Patent Application
20130196156
The Fullerene, discovered by Sir Harry Kroto, Richard Smalley and Robert Curl and others at Rice University Houston USA was identified as a new allotropic form of carbon.
[Ref. H. W. Kroto, J. R. Heat, E. C. O'Brien, R. F. Curl and R. E. Smalley (Nature 318, 162 1985).
Further work on the properties of fullerenes stimulated the interest of the global scientific research community which subsequently led to the identification of novel structural forms of carbon namely—the Carbon Nanotubes (CNTs).
[S. Iijima et al Nature 354, 56 1991]
Due to the unique chemical and electronic structures, fullerenes and CNTs exhibit remarkable mechanical, thermal and electrical properties which have gained widespread attention. The translation of the properties of individual nanotubes in to macroscopic entities such as fibres, yarns and films are bound to be interesting in terms of their cumulative properties. The potential applications of such materials range from their role as reinforcing agents in composites, alternative materials for power cables, cables for suspension bridges, biochemical and chemical sensors to catalyst supports.
Research at the Department of Materials Science and Metallurgy, University of Cambridge through the use of a high temperature reactor has resulted in bulk continuous production of high quality carbon nanotube macroscopic assemblies—in the form of fibres, films, tapes, yarns etc.
[Ref. Production of Agglomerates from Gas Phase WO/2005/07926
Cambridge University Technical Services Ltd Kinloch et al.]
Yarns, tapes, ropes and fibres are produced from either single or multifilament elements that are either natural or synthetic or a mixture of both. Natural materials are exampled by wool, silk, cotton, hemp and flax, synthetic materials by nylon, acetate and polyester. Fibre as a filament artefact can be provided by most if not all of the aforementioned materials. It can be separated into single filament and multifilament types. The term—fibre—generically encompasses materials with aspect ratios (longitudinal dimension to lateral dimension), at a minimum >2. The invention herein described is concerned with multifilament fibres and as such the word fibre will be used in subsequent descriptions. Such fibres are held together by possible filament entanglement and forces of attraction exampled by weak Van der Waals forces. Each and every individual multifilament based fibre is particular and in most cases unique.
The aforementioned multifilament fibres have basic attributes that are defined by their structure produced during manufacture. Their structural configuration can be considered a ground state and its basic attributes comprise strength, stiffness, toughness, elongation at failure, knot strength efficiency, resistance to wear and tear, electron and phonon transport leading to thermal transfer and electrical conductivity characteristics. The combination of such attributes defines the cumulative properties of each and every individual multifilament fibre.
To change and/or enhance the basic mechanical properties of such fibres it is necessary to treat them with physical stimuli, chemical processes or both. Post fibre production treatments will render the fibre more suitable for later processing into useable product.
It is within the domain of multifilament fibre that the described invention resides, specifically the sub domain of carbon nanotube fibres and the enhancement of their mechanical properties.
Carbon nanotubes are allotropic form of carbon with 1-D nanostructures that display specific properties in their own right. They manifest themselves in a variety of forms exampled by single wall, double wall, triple wall, multiwall; along with further sub divisions based on the electronic behaviour into armchair, zigzag and chiral. Each variation and example has its own identity. Typically carbon nanotubes have diameters of 1 to 100 nanometres and aspect ratios ranging from 10:1 to greater than 1000:1.
In a high temperature reactor individual nanotubes can be persuaded to form collectively in a gaseous atmosphere, exampled by hydrogen, at temperatures between 400-1500° C. The thermal degradation of a feedstock containing a carbon source, exampled by aliphatic and aromatic alcohols or hydrocarbons (or a mixture) such as ethanol, methane etc., a catalyst precursor, exampled by ferrocene, and a promoter precursor exampled by thiophene, results in the growth of nanotubes that subsequently form a smoke, in the aforementioned gaseous atmosphere, which can be harvested continuously as a fibre. The fibre exits via a clear chamber in a gas valve containing no impediments which can hinder fibre collection. The gas valve separates the highly volatile reactor gases from the oxygen of the outside air in manner that prevents an explosion. When exiting from the reactor gas valve the carbon nanotube fibre is collected in a chosen manner exampled by spindle winding or deposition on a substrate.
In fibre form, the carbon nanotubes congregate either separately and/or as bundles of mainly longitudinally aligned individual nanotubes of varying length. They are held together by the previously mentioned entanglement and Van der Waals weak forces.
The as made fibre drawn from the reactor is useful in its own right but with suitable after-treatments, its mechanical properties can be changed, enhanced and improved. The invention herein described alters the post-production fibre structure such that the mechanical properties, exampled by tensile strength, tensile stiffness, toughness, elongation to failure, knot strength efficiency, thermal and electron transfer characteristics, resistance to wear and tear are altered. Various post production processes can be applied to the fibre exampled by drawing, exposure to atmosphere controlled heat treatment (annealing), laser irradiation, any other form of electromagnetic radiation, acoustic stress, chemical procedures and densification techniques. The list is not definitive.
[Ref. Method of Increasing The Density of Carbon Nanotube Fibres or Films WO/2008/132467 A3]
High temperature reactor produced carbon nanotube fibre has a composite structure variously composed of individual nanotubes of varying length, bundles of nanotubes containing collections of tightly packed nanotubes along with gaps or vacancies. Once again the list is not definitive and nanotubes of different types, lengths, diameters and aspect ratios will be found. As aforementioned the nanotubes will typically align longitudinally parallel to the fibre axis.
For such a carbon nanotube fibre the application of a process which will produce enhancement of its mechanical properties by chemical treatments is the declared function of the described invention. Enhancement can be achieved through the addition of a chemical agent with its subsequent interaction with the post-production fibre.
Prior art documents A to D places the described invention in its historical context. Kroto et al establishes the identification of Fullerene as a carbon allotrope, and Iijima et al the discovery of the carbon nanotube.
Documents C and D provide information of the formation of carbon nanotube fibre, specifically that which is produced though the use of a high temperature reactor and harvested through the aforementioned unimpeded gas isolation valve.
Document E describes polymerisation of CMC (Carboxyl Methyl Cellulose) yarns after immersion in a bath of aqueous formaldehyde solution and as such does not suggest internal capture of the polymer within fibre filaments and bundles formed of carbon nanotubes.
Document F describes a coating process for cotton/polyester yarns using vinylic monomers and specifically states that there is no, if any internal fibre intrusion (Paragraph 5). The polymerised vinylic monomers act only as a yarn coating and do not affect the internal structure in any way and as such the document has no relevance to the described invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1007571.1 | May 2010 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2011/050798 | 4/21/2011 | WO | 00 | 1/28/2013 |
