Manufacturing and foaming of high melt viscosity of polypropylene by using electron beam radiation technology

The high melt viscosity of polypropylene was studied by grafting bifunctional monomers, 1,6‐hexanediol diacrylate (HDDA) and tripropylene glycol diacrylate (TPGDA), onto homopolypropylene (HPP) and random ter‐polypropylene (RTPP) under electron‐beam irradiation. Creation of the high‐melt‐viscosity polypropylene was possible at low radiation dosage and low monomer content, under a prohibition of both radiation degradation and homopolymerization. TPGDA monomer was more effective in increasing the melt viscosity of HPP compared with RTPP, whereas HDDA monomer was more effective for enhancing the melt viscosity of RTPP. Such different effects of monomers on melt viscosity may arise from different monomer structures, namely, TPGDA has additional three methyl groups, but HDDA has no methyl groups. Electron‐beam radiation technology, on an increase of the melt viscosity, was much more effective in HPP than RTPP, when compared with virgin polymers. Modified RTPP and HPP with high melt viscosity were capable of foaming with numerous fine cells, of which the modified HPP with 1.5 mmol TPGDA and 0.5 kGy could create more spherical foam cells and its bending strength was 1.5 times more than that of the foamed RTPP. POLYM. ENG. SCI., 46:431–437, 2006. © 2006 Society of Plastics Engineers.     

Creep and drying shrinkage of calcium silicate pastes IV. Effects of accelerated curing

The dependent deformations and evidence of structural changes were measured on pastes of C₃S containing CaCl₂, and on pastes of C₃S or a C₃S/C₂S blend cured at 65°C. It was concluded that the addition of CaCl₂ enhances the role of the “pore component” in controlling irreversible strains even when well-hydrated pastes are dried. The formation of ore stable CSH at 65°C can explain the reduction in time-dependent deformations observed for these pastes. Even though a change in pore size distribution occurs at 65°C, it is not considered to affect irreversible strains in well-hydrated pastes.     

Gamma‐ray irradiation effect of polyethylene on dimaleimides as a class of new multifunctional monomers

Multifunctional monomers, m‐xylylenedimaleimide, p‐phenylenedimaleimide, m‐phenylenedimaleimide, and p‐phenylenedinadimide, all of which have maleimide groups, were synthesized to increase thermal and radiation stabilities. The synthesized multifunctional monomers showed good compatibility with low‐density polyethylene (LDPE). Mixtures of LDPE and these multifunctional monomers were irradiated with γ‐rays from a Co‐60 source at room temperature in a nitrogen atmosphere. The absorbed dose ranged from 0 to 160 KGy. Among these multifunctional monomers, m‐xylylenedimaleimide was the best in gel fraction enhancement. Crosslinked LDPE with m‐xylylenedimaleimide displayed a higher modulus than that of crosslinked LDPE with triallyl cyanurate. For the elongation property, LDPE with m‐xylylenedimaleimide as a multifunctional monomer showed better results than that with commercial multifunctional monomers such as triallyl cyanurate (TAC) and trimethylol propane triacrylate (TMPTA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2339–2345, 2003     

The effct of asymmetries of die exit geometry on extrudate swell and melt fracture

Experimental investigations were performed to see how the die exit geometry and the extrusion velocity influence on extrudate swell and melt fracture for several polymer melts [low-density polyethylene, styrene-butadiene rubber (SBR) and SBR/HAF (carbon black) compound]. Four different types of die exit geometry were considered; 0° (symmetric. usual capillary die), and 30°, 45° and 60° (asymmetric dies) were chosen for the die exit angle. Extrudate diameters were measured without draw-down under isothermal condition. Polymer melts were extruded into an oil that has the same density and temperature as those of the extrudate. Extrudate swells from dies with different diameters were correlated with volumetric flow rates. It was observed that the extrudate swell increases with increasing volumetric flow rate and exhibits through a minimum value at about 45° die exit angle. As to the fracture phenomena, it was observed that the critical shear for the onset of melt fracture increases with the increasing die exit angle up to 45°. However, for 60° die exit angle, the onset of melt fracture is again similar to that of 0° exit angle.     

Synergic influence of a surfactant and ultrasonication on the preparation of soluble,conducting polydiphenylamine/silica‐nanoparticle composites

Conducting polydiphenylamine was used to encapsulate silica nanoparticles through the oxidative polymerization of diphenylamine in the presence of ultrasonic irradiation. The polymerization was performed in the presence of sodium lauryl sulfate as a surfactant. Experiments performed in the absence of ultrasound clearly demonstrated that the application of ultrasonication played multiple roles in the preparation of a composite of polydiphenylamine with silica nanoparticles. Ultrasonication dispersed the silica nanoparticles, converted sodium lauryl sulfate to lauryl alcohol, and augmented the dispersion of the silica‐nanoparticle/polydiphenylamine composite in an organic medium. Silica‐nanoparticle/polydiphenylamine composites were also prepared in the absence of ultrasound and/or sodium lauryl sulfate. The silica‐nanoparticle/polydiphenylamine composites were characterized with Fourier trans form infrared spectroscopy, ultraviolet–visible/near‐infrared spectroscopy, and thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3912–3918, 2006     

On the modeling of electro-hydrodynamic flow in a wire-plate electrostatic precipitator

Modeling of the flow velocity fields for the electrohydrodynamic (EHD) flow in a wire-to-plate type electrostatic precipitator (ESP) was achieved. Solutions of the steady, two-dimensional Navier-Stokes equations have been computed. The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for differential equations was used by SIMPLEST [Michel, 2002], a derivative of Patankar’s SIMPLE algorithm, to bring rapid convergence. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson’s and ion transport equations and electric body force in the momentum equation, developed in this study, was used for the numerical simulation. From calculations for the flow employing different flow models, the Chen-Kimk-ε turbulent model appeared to be the most appropriate choice to obtain a quantitative image of the resulting mean flow field and downstream wake flow of the rear wire, although this was obtained from a qualitative analysis due to the lack of experimental verification. The flow velocity field pattern showed a strong EHD secondary flow, which was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode (Re_CW=12.4). Secondary flow vortices were also caused by the EHD with increases in the discharge current     

Preparation of Monodisperse ZrO2 by the Microwave Heating of Zirconyl Chloride Solutions

Based on the principle that the solubility of a salt decreases as the dielectric constant of the solvent decreases, zirconia powders were prepared by heating a zirconyl chloride solution with a 2-PrOH-water mixture as the solvent. The morphology, size, and size distribution of the resulting particles were highly sensitive to the heating method used on the starting solution. Particles formed under conventional heating methods were polydisperse, agglomerated spherical, or irregularly shaped because of inhomogeneous precipitation through the temperature gradient, the shear force induced by stirring, compositional nonuniformity, and the low heating rate. The present study demonstrated that microwaves provide an excellent means of heating uniformly and rapidly without stirring. The particles resulting from microwave treatment were monodisperse and spherical, with a mean diameter of 0.28 μm.     

Preparation of pH‐sensitive poly(vinyl alcohol‐g‐methacrylic acid) and poly(vinyl alcohol‐g‐acrylic acid) hydrogels by gamma ray irradiation and their insulin release behavior

A series of pH‐responsive hydrogels were studied as potential drug carriers for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared by a two‐step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50 kGy) and then followed by grafting either acrylic acid or methacrylic acid onto these poly(vinyl alcohol) hydrogels with subsequent irradiation (5–20 kGy). These graft hydrogels showed pH‐sensitive swelling behavior and were used as carriers for the controlled release of insulin. The in vitro release of insulin was observed for the insulin‐loaded hydrogels in a simulated intestinal fluid (pH 6.8) but not in a simulated gastric fluid (pH 1.2). The release behavior of insulin in vivo in a rat model confirmed the effectiveness of the oral delivery of insulin to control the level of glucose. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 636–643, 2004     

Numerical study of coal particle cluster combustion under quiescent conditions

Behavior of ignition and combustion of coal particle cluster under a quiescent condition was numerically simulated by solving balance equations of mass and enthalpy with combustion kinetic models of volatiles and char. Two-flame structure, one flame penetrating into the cluster and the other moving out of the cluster, was predicted during the combustion of coal particle cluster. Effects of radiative heat transfer, group number, ambient temperature, coal particle size, and oxygen concentration on ignition and combustion of coal particle clusters were also analyzed. Simulations indicated that the gas volume fraction of coal particle cluster increases with time after devolatilization. Gas velocity passing through the cluster surface varied significantly at volatile liberation. The ignition time delay was reduced with the increase of ambient temperature. The cluster devolatilization rate and char burning rate increased while the ignition time delay decreased with the increase of ambient oxygen concentration.     

Catalytic characteristics of various rubber-reinforcing carbon blacks in decomposition of methane for hydrogen production

Carbon black has recently been reported to act as an effective catalyst for methane decomposition and to exhibit stable catalytic behavior despite carbon deposition, and thus it can be used for CO₂-free production of hydrogen from natural gas. In this work, various carbon blacks with different primary particle size were investigated with respect to methane decomposition under atmospheric pressure from 1123 to 1223 K. Catalytic characteristics, such as activity, activation energy and reaction order, were investigated and compared. It was observed that with decreasing primary particle size (or increasing specific surface area), the specific activity increased and the activation energy decreased. The reaction orders for various pelletized, rubber-reinforcing carbon blacks were 0.6–0.7, about the same regardless of the primary particle size, while they were near 1 for fluffy carbon blacks. Fluffy carbon black showed higher activity and activation energy than the pelletized carbon black of the same primary particle size. Changes of the surface morphology during carbon deposition were observed by TEM. Variations of the number of active sites were discussed in regard of the primary particle size, carbon deposition and binder. The presence of different types of active sites was also suggested.