In‐line monitoring of polyethylene density using near infrared (NIR) spectroscopy

Density and melt index are two key properties in grading commercial polyolefin polymers. For quality assurance, these properties must be controlled as accurately as possible in the production plant. However, the lack of suitable in‐line sensors for these properties makes feedback quality control difficult. In this study, an in‐line density sensor using near infrared (NIR) spectroscopy is developed. The NIR spectra of molten polyethylene in flow are collected by a fiber‐optic device attached to a single screw extruder. By the ratio of the absorption intensity at 1170 nm to that at 1213 nm, the densities of 14 grades of polyethylene were successfully measured. The results were very promising for quality control in the polyethylene production process.     

Evaluation of optimum condition for designing high‐performance electro‐driven polymer hydrogel systems

This study investigated a parameter that determines an optimum condition of the content of the ionic group and the concentration of outer solution for high‐performance electro‐driven polymer hydrogel membranes. The optimum condition for quick bending was determined by a simple method that identified the initial conditions based on Donnan equilibrium theory. Since the bending behavior depends on the initial conditions of the ionic group content and the concentration of the outer solution, it can be predicted by the ratio of the ionic concentrations at the membrane–solution interface; the inverse of the Donnan ratio (1/K) at the initial condition. The bending rate of the membranes showed a maximum value at around 1/K = 0.15. The relationship between several interrelated control factors and the bending dynamics of the gel membranes was established by using the initial system parameters alone. 1/K is the effective simple parameter to determine the optimum condition of the content of the ionic group and the concentration of the outer solution for high‐performance membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 111–118, 2000     

Development of butt welding of polymeric materials based on softening and stirring effects by hot tool

In this study, new butt welding technique was proposed to join polymeric materials in which the polymeric material is softened by a heated tool due to the Joule effect heating of the electric current flow through the tool, and the coalescence of material is done by the stirring action due to the tool rotation. A 3 mm-thick Polycarbonate (PC) sheets were joined in various joining conditions, from which joining mechanism, mechanical properties of joints and process parameters affecting joint performance were investigated. In the experiments, in situ observation with a CCD camera and material temperature measurement during the process, as well as the observation of surface appearance and cross section of the joint and tensile test were performed for these purposes. It was shown from the in situ observation and material temperature measurement that the molten and softened region is formed around the weld tool. It was also shown that sufficient heat input was required to form sound joints with acceptable performance, which depended upon the joining speed and amount of electric current flow through the tool. The observation of joint appearance and cross section revealed that the joint with comparable thickness to base material was obtained under the condition of revolution pitch below 0.08 mm, defined by the ratio of joining speed to tool rotation. It is noticed that joints obtained from the proper conditions have the same mechanical properties as the base material, and that the process parameters of this method were tool rotation speed, welding speed and amount of electric current. These results suggest proposed method is useful for joining the polymeric materials.     

High temperature water–gas shift reaction over hollow Ni–Fe–Al oxide nano-composite catalysts prepared by the solution-spray plasma technique

The effect of Fe content in Ni–Fe–Al oxide nano-composites prepared by the solution-spray plasma technique on their catalytic activity for the high temperature water–gas shift reaction was investigated. The composites showed a hollow sphere structure, with highly dispersed Fe–Ni particles supported on the outer surface of the spheres. When the water–gas shift reaction was performed over an Ni–Al oxide composite catalyst without Fe, undesired CO methanation took place predominantly compared to the water–gas shift reaction, and significant amounts of hydrogen were consumed. When appropriate amounts of Fe were added to the Ni–Al oxide composite catalyst during the plasma process, methanation was suppressed remarkably, without serious loss of activity for the water–gas shift reaction. The catalyst was characterized by STEM, XRD and H₂ chemisorption measurements.     

Multifunctional Initiator with Platinum-Acetylide Dendritic Core for Living Polymerization of Isocyanides

A novel multifunctional initiator has been developed by peripheral modification of a Pt-acetylide dendrimer. Pd–Pt μ-ethynediyl units were introduced to the first-generation dendrimer by a divergent method. The dendritic initiator was applicable to the living polymerization of aryl isocyanides, producing high molecular weight polymers with a narrow polydispersity index in quantitative yields. The ³¹P NMR spectrum of the resulting polymer suggested that all Pd–Pt μ-ethynediyl units in the dendritic molecule actually functioned as an initiator.     

H2O-tolerant monolithic catalysts for preferential oxidation of carbon monoxide in the presence of hydrogen

Pt–Fe/mordenite (4 wt% Pt–0.5 wt% Fe) powder catalysts were wash-coated onto ceramic straight-channel monoliths by using silica- and/or alumina-sol as a binder, and were evaluated for the preferential oxidation of carbon monoxide (PROX) in a hydrogen-rich gas. In a synthetic reformate gas (1% CO, 1% O₂, 5% H₂O, 20% CO₂, and balance H₂), the CO concentration was reduced to less than 20 ppm at temperatures ranging from 100 to 130 °C. After a certain period of the PROX reaction, condensation of H₂O in the pores of the mordenite-support occurred over the monolithic catalyst, which was wash-coated with alumina-sol, in the lower temperature range (100–120 °C), resulting in a rapid increase in CO concentration. The monolithic catalyst wash-coated with silica-sol, however, showed an excellent tolerance against H₂O condensation and offered a stable catalytic performance, maintaining a CO concentration of ca. 20 ppm for 200 h. The H₂O-tolerant characteristic was attributed to the relatively small adsorption amount of H₂O over the silica-modified monolithic catalyst.     

Synthesis and Reactions of Organometallic Polymers Containing Titanacyclobutene Units in the Main Chain

A new class of polymers containing titanacyclobutene units in the main chain were prepared by the reaction of organic dihalides (2) with a binuclear titanium propargyl complex (3) generated in situ from bis(pentamethylcyclopentadienyl)titanium chloride (Cp*₂TiCl, 1), SmI₂, and 1,4-bis(3-bromopropynyl)benzene (2a). The dark red colored polymers (4) thus obtained are soluble in organic solvents such as tetrahydrofuran and chloroform, and they are stable at ambient temperature under argon atmosphere. The reaction of the titanium-containing polymers (4) with hydrogen chloride was found to give organic polymers (7) containing unsaturated main chain.     

Evaluation of environmentally friendly lubricants for cold forging

The authors proposed double-layer-type environmentally friendly lubricants, which were composed of an undercoat, superior in adhering to a material, and an overcoat, superior in reducing the friction between the material and the die. The performance of these lubricants for cold forging was evaluated by the ring compression test, the combined forward rod-backward can extrusion-type friction test and the combined forward conical can-backward straight can extrusion-type friction test. The double-layer-type lubricants showed comparable friction characteristics and anti-pick-up properties to a conversion coating lubricant, when the film thickness and surface treatment before coating were improved. In a practical application by cold multistage forging, the double-layer-type lubricants showed a similar performance to a conversion coating lubricant.     

Numerical simulation of a polypropylene foam bead expansion process

The production process for expanded polypropylene foam beads (EPP), which consists of steaming, depressurizing, cooling, and ageing operations, was consistently simulated by a set of mathematical models. The models, developed from Yang and Lee's ageing models (Yang and Lee, J. Cell. Plast., 39 , 59 (2003)) for extrusion foam products, were extended in terms of the fundamental aspects of mass and heat transport phenomena. Evaporation and condensation of blowing agents and heat conduction during the steam chest molding and ageing processes were modeled. The governing equations were established by integrating the mass transfer equations of steam and air at the intercellular walls with the constitutive equations of evaporation and condensation in each cell, the equation of heat conduction from the mold to the foam, and the mechanical force balance equation on the cell walls. The models simulate the stress exerted on the steaming chest mold and predict the expansion behavior of cells in the EPP bead‐foam board throughout the ageing process. A sensitivity analysis was also performed by the models to find the key factors which might allow the theoretical determination of the ejection time and shortening of the length of the ageing process. POLYM. ENG. SCI., 48:107–115, 2008. © 2007 Society of Plastics Engineers     

Growth of β-Ga2O3 nanocolumns crossing perpendicularly each other on MgO (1 0 0) surface

β-Ga₂O₃ nanocolumns straightened and crossed perpendicularly each other were deposited on MgO (1 0 0) substrate by vapor phase transport method. Growth of the nanocolumns was examined at steps of 1000, 1050, and 1200 °C in elevation of source-boat temperature. We have drawn out the substrate from deposition-tube at each source-boat temperatures of 1000, 1050, and 1200 °C. Scanning electron microscopy of the sample with source-boat temperature of 1200 °C demonstrated that the straightened and elongated nanocolumns are crossing perpendicularly each other. Typical lengths of the nanocolumns were in the range of several hundreds nanometers below 1050 °C, and those of 1200 °C were in the range of ten to fifteen hundreds nanometers. Diameters of the nanocolumns stayed in the range of few hundreds nanometers, notwithstanding variation of the source temperature. X-ray diffraction and transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that the nanocolumns are monoclinic β-Ga₂O₃ crystal, and the (4 0 0) plane of β-Ga₂O₃ nanocolumns is parallel to the (1 0 0) plane of MgO substrate.