[0001] This invention relates to graphene nanoplatelets and composites comprising said nanoplatelets. This invention also relates to components comprising the composites. The invention also relates to methods of making the graphene nanoplatelets.

BACKGROUND

[0002] Plastics materials are often reinforced to provide composites with improved properties. One class of materials that can be used in such composites are nanomaterials. Typically this involves the solid combination of a bulk plastics matrix with nano-dimensional phase(s) differing in properties due to dissimilarities in structure and chemistry. The mechanical, electrical, thermal, optical and/or electrochemical properties of the composite will usually differ markedly from that of the component materials.

[0003] Various nanomaterials may be used, for example adding carbon nanotubes usually improves the electrical and thermal conductivity of the composite, while clay or mineral based nanomaterials may result in enhanced optical properties, dielectric properties, heat resistance or mechanical properties. Graphene represents another potential nanomaterial. For graphene to be used as a nanomaterial in a composite, it is import for sufficient quantities of the correct type of graphene to be readily available.

[0004] Quintana et al., J. Nanotechnol. 2014, 5, 2328-2338 describes solution based methods for forming graphene nanoplatelets. These however involve the use of organic solvents and / or surfactants, and the presence of stabilizing agents, which contaminates any resulting graphene nanoplatelets.

[0005] It is apparent that known methods of producing graphene nanoplatelets and the particles made by such processes are subject to a number of limitations. There is therefore a need for new methods of producing graphene nanoplatelets.

[0006] It is an aim of the invention to provide methods of producing high-quality graphene nanoplatelets and to provide such high-quality nanoplatelets. It is also an aim of the invention to provide such methods in a scalable and/or economic manner, for better commercial exploitation. It is also an aim of the invention to provide plastics composite materials comprising such graphene nanoplatelets.

BRIEF SUMMARY OF THE DISCLOSURE

[0007] The invention is based in part on the appreciation that plastics composite materials comprising particular types of graphene nanoplatelets would have excellent mechanical properties. We therefore provide the methods, graphene nanoplatelets, plastics composites and other materials and uses of the invention.

[0008] In accordance with a first aspect of the present invention there is provided a method of forming graphene nanoplatelets, comprising: (a) providing an aqueous suspension comprising expanded graphite; and (b) subjecting the suspension to exfoliation, wherein the exfoliation comprises sequential treatments of sonication and high shear mixing, thereby forming graphene nanoplatelets. The method optionally comprises isolating the graphene nanoplatelets from the suspension.

[0009] In an embodiment, the aqueous suspension comprises no organic solvents (e.g. the only solvent present may be water). In an embodiment, the aqueous suspension is a surfactant free aqueous suspension.

[0010] In an embodiment, the expanded graphite is provided at a concentration of about 0.1 % w/w to about 10% w/w of the aqueous suspension of step (a). The expanded graphite may be provided at a concentration of about 2% w/w to about 8% w/w of the aqueous suspension of step (a). The expanded graphite may be provided at a concentration of about 3% w/w to about 7% w/w of the aqueous suspension of step (a). The expanded graphite may be provided at a concentration of about 4% w/w to about 6% w/w of the aqueous suspension of step (a).

[0011] For example, the expanded graphite may be provided at a concentration of about 0.2% w/w to about 8% w/w (e.g. about 0.4% w/w to about 6% w/w, or about 0.5 to about 5% w/w) of the aqueous suspension of step (a). For example, the expanded graphite may be provided at a concentration of about 0.5% w/w to about 8% w/w (e.g. about 0.8% w/w to about 6% w/w, or about 1 % w/w to about 5% w/w) of the aqueous suspension of step (a). For example, the expanded graphite may be provided at a concentration of at least 0.1 % w/w, 0.2% w/w, 0.3% w/w, 0.4% w/w, 0.5% w/w, 0.6% w/w, 1 % w/w, 1.5% w/w, or 2% w/w (e.g. at least 0.5% w/w) of the aqueous suspension of step (a). For example, the expanded graphite may be provided at a concentration of not more than 8% w/w, 7% w/w, 6% w/w, or 5% w/w of the aqueous suspension of step (a).

[0012] In an embodiment the expanded graphite is provided at a concentration of about 2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, or about 8% w/w of the aqueous suspension of step (a).

[0013] In an embodiment the exfoliation is performed at a pressure of from about 1 to about 10 bar. The pressure may be from about 2 to about 7 bar. The pressure may be from about 3 to about 5 bar. In an embodiment the pressure may be from about 1 to about 6 bar.

[0014] In an embodiment the exfoliation is performed at a temperature of from about 5 °C to about 70 °C. For example, the exfoliation may be performed at a temperature of from about 5 °C to about 50 °C, e.g. from about 10 °C to about 40 °C. For example, the exfoliation may be performed at a temperature of from about 15 °C to about 30 °C.

[0015] In an embodiment, the sonication comprises treatment with at least one volumetric sonicator (T). In an embodiment, the sonication comprises treatment with at least one high power sonicator (F). In an embodiment, the sonication comprises treatment with at least one volumetric sonicator (T) and at least one high power sonicator (F). In an embodiment, the high shear mixing comprises mixing with a high shear mixer (S). In an embodiment, the at least one volumetric sonicator (T) provides a pretreatment prior to treatment with at least one high power sonicator (F) and/or at least one high shear mixer (S).

[0016] The exfoliation may comprise sequential treatment with at least one volumetric sonicator (T), at least one high power sonicator (F), and at least one high shear mixer (S). The sequential treatment may be selected from, for example, the following STFFS, TFF, TFFS, STSFF, TSFF, TTSFF, TFSTF, STFF and TFFSTFF.

[0017] In an embodiment, the at least one volumetric sonicator (T) comprises an output with an amplitude of at least 20 μηι (e.g. at least 30 μηι). The at least one volumetric sonicator (T) may comprise an output with an amplitude of not more than 50 μηι, e.g. an output of at least 20 μηι and not more than 50 μηι. The at least one volumetric sonicator (T) may comprise an output with an amplitude of not more than 40 μηι, e.g. an output of at least 20 μηι and not more than 40 μηι.

[0018] In an embodiment, the at least one volumetric sonicator (T) comprises a power output of at least 250 W and not more than 3500 W. The at least one volumetric sonicator (T) may comprise a power output of at least 500 W and not more than 2500 W.

[0019] In an embodiment the at least one high power sonicator (F) comprises an output with an amplitude of at least 40 μηι and not more than 150 μηι. For example, the at least one high power sonicator (F) may comprise an output with an amplitude of at least 50 μηι and not more than 100 μηι. In an embodiment, the at least one high power sonicator (F) comprises an output with an amplitude of at least 50 μηι. Without wishing to be bound by any theory, it is believed that the efficiency of exfoliation is related to the amplitude of the at least one high power sonicator (F), e.g. more efficient exfoliation may be provided by a high power sonicator (F) having an output with an amplitude of at least 50 μηι. [0020] In an embodiment, the at least one high power sonicator (F) comprises a power output of at least 1500 W and not more than 20000 W. For example, the at least one high power sonicator (F) may comprise a power output of at least 2000 W and not more than 16000 W. The power output of the at least one high power sonicator (F) is believed to relate to the production capacity and/or time required for the exfoliation. For example, a higher power output typically increases production capacity and/or reduces the time required for exfoliation.

[0021] In an embodiment the at least one volumetric sonicator (T) provides a frequency field for sonication of at least 20 and not more than 40 kHz. In an embodiment the at least one high power sonicator (F) provides a frequency field for sonication of at least 20 and not more than 40 kHz. In an embodiment the at least one volumetric sonicator (T) and at least one high power sonicator (F) each independently provide a frequency field for sonication of at least 20 and not more than 40 kHz.

[0022] In an embodiment, the exfoliation is performed for a period of from at least 1 hour to not more than 10 hours. The exfoliation may be performed for a period of from at least 2 hours to not more than 8 hours. The exfoliation may be performed for a period of from at least 3 hours to not more than 6 hours.

[0023] In an embodiment, the exfoliation is performed until the suspension reaches a viscosity of not more than about 500 cP (e.g. of not more than 250 cP). The exfoliation may performed until the suspension reaches a viscosity of not more than about 400 cP, e.g. of not more than 300 cP. The exfoliation may be performed until the suspension reaches a viscosity of not more than about 250 cP, e.g. of not more than 200 cP. In an embodiment, the exfoliation is performed until the suspension reaches a viscosity of from about 150 cP to about 250 cP (e.g. of about 200 cP).

[0024] In an embodiment, method comprises isolating the graphene nanoplatelets from the suspension. Isolating may comprise any suitable method for separating the suspended graphene nanoplatelets from the remainder of the aqueous suspension, for example filtration, centrifugation, and/or spray drying; optionally in combination with some form of pre- concentration (e.g. pre-filtration). In an embodiment the isolating comprises drying the graphene nanoplatelets. In an embodiment the isolating comprises spray drying the graphene nanoplatelets, optionally with pre-concentration of the graphene nanoplatelets prior to the spray drying.

[0025] In an embodiment, the graphene nanoplatelets have a thickness of not more than 30 nm. The graphene nanoplatelets may have a thickness of not more than 20 nm. The graphene nanoplatelets may have a thickness of not more than 15 nm. The graphene nanoplatelets may have a thickness of not more than 10 nm. The graphene nanoplatelets may have a thickness of not more than 8 nm. The graphene nanoplatelets may have a thickness of at least 5 nm (e.g. of at least 8 nm). The thickness of graphene nanoplatelets may be estimated based on the XRD data obtained for the (002) diffraction peak using the Scherrer equation. An exemplary method is set out in Andonovic et al, Journal of Chemical Technology and Metalurgy, 49, 6, 2014, pp 545-550, the content of which is incorporated herein by reference in its entirety.

[0026] In an embodiment, the graphene nanoplatelets have a lateral size of at least 0.5 μηι and not more than 100 μηι. The graphene nanoplatelets may have a lateral size of at least 1 μηι and not more than 50 μηι. For example, the graphene nanoplatelets may have a lateral size of at least 5 μηι and not more than 100 μηι, e.g. the graphene nanoplatelets may have a lateral size of at least 10 μηι and not more than 50 μηι. The graphene nanoplatelets may have a lateral size of at least 20 μηι and not more than 40 μηι. In an embodiment, the graphene nanoplatelets may have a thickness of not more than 20 nm and a lateral size of at least 5 μηι (e.g. at least 10 μηι) and not more than 50 μηι.

[0027] In an embodiment the graphene nanoplatelets have an aspect ratio (thickness / lateral size) of not more than 0.01. The graphene nanoplatelets may have an aspect ratio of not more than 0.005. The graphene nanoplatelets may have an aspect ratio of not more than 0.002. The graphene nanoplatelets may have an aspect ratio of not more than 0.001.

[0028] In an embodiment, the graphene nanoplatelets have a high platelet planarity. A high planarity in this context means a low concentration of defects, for example as measured by the Raman spectroscopy y\o ratio, where ID represents the signal for the Raman band associated with defects and IG represents the signal for the band associated with the typical vibration for the plane. An y\o ratio of less than 0.4 (e.g. less than 0.3, 0.2 or 0.1) may be considered indicative of high platelet planarity. For example, y\o ratio of less than 0.1 (e.g. less than 0.5) may indicate high platelet planarity.

[0029] In an embodiment, the graphene nanoplatelets have a specific surface area of from 40 m ² /g to 100 m ² /g. The graphene nanoplatelets may have a specific surface area of from 60 m ² /g to 80 m ² /g.

[0030] In an embodiment, the method of forming graphene nanoplatelets is a continuous flow process. In an embodiment, the method of forming graphene nanoplatelets is a batch process. [0031] In an embodiment, the expanded graphite used in the method of forming graphene nanoplatelets is expanded graphite formed according to a method of the second aspect.

[0032] A second aspect of the invention provides a method of forming an expanded graphite, comprising obtaining an expandable graphite and heating the expandable graphite in flowing gas at a temperature of at least 600 °C.

[0033] In an embodiment the expandable graphite that is converted to expanded graphite has an expansion ratio of at least 200 cm ³ /g and not more than 400 cm ³ /g. The expandable graphite may have an expansion ration of at least 250 cm ³ /g and not more than 350 cm ³ /g. For example, the expandable graphite may have an expansion ratio of about 300 cm ³ /g.

[0034] The flowing gas may be selected from air, nitrogen, argon and the like, and mixtures thereof. In an embodiment the flowing gas is selected from air, nitrogen and argon. The flowing gas may be air or nitrogen. The flowing gas may be air. The flowing gas may be nitrogen.

[0035] In an embodiment the expandable graphite is an intercalated expandable graphite. For example, the expandable graphite may be a sulphuric intercalated expanded graphite.

[0036] In an embodiment, the method of forming the expanded graphite is a continuous flow process.

[0037] The characteristics of a population of graphene nanoplatelets differ dependent on the specific method used to produce the graphene nanoplatelets. Accordingly, a third aspect provides graphene nanoplatelets having the properties of graphene nanoplatelets produced according to the method of the first aspect. A fourth aspect provides graphene nanoplatelets obtainable by the method of the first aspect. In an embodiment, the graphene nanoplatelets are obtained by the method of the first aspect.

[0038] The addition of graphene nanoplatelets of the invention, even at relatively small quantities, to plastics composites has surprisingly been found to provide significant improvements in mechanical properties (e.g. impact resistance). A fifth aspect therefore provides a plastics composite comprising the graphene nanoplatelets of the third or fourth aspect in an amount of at least 0.1 %wt.

[0039] In an embodiment, the graphene nanoplatelets are present in an amount of at least 0.2 %wt. The graphene nanoplatelets may be present in an amount of at least 0.5 %wt. The graphene nanoplatelets may be present in an amount of at least 1 %wt. The graphene nanoplatelets may be present in an amount of at least 2 %wt. In an embodiment, the graphene nanoplatelets are present in an amount of not more than 10 %wt. The graphene nanoplatelets may be present in an amount of not more than 8 %wt. The graphene nanoplatelets may be present in an amount of not more than 6 %wt. The graphene nanoplatelets may be present in an amount of not more than 5 %wt. In an embodiment, the graphene nanoplatelets are present in an amount of from 0.2 %wt to 8 %wt. The graphene nanoplatelets may be present in an amount of from 0.5 %wt to 7 %wt. The graphene nanoplatelets may be present in an amount of from 1 %wt to 6 %wt. The graphene nanoplatelets may be present in an amount of from 2 %wt to 5 %wt.

[0040] In an embodiment the plastics composite comprises a structural polymer selected from a thermoplastic, a thermoset, and a mixture thereof. The structural polymer may be or comprise at least one thermoplastic. The thermoplastic may be or comprise a polyamide, polyether sulfone, or phenoxy resin; for example the thermoplastic may be or comprise a polyamide or polyether sulfone. The polyamide may be a polyamide 6. The structural polymer may be or comprise at least one thermoset. The thermoset may be or comprise an epoxy resin. The epoxy resin may comprise bisphenol A epoxy and/or bisphenol F epoxy and/or phenol novolak epoxy resin and/or polyfunctional epoxy resin; for example the epoxy resin may comprise bisphenol A epoxy and/or bisphenol F epoxy and/or phenol novolak epoxy resin.

[0041] It is believed that plastics composites comprising both graphene nanoplatelets and conventional reinforcing agents have particularly good mechanical properties. Therefore, in an embodiment the composite further comprises a reinforcing agent. The reinforcing agent may be a fibre reinforcing agent. The reinforcing agent may be selected from any suitable organic, inorganic or natural fibre. For example, the reinforcing agent may be selected from glass fibre, carbon fibre, aramid fibre and basalt fibre; e.g. the reinforcing agent may be selected from glass fibre and carbon fibre.

[0042] In an embodiment, the reinforcing agent is present in an amount of from 5 %wt to 70 %wt. The reinforcing agent may be present in an amount of from 5 %wt to 50 %wt. The reinforcing agent may be present in an amount of from 10 %wt to 40 %wt.

[0043] A sixth aspect provides a vehicle or structure comprising a composite of the fifth aspect.

[0044] A seventh aspect provides use of graphene nanoplatelets of third or fourth aspect in a plastics composite. The plastics composite may have the features of a plastics composite of the fifth aspect as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a graphical (A) and a schematic (B) diagram indicating the numerical algorithm used for the hierarchical assessment of the overall response of the composite.

Figure 2 illustrates the effective stress-strain response of two-phase composites (structural plastic matrix and graphene nanoplatelets) under uniaxial loading plotted for aspect ratio variation (A) and volume fraction variation for aspect ratio 10 ^"3 (B).

Figure 3 illustrates the simulated effective stress-strain response of two-phase plastics composites (structural plastic matrix and graphene nanoplatelets) when modelled with an imperfect interface between the phases.

Figure 4 illustrates the effective stress-strain response for a three-phase plastics composite (structural plastic matrix, graphene nanoplatelets and fibre reinforcing agent. Figure 4(A) illustrates the results for thermoset structural polymer EM 120 with 0.78% graphene nanoplatelets (G2NAN) and 64% carbon fibres. Figure 4(B) illustrates the results for thermoplastic structural polymer PA6 with 1 % graphene nanoplatelets (G2NAN) and 35% short E-glass fibres.

Figure 5 provides a schematic diagram illustrating a method of the invention for producing graphene nanoplatelets.

Figure 6 provides SEM images illustrating the appearance of the carbon at various stages from its conversion from an expandable graphite (GIC) to expanded graphite and then graphene nanoplatelets.

Figure 7 illustrates the Young's modulus results obtained in both the flexural test (a) and tensile test (b) for EM thermoset without graphene nanoplatelets (neat) and with 2% graphene nanoplatelets (2% G2NAN, 2%AVA).

Figure 8 shows the increase in viscosity as a function of time during exfoliation of expanded graphite formed from expandable graphite IG6.

Figure 9 provides SEM images at different magnifications illustrating the morphology of plastics composite EM-120 + 2% graphene nanoplatelets.

Figure 10 provides SEM images at different magnifications illustrating the morphology of plastics composite EM-180 + 2% graphene nanoplatelets. Figure 1 1 provides optical microscopy images comparing the dispersion of EM- 120 + 2% graphene nanoplatelets after dispersion with a cowless system (a), high shear mixing after cowless (b), and comparison with reference sample EM-120 + 2% graphene nanoplatelets of Example 2.

Figure 12 illustrates the stress-strain relationship obtained for thermoplastic PA6 when neat, for the same thermoplastic as part of a plastics composite comprising graphene nanoplatelets (G2NAN or AVA).

Figure 13 illustrates the results obtained for compression testing of fibre reinforced composites.

Figure 14 illustrates the results obtained for interlaminar fracture toughness testing of fibre reinforced composites.

Figure 15 illustrates the results for the flexural test for samples of the glass fibre reinforced PA6 B3EG7 composite, neat and with 1 % graphene nanoplatelets (either G2NAN or AVA-0240). Both the flexural modulus in N/mm ² (a) and ultimate tensile strength in N/mm ² (b) are indicated.

Figure 16 illustrates the results for the tensile test for samples of the glass fibre reinforced PA6 B3EG7 composite, neat and with 1 % graphene nanoplatelets (either G2NAN or AVA-0240). Both the ultimate tensile strength in N/mm ² (a) and tensile energy in J (b) are indicated.

Figure 17 provides an illustration of the vehicle simulacra, (a) illustrates the assembled Omega simulacra, while (b) shows the outer shell and (c) illustrates the cross ribs.

DETAILED DESCRIPTION

[0046] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0047] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0048] All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

[0049] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0050] Aspect ratio, in particular in relation to graphene nanoplatelets, means the ratio of thickness / lateral size.

[0051] Table 1 defines a number of acronyms used herein:

Table 1 : List of acronyms

AFM Atomic-force Microscopy

ASTM American Society for Testing and Materials

FLGOxx Reference for exemplary graphene nanoplatelets (xx: Numbers for

different types)

BET Brunauer-Emmett-Teller

CF Carbon Fibres

D nonlinear elastic modulus

DCB double cantilever beam

DSC differential scanning calorimetry

EDS / EDX energy dispersive X-ray spectroscopy

DMA dynamic mechanical analysis

EG expanded graphite

E Young's modulus EMxxx epoxy matrix

(xxx; Numbers for different epoxy formulations, e.g 120 and 180)

EM 120 2/N, Two phase composite, where EM is the resin type; 2 is the %

graphene concentration by weight

EM 120 2/A

FAW fibre areal weight

FLG few layers graphene

FRP fibre reinforced polymer

FT-IR Fourier transform infrared spectroscopy

G2NAN exemplary graphene platelets, produced from IG6 (an exemplary

expandable graphite) by a method of the disclosure

GIC graphite intercalation compound (an exemplary expandable graphite)

Glc Mode-I interlaminar fracture toughness,

GO graphene oxide

GPLS graphene nanoplatelets

GRMs graphene related materials

IGx intercalated graphite precursor- (x: Numbers of different precursor)

LCA life cycle analysis

MPCs metal phthalocyanine

MLG multilayer graphene

OM optical microscope

PA6 Polyamide 6 (an exemplary thermoplastic polymer)

PSA particle size analysis

SEM scanning electron microscope

TEM transmission electron microscopy

Tg glass transition temperature

TGA thermo-gravimetric analysis

UD uni-directional

UTS ultimate tensile strength

XR X-ray

XRD X-ray powder diffraction

XRF X-ray fluorescence spectrometry

Simulations

[0052] The non-linear elastic moduli of the graphene sheet- re info reed polymer composites was computed using a combined molecular mechanics theory and continuum

homogenisation tools. Under uniaxial loading, linear and non-linear constitutive equations of the graphene sheet were derived from a Taylor series expansion in powers of strains such as σ = Εε + Όε ² with E and D the Young modulus and the nonlinear elastic modulus, respectively. Based on the modified Morse potential, the elastic moduli and Poisson's ratio were obtained for the graphene sheet leading to derivation of the non-linear stiffness tensor. For homogenisation purpose, the strain concentration tensor was computed by means of the irreducible decomposition of Eshelby's tensor for an arbitrary domain. Therefore, a mathematical expression of the averaged Eshelby's tensor for a rectangular shape was obtained for the graphene sheet. Under the Mori-Tanaka micro-mechanics scheme, the effective non-linear behavior was predicted for various micro-parameters (aspect ratio η = b/a and mass fractions).

[0053] In the second step, multiscale modelling techniques of hierarchical composites carbon fibres and E-glass fibres reinforced graphene polymer matrix were derived through analytical approaches. A detailed algorithm (Fig. 18) was developed accounting for material nonlinearities (rate-independency / dependency and damage initiation, as well as interfacial imperfection). As an input of the algorithm, the strain increment Δε computed from the analytical model was split between the matrix phase and inclusions. To this end, the Voigt assumption remained very useful to state the strain increment in the carbon fibres while an averaged technique expresses the strain increment in the graphene polymer matrix. Within the graphene polymer matrix which is a 2-phases composite, the strain increment at that level was always switched between the graphene inclusions and the polymer matrix. Mean- field homogenisation approaches were used to compute the overall properties of the graphene reinforced polymer composite, once the strain field was well equilibrated between phases. At the next step of the algorithm, these overall properties of the graphene reinforced polymer composite were used together with the consistent tangent operator of the carbon fibres to provide the whole composite with the global strain concentration tensor and finally the effective tangent modulus through a convergence checking. The output of the algorithm was the stress increment that describes the overall behaviour of the hierarchical composite. Based on the developed algorithm (Figure 1) numerical simulations were conducted on composites using the analysis cases of Table 2. As matrix phase, exemplary thermosets (epoxy matrices EM120, EM180) and exemplary thermoplastic (PA6) polymers were used, while graphene platelets GPLs (G2NAN) and short E-glass fibres as well as carbon fibres were considered as reinforcements.

Table 2: Analysis cases used in simulations for 2-phase composites (plastics matrix and graphene nanoplatelets) and 3-phase composites (plastics matrix, graphene nanoplatelets and fibre reinforcing agent) Analysis cases

Thermoset EM 121 + G2NAN (2%)

2-phase composites Thermoset EM 181 + G2NAN (2%)

Thermoplastic PA6 + G2NAN (1 %)

Thermoset EM121 + G2NAN (0.78%) + carbon fibres (64%)

Thermoset EM 181 + G2NAN (0.61 %) + carbon fibres (64%)

3-phase composites

Thermoplastic PA6 + G2NAN (1 %) + short E-glass fibres

(35%)

Thermoset EM 121 + G2NAN (0%) + carbon fibres (64%)

3-phase composites Thermoset EM 181 + G2NAN (0%) + carbon fibres (64%)

without graphene

Thermoplastic PA6 + G2NAN (0%) + short E-glass fibres

(35%)

[0054] Results illustrated in figure 2(A) show the analysis of variation of GPLs aspect ratio versus the effective stress strain behaviour. A high stiffer response was obtained for very low AR of the GPLs. Figure 2(B) illustrates the impact of GPLs volume fraction where it can be noticed that the composite response was enhanced with the increase of the volume fraction. In figure 3, an imperfect interface was modelled, which indicates a softening in the effective response. The results in figure 4 highlighted the contribution of high volume fraction of carbon fibres as well as short E-glass fibres in the studied 3-phase composite. For carbon fibres with a high volume fraction 64% (figure 4(A)), the effective response showed a trend similar to that of the fibres due to their high volume fraction; a nearly linear stress-strain response. However, for E-glass fibres composite (figure 4(B), a trend similar to that of the matrix was obtained since the mean volume fraction (35%) of short E-Glass fibres was used in the computation.

[0055] Also, the composite response, for all studied cases, was analysed with respect to the volume fraction of graphene nanoplatelets (e.g. G2NAN). In the composite without graphene nanoplatelets (e.g. G2NAN) i.e. 0% graphene nanoplatelets, a decrease in the overall behaviour was observed. In addition, the stress strain response for that case shifted quickly to a linear response with the increase of the fibres volume fraction. For all studied cases, the presence of graphene nanoplatelets showed significant impact on the

enhancement of the overall response.

Graphene Nanoplatelets

[0056] An embodiment provides graphene nanoplatelets. The graphene nanoplatelets may have a thickness of not more than 30 nm. The graphene nanoplatelets may have a thickness of not more than 20 nm. The graphene nanoplatelets may have a thickness of not more than 15 nm. The graphene nanoplatelets may have a thickness of not more than 10 nm. The graphene nanoplatelets may have a thickness of not more than 8 nm. The graphene nanoplatelets may have a thickness of at least 5 nm (e.g. of at least 8 nm). The thickness of graphene nanoplatelets may be estimated based on the XRD data obtained for the (002) diffraction peak using the Scherrer equation. An exemplary method is set out in Andonovic et al, Journal of Chemical Technology and Metalurgy, 49, 6, 2014, pp 545-550, the content of which is incorporated herein by reference.

[0057] The graphene nanoplatelets may have a lateral size of at least 0.5 μηι and not more than 100 μηι. The graphene nanoplatelets may have a lateral size of at least 1 μηι and not more than 50 μηι. For example, the graphene nanoplatelets may have a lateral size of at least 5 μηι and not more than 100 μηι, e.g. the graphene nanoplatelets may have a lateral size of at least 10 μηι and not more than 50 μηι. The graphene nanoplatelets may have a lateral size of at least 20 μηι and not more than 40 μηι. In an embodiment, the graphene nanoplatelets may have a thickness of not more than 20 nm and a lateral size of at least 5 μηι (e.g. at least 10 μηι) and not more than 50 μηι.

[0058] The graphene nanoplatelets may have an aspect ratio (thickness / lateral size) of not more than 0.01. The graphene nanoplatelets may have an aspect ratio of not more than 0.005. The graphene nanoplatelets may have an aspect ratio of not more than 0.002. The graphene nanoplatelets may have an aspect ratio of not more than 0.001. We have determined that graphene nanoplatelets with a low aspect ratio (e.g. an aspect ratio of not more than 0.01 or of not more than 0.005) can provide significant improvements in the mechanical properties of plastics composites, when included as a minor component in the composites.

[0059] The graphene nanoplatelets may have a specific surface area of from 40 m ² /g to 100 m ² /g. The graphene nanoplatelets may have a specific surface area of from 60 m ² /g to 80 m ² /g.

[0060] Graphene nanoplatelets of the disclosure may be produced from an expandable graphite (e.g. a graphite intercalation compound (GIC)) following the procedure outlined in figure 5. The expandable graphite may be (or be derived from) natural graphite (GN), synthetic graphite (GS) and intercalated expandable graphite (GIC) with different mesh and purity degree. This procedure outlined in figure 5 represents a continuous two-stage process, which can be used for large scale production of graphene nanoplatelets. The first phase of the two step process is the production of expanded graphite from an expandable precursor, with the second phase comprising exfoliation, converting the expanded graphite to graphene nanoplatelets. As illustrated in figure 5, the new process for nanoplatelet production involved a first phase of expansion of expandable graphite (e.g. a GIC) using continuous thermal shock and downstream a second phase exfoliation using combined ultrasound systems in a continuous working exfoliation plant. For the expansion phase, the continuous-flow system typically utilises heated gas at high temperature (e.g. a temperature of at least 650 °C), which rapidly expands the expandable graphite. The hot gas also acts as a transport vehicle for the expanded graphite obtained. The hot gas is typically air, although nitrogen or other gases (e.g. argon) may be used. The gas containing expanded material is typically merged within a cascade of sequential cyclone systems, this causes the material to cool and classifies the material according to particle size. This classification system provides separation of materials with a high degree of expansion (A Class, expanded graphite, typically over 95%) from material that is only partially expanded (B Class, typically less than 5%). [0061] This system provides a number of advantages. For example, it has a relatively low environmental impact, producing low quantities of waste material and is more energy efficient than other methods, such as the use of high temperature plasmas for expansion of expandable graphite. In addition, the process has a high rate of expansion efficiency and is readily scaled to provide industrial quantities of material.

[0062] The expanded graphite (EG) may then be exfoliated (figure 6). The exfoliation phase is generated in a closed circuit with recirculation of solvent (typically water, e.g.

without organic solvents and without surfactant), under pressure (typically set between 3 and 5 bars by a regulatory valve system) in which expanded material A is added up to a maximum concentration of 5% in weight (suspension), for example using a microdosing system. In the circuit the suspension is typically subjected to the combined action of different sonication and high shear in line mixer exfoliation devices arranged in series. In particular, it is advantageous to combine the simultaneous action of high specific power per volume unit sonicators (sonificators F), with volumetric or distributed power sonicators (sonicators T) and high shear inline systems (mixer S). The use of different combinations of these elements (sonificators F and T and mixers S) provide an high degree of exfoliation of materials (e.g. due to the resonance action in the graphitic structure and the mechanical shear stress field generated). For example, graphene nanoplatelets with a thickness lower than 10 nm, high planarity and low levels of defects may be readily obtained with a short time of treatment (typically from 3 to 5 hours, per suspension batch of 1000 liter of water). [0063] Typical configurations of the exfoliation method comprise 3 combined phases of work: pretreatment of materials with volumetric sonicator T (1), intensive treatment with sonicators F (2), intensive treatment with high shear mixer S (3), final treatment of finishing (4). The methods of the invention may comprise different configurations of the systems listed, in particular one or two systems T in series, 2 or 4 systems F and 2 systems S in different possible configurations (for example: TTSFF, TFSTF, STTFF, TFFSTFF, etc.). In these systems T and F would typically have different power outputs. Using such methods it is possible to obtain a high concentration suspension of graphene nanoplatelets (over 10% in weight equivalent to about 4.5% on dry volume). The upper limit regarding the amount (%wt) of nanoplatelets is governed by the viscosity parameters, with a maximum viscosity of about 500 cP. Above this viscosity level the sonicators do not work efficiently.

[0064] Typically, a sonicator F works on an amplitude of over 50 microns, until about 100 microns, with powers included between 2000 and 16000 Watt. A sonicator T typically has an amplitude lower than 50 microns and power output of between 500 and 2500 Watt. The frequency field used for both types of sonicator is typically between 20 and 40 kHz.

[0065] A collector system is used to recover the exfoliated material and separate it from solvent. Suitable collection systems include systems that comprise filtration, concentration methods and/or spray drying. For example, a suspension comprising the solvent and exfoliated material may be treated with a pre-filtration/concentration and subsequent drying system, or by using a spray drying system equipped with multiple material classification cyclones.

[0066] These methods typically provide high quality graphene nanoplatelets. For example, the graphene nanoplatelets may have a thickness of not more than 10 nm, a lateral size of at least 1 μηι and not more than 50 μηι, a specific surface area of at least 70 m ² /g, and high platelet planarity. In addition, the methods permit the production of significant quantities of these graphene nanoplatelets and other graphene nanoplatelets of the disclosure in a modest time, e.g. from 15 kg/day to 30 kg/day.

[0067] As the skilled person will appreciate, the expanded graphite may be obtained from the expandable graphite precursors in other manners than those illustrated in figure 5. For example, expandable graphite may be converted to expanded graphite using a microwave approach and such expanded graphite could be used as the input expanded graphite in the second phase (exfoliation) illustrated in figure 5. In addition, while GIC represent a preferred expandable graphite for use in the methods disclosed herein, other expandable graphite may also be used, for example the expandable graphite may be selected from GIC, metal phthalocyanine and carbon fibre.

[0068] The graphene nanoplatelets formed may be analysed using techniques that focus on the physical-morphological aspects (for example SEM, OM, XRD, PSA, BET) and/or chemical aspects (for example TGA, FT-I R, XRF, EDS). These techniques may also be used to analyse expandable graphite and expanded graphite.

[0069] The analytical results for a number of graphene nanoplatelets made in accordance with the methods of the disclosure are summarized in Table 3.

Table 3: Characterisation of graphene nanoplatelets

Composites

[0070] The disclosure relates to plastics composite loaded with graphene nanoplatelets of the disclosure. In relation to plastics composites, the structural polymer may act as a matrix, which may be loaded with the graphene nanoplatelets. The structural polymer may be any suitable thermoplastic or thermosetting polymer.

[0071] Exemplary plastics composites were prepared, using epoxy resin as an exemplary thermosetting polymer. Two exemplary systems of epoxy resin were developed, based on two main characteristics: (1) Epoxy matrix with a low viscosity and a glass transition temperature (Tg) of ca.120°C, after polymerisation (EM 120); (2) Epoxy matrix with medium/high viscosity and a glass transition temperature of ca.180°C after polymerisation (EM 180). While other resins could also be used, the choice of these structural polymers as exemplary epoxy matrices was based on the following main considerations: degree of homogenisation/dispersion of the various nanoparticles in graphene, in relation to the degree of viscosity of the pure resin; processability in terms of curing/activation/reaction of the epoxy resin after dispersion of graphene nanoparticles, in relation to the possible variation of viscosity and rheological behaviour of the epoxy system after the addition of graphene; different glass transition temperature (Tg), in view of automotive applications which may require operating temperatures up to 100°C (epoxy resin EM 120) or up to 160°C (epoxy resin EM180). The graphene derivatives used were the following: G2NAN; FLG01 1 (AVA); graphene oxide. The nanoparticles were typically dispersed in the resins using high shear mixing, however the dispersion could also be performed using other methods known to the skilled person, for example three roll mill or sonication mixing. When mixing industrial quantities (e.g. at least 20 kg of total material), particularly good results may be obtained by initial dispersion with a cowless system, followed by high shear mixing. Mixing may be made dry, solvent free, adding the graphene nanoplatelets powder to the polymeric resin.

[0072] The basic epoxy systems used were of Bisphenol A, which were activated through addition of curatives and accelerators, with the use of a laboratory mixer, under vacuum. After optimising the formulation through activation and reaction, the samples were cast in 10x10cm plates, thickness of 3mm, and cured according to the standard conditions and parameters of EM 120 and EM 180. Thermal analysis (DSC and DMA) were carried out, in order to compare the times and the reaction energies of the samples containing graphene, the rate of reaction and cure times, the glass transition temperatures and other properties. The mechanical properties of the polymers obtained were also tested. Specifically plates made from the same samples (10x10cm, 3mm thick) were subjected to a flexural test (per ASTM 790-03, the content of which is incorporated by reference herein in its entirety) and tensile test (ASTM D638-10, the content of which is incorporated by reference herein in its entirety).

[0073] Figure 7 illustrates the improvement in the results obtained in both the flexural test (figure 7(a)) and tensile test (figure 7(b)). In the flexural test the plastics composites comprising 2% graphene nanoplatelets of the disclosure (G2NAN nanoplatelets or AVA nanoplatelets) demonstrated a 5% and 7% improvement compared to the sample (neat) with 0% graphene nanoplatelets. In the tensile test, both graphene nanoplatelet containing composites showed an improvement of around 13%, as illustrated in figure 7(b). [0074] Exemplary plastics composites were prepared, using a nylon resin, such as polyamide 6 (PA6), as an exemplary thermoplastic polymer. Graphene nanoplatelets may be mixed with a thermoplastic resin during extrusion. Mechanical tests performed on plastics composites comprising thermoplastic structural polymer and graphene nanoplatelets of the disclosure demonstrated good mechanical properties, with improved (higher) Young's modulus compared to the neat thermoplastic structural polymer in tensile ASTM D638-10 and flexural ASTM 790-03 tests.

[0075] We have found that plastics composites comprising both graphene nanoplatelets of the disclosure and conventional reinforcing agents have particularly good mechanical properties. Plastics composites of the disclosure therefore may also comprise reinforcing agents. The reinforcing agent may be a fibre reinforcing agent. The reinforcing agent may be selected from any suitable organic, inorganic or natural fibre. For example, the reinforcing agent may be selected from glass fibre, carbon fibre, aramid fibre and basalt fibre; e.g. the reinforcing agent may be selected from glass fibre and carbon fibre. Plastics composites of the disclosure may also comprise other additives or components, such as antioxidants, fillers or other performance enhancers.

Structures

[0076] Plastics composites of the disclosure, due to their mechanical properties are suitable for use in structures. For example, plastics composites comprising graphene nanoplatelets of the disclosure and conventional reinforcing agents may be particularly suitable for use in vehicle (e.g. automotive) components, as demonstrated with automotive simulacra.

ANALYTICAL METHODS AND TESTING

Graphene nanoplatelets

[0077] SEM analysis was performed with a scanning electron microscope EVO MA10 Zeiss in secondary electron imaging. EDS analysis was performed using back scattered electrons (BSE) mode with INCA software. For the analysis, expandable graphite (e.g. GIC samples) were placed on carbon conductive tabs, while the graphene nanoplatelets were placed on a copper foil. Copper was especially useful for the EDS analysis, in order to distinguish the elements during the scan in BSE mode.

[0078] A LEICA microscope DM2500MH was used for optical microscopy in reflection mode. This was used to investigate the appearance of graphene nanoplatelets. Samples were dispersed in acetone with a mild sonication. A drop of the dispersion was placed on a laboratory glass. OM was performed after the evaporation of the solvent.

[0079] Particle size analysis (PSA) was performed with HELOS Sympatec with Sucell dispersion system. PSA was used with graphene nanoplatelet powders. The graphene nanoplatelets were dispersed in ethanol with Sucell ultrasound system.

[0080] The thermogravimetric analysis (TGA) was performed with SDT Q600 TA. The analysis were conducted on GIC samples from 25 °C to 1000 °C in air with an heating ramp of 10°C/min. For the analysis was used the quantity of about 8-10 milligrams for each GIC sample.

[0081] FT-IR analysis was performed with a PERKIN-ELMER MOD. GX. GIC samples and graphene oxide were studied. The analyses were conducted in transmission mode on KBr/Graphene pellets. The pellets were obtained by grinding and compressing (under vacuum) the dried powders of potassium bromide and graphene. The concentration of graphene was 1 %. The viscosity of the dispersion during the exfoliation process was monitored every hour with a Thermo Scientific Haake Viscotester 1 Plus.

Composite materials / structures

[0082] Compression testing was performed in accordance with ASTM D695M - 91. The size of specimens was 80.7x12.7 mm with material thickness of 3 mm. Specimens used to determine compressive strength were tabbed on each side with a distance of 4.7mm between tabs (gage length). Since the gage length was very short, it was impractical to mount instrumentation to measure strains.

[0083] Interlaminar fracture toughness (Mode-I) was measured in accordance with ASTM D5528 - 13. This test method describes the determination of the opening Mode-I interlaminar fracture toughness, Glc, of continuous fibre-reinforced composite materials using a double cantilever beam (DCB) specimen. This test method is limited to use with composites consisting of unidirectional carbon fibre and glass fibre tape laminates with brittle and tough single phase polymer matrices. The DCB consists of a rectangular, uniform thickness, unidirectional laminated composite specimen containing a non-adhesive insert on the mid-plane that served as a delamination initiator. Opening forces were applied to the DCB specimen by means of hinges or loading blocks bonded to one end of the specimen. Specimens were of 125 mm long and nominally from 20 to 25 mm wide. The ends of the specimens included a notch generated in the process of realisation of the sheet by the interposition of non-adhesive material of a thickness of 13μηι and 63mm. EXAMPLES

Graphene nanoplatelets

Example 1

[0084] IG6, an expandable graphite sample obtained from Faima, of nominal size 300 μηι, 95% carbon content and expansion ratio of 250 cc/g was expanded and exfoliated. FT-IR analysis of this expandable graphite revealed peaks in 1050 cm ^-1 (S=0 bond stretching), 1228 and 1655 cm ^"1 (CO and C = C bond stretching); 3400 cm ^"1 (OH bond stretching). The presence of CO bonds and OH indicate a partial oxidation of the graphite, confirming intercalation with sulfuric acid and nitric acid in the expandable graphite.

[0085] This expandable graphite presents a significant loss of weight after the expansion phase (about 40%). For this reason 16 kg of starting material was used to obtain about 10 kg total of final product. The continuous expansion system worked in about 3 hours on all 16 kg of graphite. The mean temperature generated in the expansion phase, was approximately 900 °C. This system provides a very strong thermal shock that causes the expandable graphite to expand very rapidly (e.g. immediately) to expanded graphite with negligible damage, because the residence time in the expansion zone is very short (a few seconds). The 10 kg of expanded graphite obtained premixed with 1000 liters of demineralised water (1 % concentration) prior to starting the exfoliation process, to ensure that all of the expanded material received the same treatment. For the exfoliation phase a configuration for intensive treatment was used, comprising mainly tip sonicators and with a system pressure to 23 bar. The system was worked in recirculation for about 6 hours with a power of 3000 Watt. Figure 8 shows the trend of the viscosity and temperature over time during the exfoliation. An increase of the viscosity is observed, according to a sigmoidal trend, especially in the range between 120 and 300 minutes. After 300 minutes the viscosity tends to stabilize according to a steady state trend, this implies that the maximum capacity of exfoliation was reached. The graphene nanoplatelets obtained in accordance with this example may be referred to herein as G2NAN nanoplatelets.

[0086] The processing parameters used were as follows:

PROCESS PARAMETERS

Expansion Continuous-flame

Temperature 650 °C

Gas Air

Precursors IG6

Amount of precursors 16 kg Total expansion Time 3 hour

Sonication Continuous system

Solvent Water

Amount of solvent 1000 It.

Configuration Intensive treatment

Concentration 1 %

Pressure 2-4 bar

Temperature 23-35 °C

Amplitude 100%

Power 3000 Watt

Total time exfoliation 6 hour

Graphene-based polymer composites (two-phase)

Example 2

[0087] Graphene nanoplatelets prepared according to Example 1 were mixed with epoxy resins EM-120 and EM-180 and formed into plastics composites. The nanoplatelets were mixed with the resin utilizing high-shear mixing. A high-shear mixer disperses, or transports, one phase or ingredient (liquid, solid, gas) into a main continuous phase (liquid), with which it would normally be immiscible. A rotor or impeller, together with a stationary component known as a stator, or an array of rotors and stators, is used either in a tank containing the solution to be mixed, or in a pipe through which the solution passes, to create shear. It is used in the adhesives, chemical, cosmetic, food, pharmaceutical, and plastics industries for emulsification, homogenization, particle size reduction, and dispersion. We identified a suitable geometry of high shear mixer for mixing Graphene Nanoparticles with resins. The tests with this equipment were carried out using the resin EM 120 preheated to 70 °C, after which the nanoplatelets in powder form were added until the mixture comprised 2% by weight nanoplatelets. When prepared in this manner, the EM-120 + 2% graphene nanoplatelets had a viscosity of 42 Pa.s at 25 °C and a viscosity of 1.17 Pa.s at 60 °C.

[0088] The composition could then be further processed using conventional methods to provide the plastics composites. Following these methods, sheets of composites of EM-120 + 2% graphene nanoplatelets (EM-120 + 2%) and EM-180 + 2% graphene nanoplatelets (EM-180 + 2%) were prepared. Morphological characterization analysis (SEM) of the cured composites was performed. In order to study nanoparticles dispersion and the interaction with the matrix, the samples were observed on a fractured section. Samples were fractured in nitrogen and metalized to make them conductive. The SEM images, illustrating the morphology at different magnifications, is illustrated in figure 9 for the EM-120 + 2% composite and in figure 10 for the EM-180 + 2%.

Example 3

[0089] A new method for mixing industrial batches (e.g. 20kg or greater) was developed. The mixing was split into two phases:

1) A first mixing phase of dispersion with cowless system (shaft mixing). This system allows you to quickly disperse the Graphene Nanoplatelets in the epoxy resin.

2) A second stage of homogenisation and distribution of the Nanoparticles with high shear mixing system. This system allows to homogenize the Graphene Nanoplatelets. The high shear breaks the agglomerates formed during the initial dry mixing. In this way also good distribution of Graphene is reached.

Using these two systems in sequence provided a reduction in overall mixing times, resulting in savings in energy consumption and expense. The level of dispersion obtained by this method were of similar quality to that obtained by the method of Example 2, as is indicated by figure 11 , which provides optical microscopy images comparing the results from this process (figure 1 1 (b)) for a dispersion of EM-120 + 2% graphene nanoplatelets with the equivalent dispersion prepared according to the method of Example 2.

Example 4

[0090] Graphene thermoplastic nanocomposites were prepared by melt compounding using several graphene nanoplatelets materials, specifically G2NAN prepared according to Example 1 and AVA graphene nanoplatelets, with unreinforced PA6 from BASF. These mixtures were carried out by dilution in Rondol 10 mm twin extruder of a previously prepared master-batch in AD30mm twin screw extruder. This procedure emulated typical industrial processing of these materials. The good degree of dispersion was confirmed by studied by SEM/EDX mappings. To study mechanical properties of these nanocomposites, tensile ASTM D638-10 and flexural ASTM 790-03 tests were used. We also calculated the Melt Flow Index (ISO 1133). Both graphene nanoplatelet materials, G2NAN and AVA improved the Young ^' s modulus of the neat polyamide in tensile test (figure 12), although elongation at the break point was smaller, comparing to neat polyamide. The use of G2NAN graphene nanoplatelets also enhanced the modulus without losing elongation in case of flexural test. Graphene-based polymer composites (three-phase)

Example 5

[0091] For three-phase plastics composites comprising thermosetting structural polymer, we impregnated UTS50(F13) carbon fibre, in uni-directional (UD) tape 600 mm wide, having 150gr/sqm FAW (Fibre Areal Weight ), with 36% by weight resin content. For the step of impregnation of the carbon fibres, we prepared five lots of resin, two with pure resin, three containing graphene nanoplatelets at the specified percentage by weight, as follows: EM 121- neat; EM121-GNAN 0.78%; EM 121 -A VA 0.78%; EM181-neat; and EM181-GNAN 0.61 %. EM 121 and EM 181 represented re-formulated versions of EM 120 and EM 180, with the re- formulation increasing the fluidity. Due to the low fluidity of the resins it was not possible to implement the hot melt process. Both resin systems, EM121 and EM 181 were hot melted and filmed on special paper substrates. The filmed resin quantities (g/sqm) were tuned to obtain the defined resin ration in the prepregs. Tables 4 and 5 below present the DSC and DMA analysis results.

Table 4: DSC values for all examined matrices

Table 5: DMA-T _a values for all examined matrices

Table 6: Impregnated materials for solid laminates

[0092] Preparing solid laminates for testing: The UD tapes mentioned above were used for the manufacturing of the following solid laminates, which were then subjected to mechanical characterisation. The laminates were cured under vacuum in autoclave, at the following conditions: positive pressure: 6 bars; heating rate: 2°C/min; Isotherm: 90 min; cooling rate: 2°C/min; curing temperature: 120°C (EM 121 laminates) and 180°C (EM 181 laminates).

[0093] Mechanical testing and characterisation: Compression testing is accordance with ASTM D695M and Interlaminar fracture toughness-Mode I testing in accordance with ASTM D5528 were performed, both of which are described herein in the "Analytical methods" section. The results for compression testing are given in figure 13. The results for interlaminar fracture toughness testing are given in figure 14.

Example 6

[0094] Automotive industry requirements are for high mechanical and impact strength properties. In an exemplary method of providing this, polyamide-6 reinforced with glass fibres (the PA6 B3EG7, obtained from BASF) was further improved by the addition of graphene nanoplatelets materials. Three different composites were studied (PA6 +35% E- glass fibres (neat); PA6 + 35% E-glass fibres+1 %G2NAN; PA6 +35% E-glass fibres

+1 %AVA-0240). The nanocomposites were produced by melt compounding in AD30mm twin screw extruder. Screw speed was 125 rpm, feeder speed 30 rpm and out pressure was 2,25 bar, with appropriated screw configuration to help dispersion and avoid agglomeration problems. Mechanical test (flexural and tensile) were carried out on each nanocomposite. The Melt Flow Index (ISO 1 133) was calculated and graphically represented. In flexural test, AVA-240 and G2NAN showed enhancement of Young ^' s modulus and UTS (Fig. 15a and b). AVA-240 improved, significantly, the strain and toughness values.

[0095] Similar behaviour was observed in case of tensile test; with significant

improvements in UTS, near to 20% (Fig. 16a) and over 1 15% in case of energy (Fig. 16b). Melt Flow Index (MFI) was significantly increased with the addition of both graphene nanoplatelets; which was related to an easier processability of the plastic. All the results related to the preparation and characterisation of GRM-PA6 reinforced composites indicated that the most suitable composites to be used as structural parts in automotive industry include PA6B3EG7-AVA240 and PA6B3EG7-G2NAN.

Example 7

[0096] Preparing automotive simulacra. Impregnated materials using the UD carbon fibres and EM polymer, as depicted in Table 4, were used to prepare the 3-phase composites solid laminates for manufacturing of the vehicle simulacra. The Omega shape beam, as shown in Fig. 17a, was used to represent a vehicle component. The mock sample was representative of some automotive parts destined for vehicle safety (anti-intrusion bars, components subject to impact, etc.). It was made of an outer "Omega shape" shell, reinforced by internal cross ribs. The outer shape (Fig.17b) was made using the thermosetting-based composites (UTS carbon fibres and EM charged graphene composites); while the ribs (Fig. 17c) were made using the thermoplastic-based composites (short E-glass fibres and PA6 charged graphene).

[0097] The outer shell was made of UTS50 carbon fibre UD tape, impregnated with EM 121 epoxy (36% wt), charged with 0.78% wt multilayers graphene with stacking sequence of (0°, +45°, -45°)s (6 layers with nominal thickness of 0.9mm). The shell was then cured under 10mbar vacuum with oven temperature of 145°C (isotherm for 60 min). After the treatment in the oven, the omega shape became solid and rigid enough, and fitted perfectly in the injection mould for the thermoplastic ribs. The injection of ribs made of PA6 thermoplastic material loaded with 2% wt of graphene was carried out through a horizontal press in the CRF area under the following conditions: Preheating of the mould: 80° C ; Injection temperature: 270 ° C; Duration: 3 sec. Three pieces were fabricated (1 outer shell only and 2 with cross ribs). The integration bonding of thermoplastic ribs with the outer shell made of carbon fibre/epoxy composites was robust. Without wishing to be bound by any theory, this was believed to be due to the injection temperature of PA6 (270°C) associated with duration (3 sec), which is presumed to induce a short glass transition on the surface/interface of the pre-cured epoxy shell, with greater compatibility in terms of bonding.