研究者詳細 - 木田　拓充

論文 - 木田　拓充

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Viscoelastic properties of copolycarbonates comprising isosorbide and 1,4-cyclohexanedimethanol 査読

Ruiqi Han, Takumitsu Kida, Masayuki Yamaguchi

Colloid and Polymer Science 2023年7月

Anomalous Postprocessing Dimensional Change of Injection-Molded Products Composed of Poly(lactic acid) and Poly(vinyl alcohol) 査読

Yamaguchi M., Shu W., Kimura T., Vo H.G.D., Kida T., Mori T., Kitani M., Aridome N., Miyamoto A.

ACS Applied Polymer Materials 5 ( 3 ) 2136 - 2143 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Polymer Materials

The present study revealed that an injection-molded product comprising poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVAL) exhibited an anomalous dimensional change, i.e., expansion in the flow direction, after postprocessing annealing (around 2.9% expansion by annealing at 80-100 °C for 3 h). Although the crystallization of the PLA during cooling was not accelerated by the addition of PVAL, the PLA showed transcrystallization from the dispersed PVAL droplets, which were deformed in the flow direction, during postprocessing annealing. Therefore, after annealing, the injection-molded products exhibited a high degree of molecular orientation, in contrast to the original unannealed products, which were not oriented. This anomalous behavior should be noted as a means of controlling dimensional change after processing.

DOI： 10.1021/acsapm.2c02155

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Role of Shear Flow on Structure Development during Post-Processing Annealing for Poly(lactic acid) 査読

Vo H.G.D., Kida T., Yamaguchi M.

Polymers 15 ( 3 ) 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymers

The effect of shear history on structure development during post-processing annealing was studied using poly(lactic acid) PLA. Since PLA shows a low crystallization rate, quenched films had no crystallinity. Moreover, molecular orientation was not detected in the films. During the annealing procedure beyond its glass transition temperature, however, molecular orientation to the flow direction occurred with the crystallization growth in the films having an appropriate shear history. This peculiar crystal growth during the annealing was most probably attributed to the crystallization from extended chain crystals generated during the applied shear history, although the amount of extended chain crystals was low. The results obtained in this study should be noted because the molecular orientation proceeded due to the annealing history applied. Furthermore, this phenomenon will be used to suppress dimensional change and increase product rigidity.

DOI： 10.3390/polym15030693

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Preparation of graded materials for miscible polycarbonate/poly(methyl methacrylate) blends by segregation under shear flow 査読

Moonprasith N., Tatsumichi M., Nakamura K., Kida T., Tsubouchi K., Hiraoka T., Yamaguchi M.

Journal of Applied Polymer Science 140 ( 1 ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Polymer Science

Exposure to shear flow produced by a pressure-driven capillary rheometer provides a concentration gradient without phase separation in miscible polymer blends of bisphenol-A polycarbonate containing low-molecular-weight poly(methyl methacrylate) (PMMA). The strand surface extruded from the rheometer contains a large amount of PMMA. However, the strand is transparent because there is no light scattering due to phase separation. The segregation behavior, that is, enrichment of the PMMA content at the strand surface, is enhanced when the molecular weight of PMMA is low. Furthermore, the segregation is also enhanced at high temperatures and at high shear rates. By contrast, the die length barely affects the degree of segregation. The segregation phenomenon should be noted because it may facilitate the modification of the surface properties of various products.

DOI： 10.1002/app.53258

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Improvement in Processability for Injection Molding of Bisphenol-A Polycarbonate by Addition of Low-Density Polyethylene 査読

Kuroda Y., Suzuki K.I., Kikuchi G., Moonprasith N., Kida T., Yamaguchi M.

Materials 16 ( 2 ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

The rheological properties and processability at injection molding were studied for bisphenol-A polycarbonate (PC) that was modified by low-density polyethylene (LDPE) having a low shear viscosity. The LDPE addition significantly decreased the steady-state shear viscosity, especially in the high shear rate region. The decrease did not originate from slippage on the die wall but due to interfacial slippage between the PC and dispersed LDPE droplets that deformed to the flow direction to a great extent. As a result of the viscosity decrease, injection pressure largely decreased from 150 to 110 MPa with the addition only 5 wt.% of LDPE. The enhanced flowability also reduced the warpage of the molded product significantly, demonstrating that the processability at injection molding was improved by the addition of LDPE.

DOI： 10.3390/ma16020866

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Direct Observation of the Effect of a High-Molecular-Weight Component on the Deformation Behavior of Polyethylene Solids Using the Rheo-Raman Spectroscopic Technique 査読

Kida T., Tanaka R., Shiono T., Yamaguchi M.

Macromolecules 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Macromolecules

We investigated the effects of molecular components of different molecular weights on the tensile properties of polyethylene (PE) by measuring the microscopic deformation of deuterated molecular chains of various molecular weights and narrow molecular weight distributions using rheo-Raman spectroscopy. The strain-hardening modulus increased by adding the high-molecular-weight chains connecting more than four to six lamellar crystalline layers. These high-molecular-weight molecular chains showed large peak shifts and orientation parameter values during strain hardening. In contrast, almost no stretching load was applied to the low-molecular-weight molecular chains that connected only two or three lamellar crystals in the strain-hardening region, and the strain-hardening modulus was unchanged by adding these low-molecular-weight chains. These results suggest that the high-molecular-weight molecular chains connecting more than four to six lamellar crystals act as stress transmitters throughout the crystal structure in the strain-hardening region.

DOI： 10.1021/acs.macromol.3c00197

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Anomalous Strain Recovery after Stress Removal of Graded Rubber 査読

Do Q.V., Kida T., Yamaguchi M., Washizu K., Nagase T., Tada T.

Polymers 14 ( 24 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymers

Mechanical responses after the uniaxial deformation of graded styrene–butadiene rubber (SBR) with a gradient in the crosslink points in the thickness direction were investigated as compared with those of homogenously vulcanized SBR samples. The elongational residual strain of a graded sample was found to depend on the part with a high crosslink density. Therefore, it showed good rubber elasticity. After stress removal, moreover, the graded sample showed a marked warpage. This suggested that shrinking stress acted on the surface with a high crosslink density, which would avoid a crack growth on the surface. The sample shape was then recovered to be flat very slowly, indicating that the shrinking stress worked for a long time. This unique rubber elasticity, i.e., slow strain recovery with an excellent strain recovery, makes graded rubber highly significant.

DOI： 10.3390/polym14245477

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Novel Transparent Films Composed of Bisphenol-A Polycarbonate and Copolyester 査読

Hasegawa H., Kida T., Yamaguchi M.

Polymers 14 ( 19 ) 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymers

In this paper, the structure and properties of transparent films composed of bisphenol-A polycarbonate (PC) and a commercially available copolyester, poly(1,4-cyclohexanedimethanol-co-2,2,4,4-tetramethyl-1,3-cyclobutanediol-co-terephthalate) (CPE), were studied. Both PC and CPE films are known to be transparent with good mechanical toughness. It was found that PC/CPE (50/50) showed miscibility in both the molten and solid states, indicating that there is a high possibility for the blend system to be miscible in the whole blend ratios. Because of the miscibility, the blend films showed no light scattering originating from phase separation. The mechanical properties of the films, such as Young’s modulus, yield stress, and strain at break, were determined by the blend ratio, and the glass transition temperature increased with the PC content, which corresponded well with the values predicted by the Fox equation. These results demonstrate that the thermal and mechanical properties of the films can only be controlled by the blend ratio. Since these transparent films showed excellent mechanical toughness irrespective of the blend ratios, they can be employed in various applications.

DOI： 10.3390/polym14194146

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Evaluation of Rheological Properties and Generation of Cross Orientation of Lamellae and Amorphous Chains in a Thermoplastic Polyester Elastomer 査読

Yamada T., Yamaguchi M., Kida T.

ACS Applied Polymer Materials 4 ( 9 ) 6322 - 6331 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Polymer Materials

Cross orientation between lamellae and amorphous chains was generated by forming residual crystals during extrusion and melt stretching under temperature-controlled processing conditions in a thermoplastic polyester elastomer (TPEE). Some crystals were not completely melted at a certain temperature slightly higher than the melting temperature of the sample during a heating process, and the survived crystals are called residual crystals. The TPEE exhibited prolonged relaxation at the temperature slightly higher than the melting temperature owing to the formation of the network structure composed of the residual crystals. The formation of the weak network affected the processability during extrusion, such as the swell ratio and the drawdown force. Although polarized microscopy images apparently showed that the average molecular orientation was along the drawing direction, it was found that the lamellar crystals oriented orthogonal to the fiber axis to reduce the hydrodynamic force during extrusion according to the results of multiple structural analyses. The orthogonal orientation of the lamellar crystals should be caused by the high aspect ratio of the lamellar crystals grown from the residual crystals. The orthogonal orientation resulted in a high Young's modulus and yield stress. The method for generating cross orientation of crystalline and amorphous chains will be applied to the preparation of high-performance fibers with high strength and modulus.

DOI： 10.1021/acsapm.2c00508

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Crystallinity enhancement of extruded polypropylene containing poly(vinyl alcohol) fibers prepared in situ 査読

Nishikawa R., Eno A., Janchai K., Han R., Kida T., Mori T., Aridome N., Miyamoto A., Yamaguchi M.

Polymer 254 2022年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

The present paper describes a novel method for reinforcing isotactic polypropylene (PP) by adding poly(vinyl alcohol) (PVA) fibers prepared by melt-stretching. Low-viscosity PVA droplets were deformed into fibers in the molten PP by melt-stretching them beyond the melting point of PVA. When the obtained composite was extruded below the melting point of PVA, the fibers became oriented toward the flow direction. The PVA demonstrated marked nucleating activity with regard to PP crystallization, which was further promoted by enlargement of the surface area by fibrillization. As a result, there was virtually no orientation relaxation of the PP chains with an increase in crystallinity, which explains the improvement in rigidity of the reinforced composite.

DOI： 10.1016/j.polymer.2022.125043

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Rheo-Raman Spectroscopic Study of Microscopic Deformation Behavior of Low- and High-Density Polyethylene Solids under Uniaxial Deformation 査読

Takumitsu Kida, Yusuke Hiejima, Koh-hei Nitta, Masayuki Yamaguchi

Nihon Reoroji Gakkaishi (J Soc Rheol Jpn) 60 ( 3 ) 287 - 294 2022年6月

Evaluation of microscopic structural changes during strain hardening of polyethylene solids using In situ Raman, SAXS, and WAXD measurements under step-cycle test 査読

Kida T., Hiejima Y., Nitta K.h., Yamaguchi M.

Polymer 250 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

We have examined the mechanism of strain hardening of polyethylene (PE) using a step-cycle test with in situ Raman spectroscopy, small-angle X-ray scattering, and wide-angle X-ray diffraction measurements. A stable fibrillar structure was formed at the onset of strain hardening. The fraction of the long-consecutive trans chains increased and decreased with increasing and decreasing strain during the stretching and unloading steps, respectively. The peak shift of the C–C stretching mode showed a red shift by applying the stretching stress to the specimen, accompanied by the broadening of the peak width. The broadening of the Raman band is interpreted as the strong stretching load becoming concentrated on the taut-tie chains. According to these results, we concluded that the strain hardening was caused by the increment of the modulus resulting from the increase in the number of taut-tie chains caused by chain pull-out from the crystalline structure.

DOI： 10.1016/j.polymer.2022.124869

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Role of Rigid–Amorphous chains on mechanical properties of polypropylene solid using DSC, WAXD, SAXS, and Raman spectroscopy 査読

Kida T., Yamaguchi M.

Polymer 249 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

We evaluated the rigid–amorphous (RA) fraction of isotactic polypropylene (iPP) samples by various measurement techniques and investigated the role of the RA chains on the mechanical properties of iPP. The RA fraction was increased by annealing above the α-relaxation temperature, although the RA fraction was almost independent of the molecular weight. The RA fraction obtained by differential scanning calorimetry increased linearly with the number of consecutive helical chains with 12–14 monomer units, suggesting that the RA chains are attributable to crystalline defects. Moreover, the α-relaxation temperature varied linearly with the RA fraction; the RA chains present as crystalline defects were removed from the crystalline structure by α relaxation. The yielding region of the stress–strain curve became broad by increasing the RA fraction; the fragmentation strength of the lamellar crystals was widely distributed owing to the large number of crystalline defects.

DOI： 10.1016/j.polymer.2022.124834

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Star polymers with norbornene/1-octene gradient copolymer arms synthesized by an ansa-fluorenylamidodimethyltitanium-[Ph<inf>3</inf>C][B(C<inf>6</inf>F<inf>5</inf>)<inf>4</inf>] catalyst system 査読

Yuan H., Kida T., Tanaka R., Cai Z., Nakayama Y., Kihara S.i., Shiono T.

Polymer 249 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

Cyclic olefin copolymers (COCs), among which ethylene (E)/norbornene (NB) copolymer have been commercialized, are novel optical plastics but their brittleness narrows their application fields. In this research, star polymers with NB/1-octene (O) gradient copolymer arms and cross-linked cores were synthesized by adding norbornadiene (NBD)/E or 1,11-dodecadiene (DOD) after NB/O copolymerization using a (tBuNSiMe2Flu)TiMe2 (I)-[Ph3C][B(C6F5)4] catalyst system with 2,6-di-tert-butyl-4-methylphenol-treated tri-n-octylaluminum (Oct3Al/BHT) as a scavenger. The obtained star polymers possessed the O-rich soft segments close to the core and the NB-rich hard segments in the outer layer. The DOD-cored star polymers had a larger number of arms (15) and a higher star polymer content (68 wt%) than the NBD/E-cored ones (6 and 58 wt%, respectively). The films of the mixtures of the star and the corresponding arm polymers were molded by a melt-pressing procedure. The tensile properties of the films of the DOD-cored star polymer mixtures were significantly improved compared to those of the arm polymers. The Young's modulus, yield stress, strength, and strain at break were controlled by the NB content, the arm length, and the gradient structure of the arms. These results clarified the novelty of the star-shaped NB/α-olefin copolymers and would expand the application fields of COCs.

DOI： 10.1016/j.polymer.2022.124844

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Segregation Behavior of Miscible PC/PMMA Blends during Injection Molding 査読

Moonprasith N., Date J., Sako T., Kida T., Hiraoka T., Yamaguchi M.

Materials 15 ( 9 ) 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

Miscible blends composed of bisphenol-A polycarbonate (PC) and poly(methyl methacrylate) (PMMA), in which one of them has low molecular weight, were employed to study the surface segregation behavior during flow. The blend samples showed typical rheological behaviors, such as simple polymer melts without a long-time relaxation mechanism ascribed to phase separation, demonstrating that they were miscible. After injection molding, the amounts of a low molecular weight component on the blend surface were found to be larger than the actual blend ratio. Because the injection-molded products were transparent despite a huge difference in refractive indices between PC and PMMA, they showed no phase separation. This result demonstrated that surface segregation of a low molecular weight component occurred under flow field, which expands the material design such as tough plastics with good scratch resistance and optical fibers with tapered refractive index.

DOI： 10.3390/ma15092994

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Viscoelastic Properties of Fully Biomass-Based Transparent Plastic Comprising Cellulose Acetate and Citrate Ester 査読

Kimura T., Kida T., Yamaguchi M.

Materials 15 ( 9 ) 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

Viscoelastic properties including melt processability were evaluated for a fully biomass-based glassy plastic comprising cellulose acetate (CA) and triethyl citrate (TEC). The TEC exerted an excellent plasticizing effect without dissolving the CA crystals. Pure CA has poor melt processability. In contrast, the TEC-plasticized CA had good melt-processability at 205◦C, which is lower than the degradation temperature of CA. Extrusion was possible even at 1000 s−1 without any flow instabilities, similar to conventional plastics showing good processability at extrusion. Furthermore, there was marked strain-hardening behavior in the transient elongational viscosity, suggesting that various processing operations are possible, such as a long-chain branched polymer. This biomass-based plastic can be used as a substitute for conventional glassy plastics because it is highly transparent and its softening temperature is above 100◦C.

DOI： 10.3390/ma15093038

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Complicated Structure Change during Capillary Extrusion of Binary Blends of Polycarbonate and Poly(methyl methacrylate) 査読

Yamaguchi M., Nakamura K., Kimura T., Moonprasith N., Kida T., Tsubouchi K., Narita T., Hiraoka T.

Materials 15 ( 8 ) 2022年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

The effects of pressure and shear rate on the miscibility of binary blends comprising bisphenol-A polycarbonate (PC) and low molecular weight poly(methyl methacrylate) (PMMA) were investigated using a capillary rheometer. Both pressure and shear rate affected the miscibility. The examination of an extruded strand of the blend provided information about the cause of the phase change. Under high pressure, pressure-induced demixing occurred at temperatures below the lower critical solution temperature (LCST) of the blend. Consequently, the extruded strand became opaque throughout. During shear-induced mixing/demixing, a part of the strand became opaque because of the distribution of the shear rate in the strand. For example, during shear-induced demixing, only the exterior of the strand, i.e., the high shear rate region, became opaque. Above the LCST, shear-induced mixing occurred, and only the center region of the strand became opaque.

DOI： 10.3390/ma15082783

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Crystallization behavior of isotactic polypropylene containing a fibrous nucleating agent in a flow field 査読

Janchai K., Kida T., Inoue T., Iwasaki S., Yamaguchi M.

Polymer Journal 54 ( 3 ) 367 - 375 2022年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer Journal

The crystallization behavior of isotactic polypropylene containing a fibrous nucleating agent in a flow field was investigated using a polarized optical microscope equipped with a parallel-plate shear device. The addition of the fibrous nucleating agent greatly enhanced the crystallization rate, although isotactic polypropylene crystallization without the nucleating agent was enhanced after exposure to shear flow at a high shear rate. The sample with the nucleating agent demonstrated high molecular orientation to the flow direction after shear flow, even at a low shear rate. This was attributed to the formation of a pseudo shish-kebab structure, in which the fibrous nucleating agent acts as the shish. Moreover, the high level of molecular orientation without spherulitic morphology was responsible for the reduced light scattering, which resulted in good transparency.

DOI： 10.1038/s41428-021-00596-7

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Raman Spectroscopic Analyses of Structure-Mechanical Properties Relationship of Crystalline Polyolefin Materials 招待査読

Takumitsu Kida

Nihon Reoroji Gakkaishi (J Soc Rheol Jpn) 50 ( 1 ) 21 - 29 2022年2月

Cyclic Olefin Copolymer Bearing Pendant Fluorenyl Groups with High Refractive Index and Low Chromatic Dispersion 査読

Yuan H., Kida T., Ishitobi Y., Tanaka R., Yamaguchi M., Nakayama Y., Shiono T.

Macromolecules 55 ( 1 ) 125 - 132 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Macromolecules

Copolymerization of norbornene (NB) and fluorene-containing alkene comonomers using the Me2Si(Flu)(NtBu)TiMe2 complex as a catalyst was investigated. The copolymerization successfully proceeded at any monomer feed ratio in high activity and gave copolymers with various comonomer contents. The structure of these copolymers would be gradient because NB was preferentially consumed in a quasi-living polymerization system. Two relaxation processes at 100-150 and 270-300 °C in dynamic mechanical analysis, which show phase-separation of the copolymer, supported the formation of the gradient structure. The obtained copolymers showed a high refractive index as hydrocarbons and extremely low photoelasticity (<10-11 Pa-1). For reducing the photoelasticity, a monomer design free from reactive tertiary carbons would be important.

DOI： 10.1021/acs.macromol.1c02101

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