Effect of graphene loading on thermomechanical properties of poly(vinyl alcohol)/starch blend

Polymer nanocomposites based on poly(vinyl alcohol) (PVA)/starch blend and graphene were prepared by solution mixing and casting. Glycerol was used as a plasticizer and added in the starch dispersion. The uniform dispersion of graphene in water was achieved by using an Ultrasonicator Probe. The composites were characterized by FTIR, tensile properties, X‐ray diffraction (XRD), thermal analysis, and FE‐SEM studies. FTIR studies indicated probable hydrogen bonding interaction between the oxygen containing groups on graphene surface and the –OH groups in PVA and starch. Mechanical properties results showed that the optimum loading of graphene was 0.5 wt % in the blend. XRD studies indicated uniform dispersion of graphene in PVA/starch matrix upto 0.5 wt % loadings and further increase caused agglomeration. Thermal studies showed that the thermal stability of PVA increased and the crystallinity decreased in the presence of starch and graphene. FE‐SEM studies showed that incorporation of graphene increased the ductility of the composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41827.     

Convenient synthesis of sulfonamides from amines and p‐toluene sulfonyl chloride mediated by crosslinked poly(4‐vinylpyridine)

A general, mild, and convenient method has been developed for the synthesis of various N‐substituted and N, N‐disubstituted sulfonamides, as a class of sulfa drugs, from the corresponding amines and p‐toluene sulfonyl chloride in the presence of readily available crosslinked poly(4‐vinylpyridine) as a catalyst, base or polymeric substrates. The use of polymeric catalyst simplifies routine sulfonylation of amines because it eliminates the traditional purification. The polymer can be removed quantitatively and it can be regenerated and reused for several cycles without losing its activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Curing enhancement and network effects in multi‐walled carbon nanotube‐filled vulcanized natural rubber: evidence for solvent sensing

Electrically and thermally conductive polymer composites offer great possibilities in various electronic fields because of their low weight and ease of processing. This paper addresses the curing behaviour and network properties of conducting multi‐walled carbon nanotube (MWCNT)‐reinforced natural rubber (NR) nanocomposites, emphasizing the sensing and diffusion performances. NR/MWCNT composites were prepared following a special master batch technique which allows the appropriate distribution of nanotubes within the elastomer. The sensing responses of the composites towards solvents were observed as variations in electrical resistance. Thermal resistance and glass transition behaviour were examined and correlated with the swelling measurements as evidence for solvent sensing. An optimum level of 3 phr of MWCNTs is understood to lead to the best properties for the NR/MWCNT composites. Finally, the structural morphology and interfacial interactions were found to have correlations with cure reactions, glass transition temperatures and sensing responses of all compositions. © 2017 Society of Chemical Industry     

Fumed SiO2 nanoparticle reinforced biopolymer blend nanocomposites with high dielectric constant and low dielectric loss for flexible organic electronics

In the present study, fumed silica (SiO₂) nanoparticle reinforced poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) blend nanocomposite films were prepared via a simple solution‐blending technique. Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to elucidate the successful incorporation of SiO₂ nanoparticles in the PVA/PVP blend matrix. A thermogravimetric analyzer was used to evaluate the thermal stability of the nanocomposites. The dielectric properties such as dielectric constant (?) and dielectric loss (tan δ) of the PVA/PVP/SiO₂ nanocomposite films were evaluated in the broadband frequency range of 10^?2 Hz to 20 MHz and for temperatures in the range 40–150 °C. The FTIR and UV–vis spectroscopy results implied the presence of hydrogen bonding interaction between SiO₂ and the PVA/PVP blend matrix. The XRD and SEM results revealed that SiO₂ nanoparticles were uniformly dispersed in the PVA/PVP blend matrix. The dielectric property analysis revealed that the dielectric constant values of the nanocomposites are higher than those of PVA/PVP blends. The maximum dielectric constant and the dielectric loss were 125 (10^?2 Hz, 150 °C) and 1.1 (10^?2 Hz, 70 °C), respectively, for PVA/PVP/SiO₂ nanocomposites with 25 wt % SiO₂ content. These results enable the preparation of dielectric nanocomposites using a facile solution‐casting method that exhibit the desirable dielectric performance for flexible organic electronics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44427.     

Dispersed air flotation and foam fractionation for the recovery of microalgae in the production of biodiesel

Microalgae biomass has great potential for being used as feedstock for the sustainable production of biodiesel, as it is able to produce 7–31 times more oil than the top terrestrial crop. It is a green alternative to the currently utilized energy sources as it can reduce CO, CO₂ and hydrocarbon emissions. However, downstream processing costs for the dilute biomass are a major challenge. Foam flotation has been recently investigated for the recovery of microalgae cells from dilute liquid suspensions. A number of variables on the effectiveness of foam flotation for microalgae have been investigated, which include surfactant type and concentration, cell concentration, pH, hydrophobicity, time, growth stage, flow rate, ionic strength, alkalinity, temperature, bubble size, and column size. It appears to be a promising method for the recovery of algae for biofuel production, as a result of the high removal recoveries, good enrichment ratios, ability to process large volumes of biomass, and its ease of operation. However, literature on this subject is scarce, and there are research gaps that should be investigated including characterization of microalgae cells and impact on foam separation and the effect of surfactant as a treatment prior to lipid extraction.     

Solution-processed white graphene-reinforced ferroelectric polymer nanocomposites with improved thermal conductivity and dielectric properties for electronic encapsulation

The recent surge in graphene research has stimulated interest in the investigation of various two-dimensional (2D) nanomaterials, including 2D boron nitride (BN) nanostructures. Among these, hexagonal boron nitride nanosheets (h-BNNs; also known as white graphene, as their structure is similar to that of graphene) have emerged as potential nanofillers for preparing thermally conductive composites. In this work, hexagonal boron nitride nanoparticles (h-BNNPs) approximately 70 nm in size were incorporated into a polyvinylidene fluoride (PVDF) matrix with different loadings (0–25 wt.%). The PVDF/h-BNNP nanocomposites were prepared by a solution blending technique and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), polarized optical microscopy (POM) and scanning electron microscopy (SEM). In addition, the thermal conductivity and dielectric properties of the nanocomposites were investigated. The incorporation of h-BNNPs in the PVDF matrix resulted in enhanced thermal conductivity. The highest value, obtained at 25 wt.% h-BNNP loading, was 2.33 W/mK, which was five times that of the neat PVDF (0.41 W/mK). The thermal enhancement factor (TEF) at 5 wt.% h-BNNP loading was 78%, increasing to 468% at 25 wt.% h-BNNP loading. The maximum dielectric constant of approximately 36.37 (50Hz, 150 °C) was obtained at 25 wt.% h-BNNP loading, which was three times that of neat PVDF (11.94) at the same frequency and temperature. The aforementioned results suggest that these multifunctional and high-performance nanocomposites hold great promise for application in electronic encapsulation.     

Latex coatings containing antifeedants: Formulation,characterization, and application for protection of conifer seedlings against pine weevil feeding

Latex-based coatings for protection of tree seedlings against pest insect feeding are evaluated with respect to surface-, mechanical-, and release properties and antifeedant activity. The latex dispersion Eudragit copolymer (EC) was used to form the coatings, 2,6-di-tert-butyl-4-methylphenol (BHT) and cis-dihydropinidine (Alk) as antifeedants, and a thickener and a alkylglucoside based nonionic surfactant were used as additives to optimize the release- and mechanical properties of coatings. Coating characterization was performed with respect to surface morphology (atomic force microscopy, AFM) and surface wetting (contact angle), as well as to mechanical (tensile stress- and tensile strain at break) properties. Surface smoothness and wettability as well as elasticity increased with addition of the surfactant. The optimized coatings were found to be elastic and water resistant at 3–6 wt.% of BHT and 3 wt.% of surfactant. BHT was released into SDS/water at very low rates. Several formulations of BHT and Alk were efficient in preventing the feeding on conifer bark by a pine insect, Hylobius abietis both in laboratory (no-choice) and in field (3 months) tests.     

MicroRNA-16 Restores Sensitivity to Tyrosine Kinase Inhibitors and Outperforms MEK Inhibitors in KRAS-Mutated Non-Small Cell Lung Cancer

Background: Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. Chemotherapy, the treatment of choice in non-operable cases, achieves a dismal success rate, raising the need for new therapeutic options. In about 25% of NSCLC, the activating mutations of the KRAS oncogene define a subclass that cannot benefit from tyrosine kinase inhibitors (TKIs). The tumor suppressor miR-16 is downregulated in many human cancers, including NSCLC. The main objectives of this study were to evaluate miR-16 treatment to restore the TKI sensitivity and compare its efficacy to MEK inhibitors in KRAS-mutated NSCLC. Methods: We performed in vitro and in vivo studies to investigate whether miR-16 could be exploited to overcome TKI resistance in KRAS-mutated NSCLC. We had three goals: first, to identify the KRAS downstream effectors targeted by mir-16, second, to study the effects of miR-16 restoration on TKI resistance in KRAS-mutated NSCLC both in vitro and in vivo, and finally, to compare miR-16 and the MEK inhibitor selumetinib in reducing KRAS-mutated NSCLC growth in vitro and in vivo. Results: We demonstrated that miR-16 directly targets the three KRAS downstream effectors MAPK3, MAP2K1, and CRAF in NSCLC, restoring the sensitivity to erlotinib in KRAS-mutated NSCLC both in vitro and in vivo. We also provided evidence that the miR-16–erlotinib regimen is more effective than the selumetinib–erlotinib combination in KRAS-mutated NSCLC. Conclusions: Our findings support the biological preclinical rationale for using miR-16 in combination with erlotinib in the treatment of NSCLC with KRAS-activating mutations.     

EXTRACTION OF SHIKIMIC AND QUINIC ACIDS

Solvent extraction using an extractant/diluent system was evaluated for the recovery of shikimic and quinic acids. Tridodecylamine (TDA) was used as the extractant, and 1-heptanol as the diluent. TDA complexes with the acid resulting in an acid-amine complex, which is solvated by the alcohol diluent. In back extraction, oleic acid was added to the organic phase as a displacer. Oleic acid competitively displaces the carboxylic acid in the acid-amine complex, thus forming a displacer-amine complex. The distribution coefficient for back extraction by competitive displacement increased by at least an order of magnitude depending on the mole to mole ratio of oleic acid to TDA

Based on results from batch extraction experiments, a mass-action analysis was introduced for modeling forward and back extraction. The mass-action analysis served as a tool for understanding the mechanism of the extraction process.