Tailoring the graphene oxide chemical structure and morphology as a key to polypropylene nanocomposite performance

Abstract

In this work, we designed and studied two synthetic routes, based on modified Hummers method, to obtain graphene oxide (GO), and investigated their influence on the performance of polypropylene (PP)/GO nanocomposites. The two synthetic routes differed in the application condition of the oxidizing agent, potassium permanganate (KMnO4), which was added either as a powder (GO‐P) or as a water solution (GO‐S). This apparently subtle synthetic change yielded GOs with different degrees of oxidation and particle sizes, where GO‐P presented a higher oxidation degree and smaller particles. The different GOs were then melt‐blended with PP and the correlation between their different chemical/morphological structures and the nanocomposites' thermomechanical/rheological properties were evaluated. The milder oxidation process suffered by GO‐S, and consequent less hydrophilic character, yielded a PP/GO‐S nanocomposite with improved performance as the consequence of a better matrix/filler chemical affinity, mainly in compositions with lower GO‐S contents. The thermal stability was increased by more than 10°C when 0.1 wt% GO‐S was inserted into PP. When compared to the composition with 0.1 wt% GO‐P, the increase was 13°C. Reinforcing effects were also observed in that sample (with 0.1 wt% GO‐S), which exhibited the highest storage modulus and complex viscosity. These results suggest that tailoring the GO's oxidation degree and morphology is a key point to obtain an ideal interfacial interaction between phases.

Probing mechanical properties of graphene oxide/epoxy composites based on nano indentation technique

“…The presence of these functional groups destroys the graphite lattice, resulting in an increase in layer spacing. 40,41 The XRD diffraction angle of GO can also analyze the degree of oxidation of graphite, that is, the smaller the diffraction angle, the larger the layer spacing, indicating that the degree of oxidation is also higher. To sum up, the graphite was adequately oxidized to GO using the modified Hummers’ method.

Figure 1.X-ray diffraction patterns of graphite and graphene oxide (a), FTIR spectra of GO and KH-GO (b), the XPS spectra of GO and KH-GO (c), and full scan spectra XPS C1s fitting spectra of GO and KH-GO (d).

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“…In Figure 1(c) are, respectively, XPS spectra of GO and KH-GO. It can be seen from the Figure that GO only contains carbon and oxygen elements, 40 while the KH-GO contains carbon and oxygen elements, and Si2p and Si2s peaks also appear in the full spectrum of KH-GO, which also indicates that silanized GO has been successfully prepared. In order to further study the types of groups on the surface of the sample, peak splitting was carried out for KH-GO and C1s of GO.…”

“…The presence of these functional groups destroys the graphite lattice, resulting in an increase in layer spacing. 40,41 The XRD diffraction angle of GO can also analyze the degree of oxidation of graphite, that is, the smaller the diffraction angle, the larger the layer spacing, indicating that the degree of oxidation is also higher. To sum up, the graphite was adequately oxidized to GO using the modified Hummers' method.…”

Comparison of mechanical properties and thermal stability of graphene‐based materials and halloysite nanotubes reinforced maleated polymer compatibilized polypropylene nanocomposites

“…Recent study has shown that PP/GO nanocomposite with higher oxygenated functional group (GO-powder) exhibited lower thermal stability compared to PP/GO nanocomposite containing very low oxygenated F I G U R E 6 Elongation at break percent of PP/GNP/MAPP, PP/GO/MAPP, and PP/HNTs/MAPP nanocomposites functional groups (GO-Solution). [70] Previous studies have shown that at high content of HNTs ca. 10 phr, PP thermal stability was considerably improved.…”

From two‐dimensional materials to polymer nanocomposites with emerging multifunctional applications: A critical review

“…All of these characteristics made GRM the most employed nanofillers to obtain nanocomposites over the last few years, [ 53–62 ] as can be seen in Figure 2. It's also important to note that by 2019, papers on graphene/polymer composites account for about 50% of all articles on graphene‐based composites.…”