Comparative Study on Strain-Induced Crystallization Behavior of Peroxide Cross-Linked and Sulfur Cross-Linked Natural Rubber

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• 作者：Yuko Ikeda ; Yoritaka Yasuda ; Kensuke Hijikata ; Masatoshi Tosaka ; Shinzo Kohjiya
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：August 12, 2008
• 年：2008
• 卷：41
• 期：15
• 页码：5876-5884
• 全文大小：300K
• 年卷期：v.41,no.15(August 12, 2008)
• ISSN：1520-5835

文摘

Strain-induced crystallization (SIC) behavior of natural rubber (NR) cross-linked by peroxide or sulfur was comparatively studied by time-resolved wide-angle X-ray diffraction measurements at SPring-8. Stretching ratio at the onset of SIC (α_c) decreased with an increase of network chain density (ν) for peroxide cross-linked NR (P-NR), while it remained constant for sulfur cross-linked NR (S-NR). But, dependence of relative crystallization rates on ν was similar for both P-NR and S-NR. Calculated entropy differences between the undeformed and the deformed states (ΔS_def) at α_c were equal for P-NR regardless of ν, whereas it became smaller with the increase of ν for S-NR. The SIC behavior of P-NR is in agreement with the prediction on homogeneous or uniform networks by Flory. Thus, the network structure of S-NR is supposed to be less homogeneous than that of P-NR. The inhomogeneity in S-NR is estimated due to the presence of domains of high ν value embedded in the rubbery network matrix, which is supported by the stress dependences of apparent lateral crystallite size. The mechanical characteristics of S-NR and P-NR are also discussed from the viewpoint of their SIC behaviors on the basis of the network structures.