Magnetically Stimulable Graphene Oxide/Polypropylene Nanocomposites

Abstract

Core-shell magnetic air-stable nanoparticles have attracted increasing interest in recent years. Attaining a satisfactory distribution of magnetic nanoparticles (MNPs) in polymeric matrices is difficult due to magnetically induced aggregation, and supporting the MNPs on a nonmagnetic core-shell is a well-established strategy. In order to obtain magnetically active polypropylene (PP) nanocomposites by melt mixing, the thermal reduction of graphene oxides (TrGO) at two different temperatures (600 and 1000 °C) was carried out, and, subsequently, metallic nanoparticles (Co or Ni) were dispersed on them. The XRD patterns of the nanoparticles show the characteristic peaks of the graphene, Co, and Ni nanoparticles, where the estimated sizes of Ni and Co were 3.59 and 4.25 nm, respectively. The Raman spectroscopy presents typical D and G bands of graphene materials as well as the corresponding peaks of Ni and Co nanoparticles. Elemental and surface area studies show that the carbon content and surface area increase with thermal reduction, as expected, following a reduction in the surface area by the support of MNPs. Atomic absorption spectroscopy demonstrates about 9-12 wt % metallic nanoparticles supported on the TrGO surface, showing that the reduction of GO at two different temperatures has no significant effect on the support of metallic nanoparticles. Fourier transform infrared (FT-IR) spectroscopy shows that the addition of a filler does not alter the chemical structure of the polymer. Scanning electron microscopy of the fracture interface of the samples demonstrates consistent dispersion of the filler in the polymer. The TGA analysis shows that, with the incorporation of the filler, the initial (T_onset) and maximum (T_max) degradation temperatures of the PP nanocomposites increase up to 34 and 19 °C, respectively. The DSC results present an improvement in the crystallization temperature and percent crystallinity. The filler addition slightly enhances the elastic modulus of the nanocomposites. The results of the water contact angle confirm that the prepared nanocomposites are hydrophilic. Importantly, the diamagnetic matrix is transformed into a ferromagnetic one with the addition of the magnetic filler.

Figure 1

XRD patterns of neat graphite, GO, and TrGO at 600 and 1000 °C (a) and TrGO-supporting Ni and Co nanoparticles (b).

Figure 2

Raman spectra of neat graphite, GO, and TrGO at 600 and 1000 °C (a) and TrGO-supported Ni and Co nanoparticles (b).

Figure 3

FT-IR spectra of GO and TrGO (a) and the PP nanocomposite (b).

Figure 4

SEM images of pure PP (a), PP-TrGO₆₀₀-Co-5% (b), PP-TrGO₁₀₀₀-Co-5% (c), PP-TrGO₆₀₀-Ni-5% (d), and TrGO₁₀₀₀-Ni-5% (e).

Figure 5

TGA thermograms of neat PP and PP-TrGO_-Co nanocomposites (a) and neat PP and PP-TrGO-Ni nanocomposites (b).

Figure 6

DSC thermograms of neat PP, PP-TrGO-Co and PP-TrGO-Ni nanocomposites (a) 5 wt % of filler (b) 1 wt % of filer.

Figure 7

(a) Effect of the concentration of MNPs on the Young modulus and (b) elongation at break.

Figure 8

Results of the water contact angle of the bare PP and nanocomposites with different filler percentages.

Figure 9

Magnetization versus magnetic field variations obtained for the TrGO-supported Co (a and b) and Ni (c and d) nanoparticles.

Figure 10

Magnetization hysteresis loops (symbols), recoil loops (solid curves), and the respective δM_R plots, measured for the PP-TrGO-Co (a–d) and PP-TrGO-Ni (e–h) nanocomposites.