Carbon nanotubes (CNTs) are nanomaterials with a high aspect ratio and are essentially tubes of graphene.
The lengths of these tubes can range from a few nm to arbitrarily long depending on the production process. These tubes are chemically and thermally stable, lightweight and yet exhibit very high tensile strengths and electrical conductivity (depending on the nanotube chirality, CNTs are either metallic or semi-conducting. The metallic configuration has theoretically 1,000 times the electric current density of copper. There is also some debate over whether CNTs have intrinsic superconductivity). Available products as follows:
- SWNTs (metallic and semiconducting)
- MWNTs
- DWNTs
Single walled nanotubes (SWNTs) have diameters of 0.4–2 nm. Coaxial or multi-walled nanotubes (MWNTs) have diameters of 2–100 nm. Double-walled nanotubes (DWNT) are a subset of MWNTs and share similar physical properties and flexibility to SWNTs with improved resistance to chemicals and thermal stability (more in-line with MWNTs). SWCNTs have been shown to provide sheet resistivity in the megaohm/square range while enabling colour when added to polymers and elastomers at loadings below 0.1 wt%.
Graphene is an allotrope of carbon first isolated in Manchester in 2004. The carbon atoms are arranged in a honeycomb configuration, forming a sheet just a single atom thick with superlative electrical conductivity and mechanical strength. Many flakes of graphene are stacked together in the material graphite. Graphene is light weight, with a single square-metre sheet weighing less than a milligram. Graphene is typically produced and supplied in two broad forms, either as a bulk powder or a thin film. All available grades of graphene shown are bulk powder grades:
Of the listed bulk powder grades these are subdivided into graphene nanoplatelets (GNPs) which are typically of more than 10 layers, multilayer graphene (MLG) which is 2-10 layers thick, few layer graphene (FLG) which is 2-5 layers. Graphene Oxides (GO) are compounds of carbon, oxygen and hydrogen in variable ratios formed by strongly oxidizing graphite. Dispersing the material in basic solutions results in Graphene Oxide flakes, which is also an intermediary stage for large scale production of graphene where the graphene oxide is reduced to from reduced graphene oxide (rGO) through a variety of processes at a relatively low cost. rGO is never pristine as there are always residual oxygen groups left on the surface, although this can aid dispersion and downstream compatibility.
Fullerenes
Carbon based molecules arranged in cage-like spheres or derivatives thereof. Configurations such as C60 (the famous Nobel prize winning buckminsterfullerene/buckyball), C70, C84 are used in a wide variety of applications such as photovoltaics, composites and hydrogen storage. Additionally, C60 fullerenes are soluble in a number of thermoset hardeners, including amine hardeners, and can provide significant improvements to mechanical properties of thermosets at loadings of 0.01% - 0.12%. The main improvements are in impact strength, which have been observed in epoxy to be 100% - 200% at these loadings. There are obvious applications with C60 here in advanced composites. Also, because C60 is partially soluble in these resin systems, they can improve resin performance while allowing the resin to remain optically clear, which opens up applications in UV curable resin systems.
Carbon nanomaterials are chemically inert and this can limit their application as pristine materials. As such, these nanomaterials are made available in a range of functionalised varieties, by adding chemical groups to the surface of the CNTs, Graphene or Fullerenes they can be utilised to greater effect in a number of applications.
Nanocarbons can be functionalised for specific applications with various surface modifications using both covalent and non-covalent chemistry. For example, chemical groups can be added to the nanocarbons through gas phase or plasma phase processing. These end-groups enhance the materials processability e.g. for dispersing in solvents and polymers, in addition to improving adhesion to composite matrix materials or providing other functionality. Surface modifications can be tailored to include:
- Carbonyl, Hydroxyl, Ether, Carboxyl, Amines, Amide, Nitrile, Nitrous Oxide, Imine and Fluorine groups.
Nanoparticles
Ultrafine particles (size generally in the range 1nm to 100nm) are increasingly in demand as new applications become known. Due to large surface area to volume ratios they are potentially preferable for use in applications such as rocket fuel catalyst, concrete additives, coatings, etc. Enhanced magnetic and electrical properties also pave the way for the production of superior conductive pastes and targeted drug delivery. Below are the different nanopowders we promote, broadly split by class:
- Metal Oxides (ZnO, Al2O3)
- Other Metal Compounds ( Al(OH)3)
Zinc Oxide (ZnO) nanoparticles are used for UV protection with transparency in films, coatings and polymers. The ZnO can be supplied in a dispersed concentrate. Alumina (Al2O3) is used for scratch protection and hardness whilst retaining optical properties also in films, coatings and polymers. Aluminium Trihydrate or ATH (chemical formula Al(OH)3) is an additive used for flame retardancy in a variety of polymer applications. At the nanoscale ATH can be used to produce masterbatch flame retardancy packages for plastics. Products such as ATH and Alumina can be supplied with surface modified properties, i.e. functional chemistry tailored to suit different applications for maximum compatibility in a particular target system.
Hexagonal Boron Nitride (aka 'White Graphene') is a relatively new 2D material with regards to commercial availability for industrial applications. h-BN provides exceptional barrier, electrically insulating, thermally conducting and mechanical properties in polymers such as PVC, PET and PE and in films/inks is also flexible and transparent.
A nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100nm. Many physical properties are vastly different to those of the bulk component materials. The main distinction between nanocomposites and conventional composites is generally that of the extremely high aspect ratios and surface area to volume ratios of the reinforcing phases in nanocomposites. Due to this high surface area, relatively small amounts of nanoscale reinforcing agent are required to have significant changes to the overall macroscale properties of the composite. There are three main classes, Ceramic, Metallic (of which CNT-MMC are an emerging subclass) and Polymer. Applications are enormous, as nanocomposites have superior physical characteristics in several areas to their conventional analogues and as a result are potential upgrades and replacements of them.
Much research in recent years has focused on polymeric nanocomposites due to the processability of plastics and therefore faster development cycle and ease of integration with existing industrial manufacturing. Plastic formulators or compounders can integrate nanoparticles via masterbatch or other suitable intermediate for use as performance additives. Polymer matrices can have a broad array of physical qualities enhanced by adding nanoscale fillers, often several at once.
For example, hexagonal Boron Nitride nano platelets (aka 'white graphene') can be added into various polymers to provide transparent, flexible barrier properties in films and sheets, while also significantly enhancing mechanical properties and thermal conductivity. C60 fullerenes can be used for wear and tribological improvements in the host polymer. Additionally, novel new behaviour not inherent in the original polymer can emerge by the addition of the right nanoparticulates. Hybrid organic nanomaterial blends can turn an insulating polymer into a very conductive one, easily bringing the volume resistivity below 1 ohm.cm. Nanomilled ATH, with many orders of magnitude higher specific surface area than conventional mineral flame retardants (and therefore superior performance/weight ratio), can significantly reduce part weight and avoid mechanially weakening the polymer.
Carbon nanotube metal matrix composites (CNT-MMC) aim to utilise the high tensile strength and conductivity of CNTs. Materials in this subgroup are currently limited to:
Still very much in the research phase, CNT-Cu nanocomposites are one of the most promising CNT-MMCs. Copper ions and carbon nanotubes are deposited through electroplating to form an evenly dispersed network of nanotubes throughout the copper matrix. CNT-Cu composites have higher electrical conductivity and multiple times the current carrying capacity (ampacity) than that of pure copper alone. Current technology availability from Fullerex producer clients is in relation to depositing CNT-Cu alloys around a copper wire core. This core can be annealed and drawn. The final ampacity of the wire is >40% higher than a wire of the same gauge, with a wide range of operating temperatures. Further work is focussed on directly integrating CNTs into copper at the refining stage.
The replacement of large scale copper power transmission can potentially be achieved with CNT cables. These cables are produced from bundles of CNT yarn spun directly from the manufacturing process. Higher ampacity, durability and equivalent conductivity, but lower density, lower creep and higher tensile strength than copper wire of the same gauge and compatible with all standard wire coating/cabling applications.
Thermoplastic
A thermoplastic polymer masterbatch is a concentrated mix of either performance enhancing additives or pigments that are embedded into a carrier resin, cooled and cut into pellets. The masterbatch can then be mixed in the desired ratio with the dilution resin, the polymer that makes up the bulk of the final product. Examples of pigments include inorganic pigments such as Titanium Dioxide. Additives are used to enhance various physical characteristics of the end product and are generally referred to as performance additives. These can include graphene, carbon nanotubes and metallic powders.
Nano-enabled thermoplastic polymer masterbatches are currently available for:
Thermoset
Thermoset resin masterbatches are a stable, homogeneous, highly loaded dispersion of nanomaterials, typically in a pourable paste with >10% nanomaterial content which can be diluted by the end buyer. Functionalisation prevents agglomeration in these systems.
Nano-enabled thermoset polymer masterbatches can currently be supplied for:
- PET resin, PUR , Epoxy, Acrylic
3D printing masterbatch polymers for FDM in pelletised form available in the following polymers:
Mechanical and conductive grades containing nanomaterials. Also available in fully compounded filament form.
Electro-Thermal Coating
PUR coating that contains carbon nanomaterials, can be sprayed, rolled or integrated into mats and is resistively heated by any type of power supply (i.e. it is an electro-thermal coating). The product has applications in Aerospace (aeroplane and helicopter blades), Wind Energy (turbine blades), Oil & Gas (pipeline heating) as an ice-protection coating or simply as a robust, resistive heater.
The producer also works with an application partner with extensive know-how in applying and wiring the product.
Foul Release Coating
Patented, durable, nanomaterial based marine coating for use on boat hulls. Non-toxic alternative to biocidal antifouling coatings. Does not contain metals. Also available as a concentrated masterbatch.
Conductive Inks
Cost-effective GNP based electrically conductive ink for screen printing. Metal-free and environmentally friendly formulation that can be applied to a range of substrates and cured at low temperature. Provides sheet resistivity of 15 Ohms per square (normalised to 20microns).
Transparent Conductive Inks
- Non-ITO high performance conductive ink
Based upon silver nanowires and developed for TCF applications, this product works well with multiple printing techniques such as inkjetting, micro-gravure coating, slot die coating. It delivers sheet resistance of 30 Ohms per square with 85% light transmittance at 1mil thickness. Samples can be provided coated onto PET film and other substrates.
For transparent conductive coating applications, a reinforcing layer in ITO based electronic displays to allow for much greater flexibility than conventional ITO capacitive touch screens. ITO is sputtered on top of the ink layer by the electronics manufacturer to achieve the desired conductivity.
- Non-ITO highly conductive ink
This ink is formulated as a highly conductive transparent ink for replacement of ITO materials in flexible TCF applications, although other application areas where transparency and conductivity are requirements would also be relevant. In particular, work is ongoing to use this ink as an electrothermal heater when applied to glass and other transparent materials.
h-BN inks can be prepared in a similar fashion to graphene inks but to provide insulating/di-electrical performance in conjunction with barrier properties. Due to the high light transmittance, h-BN ink can be coated onto films to allow for flexible, transparent films for packaging and other applications.
A proprietary formulation of thermally responsive nanomaterials which are reversibly thermochromic at formulated trigger points (i.e. the temperature trigger can be readily adjusted). The additives are VOC free, UV stable, environmentally friendly and perform well under a broad range of environmental conditions.
Thermal Spreader
These products take advantage of the exceptional thermal conductivity and low thermal mass of graphene. Thermal film products are designed to be suitable for a wide range of passive heat management applications and passively spread heat in-plane and are available in a range of thicknesses and thermal conductivities. The film is flexible and sold as free-standing sheets or laminated onto plastic films.
Thermal Paste
Graphene and other carbon nanomaterials have excellent thermal conductivity - pastes without any metallic fillers are available in the 5 - 10 W/m.K performance range.
FDM Reels
- Graphene enhanced PLA Filament from Haydale ltd
Available through global distribution network in 1.75mm or 2.85mm diameters.
Product features:
• Higher operating temperature performance
• High rigidity and good impact strength
• Ease of printing
• Excellent interlayer adhesion and surface finish
Please do not hesitate to get in touch should you wish to discuss product application areas or new product development in more detail.