Separation performance of sub-micron silica particles by electrical hydrocyclone

Separation performance of sub-micron particles by use of a special electrical hydrocyclone was studied. The effects of feed suspension waiting time, applied electrostatic potentials, and the feed suspension concentration, on the separation performance of the electrical hydrocyclone were investigated. An aqueous suspension of sub-micron silica particles with median diameter of about 0.2 µm was used as the test powder. A 20 mm diameter of electrical hydrocyclone operated at 20% of the underflow ratio was used. A negative center wire electrode was inserted vertically inside the conical section, and electrostatic potentials up to 100 V were applied in this electrical hydrocyclone.It was found that the 50% cut size of the electrical hydrocyclone increased with the increase of the feed suspension waiting time after a particle dispersion process by the beads mill. The classification of the sub-micron particles occurred under applied electrostatic potentials greater than about 40 V, while better classification performance was obtained with the increase of the applied electrostatic potentials. The 50% cut size decreased with the increase of the feed suspension concentration up to 1.5 wt.%, and further increasing of the concentration led to the increase of 50% cut size.A simple model based on the time of flight model, was developed in order to predict the 50% cut size of the electrical hydrocyclone. The model results qualitatively agreed with the experimental results.It was found that classification the sub-micron particles is possible by use of the special electrical hydrocyclone proposed in this study.     

Blends of aliphatic polyesters. IV. Morphology,swelling behavior,and surface and bulk properties of blends from hydrophobic poly(L-lactide) and hydrophilic poly(vinyl alcohol)

Blend films were prepared from hydrophobic poly(L -lactide) (PLLA) and hydrophilic poly(vinyl alcohol) (PVA) with different PLLA contents [X_PLLA (w/w) = PLLA/(PVA + PLLA)] by solution casting and melt quenching. Their morphology, swelling behavior, and surface and bulk properties were investigated. Polarizing optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, and tensile testing revealed that PLLA and PVA were phase separated in these blend films and the PLLA-rich and PVA-rich phases both formed a continuous domain in the blend film of X_PLLA = 0.5. The water absorption of the blend films was higher for the blend films of low X_PLLA values when compared at the same immersion time, and it was larger than expected from those of nonblended PLLA and PVA films. The dynamic contact angles of the blend films were linearly increased with an increase in X_PLLA. The tensile strength and Young's modulus of the dry blend films decreased with a rise in X_PLLA, but this dependence was reversed because of the large decreases in tensile strength and Young's modulus for the blend films having high X_PLLA values after immersion in water. The elongation at break was higher for the wet blend film than for the dry blend film when compared at the same X_PLLA and that of the dry and wet blend films decreased with an increase in X_PLLA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2151–2160, 2001     

Preparation of poly(acrylic acid)/poly(vinyl alcohol) membrane for the facilitated transport of CO2

Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO₂. The carrier of CO₂ was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion‐exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO₂ over N₂ and higher CO₂ permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion‐exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO₂ partial pressure in the feed gas was 0.061 atm. Effects of ion‐exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001     

Particle size measurement of standard reference particle candidates and theoretical estimation of uncertainty region

In order to confirm reliable particle size measurement technique and to prepare standard reference particles for calibrating particle size measurement devices, experimental and theoretical studies have been conducted about particle size measurement of 0.1–1 μm silica particles. The microscopic method with sample size greater than 90,000 particles was conducted for the size measurement.Theoretical equation of uncertainty region over all particle diameter range is newly proposed and compared with computer simulation. Previous paper [H. Masuda, K. Iinoya, Theoretical study of the scatter of experimental data due to particle size distribution, J. Chem. Eng. 4(1) (1971) 60–67] reported the uncertainty region only for mass median diameter, but this paper presents the uncertainty region for all particle size range. The uncertainty region increases with the increase in particle diameter and also increases as the sample size decreases. Theoretical uncertainty region agreed with the results of computer simulation.     

Synchronous and separate homo-crystallization of enantiomeric poly(l-lactic acid)/poly(d-lactic acid) blends

High-molecular-weight poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) are blended at different ratios and their crystallization behavior was investigated. Solely homo-crystallites mixtures of PLLA and PDLA were synchronously and separately formed during isothermal crystallization in the temperature (T_c) range of 90–130 °C, irrespective of blending ratio, whereas in addition to homo-crystallites, stereocomplex crystallites were formed in the equimolar blends at T_c above 150 and 160 °C. Interestingly, in isothermal crystallization at T_c = 130 °C, the spherulite morphology of blends became disordered, the periodical extinction (periodical twisting of lamellae) in spherulites disappeared, and the radial growth rate of spherulite (G) of the blends was reduced by the synchronous and separate crystallization of PLLA and PDLA and the coexistence of PLLA and PDLA homo-crystallites. However, the interplane distance (d), the crystallinity (X_c), the transition crystallization temperature (T_c) from α′-form to α-form, the alternately stacked structure of the crystalline and amorphous layers, and the nucleation mechanism were not altered by the synchronous and separate crystallization of PLLA and PDLA and the coexistence of PLLA and PDLA homo-crystallites. The unchanged d, X_c, transition T_c, long period of stacked lamellae, and nucleation mechanism strongly suggest that the chiral selection of PLLA or PDLA segments on the growth sites of PLLA or PDLA homo-crystallites to some extent was performed during solvent evaporation and this effect remained even after melting.     

Effect of apex cone shape on fine particle classification of gas-cyclone

The purpose of this paper is to study the effects of apex cone shape on particle separation performance of gas-cyclones by experiment and CFD studies. It is found that the optimum apex cone angle is 70°. The minimum 50% cut size was obtained by use of this special apex cone. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special apex cone. The clear interface between upward flow and downward flow was detected on the apex cone angle of 70°. The effect of the apex cone angle on particle separation performance decreases under high inlet velocity conditions, because most particles are moving in the area away from the apex cone.The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.     

Influence of chemical compositions on the properties of random and multiblock sulfonated poly(arylene ether sulfone)‐based proton‐exchange membranes

The influence of chemical compositions on the properties of sulfonated poly(arylene ether sulfone)‐based proton‐exchange membranes was studied. First, we synthesized three different series of random SPAES copolymers using three kinds of hydrophobic monomers, including 4,4′‐dihydroxyldiphenylether, 2,6‐dihydroxynaphthalene (DHN), and 4,4′‐hexafluoroisopropylidenediphenol (6F‐BPA) to investigate effects of hydrophobic components on the properties of SPAES membranes as proton‐exchange membranes. Random SPAES copolymers with 6F‐BPA showed the highest proton conductivity while random SPAES copolymers with DHN displayed the lowest methanol permeability among the three random copolymers. Subsequently, we synthesized multiblock SPAES using the DHN as a hydrophobic monomer and studied the effect of the length of hydrophilic segments in the multiblock SPAES copolymers on membrane performance. The results indicated that longer hydrophilic segments in the copolymers led to higher water uptake, proton conductivity, and proton/methanol selectivity of membranes even at low humidity. In addition, the morphology studies (AFM and SAXS measurements) of membranes suggested that multiblock copolymers with long hydrophilic segments resulted in developed phase separation in membranes, and ionic clusters formed more easily, thus improving the membrane performance. Therefore, both the kinds of hydrophobic monomers and the length of hydrophilic segments in SPAES copolymers would influence the membranes performance as proton‐exchange membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Precipitation polymerization in mixed monomer–solvent droplets

This contribution reports the precipitation copolymerization of lauryl methacrylate–divinylbenzene (LMA–DVB) in stable isolated droplets dispersed in water. The droplets contain either n‐hexadecane (HD) or HD–toluene (HD–T) or toluene as a nonsolvent for the resulting P(LMA–DVB) copolymer. The polymerization proceeds smoothly with an appreciably high content of DVB without the formation of coagulum and thus proves the quite high stability of the droplet reactors. The differences in the interaction between the nonsolvent–copolymer combinations allow the variation of the internal morphology of the particles between core and shell type, highly porous, and solid sphere. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41881.     

Hydrolytic degradation and crystallization behavior of linear 2‐armed and star‐shaped 4‐armed poly(l‐lactide)s: Effects of branching architecture and crystallinity

“Linear” aliphatic polyesters composed of two poly(l ‐lactide) arms attached to 1,3‐propanediol and “star‐shaped” ones composed of four poly(l ‐lactide) arms attached to pentaerythritol (2‐L and 4‐L polymers, respectively) with number‐average molecular weight (M_n) = 1.4–8.4 × 10⁴g/mol were hydrolytically degraded at 37°C and pH = 7.4. The effects of the branching architecture and crystallinity on the hydrolytic degradation and crystalline morphology change were investigated. The degradation mechanism of initially amorphous and crystallized 2‐L polymers changed from bulk degradation to surface degradation with decreasing initial M_n; in contrast, initially crystallized higher molecular weight 4‐L polymer degraded via bulk degradation, while the degradation mechanism of other 4‐L polymers could not be determined. The hydrolytic‐degradation rates monitored by molecular‐weight decreases decreased significantly with increasing branch architecture and/or higher number of hydroxyl groups per unit mass. The hydrolytic degradation rate determined from the molecular weight decrease was higher for initially crystallized samples than for initially amorphous samples; however, that of 2‐L polymers monitored by weight loss was larger for initially amorphous samples than for initially crystallized samples. Initially amorphous 2‐L polymers with an M_n below 3.5 × 10⁴g/mol crystallized during hydrolytic degradation. In contrast, the branching architecture disturbed crystallization of initially amorphous 4‐L polymers during hydrolytic degradation. All initially crystallized 2‐L and 4‐L polymers had δ‐form crystallites before hydrolytic degradation, which did not change during hydrolytic degradation. During hydrolytic degradation, the glass transition temperatures of initially amorphous and crystallized 2‐L and 4‐L polymers and the cold crystallization temperatures of initially amorphous 2‐L and 4‐L polymers showed similar changes to those reported for 1‐armed poly(l ‐lactide). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41983.     

Development of a chlorine‐resistant polyamide nanofiltration membrane and its field‐test results

For the development of chlorine‐resistant nanofiltration membranes, a thin‐film‐composite membrane was prepared by the interfacial polymerization of N‐phenylethylenediamine and 1,3,5‐benzenetricarbonyl trichloride on a microporous polysulfone support substrate. The polymerization on the substrate surface was confirmed by Fourier transform infrared measurements, and membrane surface properties such as the roughness and ζ potential were characterized. Rejections of NaCl and isopropyl alcohol of the prepared membrane were 95 and 50%, respectively. The membrane showed much higher chlorine resistance than a commercial polyamide membrane when the membranes were immersed in an aqueous NaOCl solution. A field test was carried out with a spiral‐type membrane module. Tap water was treated by this module for more than 70 days under the condition of continuous NaOCl injection. The prepared membrane module was quite stable, and no distinguished change in the rejection and flux was recognized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007