DISPERSIONS

Abstract

A method of forming a liquid dispersion of 2D material/graphitic nanoplatelets in an aqueous solution is disclosed. The method comprises the steps of (1) creating a dispersing medium; (2) mixing the 2D material/graphitic nanoplatelets into the dispersing medium; and (3) subjecting the 2D material/graphitic nanoplatelets to sufficient shear forces and or crushing forces to reduce the particle size of the 2D material/graphitic nanoplatelets using a mechanical means. The liquid dispersion comprises the 2D material/graphitic nanoplatelets, at least one grinding media, water, and at least one wetting agent, and that the at least one grinding media is water soluble or functionalised to be water soluble.

Claims

1. A method of forming a liquid dispersion of 2D

1. A method of forming a liquid dispersion of 2D material/graphitic nanoplatelets in water or an aqueous solution comprising the steps of (1) creating a dispersing medium by mixing at least one grinding media, water and at least one wetting agent until the grinding media, water and wetting agent mixture is substantially homogenous, in which the at least one grinding media is water soluble or functionalised to be water soluble and comprises an aqueous solution of a modified aldehyde resin having at least one amine group; (2) mixing the 2D material/graphitic nanoplatelets into the dispersing medium; and (3) subjecting the 2D material/graphitic nanoplatelets to sufficient shear forces and or crushing forces to reduce the particle size of the 2D material/graphitic nanoplatelets using a mechanical means characterised in that the liquid dispersion comprises the 2D material/graphitic nanoplatelets, the at least one grinding media, the water, and the at least one wetting agent, in which the 2D material/graphitic nanoplatelets are comprised of one or more of graphene nanoplatelets, graphitic nanoplatelets, and 2D material nanoplatelets and in which the graphene nanoplatelets are comprised of one or more of graphene nanoplates, reduced graphene oxide nanoplates, bilayer graphene nanoplates, bilayer reduced graphene oxide nanoplates, trilayer graphene nanoplates, trilayer reduced graphene oxide nanoplates, few-layer graphene nanoplates, few-layer reduced graphene oxide nanoplates, and graphene nanoplates of 6 to 10 layers of carbon atoms, and the graphitic nanoplatelets are comprised of graphite nanoplates with at least 10 layers of carbon atoms, the graphitic nanoplatelets are comprised of one or more of graphite nanoplates with 10 to 20 layers of carbon atoms, graphite nanoplates with 10 to 14 layers of carbon atoms, graphite nanoplates with 10 to 35 layers of carbon atoms, graphite nanoplates with 10 to 40 layers of carbon atoms, graphite nanoplates with 25 to 30 layers of carbon atoms, graphite nanoplates with 25 to 35 layers of carbon atoms, graphite nanoplates with 20 to 35 layers of carbon atoms, or graphite nanoplates with 20 to 40 layers of carbon atoms, and the 2D material platelets are comprised of one or more of hexagonal boron nitride (hBN), molybdenum disulphide (MoS.sub.2), tungsten diselenide (WSe.sub.2), silicene (Si), germanene (Ge), Graphyne (C), borophene (B), phosphorene (P), or a 2D in-plane or vertical heterostructure of two or more of the aforesaid materials.

2. (canceled)

3. A method according to claim 1 in which the 2D material/graphitic nanoplatelets comprises at least one 1D material.

4. (canceled)

5. A method according to claim 1 in which the at least one wetting agent comprises one of a polymeric wetting agent, an ionic wetting agent, a polymeric non-ionic dispersing and wetting agent, a cationic wetting agent, an amphoteric wetting agent, a Gemini wetting agent, a highly molecular resin-like wetting and dispersing agent or a mixture of two or more of these wetting agents.

6. (canceled)

7. (canceled)

8. A method according to claim 1 in which the at least one wetting agent is stored in a liquid form.

9. A method according to claim 1 in which the at least one wetting agent is stored as a solid, and the step of creating a dispersing medium comprises (i) mixing the at least one grinding media, water and wetting agent until the wetting agent is dissolved and the grinding media, water and wetting agent mixture is substantially homogenous.

10. A method according to claim 1 in which the at least one wetting agent is added to the dispersing medium at substantially the same time as the 2D material/graphitic platelets.

11. A method according to claim 1 in which the step (3) of subjecting the 2D material/graphitic nanoplatelets to sufficient shear forces and or crushing forces to reduce the particle size of the 2D material/graphitic nanoplatelets is performed using one or more of a dissolver, a bead mill, or a three-roll mill.

12. A liquid dispersion characterised in that the liquid dispersion comprises 2D material/graphitic nanoplatelets, at least one grinding media, water, and at least one wetting agent, and in which the at least one grinding media is water soluble or functionalised to be water soluble and comprises an aqueous solution of a modified aldehyde resin having at least one amine group, in which the 2D material/graphitic nanoplatelets are comprised of one or more of graphene nanoplatelets, graphitic nanoplatelets, and 2D material nanoplatelets and in which the graphene nanoplatelets are comprised of one or more of graphene nanoplates, reduced graphene oxide nanoplates, bilayer graphene nanoplates, bilayer reduced graphene oxide nanoplates, trilayer graphene nanoplates, trilayer reduced graphene oxide nanoplates, few-layer graphene nanoplates, few-layer reduced graphene oxide nanoplates, and graphene nanoplates of 6 to 10 layers of carbon atoms, and the graphitic nanoplatelets are comprised of graphite nanoplates with at least 10 layers of carbon atoms, the graphitic nanoplatelets are comprised of one or more of graphite nanoplates with 10 to 20 layers of carbon atoms, graphite nanoplates with 10 to 14 layers of carbon atoms, graphite nanoplates with 10 to 35 layers of carbon atoms, graphite nanoplates with 10 to 40 layers of carbon atoms, graphite nanoplates with 25 to 30 layers of carbon atoms, graphite nanoplates with 25 to 35 layers of carbon atoms, graphite nanoplates with 20 to 35 layers of carbon atoms, or graphite nanoplates with 20 to 40 layers of carbon atoms, and the 2D material platelets are comprised of one or more of hexagonal boron nitride (hBN), molybdenum disulphide (MoS.sub.2), tungsten diselenide (WSe.sub.2), silicene (Si), germanene (Ge), Graphyne (C), borophene (B), phosphorene (P), or a 2D in-plane or vertical heterostructure of two or more of the aforesaid materials.

13. (canceled)

14. A liquid dispersion according to claim 12 in which the 2D material/graphitic nanoplatelets comprises at least one 1D material.

15. (canceled)

16. A liquid dispersion according to claim 12 in which the wetting agent is comprised of one of a polymeric wetting agent, an ionic wetting agent, a polymeric non-ionic dispersing and wetting agent, a cationic wetting agent, an amphoteric wetting agent, a Gemini wetting agent, a highly molecular resin-like wetting and dispersing agent or a mixture of two or more of these wetting agents.

17. A liquid dispersion according to claim 12 manufactured using a method according to claim 1.

18. A liquid coating composition comprising a liquid dispersion according to claim 12.

Description

DETAILED DESCRIPTION

Examples

[0083] Typical formulations of dispersions according to the present invention are set out in tables 1 and 2 below:

[0084] All dispersions were manufactured on an Eiger Torrance 250, horizontal beadmill. Dispersions were milled for 15 minutes on recirculation mode at maximum speed.

[0085] Characterisation of Dispersions

[0086] Particle size was measured on a Mastersizer 3000 to determine the effectiveness of the grinding resin and dispersant in deagglomeration and particle size reduction.

[0087] Viscosity was measured to aid understanding of the rheological properties of the dispersion. This was done using a Kinexus Rheometer.

[0088] Storage stability was determined through the use of a Turbiscan Stability Analyser. Turbiscan stability index (TSI) is a relative measure of stability, which allows comparison of multiple samples. As a relative measure, it allows for a quantifiable assessment of closely related formulations.

[0089] Stability tests were carried out at ambient and elevated temperature (40 C).

TABLE-US-00001 TABLE 1 Component % by weight A-GNP35 0.5 Surfynol 104 0.1 Water 29.82 Laropal LR9008 69.58

TABLE-US-00002 TABLE 2 Component % by weight A-GNP10 10 Surfynol 104 2 Water 26.4 Laropal LR9008 61.6

[0090] Graphitic material A-GNP10 is commercially available from Applied Graphene Materials UK Limited, UK and comprises graphite nanoplatelets of between 25 and 35 layers of atoms thick. The graphite nanoplatelets are supplied as a powder and are generally aggregated into clumps of nanoplatelets.

[0091] Graphene/graphitic material A-GNP35 is commercially available from Applied Graphene Materials UK Limited, UK and comprises graphene/graphite nanoplatelets of between 5 and 15 layers of atoms thick. The graphite nanoplatelets are supplied as a powder and are generally aggregated into clumps of nanoplatelets.

[0092] Each of the dispersions was made up using the following steps:

[0093] 1 To the water the Surfynol 104 and Laropal LR9008 were added. This was stirred until the mixture was substantially homogenous;

[0094] 2 The A-GNP-10 or A-GNP-35 was added to the mixture and stirred until the powder was evenly dispersed in the mixture;

[0095] 3 The mixture was bead milled for 15 minutes recirculation in a bead mill using beads.

DISCUSSION

[0096] Graphene (A-GNP10) Dispersed in Water Only

[0097] A-GNP10 was dispersed in water at four different concentrations: 0.1, 1, 5 and 10%. Samples were stored for 4 weeks under ambient conditions.

[0098] Samples at 5 and 10% sedimented within 2 to 3 days of manufacture

[0099] Samples at 0.1 and 1% had not yet visibly sedimented, 4 weeks after manufacture.

[0100] The degree of heavy sedimentation seen in 5 and 10% weight additions of graphene (A-GNP10), raised the need to identify a suitable pigment dispersing resin (i.e. grinding media) and/or surfactant (i.e. wetting agent) to improve shelf life and storage stability of the product.

[0101] Graphene (A-GNP10) Dispersed in Water Comprising a Dispersing Resin (i.e. Grinding Media)

[0102] Dispersions Tested

[0103] 10% A-GNP10 was dispersed into a range of media, with increasing loadings of the grinding media Laropal LR9008: [0104] 1. Water only [0105] 2. 10% Laropal 90% water blend [0106] 3. 20% Laropal 80% water blend [0107] 4. 30% Laropal 70% water blend [0108] 5. 40% Laropal 60% water blend [0109] 6. 50% Laropal 50% water blend

[0110] Viscosity of Aqueous Dispersions of A-GNP10

[0111] All dispersions had a very low viscosity (less than 1 PaS), as shown in table 3 below. Overall, there were no significant changes to the rheological profile of these dispersions. However, the dispersion of 10% Laropal LR9008 and 90% water showed particularly high viscosity.

TABLE-US-00003 TABLE 3 Viscosity of Aqueous Dispersions of A-GNP10 10% A-GNP10 in: Viscosity (Pa .Math. s) Water only 0.024 10% Laropal + 90% 0.32 Water 20% Laropal + 80% 0.0063 Water 30% Laropal + 70% 0.026 Water 40% Laropal + 60% 0.013 Water 50% Laropal + 50% 0.0094 Water

[0112] Particle Size Distribution of Aqueous Dispersions of A-GNP10

[0113] Particle size distribution was monitored for all samples, the results of which are shown in table 4 below. With the exception of the dispersion with 10% loading of Laropal, all dispersions showed a D90 in the range of 15-25 microns.

TABLE-US-00004 TABLE 4 Particle Size Distribution of Aqueous Dispersions of A-GNP10 % Laropal D10 D50 D90 Wafer only 0.258 1.98 14.8 10% Laropal + 90% 1.04 6.63 42.4 Wafer 20% Laropal + 80% 0.486 3.63 23.2 Water 30% Laropal + 70% 0.349 2.33 15.2 Water 40% Laropal + 60% 0.402 3.35 18.2 Wafer 50% Laropal + 50% 0.342 2.55 15 Water

[0114] Storage Stability of Aqueous Dispersions of A-GNP10

[0115] Samples were tested at ambient and elevated temperature (40° C.). In general, addition of Laropal LR 9008 generally improved stability to sedimentation.

[0116] Turbiscan Measurements—Multiple Light Scattering

[0117] Static multiple light scattering was carried out on the samples, and the results are shown in Table 5 below. Static multiple light scattering is an optical method used to characterise concentrated liquid dispersions. Light is transmitted into the sample and either backscattered or transmitted by the dispersion, depending on concentration and predominant particle size. TSI numbers are used to indicate the degree of change within a sample, with high numbers indicating high degree of change within the sample i.e. instability.

TABLE-US-00005 TABLE 5 Turbiscan assessment Elevated Ambient Temperature Storage % Laropal Storage (40° C.) Wafer only 0.3 2 10% Laropal + 90% 4.5 6.4 Wafer 20% Laropal + 80% 0.2 0.5 Water 30% Laropal + 70% 0.3 0.6 Water 40% Laropal + 60% 0.7 0.6 Wafer 50% Laropal + 50% 0.3 0.6 Water

[0118] Comments

[0119] For dispersions of A-GNP10 in water, the presence of Laropal demonstrated improved stability as tested by the Turbiscan, with the only exception being the dispersion with 10% Laropal LR9008. In the absence of Laropal LR9008, dispersions were initially seen to sediment after 2 to 3 days on storage. With the use of the dispersing resin, stability to sedimentation was increased to 6 weeks.

[0120] Graphene (A-GNP35) Dispersed in Water Comprising a Dispersing Resin (i.e. Grinding Media)

[0121] Dispersions Tested

[0122] 0.5% A-GNP35 was dispersed into water/solvent and bead-milled for 15 minutes recirculation.

[0123] 0.5% A-GNP35 in [0124] Water only [0125] 10% Laropal 90% water [0126] 20% Laropal 80% water [0127] 30% Laropal 70% water [0128] 40% Laropal 60% water [0129] 50% Laropal 50% water

[0130] Viscosity of Aqueous Dispersions of A-GNP35

[0131] Dispersions of A-GNP35 in water only tend to show a very high viscosity as shown in Table 6 below. For all systems tested, viscosity was lower with the addition of Laropal LR9008. The lowest viscosity was achieved at 20% loading of Laropal.

TABLE-US-00006 TABLE 6 Viscosity of Aqueous Dispersions of A-GNP35 0.5% A-GNP35 in: Viscosity (Pa.Math. s) Water only 22.51 10% Laropal + 90% 0.07791 Water 20% Laropal + 80% 0.04852 Water 30% Laropal + 70% 0.06313 Water 40% Laropal + 60% 0.08151 Water 50% Laropal + 50% 0.1225 Water

[0132] Particle Size Distribution of Aqueous Dispersions of A-GNP35

[0133] Particle size distribution was assessed for all samples, the results of which are shown in Table 7 below. The use of Laropal LR9008 was shown to reduce particle size significantly. For the systems which included Laropal, the dispersion with 10% loading of Laropal showed the least reduction in particle size distribution. Between 20 and 50% loading of Laropal, there was not much variation in particle size distribution. For these systems, D90 was half that achieved without the use of the dispersing resin (i.e. grinding media).

TABLE-US-00007 TABLE 7 Particle Size Distribution of Aqueous Dispersions of A-GNP10 % A-GNP35 in: D10 D50 D90 Water only 8.99 41.2 123 10% Laropal + 90% 5.84 24.7 84.1 Water 20% Laropal + 80% 3.17 13.8 50.2 Water 30% Laropal + 70% 2.83 14.4 53.8 Water 40% Laropal + 60% 2.4 13 55.5 Water 50% Laropal + 50% 1.83 11 51.8 Water

[0134] Storage Stability

[0135] Samples were tested at ambient and elevated temperature. Dispersions of A-GNP35 in water typically have a high viscosity with the consistency of a thick paste. As such, they tend to be more stable than the equivalent dispersions of A-GNP10. After one week testing, there was no visible difference in the stability of the samples, either on ambient or elevated temperature (40° C.) store.

[0136] Turbiscan assessment of the samples as shown in table 8 below revealed no significant differences in the stability index of the samples, either at ambient or elevated temperature. Turbiscan stability index (TSI) is a relative measure of stability, which allows comparison of multiple samples. As a relative measure, it allows for a quantifiable assessment of closely related formulations.

TABLE-US-00008 TABLE 8 Turbiscan assessment Elevated Ambient Temperature Storage 0.5% A-GNP35 in: Storage (40° C.) Water only 0.1 0.2 10% Laropal + 90% 0.3 0.2 Water 20% Laropal + 80% 0.2 0.2 Water 30% Laropal + 70% 0.1 0.2 Water 40% Laropal + 60% 0.1 0.2 Water 50% Laropal + 50% 0.1 0.3 Water

[0137] Comments

[0138] For dispersions of A-GNP35 in water, the presence of Laropal significantly reduced dispersion viscosity, making dispersions more user friendly and easier to handle. Greater degree of particle size reduction was also achieved with the inclusion of Laropal.

[0139] Graphene (A-GNP35) Dispersed in Water Comprising a Dispersing Resin (i.e. Grinding Media) and a Wetting Agent (Surfynol)

[0140] Stability of the dispersion of Table 1 was monitored over a period of 4 months. Changes in particle size and degree of sedimentation were monitored. Four batches of the stabilised formulations were tested. Surfynol (wetting agent) was introduced to further improve pigment wetting and to act as a defoamer. The stabilised Formulation is as indicated in table 1 above.

[0141] Turbiscan—Multiple Light Scattering

[0142] Static Multiple Light Scattering is an optical method used to characterize concentrated liquid dispersions. Light is transmitted into the sample and either backscattered or transmitted by the dispersion, depending on concentration and predominant particle sizes. Any destabilization phenomenon happening in a given sample will have an effect on the backscattering and/or transmission signal intensities during the aging process. A formulation with high intensity variation, is changing in a significant way, and can be considered unstable.

[0143] Four batches of the dispersion of Table 1 were tested in order to understand stability of this dispersion. After 46 days on storage, there was development of surface separation, evidenced by the appearance of a transmitting (clear) layer near the surface. Immediately below the developing clear layer, was a slightly thicker layer where backscatter had increased.

[0144] Monitoring changes in Particle Size

[0145] Particle size distribution was assessed for the dispersion of Table 1, the results of which are shown in Table 9 below.

[0146] Changes in particle size can indicate agglomeration, aggregation or flocculation.

TABLE-US-00009 TABLE 9 Initial 1 month 4 months D10 0.0385 0.0434 0.0416 D50 4.43 4.78 4.34 D90 16.2 17.7 13.2

[0147] A slight drop in initial D90 was recorded after 4 months. The initial increase from 16.2 to 17.7 is considered to be within measurement error.

[0148] Degree of Sedimentation

[0149] The degree of sedimentation is shown in table 10 below.

TABLE-US-00010 TABLE 10 Degree of sedimentation Ease of mixing Initial No sedimentation Easy 1 month  No sedimentation Easy 4 months No sedimentation Easy

[0150] Shelf Life Recommendations

[0151] The dispersion of Table 1 should be stored for a period of 3 months at ambient temperature (15 to 25° C.). Some separation may occur and this can be mixed back into a homogenous dispersion with light mechanical agitation.