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Injection-molding was performed using ethylene–propylene copolymer as the matrix by varying the physicochemical treatment of the reinforcement, i.e., core portion of kenaf stem that was dry-distilled and coated with or without β-sheet protein derivatives. Although dry distillation reduced the moisture content, the Charpy impact strength of the molded composites was low. When molding was performed using the fillers coated with β-sheet protein derivatives, especially coated with liquid silk (LS), a satisfactory Charpy impact strength of the molded composites was markedly gained. Thus, the β-sheet protein derivatives had potential to work as a compatibilizer. Coating the fillers with β-sheet proteins was also effective in suppressing the generation of silver streaks on the surface of composites and in preventing the occurrence of defective injection molding.

Injection molding was performed using poly(l-lactide) (PLLA) as a matrix and by varying the reinforcements, i.e., dry-distilled kenaf core (D-core) or untreated kenaf bast fibers, and the physical properties for these composites were subsequently compared. The dry-distillation was able to reduce the moisture content of D-core by a maximum of 4.2% as compared with untreated control core. As a result, the hydrophobicity was increased, which contributed to favorable Charpy impact strength and tensile properties of the D-core/PLLA composite relative to the kenaf bast fiber/PLLA composite. Moreover, the puffing phenomenon, which arises when heating with a microwave oven due to the vaporization of water dispersed within the interfacial regions and associated softening of the PLLA matrix by the heated vapor, was completely suppressed for the D-core/PLLA composite, whereas a large puffing ratio was observed for the kenaf bast fiber/PLLA composite. Reducing the moisture content also effectively suppressed ...

Nonlinear stress-strain behavior of the elastomer foams of high porosity is investigated in several types of biaxial tension, and uniaxial tension and compression. The values of Poisson's ratio for the open- and closed-cell foams are estimated to be about 0.24 almost independently of the imposed tensile strain, indicating that the foams undergo finite volume increase under tension. Unequal biaxial tensile experiments reveal no explicit cross-effect of strains between different axes in the elastomer foams: The deduced strain energy density function ( W ) has no appreciable contribution from the term of I 2 which is the second invariant of deformation gradient tensor representing the explicit cross-effect of strains, while in general W for conventional non-cellular elastomers involves finite contributions from I 2 -term. No explicit cross-effect of strains result in a unique feature in biaxial tensile behavior that the effect of the strain in one direction on the stress in the other direction is considerably small. These features in tensile behavior are commonly observed for the open- and closed-cell foams. In contrast, the cell type has a pronounced effect on the compression behavior accompanying the buckling and collapsing processes of the cells, as observed in earlier studies. The stress-strain relations in compression accompanying the cell buckling are markedly different from the expectation of W obtained from the data of biaxial and uniaxial tension where the cell bucking is not possible.

Tomographic images constructed from small-angle X-ray scattering (SAXS) intensities utilizing microbeams have been examined for a model multilayered aluminum alloy sample heat-treated to form spatially modulated composition and microstructures. Spatial distributions of composition and precipitation microstructure have been examined by one-dimensional scanning SAXS measurements and two-dimensional tomographic images of attenuation parameters and integrated intensity of SAXS intensity. Reconstructed images using the integrated intensity reflected the distribution of precipitates in terms of their volume fraction over the sample inside the sample, and agreed with more detailed analysis made in the one-dimensional case.

Two novel phase-separation morphology are reported in the ternary polymer blends of poly(propylene)/nylon-12/poly(lactic acid) by utilizing a high-contrast X-ray computerized tomography. One is a “mosaic-tiling” structure, where each of three components forms equally-sized droplets in a three-dimensional tessellation manner. The other morphology is a “worm-like” structure. Two components of the three form successive droplets like stripe socks. These results strongly suggest the wide variety of the phase-separation morphologies in ternary polymer blends.

Since polymers mainly consist of the light atomic elements, the transmission of polymers against X-rays is usually too high to be visualized in X-ray microscopy, and hence it has been considered that polymers are not suitable for X-ray computerized tomography (XCT). We calculate the X-ray absorption coefficients of various polymers and find reasonably good conditions for the XCT observations of polymers: the use of 15 KeV X-rays on average can resolve the polystyrene (PS) and poly (methymethacrylate) (PMMA) in 3 µm spatial resolutions. According to this calculation, we build an XCT and experimentally confirm the visualization of the phase-separation structures of PS/PMMA blends.

Contrasts of the polymer materials under a high contrast X-ray computerized tomography (XCT) are comprehensively investigated. We developed a high contrast XCT, and demonstrated its capabilities to polymer systems, such as polymer blends. Then we got a hypothesis that the pixel values of the cross-sectional image obtained by XCT agree with the X-ray absorption coefficient at 15 keV. This hypothesis is intensively examined by using various polymers. Consequently, we propose an empirical criterion that 0.1 cm −1 difference in the X-ray absorption coefficients at 15 keV is necessary to distinguish the polymers under XCT. This criterion is also confirmed in the polymer blend systems.

Three-dimensional real-space images of the carbon fiber (CF)/polymer composites were obtained by a high-contrast X-ray computerized tomography (CT). Since both CF and polymers do not include heavy atoms, CF has not been supposed to be suitable to X-ray CT observation. In this study, we used the X-ray CT apparatus which is designed to enhance the contrast of the materials consisting only of light-weight atoms. Besides the usage of the appropriate apparatus, the experimental conditions were found to be important : cutting the sample into a thin rod, and obtaining sufficient number of projections. In our case, we used 1mm × 1mm × 4mm sample, and 720 projections with 0.25 degree intervals in order to obtain the 3μm voxel resolution in the reconstructed three-dimensional images. Eventually, each CF in polystyrene was clearly visualized in three dimensions.

Three-dimensional (3D) observation of co-continuous macropore structure was performed using laser scanning confocal microscopy (LSCM). The obtained LSCM images were reconstructed into 3D images, and further subjected to image analysis. The LSCM observation and the following image analysis provided geometrical parameters of the macropore surfaces, which cannot be obtained by classical techniques for macropore characterization, such as scanning electron microscopy (SEM) observation or mercury intrusion method. Based on the obtained structural parameters, influences of viscoelastic properties on the liquid-phase structural formation mechanism were examined.

The excess shear stress after application of large step strains in polymer blend is calculated from observed shapes of deformed droplets in immiscible matrix, based on the Doi–Ohta expression for the interface contribution to the stress. The calculation is made for droplet shapes of flat ellipsoid, rod with end caps, dumbbell and ellipsoid of revolution. The predicted excess relaxation modulus agrees very well with experimental data normalized per one droplet with the volume-averaged radius for a poly(isobutylene)/poly(dimethyl siloxane) blend with narrow distribution of droplet size. Especially, slow stress relaxation in the intermediate stage and faster relaxation thereafter predicted from the rod like and dumbbell shapes are consistent with the experimental data. For a blend of hydroxypropylcellulose solution/poly(dimethyl siloxane) with broad distribution of droplet size, the predicted excess relaxation modulus agrees reasonably well with experimental data by taking account of the size distribution.

The structural changes in the uniaxial drawing process of an unoriented amorphous film of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) and in the heating process of an oriented amorphous film of PEN were studied using X-ray diffraction apparatus equipped with imaging plates. This apparatus allows us to record a time-resolved series of two-dimensional patterns of wide-angle X-ray diffraction in rapid succession, and, therefore, we can follow the structural changes during uniaxial deformation and/or thermal treatment processes. The results are as follows: (1) When an unoriented amorphous PEN film was stretched below Tg (= 117 °C), it could be elongated up to a draw ratio (DR) of 4–5 via neck formation and became an oriented amorphous film. (2) In the heating process of the oriented amorphous film (DR = 3.6, 65 °C), crystalline reflections started to appear near 120 °C, accompanied by streaks on the off-equatorial layer lines. The existence of these streaks on such layer lines indicates a lattice distortion due to the axial shift of neighbouring chains along the chain axis with respect to one another. Finally the film exhibited a fibre structure (transverse isotropy). (3) When an unoriented amorphous PEN film was drawn at 150 °C, the film exhibited a fibre structure accompanied by a lattice distortion that is similar to that mentioned above, and thereafter frequently showed so-called double orientation (uniplanar axial orientation: (10)[001]) in which naphthalene rings in the main chain are preferentially aligned parallel to the film surface despite the fact that the film was deformed in the mode of uniaxial free-width drawing.

We report 3-dimensional structural analyses of huge spherulites of poly(oxyethylene) (PEG) by the X-ray computerized tomographic (CT) observation in blends of PEG and amorphous poly(lactide). The formation of the huge spherulites is characteristic of PEG and its direct observation by the X-ray CT is reported here for the first time. Slit-shaped cracks were clearly observed by the X-ray CT. Not only the straight cracks but also curved ones were found and it seemed that they overall formed a set of spokes. Furthermore, the scanning electron microscopic observation revealed that the cracks were parallel to bundles of lamellar crystallites. From those observations, we conclude that a set of radial cracks observed under the X-ray CT is a signature of a huge spherulite. Several aspects of an axialite structure are presented and a good agreement with the intuitively proposed structural model is obtained.