After a review of the main singularities observed in the flow behaviour of rubber compounds and their likely relationships with the unique morphology of such materials, the paper discusses the real effect of processing additives on the rheological properties of elastomer systems and introduces the concept of bulk viscosity modification (BVM) with its theoretical background. It is then explained how liquid natural rubber (LNR) and similar materials are meeting this new concept. The manufacturing process for LNR which is based on the controlled depolymerisation of natural rubber, and the associated chemistry are described in detail. New results concerning the control of rubber compounds processability with liquid natural rubber are reported and discussed in detail.
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