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Nonrubber components (NRCs) play an important role in the outstanding mechanical property of natural rubber (NR). The main inositol component of NRCs in natural rubber latex (NRL) is l-quebrachitol. In this study, the influence of l-quebrachitol on the properties of centrifuged natural rubber (CNR) was investigated. The NRL was centrifuged twice to remove most of the NRCs. After that, l-quebrachitol was added in the latex with per hundreds of rubber (phr) vary from 0% to 0.8%, and the vulcanized CNR were prepared. It is shown that the properties of vulcanized CNR were greatly changed, with T 90 reduced from 19 to 15 min, the tensile strength increased from 5 to 9 MPa, T g reduced by about 2°C, and the ability for strain-induced crystallization was enhanced. It was proved by FTIR results that l-quebrachitol was linked to the CNR crosslinking network with ester bond.

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]

Graft-copolymerization of vinyl monomer containing silica precursor, p -styryltrimethoxysilane, onto natural rubber microparticles was performed in latex stage to form three-dimensional networks of nanosilica. After the latex was cast into a film, morphology observation by transmission electron microscopy showed that the natural rubber microparticles were dispersed in organic–inorganic nanomatrix consisting of vinyl polymer and silica nanoparticles. In particular, generation of large silica particles was prevented by slow rate of hydrolysis and condensation of silicon alkoxides for p -styryltrimethoxysilane and the nanosilica networks were formed. The nanomatrix structure with the nanosilica networks increased tensile strength of the rubber, and destruction of the structure decreased the strength. Master curves of dynamic moduli of the rubber showed that the value of storage modulus at rubbery plateau region was high and it was almost flat at low-frequency region because of the nanosilica networks. [ABSTRACT FROM AUTHOR]

• Natural rubber has excellent mechanical properties due to its unique molecular chain structure. • Characterized the trans -structure in the molecular chain structure of NR by 1H-NMR. • The content of trans -structures in the molecular chain structure of NR was calculated • NR contains a large amount of cis -1,4-polyisoprene and a small amount of trans -1,4-unit. Natural rubber (NR) has excellent mechanical properties due to its unique molecular chain structure. In previous studies, the signal of the cis- and trans -isoprene units was deduced by 13C-NMR spectrum of the low molecular weight fraction of NR. In this study, through investigating the 1H-NMR spectra of ribbed smoked sheet 1 (RSS-1) and standard Chinese rubber whole fraction (SCR-WF), and Eucommia ulmoides gum (EUG), trans -1,4-polyisoprene (TPI), found that the methyl-proton in the cis- and trans -isoprene units in 1H-NMR spectra of NR showed signals at 1.61 and 1.53 ppm, respectively. Further, the content of trans -structure in the molecular chain of NR of different producing areas was calculated. The results show that the content of trans -structure in the molecular chain structure of RSS-1 and SCR-WF were 1.500 and 1.054%, respectively. [ABSTRACT FROM AUTHOR]