Characterization of Continua™ SCM – Carbonaceous Residue

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Introduction

In part 2 of this series of blogs we described the key parameters that drive the performance of the Sustainable Carbonaceous Material (SCM) created through the pyrolysis of end of life rubber articles in applications.

These have been identified as:

• Carbonaceous residue
• Bound agglomerate size
• Ash Content
• Transmittance

In this blog we will cover Carbonaceous Residue in more detail.

Carbonaceous Residue Formation

During pyrolysis of rubber goods, the organic components are thermally cracked and recovered predominantly as gash 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.

When formed on the surface of the fillers, this layer of new carbon coats the carbon black, silica, and other inorganic species binding them together and forming large, bound agglomerates. This carbon layer can be observed in high magnification TEM micrographs. Figure 1 shows areas of carbonaceous residue that coat the carbon black contained in a sample of SCM.

Figure 1: High Magnification TEM Micrograph of SCM Showing Areas of Carbonaceous Residue

This carbonaceous residue shields the active surfaces of the carbon black and silica aggregates present in the SCM. By milling the raw carbon (char) from the pyrolysis reactor, more of the active surfaces are exposed which increases an SCM's ability to reinforce elastomers.

Conclusion

The carbonaceous residue formed during the pyrolysis of rubber articles has been observed to bind together the filler and other inorganic species present in a sample of SCM. Although this cannot be measured directly, it can be inferred from the dynamic properties (Payne effect) of a reference rubber compound such as D8582.