Observation of microscopic dynamics of carbon black in rubber during the vulcanization process

We observed the dynamics of carbon black in rubber during the vulcanization (cross-linking) process, using X-ray photon correlation spectroscopy. The intensity fluctuations of scattered X-rays gradually slowed down during the vulcanization process. The evolution of the dynamics was investigated by analyzing the intensity correlation function. During the vulcanization process, the relaxation time τ changed in accordance with the changes of dynamic viscoelastic properties. An increase in the baseline of the correlation functions was observed at low-q-regions. The results indicate the formation of frozen structures, which must be related to the formation of cross-linked structures.