Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

Abstract

The effects of functionalized graphene sheets (FGSs) on the mechanical properties and strain-induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single sheets of graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain-induced crystallization of NR is compared by coupled tensile tests and X-ray diffraction experiments. Synchrotron X-ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS-filled NR samples compared with CB-filled NR, even at low loadings. Neat-NR exhibits straininduced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two-dimensional (2D) wide angle X-ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X-ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NR samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: [718][719][720][721][722][723] 2012

Mechanical and Electrical Properties of Elastomer Nanocomposites Based on Different Carbon Nanomaterials

“…Orientation of anisotropic fillers that can be evidenced by TEM or AFM of stretched samples [33,53], is expected to affect the orientation of polymer chains as well and consequently the mechanical properties of the composite. Ozbas et al [54] have compared the effect of functionalized graphene sheets (FGS) and that of carbon black on the strain-induced crystallization of NR by coupled tensile tests and X-ray diffraction Ozbas et al [54] have compared the effect of functionalized graphene sheets (FGS) and that of carbon black on the strain-induced crystallization of NR by coupled tensile tests and X-ray diffraction experiments. It is shown that only 1 wt % FGS imparts higher modulus and strength than 16 wt % CB ( Figure 5a) and induces crystallization at lower strain (ε = 1.25 for the FGS-NR sample and 1.75 for the CB-filled NR).…”

“…Below and above T g , the value of E' increases with increasing nanotube loading but the increase in the rubbery region is much more important than in the glassy state because it contains the contribution arising from the Payne effect [93]. Dynamic mechanical results reported by Ozbas et al [54] for NR composites show a much higher increase in the storage modulus for NR filled with 4 wt % FGS (functionalized graphene sheets) than for a loading of 16 wt % CB even at four times lower volume fraction (Figure 12b) which confirms the results displayed on Figure 11a. The authors believe that in the rubbery region, strain amplification combines with the effect of immobilized rubber to give the 30-to 90-fold increases in the effective volume fraction.…”

Natural rubber/graphene oxide composites: Effect of sheet size on mechanical properties and strain-induced crystallization behavior

“…It can be seen that the moduli of all the samples are increased with the addition of GO, and the moduli of the composites are consistently increased with increasing GO loading. The improvement may be explained by several reasons as follows: 1) GO have outstanding mechanical characteristics and higher specific surface area; 2) the distortions and the resultant defects of GO result in a rough and winkled topology on the nanoscale which ensure a strong rubber-to-filler interaction [45]; 3) the interactions between the rubber molecular chains and the GO nanoplatelets can provide additional entanglements or physical crosslinking and GO taking part in the vulcanization reaction can bring chemical crosslinking points according to the tube model [46]; 4) strain-induced crystallization as a substantial feature in mechanical reinforcement of NR specifically at high strain is significantly intensified in the presence of GO layers (as will discussed below) [47]. Comparing the modulus of the composites with different GO size, it is obvious that the GO with smaller size shows higher enhancements in the modulus.…”

A comparative investigation on strain induced crystallization for graphene and carbon nanotubes filled natural rubber composites

“…Ozbas et al [20] compared the effect of graphene and CB on the SIC by synchrotron X-ray scattering. The results showed that the onset of crystallization occurs at significantly lower strains for GE-filled NR samples compared with CB-filled NR Neat-NR exhibits SIC around a strain of 2.25, while incorporation of 1 and 4 wt% GE shifts the crystallization to strains of 1.25 and 0.75, respectively.…”

“…The reinforcement effect of graphene is believed to be related to its effect on strain induced crystallization (SIC). Synchrotron X-ray diffraction (WAXD) allows the in-situ examination of SIC in NR composites during stretching [13,[16][17][18][19][20]. Results from extensive studies demonstrated the preferred chain orientations and prominent enhancement of SIC upon elongation in the filled rubber composites.…”