In 2004, a single-crystalline graphite film of atomic thickness was isolated [1]. The researchers responsible for this revolutionary work, Novoselov and Geim, were shortly thereafter awarded the Nobel Prize in Physics for 'innovative experiments with graphene' in 2010. Several researchers have used graphene (Gr), graphene oxide (GO), and reduced graphene oxide (rGO) as mechanically reinforcing nanoparticles in polymeric matrices. The insertion of these two-dimensional (2D) materials considerably improves the mechanical properties of the polymers. They also increase the thermal and electrical conductivity and the dimensional stability of the composite when compared to the polymer matrix [2-7]. Important challenges still need to be overcome to produce polymer nanocomposites based on two-dimensional particles (graphene-based materials, molybdenum disulfide, hexagonal boron nitrite, and phosphorene among others) on a large scale. Essentially, there are three strategies for nanocomposites preparation: 1) solution mixing, 2) in situ polymerization, and 3) melt mixing. The first two options achieve excellent results in terms of particles dispersion, however,

The weathering behavior of polystyrene and polystyrene–montmorillonite composites containing 2.5, 5.0, and 7.5 wt% of montmorillonite (MMT) was investigated. Samples were exposed to UV radiation for periods of up to ∼12 weeks and their molecular weight, chemical changes, and mechanical properties were monitored as a function of time. The addition of MMT was shown to improve the photostability of all composites investigated, probably because of a screen effect against UV radiation and barrier effect against diffusion of oxygen promoted by the silicate layers of MMT. Scanning electron microscopy of fracture surfaces of degraded samples showed that there is a degraded layer near the surface that provided a recovery of tensile strength of the samples. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

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Surface properties are extremely important for materials applied in the biomedical areas such as poly(vinyl alcohol)-PVA. The precise control of the surface characteristics on these materials may adjust and expand its applications. Here, we present a new strategy to tune the surface properties of poly(vinyl alcohol)/graphene oxide (PVA/GO) films by manipulation of GO particles (amount and level of oxidation) and also by in situ reduction of GO. Adopting a different approach from the methods currently proposed, the reduction process of GO was carried out by exposing the PVA/GO films to hydrazine vapor to maintain the degree of particle dispersion. Raman spectroscopy, contact angle (surface energy), X-ray diffraction, and atomic force microscopy were used to evaluate the interaction between PVA and GO particles and also to characterize graphene polymer composites properties at the surface of the films. The results indicated that there is a strong interaction between the GO particles and polar PVA groups mainly at a very specific stoichiometric ratio. Consequently, the surface properties of the PVA/GO films may be tuned by altering the concentration of the particles, their level of oxidation as well as by the exposure to hydrazine vapor. The impact of these affirmations is extremely important for improving the suitability of PVA in applications such as biomaterial, membranes, packaging, and others that need a rigorous control of surface properties. POLYM. COMPOS., 00:000-000, 2017.

The weathering behavior of polystyrene (PS) and PS/montmorillonite nanocomposite with and without addition of ultraviolet (UV) absorber and/or antioxidant was investigated. Samples were exposed to UV radiation in the laboratory for periods of up to approximately 12 weeks. The samples were exposed for various irradiation intervals, and their tensile and impact strength was monitored through a factorial experimental design 2 4 . The molecular weight, yellowness, and fracture surface were also monitored. The results generated by analysis of variance (ANOVA) Table showed that UV absorber and exposure time had the most important effects positive and negative, respectively. These results could be seen for neat PS and PS/MMT nanocomposite. The presence of antioxidant alone did not have any significant effect but when mixed with UV absorber presented a small synergism. These results corroborate with molecular weight, yellowing and fracture surface of tensile and impact samples.