RESUMO
By taking advantage of design and construction of strong graphene-matrix interfaces, we have prepared modified graphene/polyimide (MG/PI) nanocomposites via a two-stage process consisting of (a) surface modification of graphene and (b) in situ polymerization. The 2 wt % MG/PI nanocomposites exhibited a 20-fold increase in wear resistance and a 12% reduction in friction coefficient, constituting a potential breakthrough for future tribological application. Simultaneously, MG also enhanced thermal stability, electrical conductivity, and mechanical properties, including tensile strength, Young's modulus, storage modulus, and microhardness. Excellent thermal stability and compatibility of interface, strong covalent adhesion interaction and mechanical interlocking at the interface, as well as homogeneous and oriented dispersion of MG were achieved here, contributing to the enhanced properties observed here. The superior wear resistance is ascribed to (a) tribological effect of MG, including suppression effect of MG in the generation of wear debris and protective effect of MG against the friction force, and (b) the increase in mechanical properties. In light of the relatively low cost and the unique properties of graphene, the results of this study highlight a pathway to expand the engineering applications of graphene and solve wear-related mechanical failures of polymer parts.
RESUMO
The conformation and arrangement of poly(ethylene oxide) (PEO) chains in clay galleries is still controversial. In our work, various spectroscopic methods have been used to explore the conformation of PEO in clay galleries. The melt intercalation process is investigated using variable-temperature Raman spectroscopy. It is found that the sharp peak at 860 cm(-1) appears with an increase of the intercalation time, suggesting the formation of a crown-ether-like association between the cations and the PEO oxygen atoms. Two-dimensional infrared correlation analysis also suggests the presence of the crown-ether-like association between them. Therefore, a distorted helical conformation may be a more accurate way to describe the conformation of the PEO chains in the clay galleries, and a single-layer arrangement is suggested.
