Plasticizing effect of fructose as an additive on the uniaxial tensile behavior of pullulan films was examined. At 100 °C, the tensile modulus determined from the stress-strain relation decreased as the fraction of fructose increased in a similar manner to glycerol, suggesting apparent plasticizing effect of this saccharide. Taking the melting point of fructose into consideration, this plasticizing effect was attributed to the “supercooled” liquid state of fructose in the pullulan films. At 29 °C, on the other hand, no plasticizing effect of fructose was observed even above the glass transition temperature. These trends were completely different from those obtained in earlier studies regarding K-carrageenan and gellan films. The network structure of pullulan film having no crosslinks was considered responsible for the unique effect.
In this research, we aim to clarify the oriented structure growth process observed under applying shear flow with isotactic polypropylene of various molecular weights in various shear rate and temperature. It was found that, polymer chains were stretched on shearing was applied, in the case of a sample having a molecular weight of 200,000 or more. In lower shear temperature conditions, the micron-scaled oriented structure growth was observed during shear flow after polymer chain orientation with polarized optical microscopy mounted with high-speed camera. On the other hand, in the case of molecular weight of 12,000, polymer chains could not be oriented in any strong shear conditions. In the micron scaled oriented structure, the stacked lamellar crystalline aligned to the shear direction, that is the so-called shish-kebab structure, were observed with approximately 22 nm with in-situ small angle X-ray scattering measurements. The production conditions of the oriented structure growth, not only depend on orientation and relaxation of polymer chains due to strong shear, but also strongly on the supercooling.
Steady plastic flow of glassy epoxy networks having various crosslink density was analyzed with Eyring equation to discuss the effect of crosslinked molecular structures on nonlinear viscoelastic behavior of glassy polymers in terms of strain-induced structural change. Steady flow stresses of the glasses were calculated with modified stress optical rule (MSOR) from stress and birefringence data observed during uniaxial stretching. Activation enthalpy ΔH, activation entropy ΔS and activation volume va of the steady flow for each material were obtained as functions of stretching conditions by means of a special fitting method of Eyring equation proposed by Nanzai. As having been reported for thermoplastic glassy polymers, ΔH, ΔS and va for each material were in unique functional relations each other. The ΔH-ΔS relation for each material agreed fairly well with that derived from WLF equation for the linear viscoelastic relaxation of the material in the molten state. This result confirms that strain-induced change of glassy structures into liquid-like ones is the essential mechanism of the nonlinear viscoelastic behavior of glassy polymers independently of crosslink density. ΔH-ΔS relations for epoxy networks showed only a weak dependence on the crosslink density, whereas va markedly increased with increasing crosslink density. The steady flow stresses at an identical straining condition was almost the same for epoxy networks with different crosslink density except for materials with extremely high crosslink density, which showed a lower flow stress. An increase of crosslink density probably makes va enlarge due to constraints introduced by crosslinked structure, resulting in the reduction of flow stresses especially at extremely high crosslink density.
We have succeeded in clarifying the influence of thermo-sensitive adhesive IntellimerTM consisting of polyacrylic acid whose main chain is polyacrylic acid and crystalline olefin with side chain on the surface structure and internal structure by tackifier by precise structural analysis. It was found that the tackifier has a role of controlling the peel properties after the high temperature treatment. For the case of the tackifier of polymerized rosin ester, it was found that the tackifier precipitates in granular-type form on the surface, and the size of the granular-type form structure increases as the concentration increases. The granular-type form structure did not show a large change even after the heat treatment, indicating that the granular structure precipitated on the surface had an influence on the peeling characteristics. On the other hand, in the internal structure, it was found that the tackifier, that is, the polymerized rosin ester was dissolved in the olefin portion of the side chain and had a large influence on the crystal structure and the nanometer scale structure. Furthermore, we discussed the case of the tackifier of a styrene oligomer having high heat resistance. In the heat treatment up to 200 °C, a scaly surface structure was observed, but a granular structure was observed on the surface by heat treatment at 250 °C. It was found that the heat treatment by high temperature caused the tackifier to precipitate more clearly and to improve the peelability after cooling. In the nanoscale structure, the styrene oligomer is present mainly in the olefin portion of the side chain from temperature dependence of the size of the phase separation.
We report on changes in grain structures upon blending of a homopolymer to a liquid-crystalline diblock copolymer which forms perpendicularly-oriented cylinders, as revealed by atomic-force microscopy (AFM). Image analyses of the AFM images have been conducted to identify grains in which the perpendicularly-oriented cylinders are uniformly ordered in a hexagonal lattice. As a result, it was found that the grains became smaller upon blending of a homopolymer. Furthermore, the grains which originally contacted to each other became isolated and were surrounded by a matrix where the perpendicularly-oriented cylinders are not regularly ordered. The degradation of the hexagonal order is due to the addition of too much homopolymer.
We developed an ethylene vinyl alcohol copolymer with 1,2 diol side chains (hereinafter new EVOH) that can be melt-molded even though the ethylene content is about 16 mol%, and the properties of polymer alloy that consists of nylon 6-66 (hereinafter PA) and new EVOH were studied. The polymer alloy showed compatibility on the PA rich side ,but the crystallinity of each component decreased at the same time. Especially when the PA content is 85wt.% for polymer alloy, PA crystals were not confirmed. The free volume of the composite increased linearly with the PA blend ratio,but the specific volume deviated from the linear relationship ,which increased on the PA rich side. The normalized free volume was calculated using the amorphous ratio calculated from solid state NMR(T1C: 13C spin-lattice relaxation time) and I 3 (the relative intensity of the long time component) from PALS. It was confirmed that high pressure hydrogen resistance of PA blended with new EVOH was improved by using normalized free volume even on the PA rich side. This result is thought to be due to the amorphous part of PA reinforced by interaction with new EVOH.
We prepared the composite materials of poly(2-methoxyethyl acrylate)-γ-poly(acryl amide) (PMEA-γ-PAAm) with cellulose nanofibers (CNF). CNF can be dispersed successfully in PMEA-γ-PAAm matrix. Dispersion effect of CNF on mechanical properties were investigated using tensile test and rheometer. Young’s modulus of the CNF composite fairly increased in comparison with the original PMEA-γ-PAAm. In addition, the rubbery plateau region was clearly observed in the viscoelastic spectra of CNF composite. It is concluded that the CNF and acrylic polymer including acryl amide group form an interaction which plays a pseudo-crossliking role.
In this study, mechanical properties and molecular motion at low temperature of novel polyolefin materials with cyclohexane moiety in the chemical structure synthesized by Takeuchi et al., Poly-alilcyclohexane (PACH-3), Poly-pentenylcyclohexane (PPCH-5), Poly-heptenylcyclohexane (PHCH-7) and Poly-undecenylcyclohexane (PUCH-11), were investigated1),2). From DSC results, the melting temperature of the samples decreased with an increase of the alkyl-chain length though, the enthalpy of heat of fusion of them increased with the alkyl-chain length. From DMA result, the α relaxation peak can be observed clearly and the temperature decreased with the alkyl-chain length. The β relaxation peak can also be observed at around -50 °C, and the peak intensity decreased with the alkyl-chain length. Moreover, the γ relaxation can be observed clearly around -100 °C, and the strength of the δ relaxation of PPCH-5 was the largest among these samples. From three-point-bending test result from -150 °C to RT, PACH-3 with the shortest alkyl-chain length had the highest modulus at -150 °C, but its modulus decreased most gradually with temperature and its modulus became the highest at room temperature. On the other hand, from Anharmonic estimation result, Grüneisen constant of PACH-5 in -150~-100 °C was the smallest in these samples. This result was consistent with the strength of the γ relaxation, indicating that an association between its anharmonicity and the molecular relaxation exits and PPCH-5 can be expected to have better mechanical properties at low temperatures because it has suitable cooperation size for a molecular motion which consists of cycro-ring and a certain alkyl-chain length.
Sulfate attack is known as one of the deterioration phenomena of concrete structure. Especially, expansion due to delayed ettringite formation (DEF) has been serious problem nowadays. According to previous researches, continuous water supply and temperature history above 70°C are needed for DEF expansion. Moreover, recent research indicated possibility that CO32- promoted DEF expansion. Therefore, the purpose of this study is to discuss that behavior of water molecules and structural changes of carbonate ettringite which is substituted SO42- for CO32- in a possible relationship to the mechanism of DEF expansion in terms of dehydration and rehydration of ettringite.From the experimental result, carbonate ettringite was amorphous on XRD by thermal dehydration and then amorphous calcium carbonate was produced. After rehydration, sample was recrystallized and calcite, isolated from ettringite structure, was produced. In addition, from 27Al NMR spectrum and XRD result, recrystallized carbonate ettringite was coexistent calcite and amorphous carbonate ettringite. Furthermore, in water adsorption and desorption isotherm, amount of adsorption of carbonate ettirngite was much larger than normal ettringite and dehydrated carbonate ettringite had significant hysteresis. Therefore, there are possibility that structure in nanometer scale of carbonate ettringite changed by heating, and thermal dehydrated carbonate ettringite can hold a large volume of water in crystal structure.
PTFE compacts fabricated using recycled PTFE powder show much lower mechanical strength than those fabricated using virgin PTFE powder. We reported in the previous paper that its main reason was the fibrous morphology which the virgin PTFE had but the recycled PTFE did not have. Then, in order to heighten the mechanical strength of the recycled PTFE compacts, we focused on the emulsion of PTFE which is called “dispersion” because the dry powder is easy to become a fiber form by suffering external stress. So in this study, PTFE compacts were fabricated using recycle PTFE and dispersion powder mixtures and the microstructure and mechanical properties of the obtained PTFE compacts were investigated. The porosity of the PTFE compacts decreased with an increase in dispersion powder content, was under 1% at more than 50wt% dispersion powder content and was 0% at 100wt% dispersion powder content. These results indicate that the PTFE compacts fabricated using recycle PTFE containing more than 50wt% dispersion powder can densify almost completely. Tensile strength of the PTFE compacts increased with an increase in dispersion powder content, that of the PTFE compact fabricated using recycle PTFE containing 50wt% dispersion powder reached 90% of that of the PTFE compact fabricated using only dispersion powder and was four times larger than that of the PTFE compact fabricated using only recycle PTFE powder, which resulted from not only poreless microstructure but also entangled structure of fibrous dispersion powder surrounding recycle PTFE particles. In addition, such PTFE compacts had lower tensile strength and larger tensile elongation, compared with those fabricated from normal virgin PTFE powders, which shows that they are particular PTFE compacts.
Some electrical appliances, such as mobile phones, have been miniaturized recently to create them in wearable form, because the size of the devices incorporated in those appliances has become remarkably smaller and thinner. For instance, a semiconductor device consisting of a laminated thin-film structure deposited onto a thin substrate by a physical vapor deposition technique is well known. When these laminated devices are designed, the mechanical property of each thin-film material is required. However, current device design is based on bulk material data. To satisfy the technical requirements, testing devices for measuring the mechanical property of a thin-film material have been developed. The devices become large despite a very small-sized specimen to precisely control the testing waveform. In this study, to achieve more-compact testing devices, a shape memory alloy wire was adopted as a new actuator, and all testing functions of an actuator, load amplification, load cell, and displacement sensor were combined in one unit. For checking the motion of the developed device and the PID control system developed based on an Arduino system, tensile and fatigue tests were conducted for SUS304 thin film. It was confirmed that the tensile and fatigue tests were carried out appropriately according to the control pattern.