Shelf‐life prediction of perilla oil by considering the induction period of lipid oxidation

Kinetic models for the induction period (IP) of lipid oxidation were developed to predict the shelf‐life of perilla oil during storage. The degree of lipid oxidation was measured in terms of peroxide values (PV). The perilla oil was stored in the dark at various temperatures. The IP was measured at the intersection point of two linear lines and in terms of time and PV at the IP. The IP was expressed by an Arrhenius‐like relationship. Before and after the IP, the reaction followed pseudo‐zero‐order kinetics. The oxidation degrees according to storage times were computed by considering the variables, IP and reaction rate constants. The prediction model equation that was developed to determine shelf‐life is more accurate than in previous studies. Conclusively, considering the IP of lipid oxidation is essential for predicting the shelf‐life of perilla oil and is expected to be applicable to other vegetable oils. Practical applications : In kinetic modeling for shelf‐life estimation in terms of lipid oxidation, induction period (IP) is rarely considered. Thus the estimation of peroxide values (PV) from such models might be inaccurate. The IP was observed in perilla oil oxidation and kinetic models involving the IP were developed. This work enables a better estimation of oxidation. Besides, a shelf‐life diagram of perilla oil has been constructed as a valuable tool for quality control in the food industry.     

Synthesis of liquid crystalline epoxy and its mechanical and electrical characteristics—curing reaction of LCE with diamines by DSC analysis

An aromatic liquid crystalline epoxy monomer based on biphenyl mesogen was synthesized and cured with three different aromatic diamines. The curing reaction characteristics were analyzed by DSC, and the data were introduced to the Kissinger equation to attain the kinetic parameters. Diglycidyl ether of 4,4′‐biphenyl (DGEBP)/4,4′‐diaminobiphenyl (DABP), and DGEBP/4,4′‐methylenediamine (MDA) systems showed an exotherm curing reaction after comelting of the monomers; the DGEBP/p‐phenylenediamine (PDA) system's curing reaction took place in the solid state without melting of monomers. The activation energy and preexponential factor for the DGEBP/DABP system were 55.6 kJ/mol and 4.0 × 10⁶ min^?1, respectively. Those values for DGEBP/MDA and DGEBP/PDA systems were 55.1 kJ/mol and 1.0 × 10⁶ min^?1 and 148.8 kJ/mol and 7.7 × 10¹⁹ min^?1, respectively. The rate constant at 100°C for DGEBP/PDA is 2 times higher than those for DGEBP/DABP and DGEBP/MDA, which have almost the same values. Strictly speaking, the rate constant of DGEBP/DABP is a little higher than that of DGEBP/MDA, and these results are in good agreement with the DSC curves. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2419–2425, 2002     

Preparation of core–shell type nanoparticles of diblock copolymers of poly(L‐lactide)/poly(ethylene glycol) and their characterization in vitro

Core–shell type nanoparticles of poly(L ‐lactide)/poly(ethylene glycol) (LE) diblock copolymer were prepared by a dialysis technique. Their size was confirmed as 40–70 nm using photon correlation spectroscopy. The ¹H‐NMR analysis confirmed the formation of core–shell type nanoparticles and drug loading. The particle size, drug loading, and drug release rate of the LE nanoparticles were slightly changed by the initial solvents that were used. The drug release behavior of LE core–shell type nanoparticles showed an initial burst during the first 12 h and then a sustained release until 100 h. The degradation behavior of LE block copolymer nanoparticles was divided into three phases: the initial rapid degradation phase, the stationary phase, and the rapid degradation phase until complete degradation. It was suggested that lidocaine release kinetics were predominantly governed by the diffusion mechanism in the initial burst phase and after that by both of the diffusion and degradation mechanisms. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2625–2634, 2002     

Poly(L‐lactic acid) with added α‐tocopherol and resveratrol: optical,physical, thermal and mechanical properties

Poly(L ‐lactic acid) (PLLA) films containing various concentrations of two natural antioxidants, α‐tocopherol and resveratrol, were fabricated by a melt compounding and compression molding process. The influence of the antioxidants on the optical properties such as color and UV‐visible light transmission was analyzed. The thermal, mechanical, rheological and physical properties of PLLA films with added antioxidants were assessed. PLLA films with added α‐tocopherol and resveratrol showed a yellowish brown color and the lightness was influenced by the presence of the antioxidants. The glass transition and melting temperatures were significantly reduced with the addition of antioxidants while enhanced thermal stability was observed, which could be a benefit and important for processing and production. PLLA films with added antioxidants were slightly more hydrophobic than neat PLLA. The combination effect of plasticizing and enhancement of the elastic modulus with differing concentrations of two antioxidants played a critical role in the mechanical and thermomechanical properties of PLLA films. The melt viscosity of the PLLA films with added antioxidants was substantially higher than that of neat PLLA. The higher melt viscosity and G′(ω) could be an indication of formation of entanglement between PLLA and the two antioxidants. Copyright © 2012 Society of Chemical Industry     

Effects of an external electric field on the collection efficiency of air filters: Filtration mechanisms with an external e-field

An external electric field was applied on the filter to improve its collection efficiency, and the collection efficiencies of the different filters under various conditions were evaluated. Dominant electrical filtration mechanisms for each condition were investigated using experimental and theoretical approaches. Four types of air filters were used as test filters: a charged fiber filter, a low-grade filter with 50% collection efficiency in the most penetration particle size (MPPS) zone, and two high-grade filters with more than 95% collection efficiency in the MPPS zone. Three different particle charge states—neutralized, single-charged and uncharged—were considered. For neutralized particles, the external electric field led to a 14.5%p. and 2.5%p. increase in the collection efficiencies of the low-grade filter and charged fiber filter, respectively. With the electric field, the collection efficiency of the low-grade filter increased by 30%p. for single-charged particles. The electric field also affected the collection efficiencies of the charged filter and high-grade filters, but the effect was not significant. For uncharged particles, the electric field did not lead to a remarkable increase in the collection efficiencies of any of the filters. Through experimental and theoretical analysis, it was found that the polarization force imposed on the charged fiber was the dominant factor for the charged fiber filter regardless of application of the external electric field. The Coulombic force imposed on the electric field was the dominant factor for the low-grade filter, while both the Coulombic and the polarization forces affected the collection efficiency of the high-grade filter.

Copyright © 2017 American Association for Aerosol Research     

Soft-, shape changing materials toward physicochemically powered actuators

A shape changing material (SCM) morphs its shape upon external stimulus, and it offers a design of complex 3-dimensional structures remotely, which can be potentially useful for biomedical tools, drug delivery, and soft robotics. To actuate such structures through a physicochemical stimulus, stimuli-responsive materials have been studied over the past few decades. Several SCMs have been reported by combining novel stimuli-responsive materials, micropatterning techniques and a unique actuation cue. In this review, we introduce a recent development in SCMs within the aspects of their materials and structures to describe how the materials can be designed and actuated on demand. Finally, we discuss the future direction and challenges for SCMs as physicochemically-powered actuators.     

Physical and mechanical properties of plasticized butenediol vinyl alcohol copolymer/thermoplastic starch blend

The poly(vinyl alcohol) (PVOH) is an eco‐friend polymer and has an excellent oxygen barrier property due to its strong intermolecular force, but difficulty in processing with conventional extrusion process gives it a limitation for various industrial applications, especially packaging industry. Many studies have attempted to plasticize PVOH to improve its processability, but high cost of PVOH is still drawback for a variety of industrial applications. Therefore, PVOH often blended with other biodegradable polymers such as starch to acquire the cost benefit. Nowadays, the butenediol vinyl alcohol copolymer (BVOH) is getting a great attention due to its melt processability and bio‐degradability, but its high cost is barrier to the industrial application as well. In this study, thermoplastic starch (TPS)/plasticized BVOH (P‐BVOH) were prepared by melt mixing technique, and the plasticization effect of glycerol on starch and BVOH with different composition was observed for optimized processing condition. Based on our preliminary study, TPS was blended with varying amount of P‐BVOH (100:0, 90:10, 80:20, 70:30, 60:40, and 50:50 weight ratio). Physical, oxygen barrier, and mechanical properties of the TPS/P‐BVOH blends were evaluated by various analytical instruments to achieve balanced property and performance. J. VINYL ADDIT. TECHNOL., 25:109–116, 2019. © 2018 Society of Plastics Engineers     

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.     

MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers chemiresistor and their application in low molecular weight alcohol vapours sensing

Herein, we fabricated MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by electrospinning and dip coating method. The amount of MWCNT–OH adsorbed to the pure electrospun nylon 6,6 nanofibers was 0.056 wt%. The electrical conductivity of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers was 5.24 × 10^?3 S cm^?1. We also investigated the sensing properties of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by measuring its response upon exposure to low molecular weight alcohol vapours such as methanol, ethanol, 1-propanol, and 1-butanol. The changes of the electrical resistance of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers were demonstrated on the basis of hydrogen bonds among the alcohol vapours and hydroxyl groups (–OH) on MWCNT–OH, and amide groups (–NHCO–) in nylon 6,6. The fabricated sensor showed good reversible and reproducible responses upon the cyclic test.     

Simulation of DME synthesis from coal syngas by kinetics model

DME (Dimethyl Ether) has emerged as a clean alternative fuel for diesel. There are largely two methods for DME synthesis. A direct method of DME synthesis has been recently developed that has a more compact process than the indirect method. However, the direct method of DME synthesis has not yet been optimized at the face of its performance: yield and production rate of DME. In this study it is developed a simulation model through a kinetics model of the ASPEN plus simulator, performed to detect operating characteristics of DME direct synthesis. An overall DME synthesis process is referenced by experimental data of 3 ton/day (TPD) coal gasification pilot plant located at IAE in Korea. Supplying condition of DME synthesis model is equivalently set to 80 N/m³ of syngas which is derived from a coal gasification plant. In the simulation it is assumed that the overall DME synthesis process proceeds with steadystate, vapor-solid reaction with DME catalyst. The physical properties of reactants are governed by Soave-Redlich-Kwong (SRK) EOS in this model. A reaction model of DME synthesis is considered that is applied with the LHHW (Langmuir-Hinshelwood Hougen Watson) equation as an adsorption-desorption model on the surface of the DME catalyst. After adjusting the kinetics of the DME synthesis reaction among reactants with experimental data, the kinetics of the governing reactions inner DME reactor are modified and coupled with the entire DME synthesis reaction. For validating simulation results of the DME synthesis model, the obtained simulation results are compared with experimental results: conversion ratio, DME yield and DME production rate. Then, a sensitivity analysis is performed by effects of operating variables such as pressure, temperature of the reactor, void fraction of catalyst and H₂/CO ratio of supplied syngas with modified model. According to simulation results, optimum operating conditions of DME reactor are obtained in the range of 265–275 °C and 60 kg/cm². And DME production rate has a maximum value in the range of 1–1.5 of H₂/CO ratio in the syngas composition.