermoset polymer composites is an area where carbon nanotubes are expected to have significant utility. However, the utilization of carbon nanotubes in these applications has been hindered due to the general inability to reliably produce individualized carbon nanotubes and the ability to disperse the individualized carbon nanotubes in a polymer matrix. Bosnyak et al in various patent applications (e.g., US2012-0183770a1 and US 2011-.

Disclosure of Invention

The present invention differs from those earlier Bosnyak et al applications and disclosures. The present invention describes compositions of discrete individualized carbon nanotubes having targeted or selective oxidation levels and/or content outside and/or inside the tube wall. The novel carbon nanotubes may have little or no oxidation of the inner tube surface, or a difference in the amount and/or type of oxidation between the inner and outer surfaces of the tube. These new discrete tubes are useful in many applications, including plasticizers, which can then be used as additives in the compounding and formulation of elastic, thermoplastic and thermoset composites to improve mechanical, electrical and thermal properties.

Other useful applications include electromagnetic interference (EMI) and Radio Frequency Interference (RFI) shielding applications. Currently, there are many developments in the electronics industry that require devices (e.g., phones and laptops) to operate in the frequency range of 1GHz-14 GHz to keep up with the high demands of data transmission. Electromagnetic interference (EMI) is interference that affects external sources of electrical circuitry, or vice versa. Electromagnetic shielding is the process of reducing the transmission of electromagnetic radiation that interferes with electronic circuits. EMI Shielding Effectiveness (SE) is measured in decibels (dB) and can be expressed in terms of power attenuation.

SE＝10log(Pi/Pt)

Where Pi is the incident power and Pt is the transmitted power. SE is the sum of three processes: reflection, absorption, and multiple reflections of incident electromagnetic waves. The reflection of radiation is due to the interaction of mobile charge carriers (electrons and/or holes) with the electromagnetic field. Absorption requires that the material have an electric or magnetic dipole that interacts with the electromagnetic field. Multiple reflections occur when radiation traverses two or more reflective interfaces.

Metals are known to have high EMI shielding effectiveness due to reflection of radiation, but are not good materials for applications such as mobile phones due to their weight, heat entrainment, and corrosion potential. Thin metal coatings are also mainly reflective and where many circuits are close together, cross talk can be problematic. More and more EMI shielding materials that absorb but do not reflect are preferred. Carbon-based polymer composites as the outer shell are most promising as lightweight, high strength composites with some shielding capability, which can be reinforced by metal flakes or fibers. However, in these discontinuous phase metal/carbon fiber-based composite materials, as the frequency increases above 2GHz, the shielding effectiveness rapidly decreases such that values of-10 dB/cm are common, and these composite materials also have relatively small absorption characteristics. With the increasing complexity and miniaturization of electronic components, shielding by metal housings is becoming increasingly difficult.

Typically, metals such as iron, chromium, aluminum, uranium, platinum, copper, cobalt, lithium, and nickel are magnetic in nature. Certain rare earth metals such as neodymium, samarium can form alloys for very strong permanent magnets. Their metal compounds and alloys, sometimes with various metals, are also magnetic in nature. For example, in the case of oxide compounds, the formation of magnetite Fe3O4 occurs by the following reaction: fe2+ +2Fe3+ +8OH- → 2Fe3O4+4H 2O. Magnetic particles having a diameter greater than about 1 micron, such as iron oxide Fe3O4, magnetite, are used at high loadings, for example greater than 70 wt% in silicone or acrylic media. These have good absorption characteristics above about 6GHz, typically up to-150 dB/cm at 25GHz, but typically have densities greater than 4g/ml and low strength or tear resistance. Workability may be so poor that plastic sheets are generally used on the surface thereof to provide workability without breakage. Therefore, there is a great unmet need for a wider band (2-50GHz) superabsorbent material with good strength or tear resistance resulting in improved handleability.

For particles smaller than a certain diameter, a further improvement of the absorption properties of the magnetic particles at frequencies smaller than 6GHz is expected, although not limited by this frequency range, so that superparamagnetism is observed. Superparamagnetic materials are so small that they consist of only one magnetic domain. For this reason, they are considered to absorb energy from an external electromagnetic field significantly more easily than compositions of the same but particles having a diameter of micrometers and above composed of multiple magnetic domains, because these multiple domains interfere not only with the external electromagnetic field but also with each other. Typical diameters of particles exhibiting superparamagnetism are less than 70 nanometers. However, these nanoscale particles are generally very difficult to disperse in their basic particulate state, and larger-scale agglomerates generally result in a reduction in the strength of the composite. Thus, there is a need to improve the dispersion of substantially magnetic particles having diameters less than about 70 nanometers in a host liquid matrix, such as but not limited to silicone, at room temperature or in a solid matrix, such as but not limited to a thermoplastic or thermoset polymer, at room temperature.

One embodiment of the present invention is an electromagnetic shielding composition comprising a plurality of discrete carbon nanotubes and at least one magnetic metal and/or alloy thereof, wherein the discrete carbon nanotubes comprise an inner surface and an outer surface, each surface comprising an inner surface oxidizing species content and an outer surface oxidizing species content, wherein the inner surface oxidizing species content differs from the outer surface oxidizing species content by at least 20% and up to 100%, preferably wherein the inner surface oxidizing species content is less than the outer surface oxidizing species content.

The inner surface oxidizing species content may be up to 3 wt% relative to the weight of the carbon nanotubes, preferably from about 0.01 to about 3 wt%, more preferably from about 0.01 to about 2 wt%, and most preferably from about 0.01 to about 0.8 wt% relative to the weight of the carbon nanotubes. Particularly preferred internal surface oxidizing species content is from 0 to about 0.01 weight percent relative to the weight of the carbon nanotubes.

The outer surface oxidizing species content may be from about 1 to about 6 weight percent relative to the weight of the carbon nanotubes, preferably from about 1 to about 4, more preferably from about 1 to about 2 weight percent relative to the weight of the carbon nanotubes. This is determined by comparing the external oxidizing species content of a given plurality of nanotubes relative to the total weight of the plurality of nanotubes.

The total content of the inner surface oxidizing species and the outer surface oxidizing species may be about 1 to about 9 wt% relative to the weight of the carbon nanotubes.

Another embodiment of the present invention is an electromagnetic shielding composition comprising a plurality of discrete carbon nanotubes and at least one magnetic metal and/or alloy thereof, wherein the discrete carbon nanotubes comprise an inner surface and an outer surface, each surface comprising an inner surface oxidizing species content and an outer surface oxidizing species content, wherein the inner surface oxidizing species content comprises from about 0.01 to less than about 0.8% relative to the weight of the carbon nanotubes and the outer surface oxidizing species content comprises from greater than about 1.2 to about 3% relative to the weight of the carbon nanotubes.

The discrete carbon nanotubes of any of the above composition embodiments preferably comprise a plurality of open-ended tubes, more preferably the plurality of discrete carbon nanotubes comprise a plurality of open-ended tubes. The discrete carbon nanotubes of any of the above composition embodiments are particularly preferred wherein the difference in oxidation of the inner and outer surfaces is at least about 0.2 wt.%.

The compositions described herein are useful as ion transport. Various classes or classes of compounds/drugs/chemicals that demonstrate this ion transport effect may be used, including ionic compounds, some non-ionic compounds, hydrophobic or hydrophilic compounds.

The novel carbon nanotubes and at least one magnetic metal and/or alloys thereof disclosed herein may also be used for groundwater remediation.

In all of the uses disclosed herein, the magnetic metal and/or alloy thereof is selected from the group consisting of iron, chromium, aluminum, uranium, platinum, copper, cobalt, lithium, nickel, neodymium and samarium. The magnetic metal and/or alloy thereof preferably comprises a metal and/or alloy oxide.

Compositions comprising the novel discrete target oxidized carbon nanotubes may also be used as components in or as sensors.

The compositions disclosed herein may also be used as components in drug delivery or controlled release formulations or as drug delivery or controlled release formulations.

In some embodiments, the compositions disclosed herein may be used as a component in or as a payload molecule delivery or drug delivery or controlled release formulation. In particular, various drugs, including small molecule therapeutics, peptides, nucleic acids, or combinations thereof, can be loaded onto the nanotubes and delivered to specific locations. Discrete carbon nanotubes can be used to help small molecules/peptides/nucleic acids that are impermeable to, or difficult to cross, cell membranes pass through the cell membrane into the interior of the cell. Once a small molecule/peptide/nucleic acid crosses the cell membrane, it can become significantly more effective. Small molecules are defined herein as having a molecular weight of about 500 daltons or less.

The pro-apoptotic peptide KLAKLAK is known to be cell membrane impermeable. By loading the peptide onto discrete carbon nanotubes, KLAKLAK is able to cross the cell membrane of LNCaP human prostate cancer cells and trigger apoptosis. The KLAKLAK-discrete carbon nanotube architecture can result in up to 100% of LNCaP-targeted human prostate cancer cell apoptosis. Discrete carbon nanotubes can also be used to deliver other small molecules/peptides/nucleic acids across the cell membrane of a variety of other cell types. The discrete carbon nanotubes may be configured to have a high loading efficiency, thereby enabling the delivery of higher amounts of drugs or peptides. In some cases, this transport across the cell membrane can be accomplished without the need for a targeting or permeation moiety to aid or effect the transport. In other cases, the discrete carbon nanotubes may be conjugated to targeting moieties (e.g., peptides, chemical ligands, antibodies) to help direct drugs or small molecules/peptides/nucleic acids to specific targets. Discrete carbon nanotubes alone are well tolerated and do not independently trigger apoptosis.

Peptides, small molecules, nucleic acids, and other drugs may be attached to the exterior of the discrete carbon nanotubes by van der waals forces, ionic bonds, or covalent bonds. As discussed, the level of oxidation can be controlled to promote specific interactions of a given drug or small molecule/peptide/nucleic acid. In some cases, a sufficiently small drug or peptide may be localized inside the discrete carbon nanotubes. The process of filling the interior of the discrete carbon nanotubes can be performed at a number of temperatures, including room temperature or below. In some cases, discrete carbon nanotubes may be filled to capacity with both small and large molecule drugs in as little as 60 minutes.

The payload molecule may be selected from the group consisting of a drug molecule, a radiotracer molecule, a radiotherapeutic molecule, a diagnostic imaging molecule, a fluorescent tracer molecule, a protein molecule, and combinations thereof.

Exemplary types of payload molecules that may be covalently or non-covalently associated with the discrete functionalized carbon nanotubes disclosed herein may include, but are not limited to, proton pump inhibitors, H2-receptor antagonists, cytoprotectants, prostaglandin analogs, beta blockers, calcium channel blockers, diuretics, cardiac glycosides, antiarrhythmics, antianginals, vasoconstrictors, vasodilators, ACE inhibitors, angiotensin receptor blockers, alpha blockers, anticoagulants, antiplatelet agents, fibrinolytics, hypolipidemics, statins, hypnotics, antipsychotics, antidepressants, monoamine oxidase inhibitors, selective 5-hydroxytryptamine reuptake inhibitors, antiemetics, anticonvulsants, anxiolytics, barbiturates, stimulants, amphetamines, benzodiazepines, dopamine antagonists, antihistamines, cholinergics, Anticholinergics, emetics, cannabinoids, 5-HT antagonists, non-steroidal anti-inflammatory drugs, opioids, bronchodilators, antiallergics, mucolytics, corticosteroids, beta-receptor antagonists, anticholinergics, steroids, androgens, antiandrogens, growth hormones, thyroid hormones, antithyroid drugs, vasopressin analogues, antibiotics, antifungals, antituberculosis drugs, antimalarial drugs, antiviral drugs, antiprotozoal drugs, radioprotectors, chemotherapeutic drugs, cytostatic drugs, and cytotoxic drugs such as paclitaxel.

Batteries comprising the compositions disclosed herein are also useful. Such batteries include lithium, nickel cadmium or lead acid types.

Formulations comprising the compositions disclosed herein may further comprise an epoxy, a polyurethane, or an elastomer. These formulations may be in the form of dispersions. The formulation may also include a nanosheet structure.

The composition may further comprise at least one hydrophobic material in contact with at least one interior surface.

The present invention relates to a composition comprising a plurality of discrete carbon nanotubes and a plasticizer, wherein the discrete carbon nanotubes have an aspect ratio of from 10 to about 500, and wherein the carbon nanotubes are functionalized with an oxygen species on the outermost wall surfaces thereof. The discrete carbon nanotubes comprise an inner surface and an outer surface, each surface comprising an inner surface oxidizing species content and an outer surface oxidizing species content, wherein the inner surface oxidizing species content comprises from about 0.01 to less than about 0.8% relative to the weight of the carbon nanotubes and the outer surface oxidizing species content comprises from greater than about 1.2 to about 3% relative to the weight of the carbon nanotubes. The oxygen species may include carboxylic acids, phenols, or combinations thereof.

The composition may further comprise a plasticizer selected from the group consisting of: dicarboxylic/tricarboxylic esters, trimellitates (timelites), adipates, sebacates, maleates, glycols and polyethers, polymeric plasticizers, biobased plasticizers, and mixtures thereof. The composition may comprise a plasticizer comprising a processing oil selected from the group consisting of: naphthenic oils, paraffinic oils, paraben oils, aromatic oils, vegetable oils, seed oils, and mixtures thereof.

The composition may further comprise a plasticizer selected from the group of water-insoluble solvents including, but not limited to, xylene (zylene), pentane, methyl ethyl ketone, hexane, heptane, ethyl acetate, ether, dichloromethane, dichloroethane, cyclohexane, chloroform, carbon tetrachloride, butyl acetate butanol, benzene, or mixtures thereof.

In yet another embodiment, the composition further comprises an inorganic filler selected from the group consisting of silica, nanoclay, carbon black, graphene, glass fibers, and mixtures thereof.

In another embodiment, the composition is in the form of free-flowing particles.

In another embodiment, the composition comprises a plurality of discrete carbon nanotubes and a plasticizer, wherein the discrete carbon nanotubes comprise from about 10 wt% to about 90 wt%, preferably from 10 wt% to 40 wt%, most preferably from 10 to 20 wt%.

Another embodiment is a method of forming a composition comprising discrete carbon nanotubes in a plasticizer, the method comprising the steps of: a) selecting a plurality of discrete carbon nanotubes having an average aspect ratio of about 10 to about 500 and a total level of oxygenated species content of about 1 to about 15 weight percent, b) suspending the discrete carbon nanotubes in an aqueous medium (water) at a nanotube concentration of about 1 to about 10 weight percent to form an aqueous medium/nanotube slurry, c) mixing the carbon nanotube/aqueous medium (e.g., water) slurry with at least one plasticizer at a temperature of about 30 ℃ to about 100 ℃ for a time sufficient to allow migration of the carbon nanotubes from the water to the plasticizer to form a wet nanotube/plasticizer mixture, e) separating water from the wet carbon nanotube/plasticizer mixture to form a dried nanotube/plasticizer mixture, and f) removing residual water from the dried nanotube/plasticizer mixture by drying from about 40 ℃ to about 120 ℃, to form an anhydrous nanotube/plasticizer mixture.

Another embodiment is a composition of discrete carbon nanotubes in a plasticizer further mixed with at least one rubber. The rubber may be natural rubber or synthetic rubber, preferably selected from the group consisting of natural rubber, polyisobutylene, polybutadiene and styrene-butadiene rubber, butyl rubber, polyisoprene, styrene-isoprene rubber, terpolymer ethylene propylene rubber, silicone, polyurethane, polyester-polyether, hydrogenated and non-hydrogenated nitrile rubber, halogen modified elastomers, fluoroelastomers and combinations thereof.

Another embodiment is a composition of discrete carbon nanotubes in a plasticizer further mixed with at least one thermoplastic polymer or at least one thermoplastic elastomer. The thermoplastic may be selected from, but is not limited to, acrylics, polyamides, polyethylenes, polystyrenes, polycarbonates, methacrylics, phenols, polypropylenes, polyolefins, such as polyolefin plastomers and elastomers, EPDM, and copolymers of ethylene, propylene, and functional monomers.

Another embodiment is a composition of discrete carbon nanotubes in a plasticizer further mixed with at least one thermosetting polymer, preferably an epoxy or polyurethane. The thermosetting polymer may be selected from, but is not limited to, epoxy, polyurethane or unsaturated polyester resins.

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions that describe specific embodiments of the present disclosure.

Drawings

Fig. 1 shows the UV spectrum of non-transparent water on top of Fe3O4 particles during washing.

Figure 2 depicts a micrograph showing particles attached to nanotubes.

Figure 3 depicts EMI shielding effectiveness of four polycarbonate compositions with and without MR.

Figure 4 shows the attenuation of NBR compounds with 5, 10 and 15% MR.

FIGS. 5A-C show the percent power transmission, reflection, and absorption in NBR compositions with 5, 10, and 15% MR.

Fig. 6 shows the TGA of Fe3O4 nanoparticles in an air protocol (air protocol).

Fig. 7 shows the TGA of the MR in an air scheme.

FIG. 8 shows TGA of MR/Fe3O4 in an air scheme at 70/30 weight ratio samples.

FIG. 9 shows TGA of MR/Fe3O4 in an air scheme at 50/50 weight ratio samples.

FIG. 10 shows TGA of MR/Fe3O4 in an air scheme at 25/75 weight ratio samples.

FIG. 11 shows TGA of MR/Fe3O4 in an air scheme at 10/90 weight ratio samples.

Detailed Description

In the following description, certain details are set forth, such as specific numbers, dimensions, etc., in order to provide a thorough understanding of the embodiments of the invention disclosed herein. It will be apparent, however, to one skilled in the art that the present disclosure may be practiced without these specific details. In many instances, details concerning such considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present disclosure and are within the skills of persons of ordinary skill in the relevant art.

Although most terms used herein are recognizable to those of ordinary skill in the art, it should be understood that when not explicitly defined, terms should be interpreted to take on the meanings that are currently accepted by those of ordinary skill. In the event that the term is constructed so that it is meaningless or substantially meaningless, then the definition should be taken from Webster's Dictionary, third edition, 2009. No definition and/or interpretation should be quoted from other related or unrelated patent applications, patents, or publications.

Functionalized carbon nanotubes of the present disclosure generally refer to chemical modification of any of the carbon nanotube types described above. These modifications may involve the nanotube ends, the sidewalls, or both. Chemical modifications may include, but are not limited to, covalent bonding, ionic bonding, chemisorption, intercalation, surfactant interactions, polymer encapsulation, cleavage, solvation, and combinations thereof. In some embodiments, the carbon nanotubes can be functionalized before, during, and after exfoliation.

In various embodiments, a plurality of carbon nanotubes comprising single-walled, double-walled, or multi-walled carbon nanotube fibers having an aspect ratio of about 10 to about 500, preferably about 40 to about 200, and an overall (total) oxidation level of about 1 wt% to about 15 wt%, preferably about 1 wt% to about 10 wt%, more preferably about 1 wt% to 5 wt%, more preferably about 1 wt% to 3 wt% are disclosed. The oxidation level is defined as the amount of oxidizing species covalently bonded to the carbon nanotubes by weight. The thermogravimetric analysis method for determining the weight percent of oxidized species on carbon nanotubes involves taking about 7-15mg of dried oxidized carbon nanotubes and heating from 100 degrees celsius to 700 degrees celsius at 5 degrees celsius per minute in a dry nitrogen atmosphere. The weight loss percentage of 200 to 600 degrees celsius is taken as the weight loss percentage of the oxidizing species. The oxidized species can also be quantified using Fourier transform infrared spectroscopy FTIR, particularly at 1730-^-1In the wavelength range of (1).

The carbon nanotubes can have an oxidizing species comprising a carboxylic acid or derivatized carbonyl-containing species and are substantially discrete individual nanotubes that are not entangled as a mass. Typically, the amount of discrete carbon nanotubes after the oxidation and shearing processes are completed is a large majority (i.e., multiple) and can be as high as 70%, 80%, 90%, or even 99% of the discrete carbon nanotubes, with the remaining tubes still partially entangled in some form. Most preferably, the nanotubes are fully converted (i.e., 100%) into discrete individualized tubes. The derivatized carbonyl species may include phenols, ketones, quaternary amines, amides, esters, acid halides, monovalent metal salts, and the like, and may vary between the inner and outer surfaces of the tube.

For example, one type of acid may be used to oxidize the tube outer surface, followed by water washing and inducing shear to break and separate the tube. If desired, the formed discrete tubes that are substantially free of (or have zero) oxidation of the inner tube wall can be further oxidized with different oxidants or even with the same oxidants as used for the outer wall surface of the tubes at different concentrations, resulting in different amounts and/or different types of internal and surface oxidation.

Carbon nanotubes made using metal catalysts such as iron, aluminum, or cobalt can retain a significant amount of the catalyst associated or entrapped within the carbon nanotube, up to 5 weight percent or more. These residual metals can be detrimental in applications such as electronics because corrosion enhances or can interfere with the vulcanization process in curing the elastomer composite. In addition, these divalent or multivalent metal ions can associate with carboxylic acid groups on the carbon nanotubes and interfere with discretization of the carbon nanotubes during subsequent dispersion processes. In other embodiments, the oxidized carbon nanotubes comprise a residual metal concentration of less than about 10000 parts per million (ppm), preferably less than about 5000 ppm. Metals can be conveniently determined using energy dispersive X-ray spectroscopy or thermogravimetric analysis.

The composition of discrete carbon nanotubes in a plasticizer can be used as an additive to various compounds and composites to improve mechanical properties, thermal and electrical conductivity. One example is as an additive in rubber compounds used in the manufacture of rubber components in oilfield applications with improved wear resistance, tear strength and thermal conductivity, such as seals, blowout preventers and drilling motors. Another example is as an additive in rubber compounds used in the manufacture of tires, seals and vibration dampers. By selecting suitable plasticizers, the additives can be used in the compounding and formulation of thermoplastics, thermosets and composites.

The carbon nanotubes produced are in the form of bundles or tangled agglomerates and can be obtained from different sources, such as CNano Technology, Nanocyl, Arkema and Kumho Petrochemical, to produce discrete carbon nanotubes. Carbon nanotubes can be prepared using an acid solution, preferably a nitric acid solution having a concentration greater than about 60 weight percent, more preferably greater than 65% nitric acid concentration. The mixed acid systems (e.g., nitric and sulfuric acids) disclosed in US2012-0183770a1 and US2011-0294013a1, the disclosures of which are incorporated herein by reference, can be used to produce discrete oxidized carbon nanotubes from fabricated bundled or entangled carbon nanotubes.

General method for producing discrete carbon nanotubes with targeted oxidation

A mixture of 0.5 to 5 wt%, preferably 3 wt% carbon nanotubes was prepared with CNano grade Flotube 9000 carbon nanotubes and 65% nitric acid. While stirring, the acid and carbon nanotube mixture was heated to 70 to 90 ℃ for 2 to 4 hours. The formed oxidized carbon nanotubes are then separated from the acid mixture. Several methods may be used to separate the oxidized carbon nanotubes including, but not limited to, centrifugation, filtration, mechanical pressing, decantation, and other solid-liquid separation techniques. The residual acid is then removed by washing the oxidized carbon nanotubes with an aqueous medium such as water, preferably deionized water, to a pH of 3 to 4. The carbon nanotubes are then suspended in water at a concentration of 0.5 to 4 wt.%, preferably 1.5 wt.%. By means of a device capable of generating 106 to 108 joules/m³The process equipment of energy density (c) subjects the solution to strong destructive forces generated by shear (turbulence) and/or cavitation. Equipment meeting this specification includes, but is not limited to, ultrasonic homogenizers, cavitators, mechanical homogenizers, pressure homogenizers, and microfluidizers (table 1). One such homogenizer is shown in U.S. patent 756,953, the disclosure of which is incorporated herein by reference. In shearingAfter treatment, the oxidized carbon nanotubes are discrete and individualized carbon nanotubes. Typically, based on a given starting amount of entangled, as-received and as-manufactured carbon nanotubes, a plurality of discrete oxidized carbon nanotubes, preferably at least about 60%, more preferably at least about 75%, most preferably at least about 95% and up to 100%, are produced from the process, with a few tubes, typically a large number of a few tubes, still entangled or not fully individualized.

Another illustrative method of preparing discrete carbon nanotubes is as follows: a mixture of 0.5 to 5 wt%, preferably 3 wt% carbon nanotubes was prepared with CNano Flotube 9000 grade carbon nanotubes and an acid mixture consisting of 3 parts by weight sulfuric acid (97% sulfuric acid and 3% water) and 1 part by weight nitric acid (65-70% nitric acid). The mixture was kept at room temperature while stirring for 3-4 hours. The formed oxidized carbon nanotubes are then separated from the acid mixture. Several methods may be used to separate the oxidized carbon nanotubes including, but not limited to, centrifugation, filtration, mechanical pressing, decantation, and other solid-liquid separation techniques. The acid is then removed by washing the oxidized carbon nanotubes with an aqueous medium such as water, preferably deionized water, to a pH of 3 to 4. The oxidized carbon nanotubes are then suspended in water at a concentration of 0.5 to 4 wt.%, preferably 1.5 wt.%. By means of a device capable of generating 106 to 108 joules/m³The process equipment of energy density (c) subjects the solution to strong destructive forces generated by shear (turbulence) and/or cavitation. Equipment meeting this specification includes, but is not limited to, ultrasonic homogenizers, cavitators, mechanical homogenizers, pressure homogenizers, and microfluidizers (table 1). After the shearing and/or cavitation process, the oxidized carbon nanotubes become oxidized discrete carbon nanotubes. Typically, based on a given starting amount of entangled carbon nanotubes as received and as manufactured, a plurality of discrete oxidized carbon nanotubes, preferably at least about 60%, more preferably at least about 75%, most preferably at least about 95% and up to 100%, are produced from the process, with a few tubes, typically a large number of few tubes, still entangled or not fully individualized.