Characterisation of Continua™ SCM – An Introduction

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In part 1 of this series of blogs we explained why you do not recover carbon black through the pyrolysis of end-of-life rubber articles, but rather create a new material, sustainable carbonaceous material (SCM).

As traditional carbon black colloidal tests have been shown not to have any relevance to application performance, in this blog the key parameters for assessing the quality of SCM are introduced.

In the subsequent blogs we will cover these parameters in more detail.

Identified Key Properties

As traditional carbon black colloidal properties are not good predictors of the performance of SCM, Birla Carbon has researched key parameters that drive product performance. These have been identified as:

Carbonaceous Residue

During pyrolysis of rubber goods, the organic components are thermally cracked and recovered predominantly as gas and oil products. A portion of this organic matter additionally cokes in-situ, creating carbonaceous residue. This carbonaceous residue can form on both the surface of the fillers in the rubber article and on other surfaces present in the reactor.

Bound Agglomerate Size

Although commonly called ‘particle size’, technically, a ‘particle’ of SCM is an agglomeration of various materials including carbon black and silica, bound together with carbonaceous residue. The size of these bound agglomerates is one of the most important parameters for SCM and is controlled by milling the raw char from the pyrolysis reactor. These agglomerates are the smallest dispersible unit for SCM and directly affect application performance.

Ash

Tyres are complex composite materials that contain a wide range of functional additives including carbon black, silica, clays and zinc compounds. When pyrolyzed, these inorganic materials remain with the SCM resulting in a significantly higher ash content compared to carbon black. The ash content for a given SCM will vary depending on the feedstock used.

Transmittance

Like carbon black, a low transmittance value indicates that there are residual hydrocarbons on the surface of the material due to the incomplete pyrolysis of the feedstock.

Conclusion

The unique characteristics of SCM result in a different method of classification compared to carbon black. The key attributes of SCM have been identified as:

• Level of carbonaceous residue.
• Bound agglomerate size.
• Ash content.
• Transmittance.