Novel Binary Solvents-Dispersive Liquid—Liquid Microextraction (BS-DLLME) Method for Determination of Patulin in Apple Juice Using High-Performance Liquid Chromatography

A simple and rapid binary solvents-based dispersive liquid–liquid microextraction (BS-DLLME) method has been developed for determination of patulin (PAT) in apple juice followed by high-performance liquid chromatography. This method involves the use of an appropriate mixture of miscible binary extraction solvents and disperser solvent to form fine droplets of extractant in a sample solution. Parameters affecting extraction efficiency such as the type and volume of high-density extraction solvent, the volume of ethyl acetate, the kind and volume of disperser solvent, and salt addition were investigated and optimized. The detection and quantification limits were 2.0 and 10.0 μg L^?1, respectively. The relative standard deviation for five measurements of 25 μg L^?1 of PAT was 3.8 %. The relative recoveries of PAT from apple juice samples at spiking levels of 25, 50, and 75 ng mL^?1 were in the range of 91.3–95.2 %.     

Comparison of cure characteristics and mechanical properties of nano and micro silica‐filled CSM elastomers

In this study, the effect of micro and nano silica and their combination on mechanical and thermal properties of Chlorosulfonated Polyethylene compounds were investigated. Cure characteristics were studied using a Monsanto Moving Die Rheometer at 155°C. Incorporation of nano silica accelerated the vulcanization whereas the micro silica particles decelerated the curing process. Both micro and nano silica increased the crosslink density as evidenced by swelling test. However, this value has been more improved in CSM/nano silica composites. The physico‐mechanical properties of CSM/nano silica are superior compared to CSM/micro silica. Nano silica provided reinforcing efficiency which is not only because of higher specific surface area but also because of various interactions and especially physical interactions which are discussed in the text. Nano silica particles also improved the thermal properties more efficiently. Incorporation of 15 phr (part per hundred) nano and 5 phr micro silica to polymer improved the initial decomposition temperature for about 51°C and 16°C, respectively, using a TGA. The combination of micro and nano silica, showed that by coupling nano and micro fillers, the loading of fillers can be minimized. In other words, the hybrid samples with a lower filler loading behave as efficient as their separate counterpart with higher loading. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42668.     

Direct-write fabrication of freestanding nanocomposite strain sensors

This paper deals with the design and microfabrication of two three-dimensional (3D) freestanding patterned strain sensors made of single-walled carbon nanotube (SWCNT) nanocomposites with the ultraviolet-assisted direct-write (UV-DW) technique. The first sensor consisted of three nanocomposite microfibers suspended between two rectangular epoxy pads. The flexibility of the UV-DW technique enables the sensor and its housing to be manufactured in one monolithic structure. The second sensor was composed of a nanocomposite network consisting of four parallel microsprings, which demonstrates the high capability of the technique when compared to conventional photolithographic technologies. The performances of the sensors were assessed under tension and compression, respectively. The sensors' sensitivities were evaluated by correlating their measured resistivities to the applied displacements/strains. Electrical conductivity measurements revealed that the manufactured sensors are highly sensitive to small mechanical disturbances, especially for lower nanotube loadings when compared to traditional metallic or nanocomposite films. The present manufacturing method offers a new perspective for manufacturing highly sensitive 3D freestanding microstructured sensors.     

Experimental identification of the phenomenon triggering the net vapor generation in upward subcooled flow boiling of water at low pressure

Observation of the bubble behavior was made using a high-speed camera to investigate the mechanisms to cause the net vapor generation in subcooled flow boiling. In the experiments, water was used as the test fluid, the flow direction was vertical upward, and the pressure was kept close to the atmospheric pressure. At high liquid subcooling close to the condition of the onset of nucleate boiling, all the bubbles were lifted off the heated surface immediately after the nucleation to disappear quickly in the subcooled bulk liquid due to condensation. It was found that the void fraction did not increase significantly unless the liquid subcooling became low enough for some bubbles to be reattached to the heated surface after the lift-off. When the reattachment took place, the bubble lifetime was substantially elongated since the bubbles slid up the vertical heated surface for a long distance after the reattachment. The reattachment therefore contributed to an increase in the void fraction. It was concluded that in the experimental conditions tested in this work, the bubble reattachment to the heated surface was a key phenomenon to cause the sharp increase of the void fraction at the point of net vapor generation.     

Liquid Metal Droplet and Graphene Co‐Fillers for Electrically Conductive Flexible Composites

Colloidal liquid metal alloys of gallium, with melting points below room temperature, are potential candidates for creating electrically conductive and flexible composites. However, inclusion of liquid metal micro‐ and nanodroplets into soft polymeric matrices requires a harsh auxiliary mechanical pressing to rupture the droplets to establish continuous pathways for high electrical conductivity. However, such a destructive strategy reduces the integrity of the composites. Here, this problem is solved by incorporating small loading of nonfunctionalized graphene flakes into the composites. The flakes introduce cavities that are filled with liquid metal after only relatively mild press‐rolling (<0.1 MPa) to form electrically conductive continuous pathways within the polymeric matrix, while maintaining the integrity and flexibility of the composites. The composites are characterized to show that even very low graphene loadings (≈0.6 wt%) can achieve high electrical conductivity. The electrical conductance remains nearly constant, with changes less than 0.5%, even under a relatively high applied pressure of >30 kPa. The composites are used for forming flexible electrically‐conductive tracks in electronic circuits with a self‐healing property. The demonstrated application of co‐fillers, together with liquid metal droplets, can be used for establishing electrically‐conductive printable‐composite tracks for future large‐area flexible electronics.     

Effect of OMMTs on flame retardancy and thermal stability of poly(ethylene‐co‐vinyl acetate)/LDPE/magnesium hydroxide composites

The aim of this study was to prepare poly (ethylene‐co‐vinyl acetate) (EVA)/ low density polyethylene (LDPE)/magnesium hydroxide (MH) composites applicable in cable industry with required flame retardancy. For this reason, two types of organo‐modified montmorillonites (OMMT) with different surface polarites (Cloisite 15A and Cloisite 30B) at various concentrations, and also combination of these two OMMTs with overall loadings of 2 wt % and 5 wt % were used. The samples were compounded using a twin screw extruder with total (MH + OMMT) feeding of 55 wt % and 60 wt %. Limiting oxygen index (LOI) of the samples containing 2 wt % of OMMTs increased about 16% and dripping was suppressed according to vertical burning test (UL‐94V). Thermogravimetric results of EVA/LDPE/MH samples containing OMMT showed that the beginning of second step degradation was shifted about 50°C to higher temperatures. The composite tensile strength results showed enhancement by incorporating some amount of nanoclays with EVA/LDPE/MH composites. Scanning electron microscopy images confirmed that MH particles had better wetting by EVA matrix in presence of nanoclays. Oxidative induction time of the EVA/LDPE/MH/OMMT nanocomposites was 140 min, which was more than that of the samples without OMMT (20 min). Employing the equal weight ratios of the two OMMTs demonstrated a synergistic effect on flame retardancy of the samples according to the both tests results (LOI, UL‐94V). X‐ray diffraction analysis of the samples confirmed the intercalation/semiexfoliation structure of nanosilicate layers in the bulk of EVA/LDPE matrix. This led to longer elongation at break and thermal stability of Cloisite 15A based nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40452.     

UV–Visible Spectrometry and Multivariate Calibration as a Rapid and Reliable Tool for Simultaneous Quantification of Ternary Mixture of Phenolic Acids in Fruit Juice Samples

Phenolic compounds are biologically important molecules existed in many different plants and fruits. There is a need for a reliable analytical method possessing speedy monitoring, ease of operation, and simple instrumentation. We have developed a fast and reliable spectrophotometric method for simultaneous determination of p-hydroxybenzoic (PHBA), vanillic (VA), and caffeic (CA) acids in fruit juice samples. To overcome the severe spectral overlapping, partial least squares (PLS) regression as a multivariate calibration method was successfully developed for the simultaneous determination of PHBA, VA, and CA in ternary solutions. The experimental calibration matrix was designed with 25 ternary mixtures of these compounds, and the calibration models were validated with six synthetic mixtures. Calibration graphs were linear in the range of 0.0–6.0, 0.0–12.0, and 0.0–12.0 μg mL^?1; limit of detections (LODs) were found to be 0.092, 0.1 l7, and 0.107 μg mL^?1 for PHBA, VA, and CA, respectively. The root-mean-square errors of prediction (RMSEPs) for the same order of target compounds were 0.084, 0.146, and 0.114. The accuracy of the method was confirmed with the recoveries ranging between 84 and 107 %. The relative standard deviations (RSDs) for the analytes in the analysis of fruit juice samples were lower than 4 %. The PLS results were found to be in good agreement with those obtained by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method. Such a chemometrics-based protocol may be a promising tool for more analytical applications in real sample monitoring, due to its advantages of simplicity, rapidity, and accuracy.     

Mechanical properties of calcium silicate hydrates

The dynamic mechanical properties of compacted samples of synthetic calcium silicate hydrate (C–S–H) were determined at variable stoichiometries (C/S ratio). The stiffness and damping properties of the C–S–H systems were monitored at various increments of mass loss from 11%RH following the removal of the adsorbed and interlayer water. The changes in the storage modulus (E′) and internal friction (tan δ) were discussed in terms of the state of water present in the nanostructure of C–S–H, the evolution of the silicate structure and the interaction of calcium ions in the interlayer region. Results were compared to those for the hydrated Portland cement paste and porous glass. It was shown that the C–S–H in the hydrated Portland cement has a complex yet analogous dynamic mechanical behavior to that of the synthetic C–S–H. The response of these systems upon the removal of water was explained by a layered model for the C–S–H. A mechanistic model was proposed to describe the changes occurring at various stages in the dynamic mechanical response of C–S–H.     

Experimental and FEM failure analysis and optimization of a centrifugal-pump volute casing

Material and geometry are two key factors in ideal mechanical performance of centrifugal-pump casings engaged in high pressures.This paper presents the model generation, static structural analysis, and geometrical modifications performed for a failed volute casing of a real centrifugal-pump. Failure would be examined under hydrostatic test conditions. Finite Element Method is employed in stage of theoretical problem investigation.To control failure phenomenon, necessary geometrical modifications are applied to the model. Geometrical modifications must have the least effect on hydraulic performance and avoid excessive manufacturing costs.Finally, some test volute casings with new geometry would be built to experimentally validate the analytical results and inspect the hydraulic performance.     

Factors Effecting the Performance of Montmorillonite/Magnesium Hydroxide/Poly(propylene) Ternary Composites, 1

A two‐level factorial experimental design was used to examine the combined effects of o‐MMT gallery polarity, surface modification of MDH, MA‐g‐PP and antioxidant addition, together with processing variables, on the burning behaviour and thermal stability of ternary composites based on PP, MDH and o‐MMT. Regression equations highlighted the detrimental effect of o‐MMT intercalants and possible improvement in the dispersion of o‐MMT at higher MDH levels. A polar gallery environment (providing quat OH groups) led to increased char formation, and MA‐g‐PP combined with o‐MMT led to a higher oxidation onset temperature. Addition of o‐MMT to PP/MDH composites can lead to a reduction in the level of MDH required for effective flame retardation.