Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution

The radiation-induced copolymerization of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water-insoluble copolymer. A water-soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation-polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.     

Bending of ionic polymer gel caused by swelling under sinusoidally varying electric fields

Deformation of poly(vinyl alcohol)–poly(sodium acrylate) composite hydrogel (PVA–PAA gel) under sinusoidally varying electric fields was studied in electrolyte solutions. The PVA–PAA gel was prepared by repeatedly freezing and thawing a mixed solution of PVA and polyacrylic acid. A cyclic bending–straightening motion of the PVA–PAA gel rods of about 1 mm in diameter have been observed in Na₂CO₃ aqueous solutions under the fields. The PVA–PAA gel had a response time of less than several hundreds milliseconds. The bending has also been observed in organic solvents containing an electrolyte when the organic solvent is electrolyzed. It was found that the motion of the gel under electric fields of less than 1 Hz occurred mainly through swelling due to the change of the osmotic pressure based upon the difference of the ion concentration. However, it has not been determined whether the motion at higher frequencies is caused by the osmotic effect. © 1993 John Wiley & Sons, Inc.     

Production of finely ground natural graphite particles with high electrical conductivity by controlling the grinding atmosphere

Natural graphite particles with high crystallinity sieved to obtain a particle size range of under 63 μm were ground with a ball mill, under various well-controlled grinding atmospheres such as N₂, O₂, He, H₂, and vacuum. The ratio, X_dif50/X_st50, i.e. between the 50 wt.% Stokes diameter and the 50 wt.% laser diffraction diameter, of the ground particles, was used as an index of the flakiness of the particles. The specific resistance of films composed of the ground graphite particles was systematically measured. The rate of reduction in the size of the particles by grinding was slow under an O₂-rich atmosphere such as 100% O₂ and dry air. On the other hand, it was relatively fast in vacuum, or under an N₂ or He atmosphere, and a gas mixture of 99% N₂ and 1% O₂. The rate of size reduction by grinding under a H₂ atmosphere was intermediate. In our experimental conditions, the flakiness of the ground particles increased with the decrease in the particles’ sizes. The electrical conductivity of the ground particles, however, tended to decrease with the decrease in their sizes. Under the condition that the Stokes diameter of the ground particles remains constant, the electrical conductivity of films made from the ground particles increases with the increase in the flakiness of the particles. It was finally determined from our systematic grinding experiments that small flaky particles, which had a size, X_st of ∼1 μm, with a high electrical conductivity can be produced by grinding in a gas mixture of 99% N₂ and 1% O₂. In this case, the flaky shape of the ground particles was visually confirmed by scanning electron microscopy.     

Effect of platelet-activating factor on lipoprotein lipase and blood lipids

We investigated the effect of platelet-activating factor (PAF) and of the PAF specific antagonist CV-6209 on plasma lipid metabolism, and particularly on post-heparin plasma lipolytic activity in male Wistar rats. Lipoprotein lipase (LPL) activity was enhanced by intravenous injection of PAF before intravenous injection of heparin when the PAF dose was low (0.2 μg/kg). PAF activated hepatic triacylglycerol lipase (HTGL) activity dose-dependently. Plasma triacylglycerols (TG) significantly decreased with the activation of LPL and/or HTGL. Plasma total cholesterol (TC) and phospholipid (PL) levels decreased at a low dose of PAF (0.2 μg/kg), but increased when higher doses were used. The PAF antagonist CV-6209 partially reversed the PAF induced effects on HTGL, TC and PL. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Preparation of Aluminum Nitride–Silicon Carbide Nanocomposite Powder by the Nitridation of Aluminum Silicon Carbide

Aluminum nitride (AlN)–silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al₄SiC₄) with the specific surface area of 15.5 m²·g⁻¹. The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich phases. The formation of homogeneous solid solution proceeded with increasing nitridation temperature from 1400° up to 1500°C. The specific surface area of the AlN–SiC powder nitrided at 1500°C for 3 h was 19.5 m²·g⁻¹, whereas the primary particle size (assuming spherical particles) was estimated to be ∼100 nm.     

Plasma developable photoresist containing electronic excitation energy quenching system

A dry developable negative working resist composition comprised of poly(methyl isopropenyl ketone) (PMIPK) and 4-methyl-2,6-di(4′-azido-benzylidene) cyclohexanone-1 was examined. The main photochemical product formed in the resist pattern was found to be a secondary amine which crosslinks PMIPK. Post-annealing forms a hydrogen-bonded product which shows a powerful electronic excitation energy quenching effect. The quencher is more powerful than the aromatic compound arising from the azide by post-annealing only. The residual resist thickness of the negative pattern is about 80 percent of the initial thickness of the coating in spite of all the azide compound remaining in the resist coating. The obtained dry developed resist pattern has a high dry etch resistance. Etchings of Si and SiO₂ were performed by plasma and reactive ion etching, respectively.     

Synthesis of High Density and Transparent Forsterite Ceramics Using Nano-Sized Precursors and Their Dielectric Properties

Forsterite (Mg₂SiO₄) ceramics were prepared using Mg(OH)₂ and SiO₂ as precursors, and the effect of powder characteristics of Mg(OH)₂ on calcination and sintering was investigated. The use of highly dispersed Mg(OH)₂ powder (HD powder) resulted in a lower calcination temperature. Forsterite powder of high homogeneity and small particle size prepared from the HD powder enabled synthesis of high-density forsterite ceramics by ordinary sintering without applying external pressure. Moreover, transparent forsterite ceramics were successfully synthesized through addition of excess Mg to the precursors to compensate for Mg evaporated during the sintering process. Subsequent dielectric measurements revealed that the transparent forsterite ceramics had a very low dielectric loss (tan δ<10⁻⁴).     

Mechanism of Mechanical Strength Increase of Soda–Lime Glass by Aging

Two models have been proposed to explain the mechanical strength increase of abraded or indented soda–lime glasses upon aging, namely, crack tip blunting and the release of residual tensile stress near the crack tip. To clarify the mechanism, the time dependence of the strengthening of an abraded soda–lime glass was investigated. Effects of aging media, such as moist air, distilled water, 1 N HCI and 1 N NaOH solutions, as well as the abrasion flaw depth, were determined. The strength increase rate in water of abraded soda–lime glass was compared with those of borosilicate and high-silica glasses. The effect of stressing during aging was also investigated. It was found that the rate of strength increase was faster with decreasing abrasion flaw depth and with decreasing chemical durability. For a given flaw depth, an acidic solution produced the fastest strengthening. The strengthening rate was found to accelerate because of the "coaxing'effect of stressing during aging. From these observations, it was concluded that the strengthening rates relate to the diffusion process and chemical reactions, especially the alkali–hydrogen (or hydronium) ion-exchange reaction, near the crack tip. The role of the residual tensile stress appears to be similar to that of the applied tensile stress, helping the diffusion process near the crack tip. The observed strength increase of soda–lime glass by aging was thus attributed to the effective blunting of the crack tip geometry by the glass–water reaction.     

Photoelastic confirmation of surface stress relaxation in silica glasses: Fiber bending and rod torsion

Silica glass samples were given various heat treatments under stress at low temperatures and subsequently their residual stress distributions in terms of retardance were observed using a polarized light microscope, confirming previously reported fast surface stress relaxation while providing more detailed characterization. Retardance profiles of silica glass fibers heat-treated under a constant bending strain in the presence of atmospheric water vapor were measured and fit to a previously developed diffusion-based relaxation model. The retardance of a cross-section of a silica glass rod heat-treated at 650°C in lab air under applied torsional shear strain was also measured to confirm the presence of residual surface shear stress which was predicted by the decrease of torque with time for the rod. Together, these results confirm the low-temperature fast surface stress relaxation which occurs when water vapor is present for both bending and shear stresses.     

Reinforcement of polypropylene by cellulose microfibers modified with polydopamine and octadecylamine

Cellulose microfibers (CMFs) having surfaces modified with polydopamine (PDPA) and octadecylamine (ODA) were prepared, and their reinforcing abilities for polypropylene (PP) were investigated. The PDPA coating was made via self-polymerization of dopamine (P-CMF), and subsequent alkylation was conducted by the reaction with ODA (OP-CMF). The modified CMFs exhibited improved dispersibility in the PP matrix due to the reduced hydrophilicity. The OP-CMF/PP composite prepared by batch mixing had a higher tensile modulus compared to that for the pure PP and composites with unmodified CMFs. However, excess alkylation lowered the tensile modulus, and the presence of an optimal degree of alkylation was demonstrated. The CMF/PP-IM composites fabricated by injection molding exhibited improved tensile properties compared to those prepared by batch mixing. Both the tensile modulus and yield stress were increased by increasing the CMF content and improved by the surface modification of the CMFs.