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Abstract: Strain‐induced crystallization of natural rubber (NR) can greatly influence the mechanical properties of NR blends. In this study, we investigated the effect of strain‐induced crystallization on the tear energy (G) of NR/styrene butadiene rubber (SBR) blends with different compositions and cross‐link densities. Using a shift factor, we could superimpose G of an SBR blend and an NR/SBR (1/9) blend onto a single master curve. In contrast, G of NR was split into two master curves. Although the master curve of G for the NR/SBR (3:7) blend was split, increasing the cross‐link density threefold made it possible to superimpose it onto a single master curve. Strain‐induced crystallization of NR in the NR/SBR blend did not occur as a result of decreasing the NR content, increasing the cross‐link density, or removing fatty acids. Together, these findings indicate that strain‐induced crystallization of NR plays an important role in the mechanical properties of the blend. [ABSTRACT FROM AUTHOR]

Effect of the nanomatrix structure on mechanical properties of natural rubber was investigated in relation to the strain-induced crystallization. Structure of natural rubber was analyzed through Fourier transform infrared spectroscopy, wide-angle X-ray diffraction measurement and transmission electron microscopy. The nanomatrix of the non-rubber components was found to be inevitably formed in natural rubber, in which natural rubber particles linking to fatty acids were dispersed in the nanomatrix of the proteins and phospholipids. The nanomatrix disappeared after deproteinization of natural rubber with urea. Tensile strength and modulus of natural rubber were reduced by removal of the fatty acids and the proteins, which resulted in disappearance of the nanomatrix structure. The effect of fatty acids on the crystallization of natural rubber in small particles as a dispersoid was proved by tensile test of blend of natural rubber and styrene butadiene rubber. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]