Preparation and properties of enhanced nanocomposites based on PLA/PC blends reinforced with silica nanoparticles

In order to lower brittleness of biobased polylactic acid (PLA), its blending with polycarbonate and nanosilica is aimed. In this line, to increase compatibility of the ingredients, dicumyl peroxide (DCP) and Cobalt (II) acetylacetonate (Co) were used as grafting and transesterification catalysts, respectively. The X‐ray diffraction (XRD) spectra demonstrated high compatibility of the ingredients by broadening of the PLA characteristic peaks and, also, good dispersion of nanosilica particles, especially in PLA/PC/Silica/Co sample. The EDX maps confirmed good nanosilica dispersion, too. The silica nanoparticle size was ranged from 20 to 100 nm in transmission electron microscopy (TEM) pictures. All nanocomposites showed improved thermal stability in thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) results demonstrated lower T_g, T_m, and crystallinity values for the fabricated nanocomposites. Notably, the dynamic mechanical thermal analysis (DMTA) curves confirmed the T_g, T_m, and T_cc trend obtained in DSC; moreover, much higher surface under tan δ peak for PLA/PC/Silica/Co sample was obtained, which implies its higher toughness. The precise tensile study of the samples confirmed significantly higher elongation at break of the nanocomposites, more considerably in PLA/PC/Silica/Co sample, with nearly negligible defect on tensile strength and modulus. In a concise, the obtained results confirmed the higher efficiency of Co catalyst, which leads to the sample with improved characteristics compared with DCP.     

Determination of pesticide residues in peaches by using gas chromatography and mass spectrometric detection

ABSTRACT

A multi-residue method using selected ion monitoring mode GC-MSD has been developed for the quantitative analysis of 30 widely used pesticides in fresh peaches produced in Swat Malakand, Pakistan. The planned methodology involved a sample extraction procedure using liquid-liquid partition with acetonitrile followed by a clean-up step based on solid-phase extraction (SPE). Method validation was performed in accordance with European Union guidelines. The European Union criteria (recovery 70–120%, RSD <20%) were met for majority of pesticides. For most of the pesticides, signal-to-noise ratios were good and background-corrected mass spectra often contained sufficient diagnostic to enable identity and confirmation. The limits of quantification (LOQs) were in the range 0.01–1.0 mg/kg. The above method was successfully applied to the analysis of peach samples (n = 30) from the field. Pesticide concentration in real peach samples was compared with the maximum residue levels (MRLs). Pesticide residues were detected in 73% of the peach samples. Most frequent residues were metalaxyl, α-cypermethrin, azoxystrobin, dimethoate, tebuconazol, λ-cyhalothrin and spiromesifin in peach samples.     

Structural and Spectral Studies of Some Geometric Isomers of N-Pivaloyl-N'-dichlorophenyl Thiourea

N-pivaloyl-Nˊ-(3,4-dichlorophenyl)thiourea (1): monoclinic, P21/a, a=11.57(1), b=9.278(8), c=13.51(1), β=103.85(1)°, V=1408(2)3 , Z=4, μ=0.598 mm-1 ; N-pivaloyl-N'-(3,5- dichlorophenyl)thiourea (2): monoclinic, P21/a, a=7.176(2), b=16.441(4), c=11.923(2), β=92.48(1)°, V=1405.3(6)3 , Z=4, μ=0.600 mm-1 ; N-pivaloyl-Nˊ-(2,6-dichlorophenyl)thiourea (3): orthorhombic, Pnma, a=26.79(1), b=8.780(4), c=5.955(3), V=1400.7(11)3 , Z=4, μ=0.601 mm-1 . All three complexes have an intramolecular hydrogen bond between NˊH and the carbonyl oxygen. Solution 1H NMR studies (CDCl3) show the NH resonance considerable downfield for each thiourea and their positions, as well as that of NH, is affected by substituents on the phenyl ring.     

Effect of Rotary Inertia on the Orientational Behavior of Dilute Brownian and Non-Brownian Fiber Suspensions

The orientational behavior of a dilute suspension of slender Brownian and non-Brownian fibers with rotary inertia in simple shear and turbulent channel flows is numerically investigated. The translational inertia of fibers is neglected. The equations describing the evolution of fibers orientation are integrated along the Lagrangian paths of the fluid elements. The fully developed turbulent channel flow at Re _τ = 180 is provided by a direct numerical simulation (DNS). The coupling between the flow field and the fiber dynamics is one way. The Brownian motion is modeled by a stochastic Wiener process. The results are compared with those of inertia-free particles. In simple shear flow, the inertial non-Brownian fibers align slower than the inertia-free fibers to the shear direction while they tend to the same steady state orientation. For Brownian fibers, the steady state orientation of inertial and inertia-free fibers differ. In turbulent channel flow, the second moment of the orientation distribution function shows an oscillatory behavior at high values of inertia for non-Brownian fibers while the oscillations disappear at lower inertia. For Brownian fibers, the oscillations are weaker due to the damping effect of the Brownian diffusivity.     

A novel polyacrylonitrile-based porous structure gel polymer electrolyte composited by incorporating polyhedral oligomeric silsesquioxane by phase inversion method

A novel polyhedral oligomeric silsesquioxane (POSS) composite polyacrylonitrile (PAN)-based porous structure gel polymer electrolyte (GPE) is prepared by phase inversion method. The POSS additive filler is firstly obtained in the dehydration condensation reaction of vinyltrimethoxysilane (VTMS) and 3-methacryloxypropyltrimethoxysilane (MPTMS). The composition and structure of synthetic POSS and the prepared POSS composite PAN-based GPEs are investigated. It is found that compared with pure PAN-based GPE, the POSS composite PAN-based GPE with 8 wt.% POSS presents the homogeneous pore distribution and abundant electrolyte uptake (540.4 wt.%), which endows GPE-8% with the excellent comprehensive performances: the highest ionic conductivity of 2.62?×?10^?3 S cm^?1 at room temperature, the higher lithium ion transference number of 0.38, the good compatibility with lithium anode, and the higher electrochemical stability window of 5.7 V (vs. Li/Li⁺). At 0.2 C, the GPE-8%-based lithium ion battery produces a satisfactory discharge capacity of 140 mAh g^?1.

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Pitting of Al and Al–Si alloys in KSCN solutions and the effect of light

The pitting corrosion susceptibility of pure Al and three Al-Si alloys, namely (Al-6%Si), (Al-12%Si) and (Al-18%Si) has been studied in 0.04 M KSCN solution. Measurements were carried out under the effect of various experimental conditions using cyclic polarization, potentiostatic and galvanostatic techniques. In all cases, the potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of a thin film of Al₂O₃ on the anode surface. The passive region is followed by pitting corrosion, at a certain critical potential, pitting potential (E_pit), as a result of breakdown of the passive film by SCN^? anions. Cyclic polarization measurements allowed the determination of the pitting corrosion parameters, namely the pitting potential and the repassivation potential (E_rp). Alloyed Si decreased the passive current (j_pass) and shifted both E_pit and E_rp towards more positive values. Thus alloyed Si suppressed pitting attack. The effect of illumination on passivity and the initiation of pitting corrosion on Al in KSCN solutions was also studied. It is observed that illumination of Al leads to an increase in its pitting corrosion resistance-apparent from j_pass, E_pit, and E_rp measurements in aggressive KSCN solutions.     

Fabrication of a nanostructured TiO2/carbon nanotube composite electrode for voltammetric and impedimetric determination of NTO explosive in the water and soil samples

An electrochemical oxidation route was developed for sensitive and selective assay of nitrotriazolone (NTO) explosive in some environmental samples on a multi-walled carbon nanotube (MWCNTs)/TiO₂ nanocomposite paste electrode, for prevention of the analytical interference of conventional reducible energetic compounds. Detailed evaluations were made for the electrochemical behaviour of NTO on the modified electrode by adsorptive stripping voltammetry, electrochemical impedance spectroscopy (EIS) and chronoamperometry techniques in the pH range of 2.0–10.0. Parameters such as diffusion coefficient constant of NTO were calculated, and various experimental conditions were also optimised. Under optimal conditions the calibration curve had two linear dynamic ranges of 130.0–3251.5 μg L^?1 and 6.5–26.0 mg L^?1 with a detection limit of 26.0 μg L^?1 (0.2 μmol L^?1) and precision of <3%. This electrochemical sensor was further applied to determine NTO in real soil and water samples with satisfactory results.     

Blow up of series solutions

We prove the convergence of series solutions of a semilinear reaction diffusion equation with quadratic nonlinearity. The solution which blows up in finite time is sought as a sum of exponential functions and is shown to be a classical one. The algorithm can be used to approximate and extend these solutions beyond blowup.