Mechanism of strain-induced crystallization in filled and unfilled natural rubber vulcanizates

• Published in: Journal of applied physics 2005-05, Vol.97 (10), p.103529-103529-9
• Main Authors: Poompradub, Sirilux, Tosaka, Masatoshi, Kohjiya, Shinzo, Ikeda, Yuko, Toki, Shigeyuki, Sics, Igors, Hsiao, Benjamin S.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1900927

Structure evolution during deformation of unfilled natural rubber (NR) vulcanizate and filled ones with carbon black or calcium carbonate was investigated by the synchrotron x-ray diffraction. The crystallization onset strain, α 0 , was found to decrease by the inclusion of the filler. However, corrected α 0 values into the effective strain ratio of deformable rubber portion were almost constant between filled and unfilled samples. Accordingly, our model of strain-induced crystallization of unfilled NR vulcanizates, assuming that melting temperature is independent of network-chain length ( n ) , was applied to the filled samples. The discrepancy between classical theories and experimental results was thought to come from the distribution of n . By the inclusion of filler, the lateral crystallite size was decreased but the orientational fluctuation increased. The lattice of the strain-induced crystallites changed almost linearly with the nominal stress. In addition, the degree of lattice deformation decreased with the filler content, especially in the carbon black-filled system. All these experimental results are consistent with the proposed model.