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Multi-walled nano tubes from waste tyres

Multi-walled nano tubes from waste tyres

By TA News Bureau:

At a time when nanotechnology is finding critical roles in the automobile industry – from tyres to light composites -researchers are discovering numerous forms of this material diversified uses. Dr S Karthikeyan, Assistant Professor at the Post-Graduate and Research Department of Chemistry, Chikkanna Government Arts College, in South India, and his team have been exploring cost-competitive ways to recover this material from end of life tyres (ELT). What they have achieved was to develop a process to synthesise multi-walled carbon nanotubes (MWRTs) by spray pyrolysis on quartz substrate using tyre pyrolysis oil as a carbon precursor with ferrocene as a catalyst. In an interview to Tyre Asia, he spoke about the research work and explained how environmental issues with ELT could be address effectively

Researchers have discovered a cost-competitive process to develop multi-walled nanotubes (MWNTs) from waste tyres. They converted end of life (ELT) into tyre pyrolysis oil using thermal process. They processed the tyre pyrolysis oil at low boiling point and used organic liquid fraction as a carbon precursor for the synthesis of MWNTs. They used the low boiling point liquid by spray pyrolysis using ferrocene as a catalyst on quartz substrate at 950°C.

This process has opened up many possibilities for the environment-friendly disposal of waste tyres and for producing nanocomposites that find increasing application in various sectors of the industry.

One of the early applications of nanostructured materials in automobiles is in the manufacture of tyres. Now-a-days, carbon nanomaterials are used by the automotive industry in tyres as a pigment and reinforcing agent. These nano materials are playing a major role in many industrial sectors as well.

Besides tyres, these nano components are used as reinforcement materials in vehicle production. They possess remarkable electrical, mechanical, optical, thermal and chemical properties. Carbon nanotubes (CNTs) and alternative carbon nanostructures are supposed to be the key components of nanotechnology. Having realized its tremendous application potential, enormous efforts are being taken in carbon nanotubes projects worldwide. “The art of synthesis of CNTs lies in the optimization of parameters for selected group materials in a particular experimental set-up,” explains Dr S Karthikeyan. The long-term key of a sustainable society lies in stable economy that uses energy and resources efficiently. As the chosen precursors like tyre pyrolytic oil (TPO) evaporate at comparatively higher temperatures under inert atmosphere, catalytically-supported chemical vapour deposition method is adopted for synthesis of MWNTs.

The spray pyrolysis method is similar to the chemical vapour deposition (CVD) method with the only difference being that the vaporization and pyrolysis of carbon source occur simultaneously in spray pyrolysis whereas in CVD it is a two-step process. “As the properties of carbon nanotubes are expected to be dependent on their morphology, efforts have been made to study growth mechanisms of CNTs in order to control the morphology of MWNTs,” he said.

Pyrolysis advantage

The well crystalline MWNTs from carbon precursor viz. as-derived TPO, was synthesized by optimizing the parameters such as reaction temperature, catalytic support ratio and flow rate of carbon precursor oil in order to obtain good yields with fascinating morphology.

“The influence of reaction parameters on yield and morphology of MWNTs synthesized from TPO have been analysed through our research,” Dr Karthikeyan elaborated.

He also explained the advantages of the pyrolysis process as an environmentally attractive method to decompose a wide variety of wastes, including scrap tyres.

Pyrolysis means thermal decomposition in an oxygen-free environment. The products of this process are: solid char (30-40 wt. %), liquid residue (40-60wt. %), and gases (5-20wt. %).

The solid residue contains carbon black and the mineral matter initially present in the tyre. It may be used as reinforcement in the rubber industry as activated carbon or as a smokeless fuel.

“This activated carbon is now used for battery and superconductor applications. The gaseous fraction is composed of non-condensable organics like H2,H2S, CO, CO2, CH4, C2H4, C3H6, etc. The gas fraction can be used as a fuel in the pyrolysis process,” he said.

The liquid product consists of a very complex mixture of organic components, permitting the derived oil to be used as fuel, petroleum refinery feedstock or a source of chemicals.

“In our research, tyre pyrolysis oil has been converted into multi-walled carbon nanotube,” he said adding that they had used minimal equipment to conduct this research.

The processing facilities needed to synthesise multiwalled carbon nanotubes included spray pyrolysis reactor, chemical vapour deposition reactor, argon gas, ferrocene catalyst, tyre pyrolysis oil and substrate in which MWNTs get deposited.

Explaining how the tyre and rubber industry can take advantage of his research, Dr Karthikeyan said that MWNTs have gained importance due to their unique combination of electrical, thermal, chemical and mechanical properties they possess.

They have found applications in diverse areas such as composite materials, energy storage and conversion, sensors, drug delivery, field emission devices and nanoscale electronic components.

The end-user or application industry is the major driver for the MWNT market to grow. They find applications in various segments like automotive, aerospace, textile and fibres, electronics and semiconductors and others.

CNTs have the intrinsic characteristics desired in materials used as electrodes in batteries and capacitors. MWNTs have tremendously high surface area, good electrical conductivity, and very importantly, their linear geometry makes their surface highly accessible to the electrolyte.

Super capacitors with carbon nanotubes electrodes can be used for applications that require much higher power capabilities than batteries and much higher storage capacities than ordinary capacitors, such as hybrid electric vehicles that can provide rapid acceleration and store braking energy electrically.

Smart materials

These nano materials are playing a major role, particularly in the automobile sector where these components are used as reinforcement materials in vehicles. They possess remarkable electrical, mechanical, optical, thermal and chemical properties.

Nanotechnology enables automobiles to be made lighter and at the same time stronger that will result in better fuel consumption and increased safety. It would also help improve engine efficiency and fuel consumption for gasoline-powered cars.

Its use as catalysts, fuel additives, lubricants etc help reduce environmental impact from hydrogen and fuel Cell-powered cars, improved and miniaturized electronic  systems and better economies such as longer service life, lower component failure rate and smart materials for self-repair.

Dr Karthikeyan recalled that a couple of years before Ford’s most powerful Mustang hit the market, the Shelby GT35OR caused a bit of a stir at the Detroit auto show when it rolled into view on carbon fibres wheels.

These lightweight 19-inch rims saved 5.9 kg of unsprung weight per wheel, while offering higher levels of stiffness than equivalent aluminium wheels. It was the first time these rims had been used by a mainstream producer, rather than a supercar specialist and for aftermarket application.

Tyres are one of the early applications of nanostructured materials in automobiles. Now-a-days, nanomaterials are used by the automotive industry in tyres as a pigment and reinforcing agent. They are utilised in the aerospace industry for improved properties that add to their functional performance such as mechanical or electrical properties or that deliver multi-functional  properties like lightweight conductive nanocomposites. CNT applications for aerospace industries include composites for lightweight structural components as well as electromagnetic interference (EMI), radio frequency interference (RFD, electrostatic discharge (ESD), de-icing, anti-fouling, lightning strike protection, anti-corrosion and fire-resistant coatings.

The cost benefits of utilizing MWNTs are high in aerospace markets. For example, satellite’s weight savings equate to lower launch costs.

In general, polymer-carbon nanotube composites are used as thermoplastics, thermosets and conductive fillers to protect sensitive electronic devices used by various industries. Waste tyres are valuable sources of nanomaterials.


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