Influence of the longest ethylene and isotactic propylene sequences on crystallization elution fractionation of ethylene/propylene copolymers

Crystallization elution fractionation (CEF) is the newest crystallization-based technique for estimating the chemical composition distribution of ethylene/1-olefin copolymers. Understanding the separation mechanism of CEF for ethylene/propylene copolymers over their full compositional range is challenging because the crystallizabilities of the copolymer chains depend on the longest ethylene sequence and on longest isotactic propylene sequence. We developed a mathematical model to describe the CEF mechanism for ethylene/propylene copolymers over the entire compositional range using population balances for the crystallization and dissolution stages. The joint distribution of longest ethylene and isotactic propylene sequences determines how the copolymer populations crystallize and dissolve. The model was validated with experimental CEF profiles of ethylene/propylene copolymers varying from pure ethylene to propylene homopolymers.     

Non-destructive functionalization of multi-walled carbon nanotubes with naphthalene-containing polymer for high performance Nylon66/multi-walled carbon nanotube composites

A new compatibilizer, poly(vinyl benzyloxy methyl naphthalene)-g-poly(t-butyl methacrylate-co-methacrylic acid), was synthesized for Nylon 66 (N66)/multi-walled carbon nanotube (MWCNT) composites. It has been shown that the naphthalene unit in the main chain of the compatibilizer interacts with MWCNTs by π–π interaction and that the carboxylic acid unit in the graft chain of the compatibilizer interacts with the amide group of N66. The use of the compatibilizer produces well-dispersed MWCNTs in N66 matrix, which results in improved mechanical and electrical properties of the composites, while the simple mixture of N66/MWNCTs without the compatibilizer exhibits poor mechanical and electrical properties due to severe aggregation of MWCNTs. It is also found that the compatibilizer with a small amount of carboxylic acids is more effective for improving the mechanical and electrical properties of N66/MWCNT composites.     

Stripe coating with a coffee‐ring effect for color filter solutions

The coffee‐ring effect of a coated narrow stripe approximately 350 μm wide was examined. The coating solution was based on a new formulation with a specific application for the production of color filters used in liquid‐crystal display panels. The basic components of this formulation were color pigments, solvents, and a novel alkali solution resin. The resin was a copolymer consisting of methacrylic acid, hydroxyl ethyl methacrylate, and methyl methacrylate. Three solvents with different boiling points were used: propylene glycol methyl ether acetate, methyl ethyl ketone, and tetrahydrofuran. The formation of a coffee ring on the coated stripe was mainly dependent on the solvent evaporation rate and the acid value of the copolymer. The acid value determined the strength of the hydrogen bonding of the copolymer. Fourier transform infrared analysis revealed that the intramolecular hydrogen bonding of the carbonyl groups of hydroxyl ethyl methacrylate was one of the critical factors affecting the formation of a coffee ring. The other factor was the rate of solvent evaporation. A proper adjustment of the acid value combined with a highly volatile solvent could effectively eliminate the formation of a coffee ring. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel electrical conductive hybrid nanostructures based on PA 6/MWCNTCOOH electrospun nanofibers and anchored MWCNTCOOH

Electrical conductive nanostructures made of nanofibers of poly (amide 6) (PA6) with carboxyl functionalized multiwall carbon nanotubes (MWCNT_COOH) and anchored MWCNT_COOH were produced. The nanotubes were surface activated with carboxyl groups, dispersed in formic acid and added to a formic acid solution of PA6. The mixture was electrospun by applying a voltage of 30 kV; afterwards, the nanofiber's mats were immersed in an aqueous dispersion of MWCNT_COOH containing a nonionic surfactant. The chemical structure, morphology, thermal stability, and electrical conductivity of the nanostructures were evaluated by UV spectroscopy, scanning (SEM), and transmission electron microscopy (TEM), thermal gravimetric analyses (TGA) and volumetric conductivity measurements. The efficiency of the functionalization was confirmed by the UV peaks in the range between 220 and 250 nm (corresponding to a carbonyl group conjugated with a carbon‐carbon double bond). SEM and TEM micrographs showed the pullout of the MWCNT_COOH from the nanofibers and the formation of a stable, percolated, and anchored MWCNT_COOH network on the nanofibers due to the anchoring of the MWCNT_COOH from the surfactant solution on the MWCNT_COOH of the nanofibers. The coated nanostructures had higher thermal stability and higher electrical conductivity than the noncoated ones, showing the efficiency of this simple procedure. POLYM. ENG. SCI., 55:1263–1272, 2015. © 2015 Society of Plastics Engineers     

Assessment of cell proliferation in knitting scaffolds with respect to pore‐size heterogeneity,surface wettability,and surface roughness

In this study, various types of poly(ε‐caprolactone) (PCL) knitting scaffolds were fabricated and analyzed to assess the cell‐culturing characteristics of knitting scaffolds with respect to pore‐size heterogeneity, surface wettability, and surface roughness. First, control knitting scaffolds were fabricated using 150‐µm‐diameter PCL monofilaments. Using chloroform and NaOH, PCL knitting scaffolds with varying roughness, pore‐size heterogeneity, and surface wettability were fabricated. Cell‐culture assessments were performed on these six types of PCL knitting scaffolds. Saos‐2 cells were used for cell assessments and cultured for 14 days on each scaffold. Consequently, heterogeneous pore‐size distribution and high surface wettability were found to enhance cell proliferation in knitting scaffolds. In addition, for highly hydrophobic knitting scaffolds exhibiting water contact angles greater than 110 degrees, smaller surface roughness was found to enhance cell proliferation. According to this study, in the case of knitting scaffold, NaOH‐treated knitting scaffold, without any control for the pore‐size homogenization, could be a candidate as the optimal knitting scaffold. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42566.     

Non‐thermal plasma degradation of dye using an underwater dielectric barrier discharge created inside a porous hydrophobic ceramic tube

An alternating‐current‐driven, atmospheric‐pressure, non‐thermal plasma reactor was applied to the degradation of dye in water. The plasma reactor, made of a porous hollow ceramic tube, was placed underwater and was able to disperse plasmatic gas containing various reactive species into aqueous dye solution as small bubbles through the micropores of the tube. The hydrophobic coating on the surface of the ceramic tube effectively prevented the water from permeating through it. This wastewater treatment system was able immediately to transfer plasmatic gas to aqueous solution across the porous ceramic tube and provide a large gas–liquid interfacial area, allowing efficient dye treatment. So as to simulate real dyeing wastewater, an aqueous solution comprising two different azo dyes was used. The effect of discharge power, treatment time, and flow rate of oxygen used for the creation of plasma was examined. The results suggest that this system may be useful for the treatment of organic wastewater.     

Facile Fabrication of Highly Transparent Yttria Ceramics with Fine Microstructures by a Hot‐Pressing Method

In this study, we report highly transparent yttria ceramics fabricated by a facile hot‐pressing method with tantalum foil shielding which effectively prevents the ceramic samples from carbon contamination caused by the graphite mold used during the process. The hot‐pressed sample was already highly transparent without a post‐annealing step or hot isostatic pressing. For a 2‐mm‐thick specimen doped with 1 at.% ZrO₂, the in‐line transmittance reaches 74.4% at 400 nm and 81.1% at 1100 nm. The sample shows a very fine microstructure with an average grain size of about 1 μm owing to the low sintering temperature of only 1600°C. The study results indicate that it is possible to produce transparent yttria ceramics with excellent optical transparency using the economical and convenient hot‐pressing method.     

Comparative evaluation of purity of green energetic material (ammonium dinitramide) depending on refining method

Although the solid propellant, ammonium dinitramide (ADN, NH₄N(NO₂)₂) is safe and thermally stable, it requires high purity for practical commercial applications. Even a small amount of impurities in ADN can create negative effects, including catalyst poisoning and thruster nozzle cloggings when it is used as a liquid propellant. Thus, we explored several purification processes for the precipitated ADN particles, such as repetition extraction, adsorption by activated carbons, and low-temperature extraction. These purifying methods help to improve the chemical purity as evaluated by FTIR, UV-vis, DSC, and IC analyses. Among the purification processes, adsorption was found to be the best method, showing a final purity of 99.768% based on relative quantification by ion chromatography.     

The role of salt abuse on risk for hypercalciuria

Background  

Elevated sodium excretion in urine resulting from excessive sodium intake can lead to hypercalciuria and contribute to the formation of urinary stones. The aim of this study was to evaluate salt intake in patients with urinary lithiasis and idiopathic hypercalciuria (IH).