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Wada, Yuki*; Tamada, Masao; Seko, Noriaki; Mitomo, Hiroshi*
Journal of Applied Polymer Science, 107(4), p.2289 - 2294, 2008/02
Times Cited Count：14 Percentile：42.04(Polymer Science)Vinyl acetate (VAc) was grafted onto poly(3-hydroxybutyrate) (PHB) film by preirradiation method. Grafting reactions were carried out in a VAc/water/surfactant emulsion, VAc/water, and VAc/methanol systems. For emulsion grafting, Nonion L-4 was ascertained to be the optimum surfactant with regard to the stability of a single emulsion layer. The emulsion with a 10:1 (w/w) ratio of VAc and surfactant yielded the highest degree of grafting (Xg) 23%. The grafting efficiency in the emulsion and the water and methanol solvent were evaluated. The results indicated that the grafting efficiency of the emulsion is 100 times that of VAc/methanol when the same 2 wt% VAc was used in the grafting reaction.
Wada, Yuki; Seko, Noriaki; Nagasawa, Naotsugu; Tamada, Masao; Kasuya, Kenichi*; Mitomo, Hiroshi*
Radiation Physics and Chemistry, 76(6), p.1075 - 1083, 2007/06
Times Cited Count：20 Percentile：78.28(Chemistry, Physical)Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.
Quynh, T. M.*; Mitomo, Hiroshi*; Nagasawa, Naotsugu; Wada, Yuki; Yoshii, Fumio; Tamada, Masao
European Polymer Journal, 43(5), p.1779 - 1785, 2007/05
Times Cited Count：115 Percentile：94.93(Polymer Science)Crosslinked materials derived from poly(lactide) (PLA) have been produced by radiation modification in the presence of a suitable crosslinker (triallyl isocyanurate: TAIC). The crosslinking structure introduced in PLA films has not only much improved the heat stability but also their mechanical properties. The properties of crosslinked samples are governed by crosslinking density and these improvement seemed to increase with radiation dose. This implied that the three dimensional networks have been introduced in material by radiation and the crosslinking density depended on the structure and length of PLA chains. Biodegradability of PLA was also determined by an enzymatic degradation test and burying in compost at 55 
C. Differing with PLLA, PDLA was insignificantly degraded by 
. The degradation rate of PLA in compost was postponed with the introduction of crosslinks.
Wada, Yuki; Mitomo, Hiroshi*; Seko, Noriaki; Tamada, Masao
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 51, 2007/02
no abstracts in English
Wada, Yuki; Mitomo, Hiroshi*; Kasuya, Kenichi*; Nagasawa, Naotsugu; Seko, Noriaki; Katakai, Akio; Tamada, Masao
Journal of Applied Polymer Science, 101(6), p.3856 - 3861, 2006/09
Times Cited Count：21 Percentile：53.53(Polymer Science)Radiation-induced graft polymerization of acrylic acid (AAc) on the surface of poly(3-hydroxybutyric acid) (PHB) film was carried out by applying pre-irradiation techniques. The PHB films grafted with AAc (PHB-g-AAc) possessed a degree of grafting higher than 5% have completely lost the enzymatic degradability. The enzymatic degradability of the grafted film was recovered by remolding. And the highest enzymatic degradation rate was observed to grafted films with AAc 10% of degree. Difference of enzymatic degradability of PHB-g-AAc film was caused by decrement of amount of enzyme contact and decrement of crystallinity of PHB by remolding.
Tamada, Masao; Wada, Yuki; Mitomo, Hiroshi*
no journal, ,
Poly(3hydroxybutiric acid) (PHB) is biodegradable polyester which can be hydrolyzed by enzyme called PHB depolymerase. In the present study, we tried to graft acrylic acid (AAc) and vinyl acetate (VAc) onto the PHB film. These AAc grafted PHB films and VAc grafted PHB films were thermally remolded and saponified, respectively. Difference of enzymatic degradability of these grafted films was evaluated.
Wada, Yuki; Tamada, Masao; Seko, Noriaki; Mitomo, Hiroshi*
no journal, ,
no abstracts in English
Wada, Yuki; Tamada, Masao; Seko, Noriaki; Mitomo, Hiroshi*
no journal, ,
no abstracts in English
Tamada, Masao; Seko, Noriaki; Wada, Yuki; Mitomo, Hiroshi*
no journal, ,
Biodegradable polyester, polyhydroxybutylate (PHB), was irradiated with 10 kGy of electron beam and then was grafted by vinyl acetate (VAc) in emulsion state and solvents of methanol and water. In the case of emulsion state, the degree of grafting reached 23% at grafting temperature of 60C after grafting time of 5h. In this case, grafting percentage of VAc was 1%. The grafting percentages were 0.67 and 0.030% for water and methanol, respectively. It was found that emulsion state can realize the effective grafting of VAc onto PHB.
