E.s.r. studies on oxidation processes in irradiated polyethylene: 2. Diffusion of oxygen into crystalline regions

The oxidation process in irradiated polyethylene was investigated by means of the e.s.r. method, and diffusion of oxygen molecules into the crystalline region of polyethylene was studied in detail. Computer simulation was carried out in order to determine various parameters of the process including diffusion constant. In the course of the simulation, the crystallite was assumed to have a plate-shaped form and the diffusion constant was considered to be larger at the region near the surface of the crystallite, D_f, and to be smaller at the inner region of the crystallite, D_s. Making these assumptions in the simulation gave a much better result than the assumption based on a sphere-shaped crystallite. $\text{D}{}_{\mathrm{f}}\text{D}{}_{\mathrm{s}}$ was found to be about 2 for thicker crystallite and it was 4 ～ 5 for thinner crystallite. Diffusion constants at various temperatures were determined, and the order of magnitude of diffusion constants in the crystalline region was found to be 10^?16 cm²/sec at about 320K both for thicker and thinner crystallites. The activation energy of diffusion of oxygen in the crystallites was found to be 32 kcal/mol.     

Use of Ozone in Night Soil Treatment Process

Ozonation is used for the tertiary treatment, particularly for removal of colour, of the effluent from a night soil treatment plant in Japan. The practical system for effectively controlling the ozone treatment was investigated. The optimum ozonation was accomplished by monitoring the colour. This treatment plant worked in response to a sudden variation in the quality of raw water, i. e., nitrite ion concentration, COD, etc, and the quality of the ozonated water was kept at the levels of COD of 20 ~ 30 mg/2, and colour of 30 units. The water treated by this ozonation plant was found to be free from coliform bocilli, and to exhibit neither so strong acute toxicity to fishes nor mutagenicity.     

ESR study on molecular motion of peroxy radicals of polytetrafluoroethylene

Temperature variations of the line shapes of e.s.r. spectra from the peroxy radicals of polytetrafluoroethylene ( ) were investigated in detail and the results were quantitatively analysed based on Kneubühl's theory on the line shape. It was found that there were two kinds of rapid molecular motions, of which the correlation times were about 10⁻⁹ s, for the peroxy radicals of ; one was the rotational motion related to the peroxy chain radical, the other was the three dimensional motion associated with the peroxy end radical. The activation energies of these molecular motions were estimated as 0·52 kcal/mol and 0·26 kcal/mol for the rotational motion and the three dimensional motion, respectively. Origins of such rapid motions were discussed in connection with the other molecular motions of polymers, which were found by other experimental methods.     

Mobility and e.s.r. spectra of alkyl free radicals trapped in irradiated mats of solution-grown polyethylene

E.s.r. studies of alkyl free radicals,a trapped in irradiated mats of solution-grown polyethylene crystals have been studied. The crystal mat was aligned so that the crystallites c-axes were perpendicular to its surface. When the angle between the direction of applied magnetic field and the c-axis of the crystallite was varied, the observed e.s.r. spectra showed apparent anisotropy due to α-proton hyperfine splitting. The principal values and directions of the $\text{A}\text{?}$ tensor due to the α-proton at 77 and 254K were determined using the line shapes of uniaxially-oriented samples. The principal axis directions, A₁ were assigned along the polymer chain axis and A₂ and A₃ were perpendicular to the chain axis. The maximum principal value A₁ did not change with temperature, but the lower principal values, A₂ and A₃ averaged out at high temperatures. Hence, it was concluded that the temperature dependence of the $\text{A}\text{?}$ tensor reflects hindered oscillation around the main chain axis at high temperature. A twisted configuration for the methylene group with 4.5° deviation from the trans-trans configuration was also evident for the rigid state configuration of the alkyl radicals at 77K. Temperature dependences of the hyperfine splitting widths due to β-protons were observed and analysed in terms of hindered oscillations of the β-methylene group.     

Relaxation spectrometry of polyethylene in urea-polyethylene complex by BL n.m.r. and e.s.r. measurements

The molecular motions of polyethylene in urea-polyethylene complexes have been studied by e.s.r. and BL n.m.r. The e.s.r. spectra of alkyl free radicals located along the polymer chains were recorded and the temperature dependences of hyperfine splitting widths due to the β-protons (ΔH_β1, ΔH_β2) and linewidths were estimated. A decrease in (ΔH_β1 ? ΔH_β2) and narrowing (which appears over a wide temperature region) was found. The motional narrowing of line widths in the _BL n.m.r. spectra were also found. Correlation times for the molecular motion of polyethylene molecules were calculated from this magnetic resonance data, taking into account the distribution of relaxation times according to Miyake's equation. It was concluded that the molecular motions studied by e.s.r. and n.m.r. were the same. Relaxation time spectra indicated higher activation energies (10 kcal) than those calculated for a system with a single correlation time.     

Chronic thromboembolic pulmonary hypertension associated with initial pulmonary involvement in Takayasu arteritis

We report a case of a 65-year-old man with intradipolic epidermoid cyst of the frontal bone. The patient presented with headache and swelling of the forehead. Skull x-ray showed massive destruction of the frontal bone. Magnetic resonance imaging (MRI) revealed an epidural mass without any encroachment of the dura mater. The cystic tumor was removed followed by cranipolasty with methylmethacrylate. Four years later, the tumor recurred in the same region. At the second surgery the bony defect was again replaced with methylemthacrylate plate. Four years after the second operation, the tumor reemerged with some subcutaneous fluid retention. At the third surgery, the remaining tumor capsule was removed as much as possible except for that part which adhered to the superior sagittal sinus. The authors discuss the relationship of tumor recurrence with utilization of methylmethacrylate for cranioplasty in this type of tumor.     

Fluorescence analysis for thermo-sensitive hydrogel microspheres

Poly(N-isopropylacrylamide) (PNIPAM) hydrogel microspheres were prepared by precipitation polymerization above the polymer's lower critical solution temperature (LCST) in water. The hydrodynamic size of PNIPAM microspheres exhibited a thermo-sensitive change around the LCST. In order to obtain information about the interface of the hydrogels, contact angle measurement, protein adsorption, and fluorescence analysis were performed. Contact angle measurement and protein adsorption showed a gradual change around the LCST similar to the change of the hydrodynamic size. However, fluorescence study exhibited a sharp change at the LCST. In addition, a quenching experiment was employed to elucidate the location of the fluorescent probes. In the PNIPAM latex, the probes were located where they were less quenchable as compared to the PNIPAM solution. It seems probable that the probes can penetrate into the crosslinked PNIPAM hydrogel and might reflect the inner environment of the hydrogel. The effect of salt on thermo-sensitive behaviour was also detected by fluorescence analysis. On the other hand, the hydrogel microsphere prepared from poly(acryloyl pyrrolidine) (PAPr) showed a gradual change in fluorescence with temperature.     

Free radicals trapped in polyethylene matrix: 2. Decay in single crystals and diffusion

The kinetics of the decay of main chain free radicals trapped in polymer matrix in vacuum was investigated. The decay behaviour of alkyl radicals trapped in the lamellar surface of the crystallites of solution grown polyethylene should be different from that of the same radicals trapped in the inner part of the crystallite, and this difference was clearly observed. The analysis of the data of the decay reaction was made, based on three-dimensional diffusion-controlled reaction theory, and reasonable interpretation of the data was made. Alkyl radicals were also observed in an irradiated urea—polyethylene complex and the decay rate of these radicals were very slow in spite of the large mobility. According to these occurrences, it was concluded that the mechanism of three-dimensional diffusion of the free radicals across the chain may occur in the inner part of the crystallites via hydrogen abstraction reactions.     

Interaction between lead‐free multicomponent alkali borosilicate glass frits and hematite in red overglaze enamels

Japanese traditional red overglaze enamel decorations on porcelain known as akae are produced using lead‐containing frits, leading to a problem of lead release. Although many lead‐free frits have been developed, a well‐colored akae has not yet been realized, mainly because of no information on the reaction between lead‐free frits and hematite during the heating process in akae production. To reveal the effect of such interaction between the frits and hematite in akae on the color tone, various akae test pieces were prepared and investigated. On using low‐melting‐point lead‐free alkali borosilicate glass system, which contain zinc oxide, the formation of zinc ferrite proceeds simultaneously with the dissolution and particle growth of hematite in the frit melt. The particle growth rate due to dissolution and precipitation in the frit melt is faster than that due to sintering of particles caused by heat treatment of hematite powder in dry process. The dissolving capacity and promoting effect of particle growth depended on frit compositions. We also showed that the composition of akae glass layer varies because of ions diffusing from the glaze layer. Compositional changes in the akae glass could strongly affect the reactivity between the frits and hematite, resulting in variation in the color tone, the crystal phases formed, and their segregated states.     

Chemical reaction between lead-free multicomponent alkali borosilicate glass frit and hematite during heat treatment

A mixture of a lead-free multicomponent alkali borosilicate glass frit containing zinc ions and hematite was heat-treated under various conditions to elucidate the reaction between the two components, which is essentially important for controlling the color of red overglaze enamels. Above the glass transition temperature, the interaction between the frit fluid and hematite was evident, as the viscosity of the frit decreased. Moreover, hematite dissolved, the iron ions diffused into the glass matrix and they precipitated on residual hematite, resulting in enhanced crystal growth through Ostwald ripening. Concurrently, the iron and zinc ions reacted to form zinc ferrite. During cooling, the supersaturated iron ions were consumed for precipitation of hematite and zinc ferrite. Because frit and hematite dramatically react during heat treatment, conventional modification of hematite alone is insufficient. Development of the frit exhibiting low reactivity toward hematite through precise control of physical properties is a future challenging issue.