3.5 Tensile and dynamic mechanical properties
The silica-filled NR with TESPT shows a higher reinforcing index (M300/M100) when compared to the compounds with ENRs as compatibilizers: Fig. 8, indicating a greater extent of interactions between the silica and rubber phases when the silane coupling agent is used, as also previously observed by the chemically bound rubber content: Fig. 6. When compared with the ENR types, the use of ENR-51 gives the highest reinforcing index. An increase of ENR content tends to decrease the reinforcing index slightly. This may be caused by the presence of two different rubber phases in the system due to the incompatibility between NR and ENR [30] and [31], as previously mentioned in section 3.1