Fumio Hosoi

Molecular weight distribution of methyl methacrylate grafted onto a microfiltration membrane by radiation-induced graft polymerization

Abstract Methyl methacrylate (MMA) was grafted onto a cellulose triacetate microfiltration (MF) membrane by radiation-induced graft polymerization (RIGP). Radicals were produced in the cellulose triacetate MF membrane after the irradiation with electron beams. The trapped radicals were then reacted with the MMA monomer both in vapor and liquid phases. In the liquid-phase grafting, the slower rate of graft polymerization was due to the occurrence of a chain transfer of radicals in the membrane. The grafted polymer branches were satisfactorily isolated from the graft copolymer by means of an acid hydrolysis method. From the gel permeation chromatogram, the graft chains prepared by vapor-phase grafting had a higher number-average molecular weight than those obtained by liquid-phase grafting at an identical degree of grafting. The length of the poly-MMA chain grafted in a vapor phase onto the cellulose triacetate MF membrane ranged from 103 to 104 monomer units and the degree of grafting ranged from 50 to 250%; its extended length was tantamount to the pore radius of the starting MF membrane.

Development of radiation crosslinking process for high voltage power cable

Abstract This work has been done to develop an electron beam crosslinking process for high voltage power cable by solving problems of the foaming and discharge breakdown of thick polyethylene insulation during irradiation. When a polyethylene plaque (d=0.92, MI=1.0) of 4 mm thick corresponding to the wall of 6.6 kV cable was irradiated by 1.5 MeV electrons, the temperature went up to 95°C and foaming was observed at a dose of 20 Mrad. On the other hand, irradiation of 24 Mrad was required for sufficient heat resistance (75% gel formation) of polyethylene. Although an addition of conventional polyfunctional monomers reduced the crosslinking dose (10 – 12 Mrad), discharge breakdown occured at relatively low doses. The present work reveals that both foaming and discharge breakdown are efficiently prevented by the use of dipropargyl succinate (DPS). A 6.6 kV type cable specimen insulated with polyethylene containing 2 phr of DPS was irradiated by 1.5 MeV electrons. While the cable had properties comparable to those of a steam cured one, very few voids were observed in the insulation.

FTIR reflection absorption spectroscopy for organic thin film on ITO substrate

Abstract Dielectric constant of indium–tin oxide (ITO) substrate was obtained by the basis of free electron model to evaluate the reflection infrared (IR) spectrum of an organic thin film on the ITO substrate in the wavenumber region from 3500 to 600 cm−1. In a wavenumber region of less than 2000 cm−1, the given spectrum was approximate to the spectrum on a metal substrate having high reflectivity. In this region, the thickness of the PVCz thin film under physical vapor deposition process was proportional to the peak intensity of reflection spectrum.

Radiation-induced polymerization of unsaturated phospholipid mixtures for the synthesis of artificial red cells

Abstract Radiation induced polymerization of phospholipid containing unsaturated acyl chains was applied to the synthesis of artificial red cells. Vesicles of 1,2-bis-(2,4-octadecadienoyl)-phosphatidylcholine (DODPC) and 1-stearoyl-2-(2,4-octadecadienoyl)-phosphatidylcholine (AODPC) were irradiated by 60 Co γ-rays to obtain polymerized bilayer structure of these monomers. It was found that the polymerization of unsaturated groups located at 2-acyl chain of DODPC polymerized faster than those of AODPC. The difference was explained by the packed state of these monomers in the bilayer vesicles. The artificial red cell was obtained by irradiating the mixture of DODPC or AODPC with hemoglobin, cholesterol and palmitic acid sodium salt. The integrity of the irradiated hemoglobin in the vesicle was maintained by keeping the suspended solution at low temperature. On the other hand, oxidation of heme part became remarkable when the vesicle was kept at 37°C. The presence of extra hemoglobin outside the vesicle was found useful to prevent this oxidation.

Development of artificial red cells (ARC) produced by γ-ray induced polymerization of liposomes

Artificial red cells (ARC) are prepared by encapsulating Hb with a polymerizable phospholipid. The polymerization of the vesicles were carried out with the irradiation of γ-rays. The irradiated ARC are physically more stable than any other known liposome type blood substitutes. Because of this stability, they can be easily stored under frozen condition for a long time. No significant changes were observed in vivo study with rats in which ARC were injected intravenously. The oxygen transport capacity of ARC was similar to that of native red blood cells.

Radiation-induced polymerization of a phospholipid for developing artificial red blood cells

Abstract A phospholipid containing two unsaturated acyl chains, 1,2-bis (2E,4E-octadecadienoyl)- sn -glycero-3-phosphocholine, was polymerized by 60 Co γ-rays at dose rates 1.65–10 kGy/h at 4°C. The kinetic treatment of the reaction was carried out. It was found that 2-acyl chain located nearer to the water surface polymerized at first, then 1-acyl chain polymerized. The rate of the former reaction was 10 times that of the latter. The polymerized phospholipid containing haemoglobin was stable at low temperature. The in vivo test with rats was successfully carried out with this artificial red blood cells.