The micromechanics of graphene oxide and molybdenum disulfide in thermoplastic nanocomposites and the impact to the polymer-filler interphase

peer reviewedThe addition of two-dimensional nanomaterials to a polymer matrix is a widely known manner to mechanically reinforce the material. The stress-transfer in the polymeric matrices, however, depends on an array of filler and matrix properties as well as on their interface. In this work, we discuss the effects of the distinct levels of interaction of graphene oxide, reduced graphene oxide and molybdenum disulfide with poly(vinyl butyral) in the reinforcement of the polymer. For that, we employed the micromechanical analysis model originally developed by Young et al., which describes the reinforcement behavior of graphene nanoplatelets in a wide range of polymer matrices. Then, using an innovative approach derived from such analysis, we propose novel methods to mathematically evaluate the effects of the filler content upon the polymer/filler interface, and for the determination of the mechanical percolation threshold

Thermal Conductivity Performance of 2D hBN/MoS 2/Hybrid Nanostructures Used on Natural and Synthetic Esters

In this paper, the thermal conductivity behavior of synthetic and natural esters reinforced with 2D nanostructures-single hexagonal boron nitride (h-BN), single molybdenum disulfide (MoS2), and hybrid h-BN/MOS2-were studied and compared to each other. As a basis for the synthesis of nanofluids, three biodegradable insulating lubricants were used: FR3TM and VG-100 were used as natural esters and MIDEL 7131 as a synthetic ester. Two-dimensional nanosheets of h-BN, MoS2, and their hybrid nanofillers (50/50 ratio percent) were incorporated into matrix lubricants without surfactants or additives. Nanofluids were prepared at 0.01, 0.05, 0.10, 0.15, and 0.25 weight percent of filler fraction. The experimental results revealed improvements in thermal conductivity in the range of 20-32% at 323 K with the addition of 2D nanostructures, and a synergistic behavior was observed for the hybrid h-BN/MoS2 nanostructures

Photooxidative Behavior of Polystyrene Nanocomposites Filled with Two-Dimensional Molybdenum Disulfide

This study aimed to investigate how an ultralow content of a molybdenum disulfide (MoS2) two-dimensional particle affects the photodegradation mechanism of polystyrene (PS). Here, an accelerated weathering study was presented on neat polystyrene and its nanocomposites produced with 0.001, 0.002, 0.003 and 0.005 wt% of molybdenum disulfide (MoS2) exposed for various irradiation intervals (up to 8 weeks). The polymer photo-transformations were monitored using size exclusion chromatography (SEC), infrared spectroscopy (FTIR), and UV-Vis spectroscopy. The FTIR and UV/Vis results indicate that the PS degradation mechanism was not altered by the presence of MoS2 particles; however, the degradation reactions were slowed down at higher MoS2 contents (>0.003%). The SEC results proved the stabilizer effect due to MoS2 particles, where M¯n, M¯w, and M¯w/M¯n values after 8 weeks were less modified when compared with the neat PS results. The MoS2 acted as a UV stabilizer, and these two-dimensional particles acted by deactivating the free radicals generated by the PS matrix, even considering the low amount of the filler (<0.005 wt%)

Melting and crystallization of poly(3-hydroxybutyrate): effect of heating/cooling rates on phase transformation

AbstractWe studied the crystallization and melting phenomena of poly (3- hydroxybutyrate) (PHB), a biodegradable and biocompatible semi-crystalline thermoplastic, obtained from renewable resources. Its high crystallinity motivated several studies on crystallization and melting behavior, and also on ways to increase the amorphous polymer fraction. The effect of heating and cooling rates on the crystallization and melting of commercial PHB was investigated by differential scanning calorimetry. Several rates, ranging from 2.5 to 20 °C min–1, were used to study the phase changes during heating/cooling/reheating cycles. The results showed that PHB partially crystallizes from the melt during the cooling cycle and partially cold crystallizes on reheating, and that the relative amount of polymer crystallizing in each stage strongly depends on the cooling rate. The melt and cold crystallization temperatures, as well as the rates of phase change, depend strongly on the cooling and heating rates.</p