Exploring the Influence of Methylene Diphenyl Diisocyanate as a Modifier for Ethylene Vinyl Acetate/Thermoplastic Polyurethane Blends

Ethylene vinyl acetate (EVA)/thermoplastic polyurethane (TPU) blend at various blend ratios has been modified via reactive processing with 4,4′-methylene diphenyl diisocyanate (MDI). Modification of the blends with even small amount of MDI shows significant improvement in physico-mechanical properties for EVA/TPU 50/50 and 30/70 blends, and it is also supported by the superior melt rheological behavior and dramatic improvement in oil resistance property. After the treatment of electron beam (dose range: 50–150?kGy), radiation crosslinked EVA/TPU (30:70) blend reveals further improvement in various properties. This particular material can find potential application as cable sheathing component.     

Physicochemical Characterization of Chrysin‐Derivative‐Loaded Nanostructured Lipid Carriers with Special Reference to Anticancer Activity

Homologues long‐chain chrysin derivatives (LCD, C _n: 8–18) were synthesized and incorporated into nanostructured lipid carriers (NLC) with the aim to treat human neuroblastoma. Mutual miscibility and attractive interactions among the NLC components, namely tripalmitin (TP), cetyl palmitate (CP), oleic acid (OA), and the chrysin (CHR) derivatives (LCD) at the air–water interface were assessed by the Langmuir monolayer approach. Optimum combination for the NLC formulations was found to be 2:2:1 (M/M/M) for TP/CP/OA, respectively. NLC formulations, both in the absence and presence of LCD, were characterized by combined dynamic light scattering, electron microscopy, atomic force microscopy, and differential scanning calorimetry. The size and zeta potential of the NLC formulations were found in the range 200–350 nm and ?12 to ?18 mV, respectively. Encapsulation efficiency and release kinetics of CHR and LCD when loaded into NLC were also evaluated. LCD exhibited maximum incorporation, drug‐loading capacity, and sustained release because of its enhanced hydrophobicity. Superior incorporation efficiency and sustained‐release profile of LCD were able to enhance their anticancer activity against human neuroblastoma cell lines, compared to CHR, making them promising agents in combating cancer.     

Design of efficient fir digital differentiators of second and higher degrees by using universal weights

We propose in this paper an efficient design of FIR digital differentiators of degree k, k= 1, 2, 3,…, and their implementation in a novel structure which allows the order to be varied without having to alter the weights used in it. More precisely, we show that by using these ‘universal weights’ in a structure of order N_max, the order can be varied from N= 3 to N_max while keeping the weights fixed and retaining the optimality of performance. Mathematical formulae have been derived for these ‘universal weights’ for differentiators performing in the low- or midband-frequency ranges.     

On separation efficiency

Rising energy costs have renewed interest in energy efficient separations. Such efficiencies can be defined as the free energy of unmixing divided by the work done on and the heat added to the process. The greatest efficiencies occur when the energy cost far exceeds any capital cost. In this limit, rate processes are not important, and efficiency is governed by thermodynamics. Efficiencies for gas absorption and stripping are then typically around 50%. The efficiencies of liquid–liquid extractions are lower, especially when one solute is wanted at higher concentration. The efficiencies of membrane separations are higher, but these require high pressure, normally obtained mechanically. As a result, membrane efficiencies should be reduced by any Carnot efficiency of generating the mechanical energy. These results, which are consistent with earlier estimates for distillation, have implications for carbon dioxide capture as a route to mitigating global warming. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Effects of neutralization on the structure and properties of an ionomer

The structure, morphology, and properties of an ionomer, poly(ethylene‐acrylic‐acid) neutralized by zinc salts (PI) depend on the free carboxylic acid content. In this work, metal acetates (Na, Zn, and Al acetates) were used to control the neutralization levels. A wide range of techniques were used, such as spectroscopic Fourier transform infrared spectroscopy (FTIR), thermal [thermogravimetric analysis, modulated differential scanning calorimetry (MDSC), and dynamic mechanical analysis (DMA)], mechanical (tensile measurement), and small angle neutron scattering (SANS). The melt rheological properties of the samples were also examined. The results show that metal acetate neutralizes free acrylic acid in the ionomer, which has the primary role in controlling ionic association. The number of ionic groups in ionic domains and multiplets in the matrix is dependent on the neutralization level. Metal valence determines the ionic domain or multiplet structure (FTIR), further properties of PI. Dynamic mechanical properties, the ionic transition behaviour, and the mechanical properties are improved compared with PI using monovalent cation (Na⁺), but decreased using trivalent cation (Al³⁺) or shows less significant changes due to steric effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Epitaxial nucleation model for chiral-selective growth of single-walled carbon nanotubes on bimetallic catalyst surfaces

An epitaxial nucleation model for single-walled carbon nanotube (SWCNT) growth on bimetallic catalysts surfaces is reported in support of experimental observations of chiral enrichment. We model the bimetallic catalyst surfaces as a 2D (1 1 1) surface consisting of Ni or a combination of Ni and Fe atoms, with varying average bond length between nearest neighbor atoms which corresponds to the crystal structure of the alloys. The energies associated with nanotube cap formation on these various surfaces are calculated using density functional theory (DFT). We find that certain cap chiralities, such as (8, 4), are more stably bound to a surface that resembles a Ni_0.27Fe_0.73 bimetallic catalyst, whereas other chiralities, such as (9, 4), are more stable on a pure Ni surface. These results help explain the predominance of certain chiralities on specific bimetallic catalysts and provide a potential route to controlling the chirality of as-grown SWCNTs.     

Solubility parameter estimation and phase inversion modeling of bentonite-doped polymeric membrane systems

Effects of bentonite concentration on morphology and permeation characteristics of bentonite-doped polysulfone membranes were investigated. Solubility sphere for bentonite was constructed to estimate its solubility parameter. Thermodynamic modeling of phase inversion of this system was carried out using Flory–Huggins theory. The trade-off between thermodynamic and kinetic parameters was used to predict the membrane morphology for bentonite concentration varying from 0 to 5 wt %. The porosity of bentonite-doped membranes decreased up to 3 wt % that increased thereafter. Morphological analysis showed dense cross section with finger-like macrovoids at 3 wt % beyond which it changed to honeycomb structure with large circular voids. Permeability of 3 wt % membrane was the lowest (5.6 × 10⁻¹² m/Pa s) with 95% bovine serum albumin rejection. Contact angle of the membranes decreased from 83 to 66° with bentonite addition making the membrane more hydrophilic. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48450.     

Benzene physical and chemical organogels: Effect of network scaffolding on the thermodynamic behavior of entrapped solvent molecules

This paper presents a thermodynamic investigation of the benzene physical and chemical organogels, using differential scanning calorimetry (DSC) and intends to draw an appropriate relationship between the gel network structure and the properties. Physical gels, formed by an aluminium soap of fatty acid, and chemical gels, created by in situ cross‐linking of a siloxane copolymer are investigated. The effects of the type and quantity of the gelators and their corresponding network mesh size distribution in the gels on crystallization, melting, and their kinetics are examined. It appears that the kinetics of crystallization of the entrapped solvent is significantly affected by the quality of the gel network scaffolding and can be treated successfully by the Avrami equation of crystallization. From the melting behavior of the entrapped solvent crystallites, quantitative information about the number of solvent molecules bound per molecule of the gelator has been extracted. DSC proves to be a reliable technique to evaluate the population distribution of solvent molecules trapped in the physical and chemical organogel network scaffolding. The state of the solvent may be treated as a probe to understand the structure of the gels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1253–1264, 2004     

Loading rate sensitivity of liquid nitrogen conditioned glass fiber reinforced polymeric composites: An emphasis on tensile and thermal responses

Glass fiber reinforced polymeric (GFRP) composites are being accepted as potential materials for ultra‐low temperature applications. The current investigation is to evaluate effect of liquid nitrogen (LN₂) conditioning (for different intervals of time) on the loading rate sensitivity of tensile response of GFRP composites. In order to assess this, tensile tests of the unconditioned and conditioned specimens were carried out at different crosshead speeds viz. 1, 10, 100, 500, and 1000 mm/min. At 1 mm/min crosshead speed, an improvement of 3.33% and 7.3% ultimate tensile strength (UTS) value was observed in case of 0.25 and 1 h conditioned GFRP composites, respectively, as compared to unconditioned GFRP composites. Similarly, the specimens tested at 1000 mm/min show an improvement of 11.39% and 12.02% UTS for 0.25 and 1 h LN₂ conditioned GFRP composites, respectively, as compared to unconditioned GFRP composites. Effect of LN₂ conditioning on crosshead speed sensitivity of modulus and strain at break are also reported. The in‐service temperature of the GFRP composite was measured using temperature modulated differential scanning calorimetry. Furthermore, dynamic mechanical thermal analyzer was used in the temperature range (40–200 °C) to correlate the mechanical and thermomechanical response of the GFRP composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45856.