About the Viscoelastic Nature of the Filler Network in Rubber Composites and Its Importance for the Optimization of Composites Containing Grained Rubber

This presentation is focusing on reinforcement mechanisms in different types of rubber nanoparticle composites and includes the results of recent studies on composites for tire treads containing grained rubber. The discussion incorporates in particular results showing temperature-dependent changes in the filler network contributions to reinforcement as obtained from strain sweeps on fresh composite samples performed at different temperatures. These results strongly indicate that the filler network of tire-related composites incorporates viscoelastic elements, i.e., an immobilized rubber fraction which strengthens the filler network at low temperatures but softens during heating [1,2]. This idea is supported by additional frequency-dependent measurements. The presented findings can be explained by simple models assuming that glassy rubber layers with nanoscopic dimensions increase the load carrying capacity of the filler network by strengthening the contacts between individual filler particles. The influence of filler type, aspect ratio of the particles and specific surface area is discussed based on a comparison of results for different rubber nanoparticle composites [3]. In a special part of this presentation, the importance of the related effects for the optimization of rubber nanoparticle composites for tire treads containing grained rubber powder is demonstrated.

[1] A. Mujtaba et al, Macromolecules 45 (2012) 6504.

[2] A. Mujtaba et al, ACS Macro Letters 3 (2014) 481.

[3] A. Mujtaba et al, (2015) to be published.