Mechanical properties and morphological changes of poly(lactic acid)/polycarbonate/poly(butylene adipate‐co‐terephthalate) blend through reactive processing

The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate‐co‐terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin‐screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05–1 μm for RP, whereas it was approximately 10 μm without RP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Shear rate dependence of viscosity and first normal stress difference of LCP/PET blends at solid and molten states of LCP

The liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder to make samples having 20, 40, 60, 80, and 100 wt % of LCP. Morphology of these samples was studied using scanning electron microscopy. The steady state shear viscosity (η), dynamic complex viscosity (η*) and first normal stress difference (N₁) were evaluated and compared at two temperatures: 265°C, at which LCP was in solid state, and 285°C, at which LCP was in molten state. The PET was in molten state at both the temperatures. The shear viscosity of the studied blends displayed its dependence on composition and shear rate. A maxima was observed in viscosity versus composition plot corresponding to 80/20 LCP/PET blend. The N₁ increased with LCP loading in PET and with the increased asymmetry of LCP droplets. The N₁ also varied with the shear stress in two stages; the first stage demonstrated elastic deformation, whereas second stage displayed dominant plastic deformation of LCP droplets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2212–2218, 2007     

Measurements of fiber bundle interfacial properties of three-dimensionally reinforced carbon/carbon composites up to 2273 K

Experimental techniques for evaluating the interfacial properties between fiber bundles and the matrix of three-dimensionally reinforced carbon/carbon composites were examined. Specially arranged fiber bundle push-out and pull-out tests were conducted up to 2273 K in vacuum. In these tests, a fiber bundle in the specimens was extruded or pulled out by external compressive or tensile loads. Post-fracture observations revealed that a shear fracture was successfully induced within the carbon matrices at the loaded fiber bundle interface. The interfacial shear strength and initial sliding stress of the fiber bundle monotonically increased with the test temperature. The relief of residual thermal stress and increases in the frictional resistance and anchor effect at the fiber bundle interface were considered to be the major mechanisms that caused the enhancements. An increase in the heat treatment temperature during the processing of the composites resulted in a significant decrease in and .     

Grafting of poly(ethylene oxide) onto C60 fullerene using macroazo initiators

In order to improve the solubility of C₆₀ fullerene in conventional solvents, grafting of hydrophilic poly(ethylene oxide) (PEO) by utilizing the radical-trapping nature of C₆₀ fullerene was investigated. Macroazo initiators containing a poly(ethylene oxide) unit, known as Azo-PEO, were prepared at various molecular weights by the reaction of 4,4′-azobis(4-cyanopentanoyl chloride) with poly(ethylene glycol) methyl ether. PEO radicals formed by thermal decomposition of Azo-PEO were successfully trapped by C₆₀ fullerene to give PEO-grafted C₆₀ fullerene. Their structures were confirmed by FT-IR spectroscopy, size exclusion chromatography, UV-vis spectroscopy, and differential scanning calorimetry. When Azo-PEO with low-molecular weight was reacted with C₆₀ fullerene, a bis-adduct, C₆₀-(PEO)₂, and a tetrakis-adduct, C₆₀-(PEO)₄, were formed. In contrast, in reactions with Azo-PEO of higher molecular weight, only the bis-adduct was formed, and no formation of the tetrakis-adduct was observed. The structure of bis-adduct was found to be 1,4-type. The solubility of C₆₀ fullerene in water, THF, methanol, and other conventional organic solvents was remarkably improved by grafting of PEO. In addition, the thermal stability of PEO was dramatically increased by grafting onto C₆₀ fullerene.     

Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior

In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO₃ was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO₃ mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO₃ maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.     

Response of Predatory Insect Scolothrips takahashii Toward Herbivore-Induced Plant Volatiles Under Laboratory and Field Conditions

We studied the response of a predatory thrips, Scolothrips takahashii, towards herbivore-induced plant volatiles emitted by Lima bean plants infested by two-spotted spider mites Tetranychus urticae (green form). Tests were conducted with a Y-tube olfactometer in the laboratory and with traps under field conditions. The odor of artificially damaged and uninfested Lima bean leaves was not more attractive than clean air in the Y-tube olfactometer. The predatory insects showed a greater preference for Lima bean leaves infested by the two-spotted spider mites than for either clean air or uninfested bean leaves. They showed the same preference towards infested leaves from which all spider mites and their visible products had been removed. Neither the spider mites themselves nor their products attracted the predators. In a satsuma mandarin grove, two traps with infested Lima bean plants as an odor source attracted 42 adult S. takahashii in 55 days, whereas no S. takahashii were trapped in two control traps with uninfested Lima bean plants during the same period. No S. takahashii were found during this period in the vicinity of either the sample traps or the control traps (5-m radius of each trap). These data showed that S. takahashii use herbivore-induced plant volatiles in their foraging behavior in natural ecosystems.     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

Surface Analysis of Cr2O3‐, CoO‐, and Al2O3‐Doped Iron–Phosphate Glasses at High Temperature

Surface structures of iron–phosphate glasses were examined using X‐ray photoelectron spectroscopy (XPS). Cr₂O₃, CoO, and Al₂O₃ were introduced to the glass by the replacement of a part of Fe₂O₃, and the simulated fission products are also added. The obtained glasses showed high chemical durabilities by MCC‐1 test. In situ high‐temperature and room‐temperature XPS measurements were conducted on the polished sample surfaces and also those after 1‐week chemical durability test. Unique trends were observed in XPS spectra on heating and after the chemical durability test, respectively. Nature of the glass surface of iron–phosphate glasses was explained from the point of view of surface energy, and the origin of high chemical durability and the effect of chromium ions were discussed based on the changes on surface composition and valence states of transition‐metal ions.     

Structural Analysis of the Complex between Penta-EF-Hand ALG-2 Protein and Sec31A Peptide Reveals a Novel Target Recognition Mechanism of ALG-2

ALG-2, a 22-kDa penta-EF-hand protein, is involved in cell death, signal transduction, membrane trafficking, etc., by interacting with various proteins in mammalian cells in a Ca²⁺-dependent manner. Most known ALG-2-interacting proteins contain proline-rich regions in which either PPYPXnYP (type 1 motif) or PXPGF (type 2 motif) is commonly found. Previous X-ray crystal structural analysis of the complex between ALG-2 and an ALIX peptide revealed that the peptide binds to the two hydrophobic pockets. In the present study, we resolved the crystal structure of the complex between ALG-2 and a peptide of Sec31A (outer shell component of coat complex II, COPII; containing the type 2 motif) and found that the peptide binds to the third hydrophobic pocket (Pocket 3). While amino acid substitution of Phe⁸⁵, a Pocket 3 residue, with Ala abrogated the interaction with Sec31A, it did not affect the interaction with ALIX. On the other hand, amino acid substitution of Tyr¹⁸⁰, a Pocket 1 residue, with Ala caused loss of binding to ALIX, but maintained binding to Sec31A. We conclude that ALG-2 recognizes two types of motifs at different hydrophobic surfaces. Furthermore, based on the results of serial mutational analysis of the ALG-2-binding sites in Sec31A, the type 2 motif was newly defined.     

Rearrangement of the main chain of the organocobalt polymers

The polymers 3 having pyridine moieties in the main chain were synthesized by the reaction of the organocobalt polymers 1 having cobaltacyclopentadiene moieties in the main chain with various nitriles 2. When brown colored 1 and excess 2 were heated in tetrahydrofuran at 80 °C for 24 h and then at 150 °C for 12 h in a sealed tube, the polymers 3 were obtained by the precipitation with methanol in good yields. From the spectroscopic measurements, the resulting polymers 3 were found to contain 35 – 90% of the pyridine moieties depending on the structures of 1. Received: 7 July 1997/Revised: 14 August 1997/Accepted: 25 August 1997