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Predecessor
Volume 53, Issue 12
Displaying 1-16 of 16 articles from this issue
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Yoshinori KAMIYA, Yasutoshi NAITO, Keishin MIZOGUCHI, Katsuhiko TERADA1996 Volume 53 Issue 12 Pages 765-773
Published: December 25, 1996
Released on J-STAGE: July 27, 2010
JOURNAL FREE ACCESSIsothermal glass transitions of polymer/gas systems, which are observed in sorption and dilation behavior, are reviewed. An inflection point of gas-sorption isotherm was correlated to the glass transition by an extension of dual-mode sorption model to polymer/gas systems in which the polymers are plasticized by sorbed gas molecules. On the basis of the extended sorption model, dilation behavior of glassy polymers due to gas sorption was theoretically and experimentally discussed in relation to the isothermal glass transition. The isothermal glass transition can be explained by assuming two modes of sorbed molecules in glassy polymers according to the dual-mode sorption model. The two modes possess different abilities of plasticizing.View full abstractDownload PDF (1612K) -
Junko HABASAKI, Isao OKADA, Yasuaki HIWATARI1996 Volume 53 Issue 12 Pages 774-787
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSMolecular-dynamics simulation of lithium metasilicate (Li2SiO3) has been performed. Saturation of the packing of the oxygen atoms is observed near the glass transition temperature (Tg) by geometric analysis of the coordination polyhedra. Diffusion in the glassy state is found to be caused by jump motions of the atoms. The changes in dynamics near Tg are discussed in relation with the structural changes. A clear two-step relaxation was observed in a density correlation function (self-part) for Li ions following an exponential decay by vibrational motion. The origin of the stretched-exponential type decay (α-relaxation) in a long time region is confirmed to be a waiting time distribution of the jump motions. The fractal dimension of space is also important to determine the relaxation behavior. The mechanism of a “mixed alkali effect” in LiKSiO3 has been also examined. The pathway of each alkali metal ion in the mixture is found to be intercepted by each other. Cooperative jumps and back-correlation are found to play an important role in the “mixed alkali effect”.View full abstractDownload PDF (4272K) -
Yasuo SARUYAMA1996 Volume 53 Issue 12 Pages 788-794
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSModulation calorimetry is a thermal analysis technique which was recently developed. Here the modulation calorimetry around the glass transition temperature was carried out on several samples, paying attention to features of the modulation calorimetry, conformation of the experimental apparatuses and interpretation of experimental data. In our laboratory an ac calorimeter and dynamic DSC were constructed. Results of ac calorimetry obtained from at-polypropylene and low molecular weight at-polystyrene and those of dynamic DSC from at-polystyrene are shown. The modulation calorimetry can be used to measure the dynamic heat capacity of polymeric materials, it is also a useful method for studies of the effects of thermal history of polymers.View full abstractDownload PDF (1502K) -
Tatsuko HATAKEYAMA, Kunio NAKAMURA, Hyoe HATAKEYAMA1996 Volume 53 Issue 12 Pages 795-802
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe behavior of glass transition of polysaccharide electrolyte-water systems was investigated by differential scanning calorimetry (DSC). Samples used in this report are sodium cellulose sulfate (NaCS), sodium carboxymethylcellulose (NaCMC), xanthan gum (Xan), sodium hyaluronate (NaHA), and sodium alginate (NaAlg). The above polysaccharide-water systems showed glass transition in the water content, Wc [= (weight of water) / (weight of dry sample), (g/g)] ranging from almost 0 to 3.0. The DSC observation leads to the following conclusions: (1) when water molecules are bound to hydrophilic groups and counter ions of polysaccharides as non-freezing water, glass transition temperature (Tg) was observed in a wide temperature range between 180 to 350 K depending on Wc, (2) although the amount of non-freezing water was dependent on the chemical structure of each polysaccharide, the minimum value of the Tg of each polysaccharide-water system was very similar and was 180+5 K, (3) the above Tg minimum was observed in the Wc range when the amount of non-freezing water (Wnf) became maximum in each polysaccharide-water system, and (4) the NaHA-water system showed lower Tg than the other polysaccharide-water systems because of its specific chemical structure.View full abstractDownload PDF (1324K) -
Motosuke NAOKI1996 Volume 53 Issue 12 Pages 803-813
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSGeneral aspects of the glass transitions, the dispersions pertaining to the Brownian motions near the glass transition temperature, and the local mode of motions in the glasses of o-terphenyl, triphenylchloromethane, poly (vinyl chloride), and D-sorbitol are discussed. The configurational internal energy and/or the configurational entropy govern the molecular mobility in the supercooled liquids of molecular liquids, including polymer liquids. The intermolecular inefficient spaces of futile interstices among molecules, but not the intramolecular conformational degrees of freedom in polymers, may be the essential origin of the failure of free volume theories for mobility in molecular liquids. The distribution of configurational energy, but not individual small groups and intramolecular chain flexibility, governs the local mode of motions in the molecular glasses, the polymer glasses, and the hydrogen-bonded glasses. A macroscopic way to analyze the contribution from hydrogen bonds is proposed. This explains well the peculiar properties of the molecular mobility and the glass transition in associated liquids.View full abstractDownload PDF (2621K) -
Shinjiro MACHIDA, Kazuyuki HORIE1996 Volume 53 Issue 12 Pages 814-822
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSWe measured hole burning properties of porphyrin dyes doped into polymer glasses. From the energy difference between zero-phonon holes and pseudo-phonon sideholes we could estimate low-energy excitation modes of host matrices. Irreversible increase of holewidth during temperature-cycling experiment agreed well with the relaxation behavior of each polymer, such as sidechain rotation. A mechanism of non-photochemical hole burning in polymers containing carboxylic acid was proposed from the deuterium effect and other results. We clarified the cause of laser-induced hole filling to be a non-siteselective excitation of a dye and discussed the important factor for inhomogeneous broadening, by burning holes at various wavelengths and temperatures.View full abstractDownload PDF (1580K) -
Katsuhiro YAMAMOTO, Shigetaka SHIMADA, Yoshiharu TSUJITA, Masato SAKAG ...1996 Volume 53 Issue 12 Pages 823-828
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSPoly (methyl methacrylate) s, (PMMA) s, were spin-labeled in methanol to study the surface molecular mobility. Transition temperature in molecular motion, T5.0mT, obtained by ESR was found to be lower than that in the bulk. Glass transition temperature near the solid surface can be estimated using the ESR data and WLF equation. The glass transition temperature near the solid surface of PMMA was estimated to be approximately 30-40 K lower than that in the bulk. This fact indicates that the segmental density near the solid surface is lower than that of the bulk polymer. In addition, it was found that the molecular mobility near the solid surface depends on the tacticity of PMMA.View full abstractDownload PDF (1024K) -
Akiji HIGUCHI, Katsuhiko KATSUMA, Yasuhiko SHIROTA1996 Volume 53 Issue 12 Pages 829-833
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSFor the purpose of developing novel amorphous molecular materials and also gaining information on the relationship between molecular structure and glass-forming properties, a novel organic π-electron system, 1, 3, 5-tri- (N-carbazolyl) benzene (TCB), was synthesized and its glass-forming properties investigated. Whereas 1, 3, 5-triphenylbenzene and 1, 3, 5-tris (diphenylamino) benzene instantly crystallized even when their melt samples were rapidly cooled with liquid nitrogen, TCB was found to readily form an amorphous glass via a supercooled liquid when the melt sample was cooled even at a cooling rate of 5°C min-1 as well as with liquid nitrogen, as characterized by DSC, XRD, and polarizing microscopy. It is suggested from the CPK model that a nonplanar molecular structure of TCB with a bulky, planar carbazole ring significantly twisted from the plane of the central benzene ring is responsible for the formation of the glass. The TCB glass was found to exhibit a much higher glass-transition temperature (Tg) of 122°C than the glass of a related compound, 1, 3, 5-tris (4-methylphenylphenylamino) benzene (Tg: 58°C). This result indicates that the incorporation of a rigid moiety such as carbazole serves as a guiding principle for increasing Tg. TCB was found to exhibit polymorphism, taking two different crystal forms. That is, the crystal obtained by sublimation in vacuo differs from the crystal formed when the amorphous glass is heated above the Tg.View full abstractDownload PDF (902K) -
Kazuhiro TANAKA, Masamichi ITO, Hidetoshi KITA, Ken-ichi OKAMOTO, Yasu ...1996 Volume 53 Issue 12 Pages 834-841
Published: December 25, 1996
Released on J-STAGE: July 27, 2010
JOURNAL FREE ACCESSDiffusion coefficients D for CO2 and CH4 as well as lifetime τ3 and intensity I3 of ortho-positronium (o-Ps) were measured for five polymers at temperatures T from glass transition temperature Tg down to Tg-150 K. There was a fairly good correlation between τ3 and log (D/T) in the temperature range above Tg-90 K. Assuming exponential distribution of the size of free volume holes in the glassy state, a mean size of the free volume holes (vh) was evaluated from τ3 by using a method previously applied for rubbery polymers. There was a good correlation between log (D/T) and 1/<vh> for these glassy polymers and the previously investigated rubbery polymers, indicating that a free volume model for diffusion is applicable in the glassy state at temperatures not much below Tg as well as in the rubbery state. Even in the glassy state, generation, and dissipation of the free volume holes with smaller sizes might occur rapidly in concert with local motion of polymer chains and side groups. This rapid generation/dissipation process enables penetrants in glassy polymers to have frequent chances of diffusion jump, as is the case in the rubbery state.View full abstractDownload PDF (1203K) -
Noritaka YAMAGUCHI, Saburo AKIYAMA, Makio TOKOH1996 Volume 53 Issue 12 Pages 842-845
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSIn this paper, the miscibility of poly (ethylene-co-vinyl alcohol) (EVOH) /Nylon 6 (PA 6) blends was investigated by using differential scanning calorimetry (DSC) and dynamic mechanical measurements (DMA). Tg determined by DSC shifted after the material was annealed at 235°C and reached constant values after an annealing time of 15 min. After spontaneous cooling from Tm, a mixed amorphous phase of this system was found to be miscible, in spite of coexisting with two distinct crystalline phases. In addition, the shapes of tan δ-temperature curve originating from glass transition temperature (Tg) obtained by DMA showed a single peak. And the composition dependence of the peaks was fit the Gordon-Taylor equation. Therefore, it was suggested that poly (ethylene-co-vinyl alcohol) /Nylon 6 blends were also miscible above the melting temperature.View full abstractDownload PDF (658K) -
Hiroyuki TAKENO, Satoshi KOIZUMI, Hirokazu HASEGAWA, Takeji HASHIMOTO1996 Volume 53 Issue 12 Pages 846-851
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSWe have investigated the thermal concentration fluctuation in a single phase state of polymer blends with a large difference in glass transition temperatures Tg's for each pure component in a wide temperatures range from far above Tg of the blend to below it by using small-angle neutron scattering. While at high temperatures, free from vitrification of polymers, neutron scattering behavior is well described by the scattering formula based on the random phase approximation (RPA), anomalous scattering behavior was observed near the glass transition temperature. Near Tg of the blend, the scattering intensity is suppressed relative to that expected from RPA and the Flory-Huggins parameter χ is q dependent. Our scattering results predicted that microphase separation in polymer blends will take place under a specified condition, though we could not observe it in this study.View full abstractDownload PDF (1117K) -
Kenji MORIKAMI, Eiji KUCHIKI, Tetsuya KAWAMURA, Yuji FUJITA, Shigeyuki ...1996 Volume 53 Issue 12 Pages 852-859
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSBulk moduli of amorphous polymers such as polyethylene, polypropylene, and polyisobutylene were investigated in the wide temperature range near the glass transition temperatures by means of molecular dynamics simulations. The large changes in the bulk moduli from 1-2 GPa to 3-4 GPa with lowering temperature below the glass transition temperatures were calculated in the case of polyethylene and polyisobutylene. These calculations agreed well with experimental results that these polymer materials having an amorphous phase lose their rubber elasticity at temperatures below their glass transition temperatures. With some exceptions, the calculated values of bulk moduli in the wide temperature range were almost the same as the experimentally observed ones.View full abstractDownload PDF (1311K) -
Kunio NAKAMURA, Tatsuko HATAKEYAMA, Hyoe HATAKEYAMA1996 Volume 53 Issue 12 Pages 860-865
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSHeat capacities (Cp) of carboxymethylcellulose (CMC) and CMC-water systems were measured by differential scanning calorimetry (DSC). Molecular weight (Mw) of CMC ranged from 1.7×104 to 3.8×105, and degree of substitution (DS) ranged from 0.6 to 1.7. Cp's of CMC in the dry state were 1.2 to 1.5 J/g·°C in the glassy region, regardless of Mw and DS. Glass transition temperature (Tg) of CMC in the dry state was maintained at around 135°C, regardless of Mw (DS=1.4), and Tg slightly increased with increasing DS. Tg of CMC decreased from ca. 135°C to -85°C on addition of 0.2 to 0.5 (g/g) of water (water content, Wc= mass of water/mass of dry sample). Water molecules in the above systems are categorized into nonfreezing water which is calculated by subtraction of the mass of freezing water from the total mass of water. It was found that Cp's at the glassy state markedly decreased in the presence of nonfreezing water. The minimum Cp value (ca. 0.5-1.4 J/g·°C) was found at around Wc = 0.3. The above facts suggest that CMC molecules take more stable states in the presence of nonfreezing water.View full abstractDownload PDF (1009K) -
Noritaka KIMURA, Keisuke AIZAWA, Yoshiyuki NISHIO, Hidematsu SUZUKI1996 Volume 53 Issue 12 Pages 866-868
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSAlthough the Richardson method is known as an accurate method for determining the glass transition temperature of a polymer from its thermogram obtained by differential scanning calorimetry (DSC), the application of this method is limited in the literature. It was shown that the analysis by this method may be carried out on a personal computer with a commercially available software: it is no longer necessary to write, for this purpose, a program compatible to a particular DSC apparatus.View full abstractDownload PDF (573K) -
Kazuto INOUE, Yoshio IMAI1996 Volume 53 Issue 12 Pages 869-873
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe relationship between the thermal properties and molecular structures of aromatic polyamides was investigated with the polyisophthalamides and polyterephthalamides containing 3, 4′- (or 4, 4′-) bibenzyl, trans-stilbene, and tolan structures in the diamine components by differential scanning calorimetry. Amorphous 3, 4′-series polyisophthalamides displayed prominent glass transition temperatures (Tg) between 203°C and 272°C. Poly (3, 4′-bibenzylterephthalamide) had Tg and crystallization temperature (Tc) at 203°C and 235°C, respectively. On the other hand, highly crystalline 4, 4′-series polyterephthalamides had melting temperatures above 500°C but no Tg and Tc. All polyamides containing the tolan structure showed a large broad exothermic peak from about 300°C and changed to crosslinked polymers insoluble in organic solvents.View full abstractDownload PDF (774K) -
Hirohisa YOSHIDA1996 Volume 53 Issue 12 Pages 874-876
Published: December 25, 1996
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSEnthalpy relaxation processes of amorphous polymers, such as conventional polymers (polystyrene (PS) and poly- (methyl methacrylate) (PMMA)) and engineering plastics (polysulfone (PSF), polyetherimide (PEI), and poly-ethylenesulfone (PES)), were analyzed with the stretched exponential of KWW function. Enthalpy relaxation times showing Arrhenius type temperature dependency of conventional polymers were longer than those of engineering plastics and were in the following order: τ (PS) -τ (PMMA) >τ (PES) >τ (PEI) >τ (PSF). “Fragility” values defined by d log τ/d (Tg/T) at Tg were ca. 100 and 55 for conventional polymers and engineering plastics, respectively. This result indicates that conventional amorphous polymers were more fragile than engineering plastics in the glassy state, which was in accord with mechanical properties of these polymers.View full abstractDownload PDF (524K)
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