Fazhong Zhang

High Performance Graphene Oxide Based Rubber Composites

In this paper, graphene oxide/styrene-butadiene rubber (GO/SBR) composites with complete exfoliation of GO sheets were prepared by aqueous-phase mixing of GO colloid with SBR latex and a small loading of butadiene-styrene-vinyl-pyridine rubber (VPR) latex, followed by their co-coagulation. During co-coagulation, VPR not only plays a key role in the prevention of aggregation of GO sheets but also acts as an interface-bridge between GO and SBR. The results demonstrated that the mechanical properties of the GO/SBR composite with 2.0 vol.% GO is comparable with those of the SBR composite reinforced with 13.1 vol.% of carbon black (CB), with a low mass density and a good gas barrier ability to boot. The present work also showed that GO-silica/SBR composite exhibited outstanding wear resistance and low-rolling resistance which make GO-silica/SBR very competitive for the green tire application, opening up enormous opportunities to prepare high performance rubber composites for future engineering applications.

Network evolutions in both pure and silica-filled natural rubbers during cyclic shear loading

Evolutions of chemical cross-linking and filler networks during sinusoidal small-strain (10%) shear loading (fatigue) process were studied in pure (unfilled) and silica-filled natural rubbers. The experimental results of dynamic mechanical analysis (DMA) and nuclear magnetic resonance (NMR) of pure natural rubber (PNR) indicated that the fatigued PNR has a more homogeneous cross-linking network than that of the virgin one, which can lead to a slight increase of the storage modulus; however, the change of cross-linking density and its effect on the viscoelastic properties of PNR are very limited. By analyzing the variation of storage and loss moduli and the transmission electron microscopy (TEM) images of silica-filled natural rubber (SFNR) during the cyclic loading process, we found that the loosely packed agglomerates were first disrupted, and then the closed ones could also be gradually broken down. Such a filler network evolution process also can be seen from our non-equilibrium molecular dynamics (NEMD) simulation results.

Luminescence of EPDM rubber ultrafine fibers containing nanodispersed Eu-complexes

Abstract Polyvinylpyrrolidone/ethylene-propylene-diene terpolymer (PVP/EPDM) sheath/core fibers, with the incorporation of Eu(TTA) 3 Phen (TTA=2-thenoyltrifluoroacetone, Phen=1,10-phenanthroline) complex (Eu-complex) in EPDM, were prepared by coaxial electrospinning. The composite fibers were further vulcanized by peroxide. Scanning electron microscopy (SEM) observations showed that the composite fibers had an average diameter of about 200 nm and a smooth surface. The dispersion of Eu-complexes in the fibers was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The studies revealed that the Eu-complex was dispersed in the EPDM fibers in the form of molecular clusters and/or nanoparticles with a diameter smaller than 10 nm. Fluorescence spectra and Judd-Ofelt parameters analysis showed that the luminescent quantum efficiency of the composite fibers was greatly improved when the Eu-complex content was 15 wt.%, because the fine dispersion of Eu-complex in EPDM facilitated the increase of radiative transition rate of the composite fibers over that of the neat complex powder.