Comparison of Conductivity Additives: Carbon Black vs. Graphite

Conductivity in Industrial Applications

In numerous modern industrial applications, the targeted adjustment of electrical properties plays an important role. Whether for avoiding electrostatic charge, protecting sensitive electronics or dissipating currents – conductive components have become indispensable. For decades, carbon black has been the standard additive in this field for enhancing electrical conductivity. It is well-established, widely available and proven in many formulations. However, there is an alternative that is just as black, technically highly interesting and often underestimated: natural graphite. Thanks to its layered crystal structure, graphite offers excellent intrinsic conductivity properties. Depending on particle size, processing and purity, it opens up new possibilities for a wide range of applications. 

An Overview of the Materials

At first glance, both materials appear almost identical. Carbon black and graphite are both allotropic modifications of carbon. Both appear black, are finely incorporated into the plastic during processing and are visually almost indistinguishable in finished compounds. Yet, despite these external similarities, carbon black and natural graphite show fundamental differences in their origins, structure and technical behaviour. Taking a closer look at the materials helps to better classify their respective strengths and find the right solution for specific requirements.

What is Carbon Black?

Industrial carbon black, often referred to as Carbon Black, is a technically produced carbon product. It is created by the incomplete combustion or thermal decomposition of hydrocarbon-based raw materials such as crude oil or natural gas. Carbon black has been established for decades and is widely used in various substances such as plastics, rubber, or as a black pigment in paints. 

• Produced industrially
• Intense black colouration
• Ultra-fine particles
• Usually about 95 – 99% carbon
• Primarily electrically conductive

What is Graphite?

In principle, a distinction is made between synthetic and natural graphite. While synthetic graphite is produced industrially, natural graphite is a mineral raw material formed by geological processes and mined. It consists of crystalline carbon with a characteristic layered structure that gives the material its typical properties. After mining, natural graphite is processed by targeted methods to make it usable for technical applications.

• Naturally occurring raw material
• Black with a metallic sheen
• Crystalline layered structure
• Purities up to 99.9%
• Electrically and thermally conductive

The Properties of Carbon Black and Graphite: A Technical Comparison

Carbon black and graphite are used in numerous conductivity applications. From the plastics industry, for example in antistatic housings or ESD packaging, to the automotive industry, such as in tank and battery systems, all the way to use in corrosive systems like pump housings, piping components or parts in chemical plants. To select the right conductivity additive for the respective application, it is worth taking a closer look at the technical properties of both materials in direct comparison.

Electrical Conductivity

Carbon black consists of extremely fine particles, which form a conductive network once a certain concentration is reached. Types especially used for this purpose are also referred to as conductive carbon black or conductivity carbon black. In polymer applications, depending on the fill level and distribution, electrical conductivities of around 10⁰ to 10² S/m can typically be achieved with conductive carbon black.

Graphite is also electrically conductive, thanks to its crystalline layered structure. This structure enables especially high conductivity within the planes. The intrinsic electrical conductivity of graphite is typically in the range of about 10³ to 10⁴ S/m. However, just as with carbon black, the conductivity achieved in the finished component mainly depends on filling level and processing.

Thermal Conductivity

Both carbon black and graphite are not only electrically but also thermally conductive. However, the thermal conductivity of carbon black is significantly lower compared to graphite. For carbon black, it typically falls in the range of 0.1 to 1 W/mK. Pure graphite, on the other hand, has a very high thermal conductivity of about 150 W/mK, although the actual value can vary depending on processing.

Thus, while carbon black can slightly increase the thermal conductivity of a plastic, it is not specifically used as a thermal conductive additive. In contrast, graphite enables improved thermal management and contributes to a more uniform heat distribution within the component. This makes graphite particularly attractive for applications where both increased electrical and thermal conductivity are required.

Processing & Metering

Carbon black particles have a high specific surface area, which is desirable in many applications but can also make processing more difficult. In plastics applications, the high surface area binds a lot of polymer at the particle surface, making the melt more viscous and requiring more mixing energy. Additionally, fine carbon black is very dusty and tends to form agglomerates, which can further complicate accurate metering. For this reason, it is often used in pelletised form or as a masterbatch to ensure more uniform processing.

In comparison, natural graphite has a crystalline, platelet-like structure with a lower specific surface area. As a result, it usually has less impact on viscosity and can often be processed more stably. Graphite-containing plastic compounds also offer high flexibility in design. They are easy to mould and even with complex parts, conductivity can be specifically adjusted. Even demanding applications can thus be tailored to specific requirements.

Required Filling Level

The required filling level for both materials depends heavily on the desired electrical conductivity. Depending on its structure, carbon black often reaches the necessary conductivity values at comparatively low dosages. This is advantageous for many applications, as the mechanical and processability properties of the polymer are largely preserved.

However, conductivity can also be specifically adjusted with natural graphite. In addition to the filling level, the selected type of graphite is important, e.g. in terms of particle size and purity. Depending on requirements, from antistatic to highly conductive, appropriately adjusted and sometimes higher filling levels are used.

Material density is also a relevant factor:

• Carbon black: approx. 1.7–1.9 g/cm³
• Natural graphite: approx. 2.1–2.3 g/cm³

Thus, graphite is denser and heavier than carbon black. Nevertheless, it is often associated with weight reduction. This does not derive from its density itself, but rather from the fact that, due to the combination of electrical and thermal conductivity, both functions can be integrated and metal parts replaced – which can result in overall weight savings.

Resistance

As carbon black consists predominantly of carbon, it is relatively thermally stable. In an oxygen-free atmosphere, it is resistant to temperatures of approximately 800 to 1,000 °C. Graphite achieves even higher thermal stability of over 3,000 °C. Both materials have good chemical resistance. Carbon black is resistant to many acids, alkalis and solvents. Natural graphite is considered chemically inert and has especially high resistance to numerous chemical media, including many acids. These attributes make both carbon black and graphite attractive for demanding applications, particularly in chemically aggressive or thermally challenging environments.

Sustainability

There are also differences between carbon black and graphite in terms of sustainability. Carbon black is produced industrially from fossil raw materials such as oil or natural gas derivatives. The production process is energy-intensive and associated with corresponding CO₂ emissions. In contrast, natural graphite is a mineral raw material that is mined. While extraction and processing also require energy and result in emissions, natural graphite generally has a lower CO₂ footprint than industrially produced carbon black. However, it is important to distinguish natural graphite from synthetic graphite, whose production is significantly more energy-intensive and therefore has a higher CO₂ footprint than natural graphite.

Typical Applications for Conductivity Additives

Due to their sometimes differing properties, carbon black and graphite each have preferred areas of use.

Carbon black, for example, is used in:

• ESD packaging for electronic components
• Transport containers for electronics components
• Antistatic housings
• Cable sheathing
• Fuel systems in the automotive sector
• Standard conductivity compounds

Typical applications for natural graphite include:

• Battery housings and components for electric vehicles
• Bipolar plates in fuel cells, e.g. in stationary energy plants or emergency power systems
• Thermally conductive electronics housings, e.g. in power supplies or components close to cooling in computers
• Pump and piping components in chemical plants
• EMC/EMI shielding

When is Graphite the Better Choice?

Whether graphite or carbon black is better suited as an additive ultimately depends on the specific conductivity application and the requirements of the component. However, natural graphite plays to its strengths especially when …

• simultaneous electrical and thermal conductivity is required
• the electrical conductivity of carbon black alone is insufficient and a synergistic effect is desired
• processing with carbon black reaches its limits, for example due to certain binder requirements
• metal components are to be replaced and thus overall weight is to be reduced
• a more sustainable solution is desired

Reliable Conductivity Applications with LUH Natural Graphite

We at LUH GmbH specialise in conductivity applications with natural graphite. We are happy to assist you in selecting the best additive for your specific application. Our natural graphite is available in various forms. In addition, through our partners, we offer individually developed plastic compounds. This way you receive customised solutions, specifically tailored for reliable electrical and thermal conductivity as well as the requirements of your application.