Post Curing as an Effective Means of Ensuring the Long-term Reliability of PDMS Thin Films for Dielectric Elastomer Applications

Post curing can be used to facilitate volatile removal and thus produce polydimethylsiloxane (PDMS) films with stable elastic and electrical properties over time. In this study, the effect of post curing was investigated for commercial silicone elastomer thin films as a means of improving long-term elastomer film reliability. The Young’s moduli and electrical breakdown strengths of commercial (silica-reinforced) PDMS elastomer films, with and without additional 35 parts per hundred rubber titanium dioxide (TiO₂), were investigated after high-temperature (200°C) post curing for various time spans. The elastomers were found to contain less than 2% of volatiles (significantly higher for TiO₂-filled samples), but nevertheless a strong effect from post curing was observed. The young’s moduli as well as the strain-dependent behavior were found to change significantly upon post curing treatment, where Young’s moduli at 5% strain increase with post curing. Furthermore, the determined dielectric breakdown parameters from Weibull analyses showed that greater electrical stability and reliability could be achieved by post curing the PDMS films before usage, and this method therefore paves a way toward more reliable dielectric elastomers.     

Effects of varying melt flow rates on laser melt-electrospinning of low-density polyethylene nanofibers

The ultimate functionality and applicability of polymeric nanofibers are mainly to subject on its diameter. This study explores the influence of melt flow rates (MFRs) of low-density polyethylene (LDPE) on the diameter of laser melt electrospun nanofibers. Ethylene-vinyl alcohol (EVOH) copolymer was added to the nonpolar LDPE as a spinning aid. After electrospinning, the EVOH was removed from LDPE/EVOH blend fiber by treating with isopropanol/water solution and LDPE nanofiber was obtained with a diameter of only 190 ± 85 nm for the highest MFR. A linear diameter reduction was observed for pure LDPE and EVOH removed LDPE fiber with the increase of MFR. However, a slight diameter increment was reported for the LDPE/EVOH blend fiber with higher MFR due to the improved melt viscosity of the component. A massive diameter decrement was found after EVOH removal from the blended fiber, resulting in the renovation of microfiber to a stable nanoscale dimension.     

A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins

Summary A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins is described. Aflatoxins B₁, B₂, G₁, and G₂, are extracted by methanol/water (85+15) and partitioned into methylene dichloride. The methylne dichloride solution is cleaned up on a polypropylene column, filled with 0.5 g silica gel 60. The aflatoxins are eluted with cloroform-acetone (90:10) and are detected using bidirectional thin-layer chromatography (TLC) with aluminium silica gel foil. The mean recovery of aflatoxins B₁, B₂, G₁, and G₂, in corn samples was 73, 78, 80, and 64%, respectively; the limit of detection was 0.5 g/kg. The results can also be confirmed by derivative formation using trifluoroacetic acid on the TLC plate. The method has been applied to a wide range of foods with good results.

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Eine schnelle, empfindliche und kostengünstige Methode zum Nachweis, zur Bestimmung und Bestätigung von Aflatoxinen

Zusammenfassung Es wird eine schnelle, empfindliche und kostengünstige Methode zum Nachweis, Bestimmung und Bestätigung von Aflatoxinen beschrieben. Die Aflatoxine B₁, B₂, G₁ und G₂ werden mit Methanol/Wasser (85+15) extrahiert und in Dichlormethan überführt. Der Dichlormethanextrakt wird auf einer mit 0,5 g Kieselgel 60 gefüllten Polypropylensäule gereinigt. Die Aflatoxine werden mit Chloroform/Aceton (90+10) eluiert und mit zweidimensionaler DC auf Kieselgel-Alufolien nachgewiesen. Die mittleren Wiederfmdungsraten für die Aflatoxine B₁, B₂, G₁ und G₂ in Maismehl betragen 73, 78, 80 und 64%, die Nachweisgrenzen liegen durchschnittlich bei 0,5 g/kg. Zur Bestätigung verdächtiger Befunde kann auf der Platte mit Trifluoressigsäure derivatisiert werden. Die Methode ist bisher an einer Vielzahl von verschiedenen Lebensmitteln mit gutem Erfolg getestet worden.

     

Mesocosm study of enhanced bioretention media in treating nutrient rich stormwater for mixed development area

A well-designed engineered soil for bioretention is important as it ensures that pollutant removal requirements are met. This laboratory study investigated the nutrient removal efficiency of bioretention media enhanced with 10% (by volume) additives from various waste materials (cockle shell, newspaper, printed paper, coconut husk and tyre crumb) and planted with Red Hot Chinese Hibiscus (Hibiscus rosa-sinensis), a common landscape shrub in tropical countries. The results showed that media enhanced with shredded newspaper demonstrated a significant improvement in total nitrogen (TN) removal (80.4%), compared to standard bioretention media (57.5%) without compromising total suspended solids (TSS) and total phosphorus (TP) removal, when dosed with actual runoff. The thick root system and rapid growth rate of the plant was proven to contribute to TN removal. This study concluded that shredded newspaper can be a potential addition to enhance bioretention media performance in treating stormwater, especially nutrient rich runoff from mixed development areas.     

Characterization of magnetic paper using Fourier transform infrared spectroscopy

Magnetic papers were prepared by using the co-precipitation method. The spectral data of the magnetic fibres were obtained by using the photoacoustic Fourier transform infrared spectroscopy (FTIR-PAS) and attenuated total reflection (ATR). It was found that the elevated loading degree increased the IR absorption and reduced the tensile strength of the paper. The partial-least-squares analyses showed that the FTIR-ATR data were strongly correlated with the degree of loading and the correlation obtained was better than that of the FTIR-PAS spectral data.     

Optimization of the extraction conditions of cane wax from filter press mud

The solvent extraction of cane wax from filter press mud is dependent on various factors such as the temperature of extraction, solvent ratio, time of extraction and the particle size of the mud. Optimization studies of these parameters are given. This investigation provides laboratory data, which are useful for designing a cane wax extractor under these optimized conditions, which can be easily adopted by sugar factories to utilize their waste.     

Synthesis of some novel 2(1H)-quinazolinones and 2-thioxo analogues from newly synthesised 1-acyl-3-alkoxyphenylureas and thioureas

A convenient route for the synthesis of new 2(1H)-quinazolinones (IIc—h) and 2(1H)-quinazolinethiones (IIi—j) is discussed. It involves the cyclodehydration of 1-acyl-3-(alkoxyphenyl)ureas (Ic—h) and the corresponding thioureas (Ii—j) in polyphosphoric acid. Elucidation of structures of the isolated products have been proved in the light of their elemental analysis and spectroscopic data.     

Observations relating to oxygen permeability measurements on membranes

A cell for electrochemically measuring dissolved oxygen permeability coefficients (P_d) has been constructed and tested successfully with Teflon^® FEP membranes of previously established P_d values. Mixtures of n-butyl acrylate, N-vinyl-2-pyrrolidone and a crosslinking agent have been copolymerized to complete conversion via γ-irradiation. Thin discs of the products have been swollen in water to yield new hydrogels with equilibrium water contents (EWC) of 39–73%. The observed exponential increase in P_d with EWC was of a similar form to that reported by other workers for chemically different hydrogels. At a fixed EWC, there was an increase in P_d with thickness of membrane, in accord with the theoretical model for multilayer diffusive transport. However, the results also indicate the effect of the aqueous boundary layer on the measured value of P_d. The need is demonstrated for measurements on highly permeable hydrogels with aqueous environments to be conducted under well-defined transport controlled conditions, if reliable values of P_d are to be obtained.     

Photo-Thermoelastic Model with Time-Fractional of Higher Order and Phase Lags for a Semiconductor Rotating Materials

Silicon - In this work, a modified generalized fractional photothermeolastic model is constructed on the basis of the fractional calculus technique. For the considered model, Fourier law is...