Effect of the reaction bath temperature in a fixed-bed reactor for oxidation of oxylene over V2O5/TiO2 catalysts

The effects of the reaction variables in the operation of a fixed-bed reactor for oxidation ofo-xylene over V₂O₅/TiO₂ catalysts were studied experimentally using a bench reactor. Reaction temperature, feed flow rate and feed concentration ofo-xylene were found to have significant effects on the product distribution and the temperature profile in the reactor. Drastic enhancements ofo-xylene oxidation reaction were observed at some conditions, which was ascribed to the effect of heat accumulated in the bed and indicated a possible way to increase the productivity in the industrial condition. This paper was presented at the 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Properties of molecular composite film of poly(4,4'-diamino-2'-carbamoylbenzanilide terephthalamide)(p-PDCBTA) and poly(4,4'-diamino-2'-chlorobenzanilide terephthalamide) (P-LCI)

Summary A new thermally stable, high strength and high modulus aromatic polyamide film was obtained via the formation of the molecular composite of p-PDCBTA and P-LCl. The two polymers exhibited good miscibility identified with the measurement of dynamic mechanical property and FTIR spectra. By the combination of drawing by 40% and subsequent heat treatment, the tensile property of the composite film could be achieved to the strength of 450 MPa and the modulus of 24 GPa, which were sustainable upto 400 °C. Received: 31 August 1999/Revised version: 19 November 1999/Accepted: 25 November 1999     

Frequency response of continuous-flow adsorber for multicomponent system

In this paper, we present a theoretical analysis of the frequency response of a continuous-flow adsorber with periodic modulation of the inlet flow-rate to measure multicomponent diffusion kinetics in porous media. Micropore diffusion kinetics is assumed for the intraparticle mass transfer mechanism and three different shapes of microparticle are considered: slab, cylinder, and sphere. Simulation results for a binary system show that the frequency response of the faster diffusing component is strongly influenced by the slower component. The out-of-phase characteristic function of the frequency response of the faster diffusing component shows maximum and minimum points. The deviation between these maximum and minimum values becomes smaller when the cross-terms of diffusivity go to zero, while the deviation becomes larger when the cross-terms of the adsorption equilibrium constant go to zero. Contrary to the behaviour of the out-of-phase function of the faster diffusing component, the out-of-phase function of the slower diffusing component shows no extrema at all. The in-phase characteristic function of the frequency response of the continuous-flow adsorber is not affected by the overflow parameter.     

New AB or ABA type block copolymers: atom transfer radical polymerization (ATRP) of methyl methacrylate using iodine-terminated PVDFs as (macro)initiators

Summary PMMA homopolymer with CF₃(CF₂)₂CF₂- end group was prepared by the ATRP of MMA using CF₃(CF₂)₂CF₂-I as an initiator and copper(I) salts/bipy catalysts. This indicated the production of perfluorobutyl radicals by ATRP mechanism and successful polymerization by them. Di- and triblock copolymers were also prepared by the ATRP of MMA using iodine-terminated PVDF as (macro)initiators. The kinetic plots (ln[M]_o/[M] vs. time) showed nearly first-order with respect to monomer concentration and the M_n,NMR of block copolymers increased linearly with conversion. However, iodine-terminated PVDF showed low initiator efficiency because propagating rate was much faster than initiating rate Received: 6 September 1999/Revised version: 27 December 1999/Accepted: 28 December 1999     

Synthesis of poly[(2‐oxo‐1,3‐dioxolan‐4‐yl)methyl vinyl ether‐co‐N‐phenylmaleimide] and its miscibility in blends with styrene‐acrylonitrile or poly(vinyl chloride)

The aim of the study was to investigate the synthesis of a copolymer bearing cyclic carbonate and its miscibility with styrene/acrylonitrile copolymer (SAN) or poly(vinyl chloride) (PVC). (2‐Oxo‐1,3‐dioxolan‐4‐yl)methyl vinyl ether (OVE) as a monomer was synthesized from glycidyl vinyl ether and CO₂ using quaternary ammonium chloride salts as catalysts. The highest reaction rate was observed when tetraoctylammonium chloride (TOAC) was used as a catalyst. Even at the atmospheric pressure of CO₂, the yield of OVE using TOAC was above 80% after 6 h of reaction at 80°C. The copolymer of OVE and N‐phenylmaleimide (NPM) was prepared by radical copolymerization and was characterized by FTIR and ¹H‐NMR spectroscopies and differential scanning calorimetry (DSC). The monomer reactivity ratios were given as r₁ (OVE) = 0.53–0.57 and r₂ (NPM) = 2.23–2.24 in the copolymerization of OVE and NPM. The films of poly(OVE‐co‐NPM)/SAN and poly(OVE‐co‐NPM)/PVC blends were cast from N‐dimethylformamide. An optical clarity test and DSC analysis showed that poly(OVE‐co‐NPM)/SAN and poly(OVE‐co‐NPM)/PVC blends were both miscible over the whole composition range. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1809–1815, 2000     

Foaming of PS/wood fiber composites using moisture as a blowing agent

This paper presents an experimental study on foam processing of polystyrene (PS) and high‐impact polystyrene HIPS/wood‐fiber composites in extrusion using moisture as a blowing agent. Wood‐fiber inherently contains moisture that can potentially be used as a blowing agent. Undried wood‐fiber was processed together with PS and HIPS materials in extrusion and wood‐fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood fiber. The effects of a small amount of a chemical blowing agent and mineral oil on the cell morphologies of plastic/wood‐fiber composite foams were also investigated.     

Biodegradable polymer blends of poly(L‐lactic acid) and gelatinized starch

Gelatinized starches were prepared with various content of glycerol and were investigated in terms of the effect of the glycerol addition on characteristics of starch and its blends. Poly (L‐lactic acid) (PLA) with various ratios of linear/star shaped PLA and starch gelatinized with various ratios of water/glycerol were melt‐blended by using twin screw mixer. The blends were characterized by DSC thermal analysis, tensile test and morphological analysis. Gelatinization of starch was found to lead to destruction or diminution of hydrogen bonding in granules and a decrease of crystallinity of starch. DSC data showed that starch played a role as a nucleating agent and glycerol as plasticizer contributed to an improvement in crystallinity in PLA blends. When the content of starch increased, the size of spherulites in PLA blends was smaller and less regular. In the case of PLA/pure starch blends, the voids appeared, which were formed by the separation of starch particles from the matrix. But for PLA/gelainized starch blends, these voids were not observed. In the case of blends with linear PLA and starch gelatinized with water/glycerol ratio of 100/40, the greatest superiority of mechanical properties was shown and the toughness was improved compared with PLA/pure starch blends.     

Effects of acrylonitrile content on PC/ABS alloy systems with a flame retardant

To investigate the effect of a flame retardant on PC/ABS alloy systems, a reactive‐type brominated epoxy resin was used as a flame retardant, and mixed with PC/ABS at various amount using a twin‐screw extruder. The rheological, morphological, mechanical, and thermal properties were investigated as a function of acrylonitrile (AN) content in ABS. The shear viscosity of the PC/ABS blend increased as the AN content in ABS increased. Temperature drastically affected the shear viscosity in the ABS matrix, but not as much in the PC matrix. A blend of PC 50% containing AN 22% is suitable to process because its shear viscosity is low in the high shear rate region and its mechanical properties drastically increase in the beginning of the PC matrix. In addition, gradual increases of heat distortion temperature were observed in the entire range of the PC content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 417–423, 2000     

Thermochemistry and Aqueous Durability of Ternary Glass Forming Ba-Titanosilicates: Fresnoite (Ba2TiSi2O8) and Ba-Titanite (BaTiSiO5)

Barium titanosilicates are possible oxide forms for the immobilization of short-lived fission products in radioactive waste. Ba₂TiSi₂O₈ (fresnoite) and BaTiSiO₅ (Ba-titanite) samples were prepared by a solid-state synthesis. The enthalpies of formation of Ba₂TiSi₂O₈ crystal and glass at 25°C and of BaTiSiO₅ glass were obtained from drop solution calorimetry in a molten lead borate (2PbO–B₂O₃) solvent at 701°C. The enthalpy of formation for fresnoite composition samples from constituent oxides was exothermic and became more exothermic with increasing crystallinity. Differential scanning calorimetry revealed that the crystallization rate of the fresnoite glasses increased with increasing devitrification. A modified Product Consistency Test-Procedure B (PCT-B) was used to collect solubility data on the fresnoite and titanate phases. The tests suggest that both glassy and crystalline fresnoite exhibit favorable aqueous stability and should be explored further as radioactive waste forms for long-term storage.     

Effects of a Conducting LaNiO3 Thick Film as a Buffer Layer of a Pb(Zr,Ti)O3 Film on Titanium Substrates

A conducting 8-μm-thick LaNiO₃ (LNO) film was deposited on a Ti substrate by aerosol deposition for use as a diffusion barrier between a lead zirconate titanate (PZT) and a Ti substrate during postannealing. The deposited 20-μm-thick PZT films were annealed at 800°C. The PZT film deposited without LNO was cracked and partially detached from the substrate after postannealing, presumably due to a severe reaction with the Ti substrate, while no significant reactions were observed when the LNO buffer layer was used. The remnant polarization and relative dielectric constant of the 20-μm-thick annealed PZT films deposited on the LNO-buffered Ti substrate were 43 μC/cm² and 1010, respectively.