Conductive Additives - Using Carbon Nanotubes to Increase the Electrical Conductivity of Polymer Composites

Interview conducted by Jake WilkinsonNov 28 2016

Single Wall Carbon Nanotubes (SWCNTs) are extremely effective additives for improving the conductivity of polymer based materials. When compared to the current most popular additive, carbon black, they are up to 1,000 times more powerful and don't result in any loss in material strength or appearance. However, the technology is still developing and the addition of SWCNTs to composites can be tricky.

AZoM spoke to Zakhar Bolshakov, of OCSiAl, about a novel SWCNT additive solution, TUBALL, that they have developed. TUBALL promises to make the addition of SWCNTs to polymer composites as simple and effective as possible.

If single wall carbon nanotubes (SWCNTs) are so effective at increasing polymer conductivity why are they are not the most popular additive used for this purpose?

If you look at the history of any material, it is evident that it takes time between the invention of the material and it being used in high volumes by industry. Nanotubes were discovered quite recently, in the 1990s, meaning the technology is still developing. However, we are now seeing an increase in investment in this sphere.

Carbon black is currently the most widely used conductive additive. As it was discovered a very long time ago, in the 1880s, there are a number of well-established companies that produce high volumes of conductive carbon black. The technology for conductive carbon black production has reached the limit of manufacturing efficiencies and the point at which you can not drive costs down further.

However, if you look at SWCNTs, they are just at the beginning of their development, in terms of manufacturing capacity and in terms of driving costs down.

Carbon nanotubes are making a steady, if not very fast, way in to the market. Soon we will see significant improvements in the technology used to produce them and a further decrease in the costs of single wall nanotubes. This will bring about revolutionary changes in the market.

Schematic of a single walled carbon nanotube. shutterstock.com | Sebastian Kaulitzki

What issues are associated with additives such as carbon black?

When you add the widely used conductive additive carbon black to materials, you face three key problems.

The most basic of these problems is that you have to add a lot. For example, if you need to reach a volume resistivity level of 104 Ohm•cm in a polymer using standard conductive carbon black, this will require up to 10% or even more of the additive. This is problematic in itself due to the cost associated with the addition.

This large volume of carbon black also results in another problem - having such a high volume of carbon black results in a reduced mechanical strength of the material. This means manufacturors frequently need to compromise between strength and conductivity.

The third problem is aesthetic, as a high dose of carbon black is required it turns the material completely black.

How does the addition of SWCNTs solve these issues?

Just by looking at microscope images of conductive carbon black and of SWCNTs, you will see very clearly that the SWCNT is the ultimate form of carbon.

There is basically no reason why, now that the technology for industrial-scale synthesis of SWCNTs has been developed, these nanotubes should not replace all of the carbon black used today.

SWCNTs have a very high aspect (length of diameter) ratio which can reach values of over 2.5 thousand. This high aspect ratio means that the percolation threshold, above which resistance drops significantly, can be reached using much lower loadings. So you need to add notably less of conductive SWCNTs than you would of conductive carbon black or other additives to reach the targeted conductivity level.

For example, to achieve a volume resistivity of 104 Ohm•cm in a polymer, you do not have to add 10% of SWCNTs but only 0.05%, which is 1000 times less than required when using carbon black.

Another advantage is that the low loading of SWCNTs that is required means that there is no degradation of mechanical strength. In fact, the mechanical strength is enhanced by the long and thin nanotube 'wires' which mesh together, forming a 3D network which strengthens the material.

Additionally, the small loading required means the color of the material is not effected. This allows manufacturers to produce colorful conductive materials, which is unachievable using any other standard conductive additive.

SWCNTs form a 3D network that increases the strength of materials that they are added to.

What materials can OCSiAl's SWCNT additive, TUBALL, be effectively added to?

At the moment, SWCNTs can be applied to any material, except for steel. We have already developed pilot technologies for different polymers, including polyester and epoxy resins, polyurethane and PVC. We can apply them to all elastomers, such as silicones, rubbers and latex. They can also be applied to coatings and to lithium batteries.

These results have been validated by independent research organizations such as The Hamburg University of Technology, Germany and numerous clients.

Right now, we have some positive laboratory results with the use of nanotubes in cement and aluminum. However, it will take time for us to develop large-scale industrial manufacturing technology for these materials. Taking into account the high production volumes of these materials, I believe that, as soon as we achieve the desired results in these industries, there will be a huge impact on the material world.

How do you simplify the addition of TUBALL to a material’s matrix?

Due to the nature of single wall carbon nanotubes, the addition of them into a material's matrix is not straightforward.

Attractive Van der Waals forces between nanotubes results in them sticking to one another and agglomerating, which make nanotubes stick to one another and which also result in further agglomeration. Ideally we need to disperse separate nanotubes into the material to achieve the strengthening and conductive network. However, this is not very easy.

We have realized is that OCSiAl has had to invest significantly in the development of dispersion technologies. Currently, the company develops intermediate products that are represented by concentrates and masterbatches based on single wall carbon nanotubes and which are tailored for various applications such as polymers, thermoplastics, resins, elastomers, coating and so on.

It is a very complex process. Our masterbatches are very easy to dilute and they can be processed using standard equipment, which greatly simplifies the use of our products.

A high resolution TEM image of TUBALL bundles

Which of your wide range of TUBALL-based solutions do you think has the most potential, and for what applications?

We believe that today there are two main areas where our products can find application.

The first main area of application is electrical conductivity.

The pioneer here is the battery industry, lithium batteries in particular. Next I would mention thermosets: epoxy, polyester and polyurethane resins. We already have a number of leading companies in Russia, Europe and other countries that are using TUBALL to produce commercially successful products for conductivity applications in thermosets resins.

Then I would have to mention thermoplastics, which is probably the largest area with the highest potential where conductive carbon black is currently used; OCSiAl has impressive plans for this industry in the near future.

The second is where the enhancement of mechanical strength is needed – a phenomenon where we have no limits.

Today up to 35% of CO2 emissions are related to materials, including emissions arising from their production process and a number of other activities such as transportation. When we succeed in improving materials’ mechanical properties, by making them stronger and lighter, we could improve human life and mitigate the global warming problem.

In my opinion, there is huge potential in this sphere, and we are working very actively to develop masterbatches and concentrates specially designed for solving these kinds of problems.

OCSiAl has recently developed TUBALL MATRIX. Could you tell us more about it?

I think that TUBALL MATRIX is most effective in epoxy and polyester resins. It can also be used in the manufacturing of polyurethane (PU) resin and polyvinyl chloride (PVC).

One of the key advantages of TUBALL MATRIX is that it enables the targeted level of permanent and uniform conductivity to be achieved with an ultralow dosage starting from 0.1%. Due to the ultralow dosages, TUBALL MATRIX allows the production of conductive parts that can retain their original colors and it does not lead to a significant increase of viscosity or density of the host materials compared with impact by other additives. Furthermore, TUBALL MATRIX maintains and even enhances various mechanical properties.

But the most important point, which is worth emphasizing, is that, when using TUBALL MATRIX, manufacturers do not have to make any changes to their production technology. The only recommended requirement is mixing the compound at up to 2000 rpm for 20 minutes and using a ten-blade impeller.

Which industries do you expect TUBALL MATRIX to impact the most?

TUBALL MATRIX is probably one of the best conductive concentrates currently available on the market. It can be used in thermosets, plastics, resins and elastomers and so on. The industries that will definitely experience a great impact include the automotive, oil, petrochemical, gas, electronics, mining, chemical, healthcare and pharmaceutical industries.

TUBALL MATRIX can be widely used in equipment for mines, electronics and chemical plants, and petrol stations. It can also be used in products where dust is aesthetically undesirable, for example in automotive interiors. TUBALL MATRIX is a good solution for antistatic epoxy-based floors and for producers of packaging for electronics, combustible powders or liquids.

Where can our readers find out more about OcSiAl and your TUBALL range of SWCNT additives?

The first place to look would be our website where you can find information on our technology and the different TUBALL additives that we supply.

We'd also be more than happy to hear from you. If you have any questions about how TUBALL could improve your materials don't hesitate to get in touch.

About Zakhar Bolshakov

Specialized in development of single wall carbon nanotubes-based solutions for polymers.

Experience: Marketing research assistant in A.C.NIELSEN, a company of DUN & BRADSTREET Corp.; deputy chief-editor of the corporate journal “Economic Strategies”; project manager in Institute for Economic Strategies; head of market research and strategic planning in Agromasholding strategic marketing director in Sibmashholding; marketing director of joint venture company AGCO SM.group; marketing director of Agromarket; director for special projects in SYGMA.innovations; OCSiAl Group Vice President.

Education: Moscow Institute of Electronic Technology (Moscow, 1996); Case Western Reserve University (Cleveland, USA); MBA from Business School of Kingston University (London, U.K.; Moscow, 2000); Ph.D. in economics (global aerospace and defense industry) - IMEMO RAN (Moscow, 2003).