Preparation and Evaluation of Thermally Depolymerized Natural Rubber in Rubber Compound Formulations

Natural rubber was depolymerised into a viscous oil by a low temperature pyrolytic process. The preparation process is reported together with a H-NMR and FT-IR characterization of the resulting product. After the thermal degradation, natural rubber substantially retains its 1,4-polyisoprene structure although there are clear evidences about extensive cis-trans isomerization and chain scission phenomena. Liquid natural rubber was tested as plasticizer in two rubber formulations. A natural rubber-based formulation and a natural rubber/styrene-butadiene blend were compounded with depolymerised natural rubber in place of the traditional plasticizer based on aromatic extracts. The cure kinetics, the mechanical and dynamic properties of the compounds were tested and discussed. The performances offered by depolymerised natural rubber as plasticizer were satisfactory in comparison to aromatic oil and surprisingly it was found that the natural rubber oil gives higher hysteresis in comparison to a traditional aromatic extract. The environmental impact of the results of the present study has been emphasised.