Search

Polycarbonate (PC) /graphene nanocomposite was prepared using multilayer graphene (MLG) with loadings of 0.5, 1, and 3 wt% via melt mixing process. Morphological, structural, and thermal properties of the PC/MLG nanocomposites are investigated to look into the influence of MLG on the nanocomposite. A significant increase (∼6.4°C) in glass transition temperature is observed upon the addition of 3 wt% of MLG into the polycarbonate matrix. This increase in glass transition temperature may be due to the interaction between the MLG and polycarbonate polymer matrix. The specific heat capacity of pure PC and PC/MLG nanocomposites varies linearly with temperature below their glass transition. Upon the addition of MLGs, the overall thermal stability of PC/MLG nanocomposites increases with MLG loadings. A maximum increase about 29.23°C in T onset of thermal decomposition is observed in PC/MLG nanocomposite having 3 wt% of MLG loading. The activation energy (Ea) of thermal decomposition is also calculated by kinetic analysis of thermal decomposition of the PC/MLG nanocomposites using Horowitz–Metzger and Broido's methods. [ABSTRACT FROM AUTHOR]

The aim of this study was to produce new nanocomposites with antimicrobial, antioxidant and anticancer properties that can be used in biomedical research based on carboxymethyl cellulose (NaCMC) biopolymer. First, poly(2-oxo-2-(pentafluorophenoxy)ethyl-2-methylprop-2-enoate) (PPFMA) was synthesized and characterized by FTIR and NMR techniques. It was then blended with NaCMC by in situ/hydrothermal method to produce a semi-synthetic functional material. Changes in the FTIR data of the blend and the single Tg value from DSC confirmed the compatibility of the blend. To enhance the thermal and biological properties of the NaCMC-PPFMA blend, biosynthesized Ag-ZnONPs were hydrothermally incorporated into the blend at different weight ratios. The prepared materials were characterized by SEM, EDX, TEM, XRD and FTIR. The thermal stability of the materials was determined by thermogravimetric analysis (TGA), and glass transition temperatures (Tg) was determined by differential scanning calorimeter (DSC). The oxidant, antioxidant, antimicrobial, and cytotoxic properties of PPFMA, Ag-ZnONPs, PPFMA-NaCMC blend, and nanocomposites were investigated in detail. The total oxidant state (TOS) value of the NaCMC-PPFMA blend, which was 0.72 μmol equivalent H 2 O 2 /L, increased to 7.2–10.4 μmol equivalent H 2 O 2 /L with the addition of Ag-ZnONPs. Ag-ZnONPs decreased total antioxidant state (TAS) levels of the nanocomposites while increasing their oxidant activity. Therefore, an increase in the antimicrobial activity of the nanocomposites was observed. Adding Ag-ZnONPs to the NaCMC-PPFMA blend increased the thermal stability by 22 °C and the Tg value by 9 °C. Finally, the potential of Ag-ZnONPs containing nanocomposites in wound healing therapies was examined. The findings suggest that nanocomposites prepared by incorporating Ag-ZnONPs into the semi-synthetic NaCMC-PPFMA blend can be a source of bio-safe raw materials and can be used as potential wound healers. [ABSTRACT FROM AUTHOR]

This article describes micro‐ and nanostructural, mechanical, and thermal properties of nanocomposites based on polyvinyl chloride (PVC) and graphene nanoplatelets (GNP). The primary objective of this study was to extend restricted application area of PVC due to its low thermal stability and limited mechanical properties. GNP‐filled PVC nanocomposites were prepared (0, 0.1, 0.3, 0.5, and 1.0 wt%) by colloidal blending method and characterized in detail. The highest value of the tensile strength 13.73 MPa (an increase of 58%) and the highest value of microhardness 83.42 MPa (an increase of 82%) were obtained with GNP loading content of 0.5 wt% compared neat PVC. The mechanical properties started to decrease at loading higher than 0.5 wt%; however, the thermal properties continued to increase. The differential scanning calorimetry and Fourier transform infrared analysis results of this nanocomposite confirmed that the increase in glass transition temperature from 34.99°C to 44.36°C and the decrease in the height of functional groups peaks proved to prevented segmental relaxation and intermolecular vibrations of PVC, respectively. Thermogravimetric analysis results were showed that the percentage of carbonaceous residue increased to 15.77% by increasing the GNP content from 0.1 to 0.5 wt%. As a result, the best GNP loading was at 0.5 wt% for PVC/GNP nanocomposites where mechanical and thermal properties of PVC/GNP were both enhanced. [ABSTRACT FROM AUTHOR]

In this study, poly(2-(3,5-dichloroanilino)-2-oxoethyl 2-methylprop-2-enoate) (PDCOEMA), a new synthetic polymer based on methacrylate, was synthesized and characterized. The blend of PDCOEMA with chitosan (CS) was prepared by the hydrothermal method and the DSC technique confirmed its formation. It was observed that PDCOEMA increased the thermal stability and glass transition temperature (Tg) of CS. The Tg value of the PDCOEMA-CS blend was increased at about 7 °C with the highest ZnO NPs contribution rate. PDCOEMA-CS/ZnO nanocomposites were prepared by adding ZnO NPs produced by biosynthesis at different weight ratios to the PDCOEMA-CS blend by hydrothermal method. When the thermal stability of nanocomposites determined by TGA was examined, it was observed that it increased significantly compared to CS. While the initial decomposition temperature of CS was 270 °C, this value increased to 293 °C after blending with DCOEMA, and to 317 °C with the addition of 7 % ZnO NPs. Antimicrobial, anticancer, cytotoxic, antioxidant, and wound healing properties of PDCOEMA, CS, PDCOEMA-CS blend, and nanocomposites were determined. According to the obtained results, it was observed that nanocomposites containing 5 % and 7 % ZnO NPs showed good anticancer activity against A549 cells at a dose of 10 μg/mL. The results show that the produced nanocomposites can contribute to developing CS-based materials. [ABSTRACT FROM AUTHOR]

Several composites and nanocomposites based on a polymeric matrix and ceramic fillers are being pursued for use as multifunctional and innovative materials. Nevertheless, there is a series of challenges to be solved in this area such as the understanding of the role of interfaces and the synergy between matrix and fillers. In this work, vulcanized natural rubber nanocomposites were prepared with different concentrations of two kinds of ceramic nanoparticles, potassium strontium niobate (KSrNbO or KSN) and nickel-zinc ferrite (NiZnFeO or NZF), synthesized by a chemical method known as the modified polyol method. Morphological and thermal characterizations were carried out by AFM, TG/DTG, TG/FTIR and DSC. The thermal properties of nanocomposites were compared and discussed as functions of concentration, type and surface of nanoparticles. The results obtained suggest that the base concentration for both types of nanoparticles inside the polymer matrix volume greatly adds to the increase in thermal stability up to 11 % and the glass transition temperature up to 10 °C. A similar evolution for the glass transition temperature ( T ), thermal stability temperature ( T ) and dielectric permittivity ( ε′) was identified, suggesting that these phenomena are mainly dominated by the same mechanisms. These results point to the possibility for the thermal parameter modulation in magnetic and ferroelectric nanocomposites by means of a suitable control of concentration and properties of the KSN and NZF nanoparticles. [ABSTRACT FROM AUTHOR]

Introducing nano-sized fillers increases the matrix/reinforcement interface in polymer nanocomposites (PNC) and improves the performance of these materials. In this work, sol-gel prepared PbO, MgO, and Pb 0.5 Mg 0.5 O powders were incorporated into a poly (vinyl acetate)/poly (vinyl chloride) [PV(Ac–C)], blend. FE-SEM, HR-TEM, and XRD analyses indicated that PbO was composed of nanoparticles (NP) in two phases (tetragonal and orthorhombic) and MgO had a nanoneedle-like morphology with varying lengths and cubic crystal structure. MgO was well distributed in the PV(Ac–C) matrix without affecting its structure. FTIR spectroscopy confirmed the presence of Mg–O and Pb–O vibrations, and the tendency of the materials to adsorb gases (H 2 O and CO 2) from the surrounding atmosphere. The addition of MgO and PbO effectively reduces the intensity of the vibrations of all the blended functional groups, while Pb 0.5 Mg 0.5 O improved the vibrational properties of the blend. The pure blend showed high transmittance (89 % at λ = 700 nm) and 1.0 wt % of MgO, PbO, and Pb 0.5 Mg 0.5 O decreased this value to 67.82, 38.13 and 55.73 % , respectively. Moreover, the optical bandgap decreased and the ratio of charge carriers to electron effective mass (N/m*) were influenced by the dopants. 1.0 wt % MgO greatly improved the mechanical properties of the blend. Furthermore, thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) showed that the films exhibit thermal stability in the temperature range of 120–240 °C. The effect of the dopants on the glass transition temperature (T g) and melting temperature (T m) has been reported. Our results indicate the doped PV(Ac–C) blend is a suitable candidate for coatings and packaging applications. • PbO, MgO and Pb 0.5 Mg 0.5 O/PV(Ac–C) nanocomposites were prepared by facile chemical methods. • The structure and samples' morphology were studied by FE-SEM, HR-TEM, XRD and FTIR. • The optical properties and optical parameters of PV(Ac–C) blend influenced by doping. • MgO improved the mechanical properties and PbO enhanced the thermal stability of the blend. [ABSTRACT FROM AUTHOR]

A new series of four different linear aliphatic ether linked aromatic bismaleimides (AEBMIs) were synthesized from the respective linear aliphatic ether-linked aromatic diamines and maleic anhydride. Further, the POSS-AEBMI nanocomposites were developed by Michael addition reaction of bismaleimide with varying mass percentages of octa(aminophenyl)silsesquioxane and were characterized by the fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Data from thermal studies revealed that the POSS-reinforced AEBMI nanocomposites possesses higher glass transition temperature ( Tg), thermal stability, limiting oxygen index, and lower dielectric constant when compare to that of neat AEBMI. X-ray diffraction and transmission electron microscopy analysis confirmed the molecular level dispersion of POSS in the AEBMI matrix. [ABSTRACT FROM AUTHOR]

Nanocomposites of polystyrene (PS) with modified CoAl-layered double hydroxide (CoAl–LDH) were preparedviasimple solvent blending method and the effect of CoAl–LDH content on the structural and thermal properties was investigated. The structural and thermal properties of the nanocomposites were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The nano-scale dispersion of the CoAl–LDH layers in the PS matrix is verified by the (0 0 3) XRD reflection of the modified CoAl–LDH. The XRD data show that the exfoliated PS/CoAl–LDH nanocomposites can be obtained by controlling the LDH loading of about 5 wt%. TEM analysis also confirms the formation of exfoliated PS nanocomposites with 3 wt% and 5 wt% LDH loading. The thermal degradation temperature of the PS nanocomposite containing 5 wt% CoAl–LDH is found to be 12°C higher than that of pure PS when 50% weight loss is selected as a point of comparison. The glass transition temperature (Tg) of PS nanocomposites is about 14°C higher than that of pure PS. [ABSTRACT FROM AUTHOR]

Low-temperature transmission electron microscopy (TEM) studies were performed on polystyrene (PS, M = 234 K) - Au nanoparticle composite thin films that were annealed up to 350°C under reduced pressure conditions. The composite thin films were prepared by wet chemical approach and the samples were then subsequently spin-coated on a carbon-coated copper grid for TEM measurements. TEM measurements were performed at liquid nitrogen temperatures to reduce the electron-beam-induced radiation damage. The results showed a marginal increase in Au nanoparticle diameter (2.3 nm-3.6 nm) and more importantly, an improved thermal stability of the polystyrene (PS) composite film much above its glass transition temperature. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA)/graphene GNP nanocomposites with 0, 3, 5, 7% wt.% GNP concentrations have been prepared using the novel Spark Plasma Sintering (SPS) technique. This was performed under a fixed operating temperature of 160 °C, pressure of 25 MPa, heating rate of 20 °C/min and holding time of 10 min. The appearance of peak around 26.5° for PLA/GNP nanocomposites in the X-ray diffraction (XRD) analysis is typical of the presence of GNP. The thermogravimetric-fourier transform infrared radiation (TG-FTIR) analysis and differential scanning calorimetry (DSC) were carried out to investigate the thermal behaviour of the sintered nanocomposite. The surface morphology of the nanocomposite was performed using the scanning electron microscopy (SEM). The result shows that the thermal degradation temperature of PLA has been enhanced by an approximate double-fold increase via the novel SPS technique. The crystallinity and melt temperature of the sintered nanocomposites only improves slightly as compared to sintered pure PLA. The thermal stability, residual content, and stiffness of the nanocomposites also increases with increasing GNP filler content in the PLA matrix. Furthermore, the dynamic mechanical analysis (DMA) confirmed a better enhancement in thermal stability of the nanocomposites through increase in glass transition temperature than the DSC report. This is own to the better sensitivity of DMA to local segmentation motion compared to DSC. However, the SPS processing technique can be said to have contributed greatly to the enhancement in thermal stability than the inclusion of GNP as-sintered pure PLA exhibited similar patterns and close thermal properties to the sintered PLA/GNP nanocomposites samples. Furthermore, this process route enables the development of highly densified, lightweight polymer nanocomposite material within a short processing time. Image 1040 • SPS technique was engaged to prepare PLA and PLA/GNP nanocomposites. • The thermal degradation temperature of PLA was improved by over 100% via SPS process route. • PLA/GNP nanocomposites stiffness increases with increasing GNP content in the matrix. • Sintered-PLA/GNP nanocomposites have higher residual content than sintered PLA. • DMA results proved to be more sensitive compared to DSC in measuring the glass transition temperature (Tg). [ABSTRACT FROM AUTHOR]