19 results on '"Takumitsu Kida"'
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2. Optimum processing conditions for the maximum crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)
- Author
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Khunanya Janchai, Takumitsu Kida, Masayuki Yamaguchi, Takenobu Sunagawa, and Tetsuo Okura
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Medicine ,Science - Abstract
Abstract The effect of thermal and shear histories on the crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was studied. As with other crystalline polymers, the shear history greatly affected the crystallization rate when the shear rate was beyond a critical value, i.e., the inverse of the Rouse relaxation time. Even after the formation of extended chain crystals, spherulite texture was clearly discernable. It grew from certain points on the extended chain crystals. Consequently, a row of spherulites appeared along the flow direction. The resin temperature in the molten state was also significant. When the sample was heated to 170 °C, which is beyond the main melting peak in the differential scanning calorimetry curve, unmolten crystals did not affect the linear viscoelastic properties. They acted as effective nucleating agents for the rest of the polymer during cooling. Therefore, the shear history hardly affected the crystallization rate and the number of spherulites.
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- 2023
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3. Role of Shear Flow on Structure Development during Post-Processing Annealing for Poly(lactic acid)
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Hoang-Giang Dai Vo, Takumitsu Kida, and Masayuki Yamaguchi
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poly(lactic acid) ,molecular orientation ,crystallization ,annealing ,Organic chemistry ,QD241-441 - Abstract
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.
- Published
- 2023
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4. Improvement in Processability for Injection Molding of Bisphenol-A Polycarbonate by Addition of Low-Density Polyethylene
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Yuki Kuroda, Ken-Ichi Suzuki, Genzo Kikuchi, Nantina Moonprasith, Takumitsu Kida, and Masayuki Yamaguchi
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polymer blend ,shear viscosity ,injection molding ,polycarbonate ,low-density polyethylene ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
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.
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- 2023
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5. Anomalous Strain Recovery after Stress Removal of Graded Rubber
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Quoc-Viet Do, Takumitsu Kida, Masayuki Yamaguchi, Kensuke Washizu, Takayuki Nagase, and Toshio Tada
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graded rubber ,rubber elasticity ,styrene–butadiene rubber ,Organic chemistry ,QD241-441 - Abstract
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.
- Published
- 2022
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6. Novel Transparent Films Composed of Bisphenol-A Polycarbonate and Copolyester
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Hiroyuki Hasegawa, Takumitsu Kida, and Masayuki Yamaguchi
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polymer blend ,transparent film ,polycarbonate ,polyester ,Organic chemistry ,QD241-441 - Abstract
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.
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- 2022
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7. Complicated Structure Change during Capillary Extrusion of Binary Blends of Polycarbonate and Poly(methyl methacrylate)
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Masayuki Yamaguchi, Kodai Nakamura, Takeyoshi Kimura, Nantina Moonprasith, Takumitsu Kida, Kyoko Tsubouchi, Takaaki Narita, and Tatsuhiro Hiraoka
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polymer blends ,pressure ,shear ,miscibility ,polycarbonate ,poly(methyl methacrylate) ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
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.
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- 2022
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8. Segregation Behavior of Miscible PC/PMMA Blends during Injection Molding
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Nantina Moonprasith, Jitsuhiro Date, Takumi Sako, Takumitsu Kida, Tatsuhiro Hiraoka, and Masayuki Yamaguchi
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polymer blends ,viscoelastic properties ,injection molding ,segregation ,polycarbonate ,poly(methyl methacrylate) ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
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.
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- 2022
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9. Viscoelastic Properties of Fully Biomass-Based Transparent Plastic Comprising Cellulose Acetate and Citrate Ester
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Takeyoshi Kimura, Takumitsu Kida, and Masayuki Yamaguchi
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cellulose acetate ,triethyl citrate ,viscoelastic properties ,rheology ,elongational viscosity ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
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.
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- 2022
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10. Effect of Ultra-High-Molecular-Weight Molecular Chains on the Morphology, Crystallization, and Mechanical Properties of Polypropylene
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Takumitsu Kida, Takeyoshi Kimura, Ayaka Eno, Khunanya Janchai, Masayuki Yamaguchi, Yasuhiko Otsuki, Tokutaro Kimura, Tomoaki Mizukawa, Tomoya Murakami, Kazuki Hato, and Tomoya Okawa
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ultra-high molecular weight component ,rheological property ,crystallization behavior ,mechanical property ,polypropylene ,Organic chemistry ,QD241-441 - Abstract
The effects of the ultra-high-molecular-weight (UHMW) component of polypropylene (PP) on its rheological properties, crystallization behavior, and solid-state mechanical properties were investigated using various measurement techniques. The terminal relaxation time—determined by measuring the linear viscoelasticity—was increased by adding the UHMW component. The increase in the melt elasticity produced by adding the UHMW component was observed by measuring the steady-state shear flow, although the shear viscosity was not greatly affected. Owing to the long characteristic time of the Rouse relaxation of the UHMW component, PP with the UHMW component formed highly oriented structures through a shear-induced crystallization process. The addition of the UHMW component enhanced the orientation and regularity of crystalline structure for extruded films. Therefore, the Young′s modulus, yield stress, and strength were higher in the PP film containing the UHMW component than in one without the UHMW component, irrespective of the direction of tensile deformation.
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- 2021
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11. Impact of Magnesium Salt on the Mechanical and Thermal Properties of Poly(vinyl alcohol)
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Riza Asmaa Saari, Muhammad Shahrulnizam Nasri, Takumitsu Kida, and Masayuki Yamaguchi
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mechanical properties (B) ,dynamic mechanical thermal analysis (D) ,polymers (A) ,stress/strain curves (B) ,rheology (D) ,Organic chemistry ,QD241-441 - Abstract
The effects of magnesium salts with various anion species on the structure and properties of a poly(vinyl alcohol) (PVA) film were studied. The glass transition temperature of the PVA film increased following the addition of a magnesium salt. Furthermore, the salt greatly enhanced the modulus and yield stress and reduced the crystallinity of the film. These effects were attributed to the strong ion–dipole interactions between the magnesium salts and the PVA chains. The strength of interaction, i.e., the reduction of segmental motions, depended on the anion species in the following order: Mg(ClO4)2, MgBr2, MgCl2, Mg(CH3COO)2, and MgSO4. The order corresponded to the Hofmeister series, which predicts the ability to break the structure of water.
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- 2021
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12. Synthesis, Properties, and Biodegradability of Thermoplastic Elastomers Made from 2-Methyl-1,3-propanediol, Glutaric Acid and Lactide
- Author
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Lamya Zahir, Takumitsu Kida, Ryo Tanaka, Yuushou Nakayama, Takeshi Shiono, Norioki Kawasaki, Naoko Yamano, and Atsuyoshi Nakayama
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poly(L-lactide) ,triblock copolymers ,thermoplastic elastomer ,poly(2-methyl-1,3-propylene glutarate) ,biodegradability ,Science - Abstract
An innovative type of biodegradable thermoplastic elastomers with improved mechanical properties from very common and potentially renewable sources, poly(L-lactide)-b-poly(2-methyl-1,3-propylene glutarate)-b-poly(L-lactide) (PLA-b-PMPG-b-PLA)s, has been developed for the first time. PLA-b-PMPG-b-PLAs were synthesized by polycondensation of 2-methyl-1,3-propanediol and glutaric acid and successive ring-opening polymerization of L-lactide, where PMPG is an amorphous central block with low glass transition temperature and PLA is hard semicrystalline terminal blocks. The copolymers showed glass transition temperature at lower than −40 °C and melting temperature at 130–152 °C. The tensile tests of these copolymers were also performed to evaluate their mechanical properties. The degradation of the copolymers and PMPG by enzymes proteinase K and lipase PS were investigated. Microbial biodegradation in seawater was also performed at 27 °C. The triblock copolymers and PMPG homopolymer were found to show 9–15% biodegradation within 28 days, representing their relatively high biodegradability in seawater. The macromolecular structure of the triblock copolymers of PLA and PMPG can be controlled to tune their mechanical and biodegradation properties, demonstrating their potential use in various applications.
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- 2021
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13. Neutron Reflectivity Study on the Adsorption Layer of Polyethylene Grown on Si Substrate.
- Author
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Keisuke Shimokita, Katsuhiro Yamamoto, Noboru Miyata, Motoki Shibata, Yohei Nakanishi, Masato Arakawa, Mikihito Takenaka, Takumitsu Kida, Katsuhisa Tokumitsu, Ryo Tanaka, Takeshi Shiono, Masako Yamada, Hideki Seto, Yamada, Norifumi L., Hiroyuki Aoki, and Tsukasa Miyazaki
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- 2024
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14. Rheo-Raman Spectroscopic Study on Uniaxial Deformation Behavior of High-Density Polyethylene Solids with Various Molecular Weight Distributions
- Author
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Koh-hei Nitta, Yusuke Hiejima, and Takumitsu Kida
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In situ ,Morphology (linguistics) ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Dispersity ,technology, industry, and agriculture ,02 engineering and technology ,Polyethylene ,Deformation (meteorology) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Materials Chemistry ,symbols ,High-density polyethylene ,Composite material ,0210 nano-technology ,Raman spectroscopy - Abstract
金沢大学理工研究域フロンティア工学系, The influences of the polydispersity index (Mw/Mn) on the morphology and deformation behavior of high-density polyethylene solids under uniaxial stretching were investigated using in situ Raman spectroscopy. An increase in Mw/Mn led to a larger fraction of tie molecules connecting several lamellar crystals, whereas no obvious influence on the crystalline structures was observed. Although the stress-strain curves essentially remained unchanged up to the neck propagation region irrespective of Mw/Mn, the strain-hardening modulus was higher for higher Mw/Mn samples. These results indicate that the mechanical response of the network structure appears in the strain-hardening region because of the tie molecules connecting several lamellar crystals fragmented at the yield point. In addition, the molecular orientation of the crystalline chains into the stretching direction and the formation of long consecutive trans chains were enhanced for higher Mw/Mn samples. Copyright © 2019 American Chemical Society., Embargo Period 12 months
- Published
- 2019
15. Cyclic Olefin Copolymer Bearing Pendant Fluorenyl Groups with High Refractive Index and Low Chromatic Dispersion.
- Author
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Haobo Yuan, Takumitsu Kida, Yuma Ishitobi, Ryo Tanaka, Masayuki Yamaguchi, Yuushou Nakayama, and Takeshi Shiono
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- 2022
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16. Molecular orientation behavior of isotactic polypropylene under uniaxial stretching by rheo-Raman spectroscopy
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Takumitsu Kida, Yusuke Hiejima, and Koh-hei Nitta
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Materials science ,Polymers and Plastics ,General Chemical Engineering ,Mechanical properties ,02 engineering and technology ,Orientation (graph theory) ,010402 general chemistry ,lcsh:Chemical technology ,01 natural sciences ,symbols.namesake ,Tacticity ,Ultimate tensile strength ,Materials Chemistry ,Cluster (physics) ,lcsh:TA401-492 ,Lamellar structure ,lcsh:TP1-1185 ,Physical and Theoretical Chemistry ,molecular orientation ,Organic Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,isotactic polypropylene ,Crystallography ,Distribution function ,Raman spectroscopy ,symbols ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology - Abstract
The molecular orientation behavior of isotactic polypropylene (iPP) is investigated by using in situ Raman spec- troscopy under tensile tests. A versatile method of the tilt-angle correction for the orientation parameters is newly developed, where the molecular orientation in highly oriented specimens is assumed to be entropically favorable. The real-time changes of orientation parameters and orientation distribution functions are determined for the molecular chain axis of iPP during uniaxial stretching. The molecular orientation remains random in the elastic region, and increases after the first yield point. In the yielding region, a broad distribution of orientation toward an intermediate angle of 30-70° from the stretching direction is observed. This is interpreted as reorientation of the crystalline chains being hindered by rigid, bulky lamellar cluster units. After the yielding region, orientation toward the stretching direction proceeds rapidly, approaching highly oriented states.
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- 2016
17. Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching
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Koh-hei Nitta, Yusuke Hiejima, and Takumitsu Kida
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Materials science ,Strain (chemistry) ,Internal pressure ,02 engineering and technology ,Polyethylene ,Strain rate ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Stress (mechanics) ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,lcsh:TA1-2040 ,Phase (matter) ,symbols ,Deformation (engineering) ,Composite material ,0210 nano-technology ,Raman spectroscopy ,lcsh:Engineering (General). Civil engineering (General) - Abstract
The microscopic deformation behaviors such as the load sharing and the molecular orientation of high-density polyethylene under uniaxial stretching at various strain rates were investigated by using in-situ Raman spectroscopy. The chains within crystalline phase began to orient toward the stretching direction beyond the yielding region and the orientation behavior was not affected by the strain rate. While the stretching stress along the crystalline chains was also not affected by the strain rate, the peak shifts of the Raman bands at 1130, 1418, 1440 and 1460 cm -1 , which are sensitive to the interchain interactions obviously, depended on the strain rate; the higher strain rates lead to the stronger stretching stress or negative pressure on the crystalline and amorphous chains. These effects of the strain rate on the microscopic deformation was associated with the cavitation and the void formation leading to the release of the internal pressure.
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- 2017
18. In situ monitoring of orientation parameters and orientation distribution functions of polyethylenes during tensile tests
- Author
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Yusuke Hiejima, Takumitsu Kida, and Koh-hei Nitta
- Subjects
polyethylene ,Materials science ,Polymers and Plastics ,orientation distribution function ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Orientation (geometry) ,tensile deformation ,Ultimate tensile strength ,Materials Chemistry ,rheo-Raman spectroscopy ,Lamellar structure ,Composite material ,Organic Chemistry ,Polyethylene ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,orientation parameters ,Low-density polyethylene ,Distribution function ,chemistry ,High-density polyethylene ,Deformation (engineering) ,0210 nano-technology - Abstract
金沢大学理工研究域自然システム学系, In situ polarized Raman spectroscopy is applied for the tensile deformation of high- and low-density polyethylenes (HDPE and LDPE), and the orientation parameters as well as the orientation distribution function (ODF) are determined. While random orientation is maintained in the elastic region, the orientation of the polymer chains begins after the first yield point. The ODF for LDPE shows a peak at the stretching direction throughout the elongation process, and the maximum value of the ODF monotonously increases with the strain. For HDPE, the ODF in the yielding region has a broad peak at an intermediate angle of 30–70° from the stretching direction, while the orientation at the stretching direction is restored in the strain-hardening region. The tilted orientation is explained with the concept of the lamellar cluster units formed in the yielding region after the collapse of the spherulites. The HDPE with lower molecular weight and that with wider molecular weight distribution show high orientation, which is explained with the smaller size of the lamellar cluster units and the higher network density in the amorphous phase, respectively. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- Published
- 2018
19. Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching.
- Author
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Takumitsu Kida, Yusuke Hiejima, and Koh-hei Nitta
- Published
- 2017
- Full Text
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