Abrasion resistance

Abstract

According to various, but not necessarily all, embodiments there is provided a coating composition for protecting a substrate. The composition comprising: a carrier medium; and polyhedral graphitised carbon particles.

Description

[0001] TITLE

[0002] Abrasion Resistance

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to abrasion resistance. Some relate to coating compositions for protecting a substrate from abrasion.

[0005] BACKGROUND

[0006] Coatings provide a interface between substrates of articles and the environment. This interface may provide a number of important properties such as corrosion prevention and chemical resistance. A key coating requirement in several environments such as construction, petrochemical, infrastructure or marine environments is protection from damage by abrasive materials such as sand, dirt, and chippings.

[0007] Mechanical damage to a coating may have both short and long-term deleterious effects. Short term effects may include loss of gloss and enhanced dirt pick up. Long term impacts may include enhanced mechanical breakdown; increased water and salt penetration resulting in corrosion, increased chemical attack, faster mechanical breakdown due to stress cracking on environmental exposure and greater build up and adhesion of biofilms on environmentally exposed surfaces.

[0008] Abrasive resistant coatings resist mechanical damage and so prolong the life of the coating and the substrate. The substrate could be for instance flooring, a bridge, a vehicle, decking, a storage tank, a concrete structure, a beam or a pipe. A coating is often applied to these substrates to provide protection from abrasion.

[0009] A number of abrasion resistant coatings are known, such as those including waxes, silicone-based agents, or colloidal silica. However, many of these known coatings do not provide adequate protection for the substrate, require a thick coat, or require multiple coats. The use of thicker coatings can cause significant stress within the coating, leading to microcracking and / or disbondment, which leads to further degradation in the performance or the coating. It is therefore desirable to provide improved abrasion resistant coatings to provide better protection of a substrate. BRIEF SUMMARY

[0010] According to various, but not necessarily all, examples there is provided a coating composition for protecting a substrate. The composition comprising: a carrier medium; and polyhedral graphitised carbon particles.

[0011] In some but not necessarily all examples, the polyhedral graphitised carbon particles are produced by flash joule heating of a carbon feedstock.

[0012] The polyhedral graphitised carbon particles may comprise aggregates of primary particles. The primary particles may comprise concentrically orientated stacked graphitic carbon layers. The primary particles may be substantially spherical.

[0013] The primary particles may comprise a hollow or amorphous core. The graphitic carbon layers may be concentrically orientated around the core. The graphitic carbon layers may be turbostratically stacked.

[0014] At least some of the primary particles may be fused with neighbouring primary particles. At least 50 wt.% of the primary particles may comprise 10 to 100 graphitic carbon layers.

[0015] The polyhedral graphitised carbon particles may have a D50 particle size of less than 30 pm. The polyhedral graphitised carbon particles may have a D50 particle size of less than 10 pm. The polyhedral graphitised carbon particles may have a D50 particle size of 0.2 to 6 pm.

[0016] The composition may comprise 0.01 wt.% to 10 wt.% of the polyhedral graphitised carbon particles.

[0017] The polyhedral graphitised carbon particles may have a specific surface area of 1 to 250 m2 / g. The polyhedral graphitised carbon particles may have a specific surface area of 5 to 150 m2 / g. The polyhedral graphitised carbon particles may have an average crystallinity of greater than 70%. The polyhedral graphitised carbon particles may comprise greater than 90 wt.% carbon.

[0018] The coating composition is for protecting a substrate from abrasion.

[0019] The carrier medium may comprise a crosslinking resin or a medium which may film form by air drying.

[0020] The carrier medium may comprise at least one of an epoxy resin, a thermosetting acrylic, a phenolic resin, chlorinated rubber, an aminoplast, a urethane, a carbamate, a polyester, an alkyd resin, coal tar epoxy, a polyaspartic resin, a polyurea resin, nonisocyanate resins formed by Michael addition, a silicone, a novolak, a polyurea, a silicate, a vinyl ester, a fluoropolymer, an unsaturated polyester, an organic or biobased solvent or mixtures and / or combinations thereof.

[0021] The coating composition may further comprise a dispersant, a defoamer, wetting agents, adhesion promoter and / or pigments / fillers.

[0022] According to various, but not necessarily all, examples there is provided an abrasionresistant coating system comprising a coating formed from the composition of any of the preceding claims, the coating being formed on a substrate.

[0023] The coating may have a dry film thickness of 25 microns to 200 microns. The system may comprise multiple layers of the coating. The substrate is metallic or non-metallic.

[0024] According to various, but not necessarily all, examples there is provided a method of coating a substrate comprising: applying the coating composition.

[0025] According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

[0026] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa.

[0027] BRIEF DESCRIPTION

[0028] Some examples will now be described with reference to the accompanying drawings in which:

[0029] FIG. 1 shows an SEM image of part of a polyhedral graphitised carbon particle;

[0030] FIG. 2 shows an SEM image of a polyhedral graphitised carbon particle;

[0031] FIG. 3 shows a graph illustrating the results of an abrasion test for various example compositions; and

[0032] FIG. 4 shows the a graph illustrating results of a further abrasion test for various example compositions.

[0033] The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0034] DETAILED DESCRIPTION

[0035] FIG. 1 shows an scanning electron microscope (SEM) image of part of a polyhedral graphitised carbon (PGC) particle 100 according to examples of the disclosure. FIG. 2 shows an SEM image of the entirety of a polyhedral graphitised carbon particle 100 according to examples of the disclosure. As can be seen from the respective scale bars, FIG. 2 is at a significantly larger scale than FIG. 1.

[0036] Examples of the disclosure provide a coating composition for protecting a substrate, the composition comprising: a carrier medium; and polyhedral graphitised carbon particles 100. In some examples, the coating composition is for protecting a substrate from mechanical damage, such as for protecting a substrate from abrasion. As can be seen in FIGs 1 and 2, the polyhedral graphitised carbon particles 100 comprise a 3D structure which is a multiloculate structure. The PGC particles 100 may exhibit a branched structure, and may exhibit a random structure. The PGC particles 100 comprise aggregates / clusters of primary particles 110. The PGC particles 100 may comprise agglomerates of the aggregates of primary particles 110. The primary particles 110 comprise concentrically orientated stacked graphitic carbon layers 120.

[0037] The polyhedral graphitised carbon particle 100 illustrated in FIGs 1 and 2 comprises a significant number of primary particles 110. In each of these figures only two of the primary particles 110 are labeled because labelling all of the primary particles 110 would obscure the image.

[0038] The primary particles 110 may be nanoparticles. The primary particles 110 can be substantially spherical and can comprise an onion like structure or a polyhedral structure. The primary particles 110 comprise a hollow or amorphous core 130. The graphitic carbon layers 120 are substantially concentrically orientated around the core 130. The graphitic carbon layers 120 are turbostratically stacked. As such, the graphitic carbon layers 120 are rotationally offset from layers 120 above or below. In some examples, the angle of rotational offset between successive layers may be approximately 20°.

[0039] The carbon layers 120 comprise basic structural units of crystalline graphitic domains, and the basic structural units may comprise several carbon layers 120. The primary particles 110 can be considered to comprise a gradient skin-core structure constructed from small graphitic like domains with a hollow or amorphous core 130. In some examples, the lateral size of a basic structural units may range from 2 nm to 100 nm.

[0040] In the illustrated examples, it can be seen that at least some of the primary particles 110 are fused with neighbouring primary particles 110. For example, on the far left in FIG. 2 it can be seen that a number of primary particles 110, including the two labeled primary particles 110, share the same outer graphitic carbon layers 120. The primary particles 110 are thus fused, have interconnected walls and are covalently bonded with neighbouring primary particles 110. The PGC particles 100 comprise layers I chains 120 of carbon atoms which pass through multiple primary particles 100. These can form complex chains 120 of a complex three dimensional structure which in some cases can extend through the majority of the length of the PGC particle 100.

[0041] In some examples, the polyhedral graphitised carbon particles 100 are produced by flash joule heating of carbon black, such as conductive carbon black. In other examples, other carbon feedstocks may be used, including recycled tyre carbon, coke, coal, and plastic waste. Flash joule heating is a high energy process where the temperature of a carbon feedstock is raised to approximately 3000° C through flash process steps. High voltage flashes may be passed though the carbon feedstock in a short time frame, with time frames ranging from less than 1 second to several seconds, heating the sample. This induces morphological changes in the carbon feedstock resulting in the restructuring of molecules and formation of ordered domains, i.e. graphitisation of the carbon feedstock. Flash joule heating is described in more detail in PCT International Application No. W02020 / 051000. When carbon black is flash joule heated, the carbon layers 120 graphitise. This graphitisation can be considered to be growth of the basic structural units.

[0042] In examples, the carbon feedstock is carbon black. It will be appreciated by someone skilled in the art that the use of different conductive carbon black particles as feedstock can lead to polyhedral graphitised carbon particles 100 with different properties, such as different sizes.

[0043] In some examples, at least 50 wt.% of the primary particles 110 comprise 5 to 250 graphitic carbon layers 120 and preferably 10 to 100 graphitic carbon layers 120. In some examples, the primary particles 110 have a D50 particle size of 5 to 250 nm, or 5 to 100 nm, or 15 to 30 nm as measured by SEM. In some examples, at least 50 wt.% of the PGC particles 100 comprise 100 to 1 ,000,000 primary particles 110.

[0044] In some examples, the polyhedral graphitised carbon particles 100 of the coating composition have a D50 particle size of less than 30 pm. Preferably, the polyhedral graphitised carbon particles 100 have a D50 particle size of less than 10 pm. Most preferably, the polyhedral graphitised carbon particles 100 have a D50 particle size of 0.2 to 6 pm. In other examples the PGC particles 100 have a D50 particle size of: less than 1 pm, less than 3 pm, less than 4 pm, less than 5 pm, less than 10 pm, less than 30 pm, 0.1 to 10 pm, 0.1 to 5 pm, 0.2 to 3 pm, 0.2 to 4 pm, 0.5 to 3 pm, or 1 to 3 pm. D50 particle sizes may be as measured by laser diffraction, such as using a Mastersizer 3000. In other examples D50 particle sizes may be as measured by SEM or as measure by transmission electron microscopy (TEM).

[0045] In some examples, the composition comprises 0.01 wt.% to 5 wt.% of the polyhedral graphitised carbon particles 100. In other examples, the composition comprises 0.001 wt.% to 10 wt.% 0.01 wt.% to 5 wt.%, 0.025 wt.% to 5 wt.%, 0.05 wt.% to 3 wt.%, 0.1% to 2% at least at least 0.03 wt.%, at least 0.05 wt.%, or at least 0.1 wt.% of PGC particles 100.

[0046] In some examples, the PGC particles 100 have a specific surface area of 0.5 to 500 m2 / g. Preferably, the PGC particles 100 have a specific surface area of 1 to 250 m2 / g or 5 to 150 m2 / g. Most preferably the PGC particles 100 have a specific surface area of 20 to 100 m2 / g. Specific surface area may be as measured using Brunauer- Emmett-Teller (BET) analysis.

[0047] In some examples, the polyhedral graphitised carbon particles 100 have an average crystallinity of greater than 70%. In other examples, the PGC particles 100 have an average crystallinity of greater than 50%, greater than 60%, or greater than 80%. Crystallinity values may be as measured by x-ray diffraction.

[0048] In some examples, the polyhedral graphitised carbon particles 100 comprise greater than 90 wt.% carbon. In other examples, the PGC particles 100 comprise greater than 80 wt.% carbon, greater than 95 wt.% carbon, or greater than 98 wt.% carbon. Determination of carbon content may be performed in accordance with ASTM D5291.

[0049] In some examples, the PGC particles 100 have a bulk density of 100 to 600 kg / m3, or 50 to 2000 kg / m3. The polyhedral graphitised carbon particles 100 are preferably homogeneously dispersed within the carrier medium.

[0050] In some examples, the carrier medium comprises a polymer. In some examples, the carrier medium comprises a curable resin, which may be in the form of a liquid curable resin. The carrier medium may comprise at least one of an epoxy resin, a thermosetting acrylic, a phenolic resin, chlorinated rubber, an aminoplast, a urethane, a carbamate, a polyester, an alkyd resin, coal tar epoxy, a polyaspartic resin, a polyurea resin, nonisocyanate resins formed by Michael addition, a silicone, a novolak, a polyurea, a silicate, a vinyl ester, a fluoropolymer, an unsaturated polyester, an organic or biobased solvent or mixtures and / or combinations thereof. The resin is generally present in the coating composition in the form of the resin precursor(s) (i.e., a curable resin), rather than the cured resin.

[0051] In some examples, the carrier medium comprises additional components as is conventional, such as dispersing agents, wetting agents, surfactants, solvents or water as an alternative media, adhesion promoters and / or rheology modifiers. The solvent may comprise an organic solvent such as xylene or butanol. The carrier medium may also comprise a surface wetting agent such as Tego ® Wet 270. The adhesion promoter may comprise an aminosilane or an epoxysilane (such as Addid ® 911). Alternatively, or additionally, the adhesion promoter may comprise a phosphate ester (such as Lubrizol ® 2061), a zirconate (such as Manchem ® 441), a titanate (such as Ken-React® KR® 12), or a chlorinated paraffin.

[0052] The example coating compositions described herein can be applied to a substrate where the substrate may be metallic, non-metallic or primer / undercoats of previously applied coatings , to provide a final abrasion resistant coating system once the carrier medium has cured and / or dried. In some examples, the coating compositions may be applied to the substrate using a drawdown bar, for example with the drawdown bar thickness set to 300 microns. In other examples, the coating compositions can be sprayed onto the substrate, or alternatively application may be made using roller or brush application. In some examples, the substrate is non-metallic (i.e. the bulk of the substrate is made from a non-metallic material, such as concrete, brick, wood or stone). In other examples, the substrate is metallic (i.e. the bulk of the substrate is made from a metallic material, such as steel or zinc). The substrate could be for instance flooring, a bridge, a vehicle, decking, a storage tank, a concrete structure, a beam or a pipe.

[0053] In some examples, only a single layer of the coating is applied to the substrate. In other examples, multiple layers of the coating are applied to the substrate.

[0054] Two examples of polyhedral graphitised carbons 100 are provided in table 1 below. The particle sizes were determined using laser diffraction.

[0055] After curing and / or drying, the polyhedral graphitised carbon particles 100 may be encased within the solidified carrier medium in the coating. Furthermore, the polyhedral graphitised carbon particles 100 be homogeneously dispersed through the solidified carrier medium. The applied coating may have a dry film thickness of 25 microns to 200 microns. Preferably, the coating has a dry film thickness of 25 to 125 microns. Most preferably, the coating has a dry film thickness of 25 to 75 microns. The dry film thickness values referred to herein are the mean values. The mean dry film thickness of the coating can be measured using an ultrasonic coating thickness gauge. When the coating is applied to ferrous substrates, electromagnetic induction or a magnetic pull-off gauge can also be used to measure the mean dry film thickness.

[0056] Experimental

[0057] Table 1

[0058] In two different experiments, the above example polyhedral graphitised carbons 100 were used in example coating compositions which were applied to substrates to provide example coatings. Experiment 1

[0059] Preparation of dispersions: For each of the two example polyhedral graphitised carbons 100, a 10% by weight dispersion of the PGC 100 was added to Epikote 828 epoxy resin and processed on a Exakt Three Roll Mill.

[0060] Dispersion formulations:

[0061] Coating formulation and manufacture: Each of the above dispersions was added to West 105 epoxy resin at 5%, to achieve a 0.5% loading of the PGC 100 in the epoxy part of formulation. Additionally a control coating composition was created by mixing 95% West 105 with 5% Epikote 828.

[0062] Table 4

[0063] The epoxy mixtures above were mixed on an orbital mixer for 3 minutes at 2000rpm, before addition of the two amine components, West 206 and Curamine 32-805. The final formulations tested are detailed in table 5 below:

[0064] Table 5

[0065] Films were applied using a 150 micron drawdown bar to onto 100mm * 100mm rigid steel panels achieve a dry film thickness range of 80 to 100 microns. Two sample panels were used for each composition.

[0066] Abrasion resistance testing was performed following ASTM D4060 - Standard Test Method for Abrasion Resistance of Organic Coatings using a Taber Abrader.

[0067] Coated test pieces were weighed on a 4 decimal point balance and placed on the abrasor. Samples were run for 100 cycles at 60rpm. Test pieces were removed and reweighed on 4d.p. balance. Wear index was then calculated for 1000 cycles.

[0068] Results:

[0069] Table 6 The results of this abrasion resistance testing is given in the table above. FIG. 3 shows a graph illustrating the results of an abrasion test for the example compositions.

[0070] It can be seen that both of the polyhedral graphitised carbon 100 containing compositions, composition 1 and composition 2, exhibited significantly less wear than the control composition.

[0071] It can also be seen that the coating of composition 2 containing PGC 2 exhibited significantly less wear than the coating of composition 1 containing PGC 1. The polyhedral graphitised carbon particles 100 of PGC 2 are smaller than the polyhedral graphitised carbon particles 100 of PGC 1. Thus, it appears that coatings containing the smaller PGC 2 particles 100 are more effective for abrasion resistance.

[0072] Experiment 2

[0073] Preparation of dispersions: The dispersion was formulated using the materials and wt.% seen in Error! Reference source not found.7. The initial mix of dispersant and cyrene solvent was mixed for 5 minutes on an overhead high-speed dispersal machine (HSD) at 850 RPM before addition of polyhedral graphitised carbon 100 material with hand mixing. This was then further mixed for 10 minutes at 900 RPM on the HSD. The mixture was then recirculated through a horizontal bead-mill containing 1.4 to 1.6 mm ZY-S beads (60% charge) for 15 minutes.

[0074] Table 7

[0075] Coating formulation and manufacture: The coating mixtures were prepared using an orbital mixer to blend the amine-acrylic, epoxy-acrylic and dispersion components together. The mixtures were mixed for 3 minutes at 2000 rpm. The final formulations tested are detailed in the table below:

[0076] Table 8

[0077] Coatings were applied using a 200-micron drawdown bar applied to 100m * 100m rigid steel panels for a functional dry film thickness range of 63±15 microns. Three sample panels were used for each composition.

[0078] Abrasion resistance testing was performed following ASTM D4060 - Standard Test Method for Abrasion Resistance of Organic Coatings using a Taber Abrader. The abrasion resistance test utilises CS-10 standardised abrasion test wheels with 1 kg weights attached to the test machine. The samples were subjected to a 100 cycle test with an RPM of 60 cycles / min. The wheels were then re-ground for 25 cycles at 60 cycles / min.

[0079] Results:

[0080] FIG. 4 shows a graph illustrating the results of an abrasion test for the example compositions.

[0081] It can be seen that both of the PGC 100 containing compositions exhibited significantly less wear than the control composition.

[0082] It can also be seen that the coatings of composition 5 and 6 containing PGC 2 exhibited significantly less wear than the coatings of compositions 3 and 4 containing PGC 1. The polyhedral graphitised carbon particles 100 of PGC 2 are smaller than the polyhedral graphitised carbon particles 100 of PGC 1. Once again indicating that the smaller PGC particles 100 are more effective for abrasion resistance. The coatings formed from the example coating compositions thus provides coatings that are highly resistant to abrasion. This advantage can be achieved using a relatively thin (i.e., low dry film thickness) coating when compared to known coatings, thereby requiring less of the coating material. Furthermore, the advantages can be achieved using a single coat, whereas known coating systems often utilise multiple coats or are used as a top coat to provide additional protection where primers and / or undercoats are present to provide additional substrate protection.

[0083] The increase in abrasion resistance caused by the PGC particles 100 is a surprising effect. Without being bound by theory, it is thought that is due to two effects. Firstly the presence of the PGC particles 100 and their crystalline structures increases the hardness of the coating, thus improvising the abrasion resistance. Secondly, other components of the coating, such as a resin, are mechanically trapped I entrained within the complex 3D structure of the PGC 100. This reduces the tearing of the components, such as reducing the tearing of a polymer. This may be caused by carbon chains I layers 120 of the PGC 100 passing through multiple primary particles 110, which means that the chains 120 are harder to pull out from the PGC particles 100 which improves tearing resistance.

[0084] The effect of the smaller PGC particles 100 being more effective for abrasion resistance is thought to be because for smaller particles 100 there is more particles 100 per weight and so there may be more entrainment / mechanical trapping of other components of the coating within the structure of the polyhedral graphitised carbon particles 100.

[0085] Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0086] Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims. Different carrier mediums could be used as required. For instance, the carrier medium could comprise water soluble polymers or emulsion polymers, which may be crosslinked as required. Particles of emulsion polymers are generally formed from very high molecular weight polymers, and the particles are generally not crosslinked with one another. However, if desired, polymer particles within emulsion coatings can be crosslinked using self-crosslinking reactions, such as keto-hydrazide crosslinking.

[0087] The coating composition may be applied to the substrate in a number of different ways, for instance using a brush, using a roller, or by spray coating. Types of spray coating include compressed air spray methods, high volume low pressure (HVLP) spraying methods or airless spray methods. The abrasion resistant coating may be used in combination with a different type of coating on the substrate.

[0088] The term coating composition used in relation to various examples herein could describe compositions prior to the addition of a curing agent, and also could describe compositions after the addition of a curing agent.

[0089] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0090] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0091] Features described in the preceding description may be used in combinations other than the combinations explicitly described above. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0092] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0093] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0094] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0095] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim:

Claims

CLAIMS1. A coating composition for protecting a substrate, the composition comprising: a carrier medium; and polyhedral graphitised carbon particles.

2. The coating composition of claim 1 , wherein the polyhedral graphitised carbon particles are produced by flash joule heating of a carbon feedstock.

3. The coating composition of claim 1 or 2, wherein the polyhedral graphitised carbon particles comprise aggregates of primary particles, wherein the primary particles comprise concentrically orientated stacked graphitic carbon layers.

4. The coating composition of claim 3, wherein the primary particles are substantially spherical.

5. The coating composition of claim 3 or 4, wherein the primary particles comprise a hollow or amorphous core, and wherein the graphitic carbon layers are concentrically orientated around the core.

6. The coating composition of claim 3, 4 or 5, wherein the graphitic carbon layers are turbostratically stacked.

7. The coating composition of any of claims 3 to 6, wherein at least some of the primary particles are fused with neighbouring primary particles.

8. The coating composition of any of claims 3 to 7, wherein at least 50 wt.% of the primary particles comprise 10 to 100 graphitic carbon layers.

9. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have a D50 particle size of less than 30 pm.

10. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have a D50 particle size of less than 10 pm.

11. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have a D50 particle size of 0.2 to 6 pm.

12. The coating composition of any of the preceding claims, wherein the composition comprises 0.01 wt.% to 10 wt.% of the polyhedral graphitised carbon particles.

13. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have a specific surface area of 1 to 250 m2 / g.

14. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have a specific surface area of 5 to 150 m2 / g.

15. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles have an average crystallinity of greater than 70%.

16. The coating composition of any of the preceding claims, wherein the polyhedral graphitised carbon particles comprise greater than 90 wt.% carbon.

17. The coating composition of any of the preceding claims, wherein the coating composition is for protecting a substrate from abrasion.

18. The coating composition according to any of the preceding claims, wherein the carrier medium comprises a crosslinking resin and / or a medium which may film form by air drying.

19. The coating composition according to any of the preceding claims, wherein the carrier medium comprises at least one of an epoxy resin, a thermosetting acrylic, a phenolic resin, chlorinated rubber, an aminoplast, a urethane, a carbamate, a polyester, an alkyd resin, coal tar epoxy, a polyaspartic resin, a polyurea resin, non-isocyanate resins formed by Michael addition, a silicone, a novolak, a polyurea, a silicate, a vinyl ester, a fluoropolymer, an unsaturated polyester, an organic or biobased solvent or mixtures and / or combinations thereof.

20. The coating composition of any of the preceding claims, wherein the coating composition further comprises a dispersant a defoamer, wetting agents, adhesion promoter and / or pigments / fillers.

21. An abrasion-resistant coating system comprising a coating formed from the composition of any of the preceding claims, the coating being formed on a substrate.

22. The abrasion-resistant coating system according to claim 21, wherein the coating has a dry film thickness of 25 microns to 200 microns.

23. The abrasion-resistant coating system according to claim 21 or 22, wherein the system comprises multiple layers of the coating.

24. The abrasion-resistant coating system according to any of claims 21 to 23, wherein the substrate is metallic or non-metallic.

25. A method of coating a substrate comprising: applying the coating composition of any of claims 1 to 20 to the substrate.

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