Preparation of high molecular weight poly(vinyl pivalate) with high yield and high molecular weight poly(vinyl alcohol) by emulsion polymerization of vinyl pivalate and saponification

To prepare high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with high yield and high linearity which is a promising precursor for syndiotactic poly (vinyl alcohol) (PVA), vinyl pivalate (VPi) was emulsion polymerized, using 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) as an initiator and sodium dodecyl sulfate (SDS) as an emulsifier. The effect of the polymerization conditions on the conversion, molecular weight, and degree of branching was investigated. PVA with maximum number‐average degree of polymerization (P_n) of 6200 could be prepared by complete saponification of PVPi, with P_n of 13,300–16,700 obtained at polymerization temperature of 50°C, using SDS and AAPH concentration of 2.0 × 10^?3 mol/L of water and 1.0 × 10^?3 mol/L of water, respectively, and the maximum conversion was about 90%. From the emulsion polymerization of VPi, spherical PVPi with high yield was effectively prepared, which might be useful for the precursor of syndiotactic PVA micro‐ and nano‐spheres with various surface properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 410–414, 2007     

Comparative Analysis of Single‐Cascade Five‐Zone and Two‐Zone SMB Systems for the Separation of a Ternary Amino Acid Mixture

A ternary separation usually requires the use of two simulated moving bed (SMB) units in series. Since an increase in the number of SMB units leads to a significant increase in capital and operational costs, the use of a single SMB unit is preferred if its structure can be modified to treat a ternary separation. Such a modified single SMB unit has been typified by a five‐zone SMB or a two‐zone SMB so far. The separation performances‐of a five‐zone SMB and a two‐zone SMB are compared in this paper by using the ternary amino acid mixture as a model system. A five‐zone SMB is designed with the safety margin method while a two‐zone SMB is optimized using genetic algorithm. A five‐zone SMB based on the maximum allowable safety margin, although it may not guarantee the global optimum solution, results in much better separation performance than a two‐zone SMB at its global optimum state.     

Effect of solvent on electrical conductivity and gas sensitivity of PEDOT: PSS polymer composite films

Poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) was blended with polyethylene oxide (PEO) and polyvinyl alcohol (PVA) and composite film was cast. Additional solvents of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) were mixed and their effects on electrical conductivity and structural changes were investigated. The electrical conductivity increased in response to the additional solvent, leading to an increase in the PEDOT ratio relative to the control. PEDOT:PSS/PEO composite film had a much higher electrical conductivity than PEDOT:PSS/PVA. When blended with PEO, the quinoid structure revealed by Raman spectroscopy increased relative to the PVA‐blended case, indicating higher electrical conductivity. The current–voltage response and gas sensitivity showed much better performance in PEDOT:PSS/PEO/DMSO composite film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42628.     

Polyurethane nanocomposites with click‐coupled nanodiamonds exhibiting enhanced mechanical and shape memory effects

Poly(?‐caprolactone)diol (PCL)–functionalized nanodiamonds (f‐NDs) were synthesized using a click chemistry reaction between the azide‐moiety PCL and alkyne‐moiety NDs and were incorporated into shape memory polyurethane (PU) at f‐ND concentrations of 0, 0.5, 1, and 2 wt % to produce high‐performance shape memory nanocomposites. The PU/f‐ND nanocomposites exhibited better shape recovery, shape recovery stress, and breaking stresses than pure PU. Shape recovery of greater than 95% was demonstrated for all the nanocomposites in the third cycle, and the shape recovery stresses increased significantly with the f‐ND content. These enhanced mechanical and shape recovery properties are ascribed to increased interactions between the f‐NDs and PU matrix due to incorporation of click‐coupled f‐NDs. The click‐coupled NDs can be used as nanofillers to enhance the mechanical and shape memory properties of polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45465.     

Determination of twisting angle of electrospun nanofiber bundle for continuous electrospinning system

Electrospinning continuously produced twisted nanofibers with a convergence coil and a rotating ring collector. The positively charged nozzle was used in the electrospinning process to deposit electrospun fibers of polyacrylonitrile onto a rotating ring collector. By withdrawing the electrospun fibers from the rotating ring collector, it was possible to spin the electrospun fibers yarn. In this study, theoretical approaches and numerical simulations were used to determine the twisting angle of the yarn. Using the equations developed in this study, we performed numerical simulations and compared the experimental results with the numerical simulation results. Mechanical properties of the fiber bundle were analyzed for twisting angle. It was confirmed the relationship among the winding drum, the ring collector, and flux of the fibers mass per time during electrospinning in the developed system. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45528.     

Tailored blank welding between low carbon steel sheet and STS 304 stainless steel sheet by CO2 laser beam

A basic reseach of tailored blank welding between a low carbon steel sheet and a STS 304 stainless steel sheet was carried out with CO₂ laser beam. The materials used in this work were a low carbon steel sheet with a thickness of 0.9 mm and a STS 304 stainless steel sheet with the same thickness. Experiments were carried out by applying the Taguchi method to obtain optimized conditions in order to apply this tailored blank laser welding method in the practical manufacturing process. In order to compare the laser welding results with the conventional welding process, GTA welding was carried out for the same materials. Optical microscopy, SEM and XRD analyses were performed to observe the microstructures and to analyze the various phases. A tensile test, hardness test and Erichsen test were performed to evaluate the formability of welded specimens. In addition, immersion test was carried to estimate corrosion resistance. A WDS analysis showed that laser welding resulted in almost the same dilution of both low carbon steel and stainless steel in welded metal, meanwhile, GTA welding resulted in more dilution of stainless steel due to its slower heat conductivity. The formability of the laser welded specimen reached 83% of that in base metal. On the other hand, it was 63% in the case of GTA welding. During the tension test, base metal was fractured in the case of a laser welded specimen, meanwhile the welded zone was fractured in the case of the GTA welded specimen. The corrosion test showed that weight loss per unit area was less in the laser welded specimen than that of the GTA welded specimen.     

Directivity analysis of ultrasonic waves on surface defects using a visualization method

Ultrasonic testing uses the directivity of the ultrasonic wave, which propagates in one direction. The directivity is expressed as the relationship between the propagation direction and its sound pressure. The directivity of an ultrasonic wave is related to the choice of probe arrangement, testing sensitivity and scanning pitch, and correct measurement of defect size and location. This paper investigated the directivity of ultrasonic waves, which are scattered from a slit defect located in simulated butt weld joint using a visualization method. When the defect size was smaller than the wavelengths, clear directivity in the reflected wave was observed. When the ratio of defect size to wavelength is greater than 1.5, measured directivities almost agree with the theoretical directivity. The directivity of shear waves scattered from the slit defect varied according to probe direction (Far defect, Near defect). The angle of reflection wave became similar to angle of incidence as the height of excess metal in welded joint increased.     

The noise reduction of a DC motor using multi-body dynamics

The DC motor of a vehicle may cause noise and vibration due to high-speed revolution, which can make a driver feel uncomfortable There have been various studies attempting to solve these problems, mostly focusing on the causes of noise and vibration and a means of preventing them The CAE methodology is more efficient than a real test for the purpose of looking for various design parameters to reduce the noise and vibration of the DC motor In this study, a design process for reducing brush noise is presented with the use of a computer model, which is made by using a multi-body dynamics program (DADS) The design parameters to reduce the brush noise and vibration were proposed using a computer model They were used to reduce the noise and vibration of the DC motor and verified by the test tesults of the fan DC motor in the vehicle This method may be applicable to various DC motors     

Lamellar boundary alignment of DS-processed TiAl−W alloys by a solidification procedure

In this study, a β solidification procedure was used to align the lamellae in a Ti-47Al-2W (at.%) alloy parallel to the growth direction. The Bridgman technique and the floating zone process were used for directional solidification. The mechanical properties of the directionally solidified alloy were evaluated in tension at room temperature and at 800°C. At a growth rate of 30 mm/h (with the floating zone approach), the lamellae were well aligned parallel to the growth direction. The aligned lamellae yielded excellent room temperature tensile ductility. The tensile yield strength at 800°C was similar to that at room temperature. The orientation of the γ lamellar laths in the directionally solidified ingots, which were manufactured by means of a floating zone process, was identified with the aid of electron backscattered diffraction analysis. On the basis of this analysis, the preferred growth direction of the bcc-β dendrites that formed at high temperatures close to the melting point was inferred to be [001]_β at a growth rate of 30 mm/h and [111]_β at a growth rate of 90 mm/h.     

The effect of polystyrene-block-poly(4-vinylpyridine) prepared by a RAFT method in the dispersion polymerization of MMA

The dispersion polymerization of methyl methacrylate (MMA) has been carried out using polystyrene-block-poly(4-vinylpyridine) copolymer [P(S-b-4VP)], which was prepared by a reversible addition-fragmentation chain transfer (RAFT) method, as a steric stabilizer in an alcohol media. The stable polymer particles were obtained when the block copolymer concentrations increased from 1 to 10 wt% relative to the monomer and the average particle sizes decreased from 5.3 to 3.4 μm with the increasing concentration of the block copolymer. In particular, the incorporation of 2 wt% polystyrene-block-poly(4-vinylpyridine) produced 4.3 μm of monodisperse PMMA particles with 2.14% of C_v. Thus, the P(S-b-4VP) block copolymer prepared by the RAFT method is working not only as a steric stabilizer, but also in providing monodisperse micron-sized PMMA particles.