Effect of unsaturated chain end‐group on thermal oxidative behavior of polypropylene

In order to clarify the influences of unsaturated chain end‐groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy (ΔE) for the oxidative degradation reactions of Ziegler‐catalyzed iPP (ZiPP) and metallocene‐catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature dependence of the oxidation induction time as determined by thermogravimetric analysis over the range 130–145 °C. The correlation between the content of unsaturated chain end‐groups and the change of ΔE was also studied. The results obtained indicated that the unsaturated chain end‐groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer‐like MiPP having unsaturated chain end‐groups, the ΔE value of ZiPP became lower, suggesting that iPP having unsaturated chain end‐groups served as an infectious agent of the degradation. Copyright © 2007 Society of Chemical Industry     

Synthesis of β-MoO3 whiskers by the thermal evaporation method with flowing oxygen gas

β-MoO₃ is a monoclinic phase of MoO₃; it has been shown to be a promising material that can replace α-MoO₃ in chemical, optical, electronic, and electrochromic applications. However, the difficulty in synthesizing β-MoO₃ with a one-dimensional (1D) morphology has limited its use in applications requiring a large specific surface area. In the present work, β-MoO₃ whiskers were prepared by thermally evaporating α-MoO₃ powder in a tube furnace at temperatures (T_f) from 750 to 1000°C and under flowing O₂ gas. The collected samples were identified as mainly β-MoO₃ by X-ray diffraction measurements, and the highest purity β-MoO₃ was obtained at T_f = 1000°C. Scanning and transmission electron microscopy observations showed that whiskers with a width of 10 nm were successfully synthesized by this method. The whiskers were confirmed to be β-MoO₃ via lattice image analysis. Measurements of the temperature distribution in the tube furnace and comparisons with the Mo–O phase diagram led to the conclusion that the whiskers formed via a vapor–solid route. Prepared β-MoO₃ whiskers were compared with α-MoO₃ powder via the X-ray photoelectron spectroscopy characterization method. By elucidating the β-MoO₃ whisker synthesis mechanism, this research provides guidance for the large-scale production of β-MoO₃ whiskers.     

Additive effects of tripalmitin on morphologies and tensile properties of polybutene-1 and its composite with micro fibrous cellulose

Morphologies and tensile properties of polybutene-1 (PB)/tripalmitin (TP) blend and PB/micro fibrous cellulose (MFC)/TP composite were studied. The scanning electron microscope observation showed that the PB(70 %)/TP(30 %) had a microphase-separated structure. The DSC measurement showed that the crystallization of the PB part was affected by the TP existence. A new crystal structure was observed in the X-ray diffraction pattern of the PB(70 %)/TP(30 %). Quicker saturation of the PB crystal phase transformation from the metastable tetragonal (II) to the stable hexagonal (I) phase was observed in the PB(70 %)/TP(30 %) under the aging at r.t. The saturation controlled the Young’s modulus increment of the PB(70 %)/TP(30 %) in the aging process. The elongation at break value of the PB/TP increased by the loading of the TP, suggesting that the TP worked as the plasticizer. The thermogravimetry measurement of the PB(70 %)/TP(30 %) suggested that there existed an interaction between them. The TP addition provided a good dispersibility and ductility enhancement for PB/MFC composite. It was found that the TP worked as a good compatibilizer for the composite.     

Dehydrochlorination of poly(vinyl chloride) modified with titanium dioxide/poly(ethylene oxide) based paint photocatalysts

The dehydrochlorination of poly(vinyl chloride) (PVC) film samples modified with titanium dioxide (TiO₂)/poly(ethylene oxide) (PEO) based paint photocatalysts [the addition of methyl linoleate (ML) or methyl oleate (MO)] was performed. After 24 h of UV photoirradiation, the sample with TiO₂/PEO showed that there existed a structure with the longest polyene length, whereas that with TiO₂/PEO/ML contained the most polyene structures. The chloroform‐soluble fraction of the sample with TiO₂/PEO contained a poly(vinyl alcohol) (PVA) structure instead of a polyene one and showed a novel method of PVA production via PVC photodegradation. The molecular weight curve of the fraction shifted slightly to a lower molecular weight compared to that without the photocatalyst; this showed that slight polymer chain scission occurred. The ¹H‐NMR and ¹³C‐NMR spectra showed that the content of PVA units was about 20%, and the PVA sequence was blocky. The fraction of the sample with TiO₂/PEO/ML contained the highest methyl group content; this showed that the branch degree was highest as was the polyene content. These highest contents were due to the existence of the grafted ML. Pyrolysis gas chromatography/mass spectroscopy measurements suggested that there existed more polyene and graft units in the chloroform‐insoluble fractions of the samples with TiO₂/PEO, TiO₂/PEO/ML, and TiO₂/PEO/MO, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40760.     

Comparison of glass–epoxy interface strengths examined by cruciform specimen and single-fiber pull-out tests under combined stress state

A cruciform specimen test and a single-fiber pull-out test are used to examine two glass–epoxy interface-failure envelopes under a combined stress state. A single fiber embedded in various off-axis directions for the cruciform specimen test creates various combined stress states. Finite-element analysis considering an inelastic constitutive equation of matrix resin and thermal residual stress is implemented for both tests. For the single-fiber pull-out test, a resin cone serving as the fiber entrance part, called the resin meniscus in this study, is modeled in finite-element analysis. This enables more precise calculation of interface stress around the interface failure point than calculations not considering the resin meniscus. The interface failure strengths obtained using the cruciform specimen and single-fiber pull-out tests show good agreement for both interfaces.     

Polarization reversal of telluric acid ammonium phosphate

Experimental studies are reported concerning polarization reversal in the single crystal of telluric acid ammonium phosphate (TAAP). The switching currents have been measured under various temperatures and external electric fields. The experimental results have been used in order to obtain the effective growth dimension of reversed domain and the characteristic time of the polarization reversal on the basis of the Avrami theory. It becomes clear that the effective growth dimension depends on temperature and applied electric field.     

Facile preparation of a polysiloxane-based hybrid composite with highly-oriented boron nitride nanosheets and an unmodified surface

A facile technique was developed to fabricate polysiloxane-based hybrid composite films containing boron nitride (BN) nanosheets using a nanopulse-width electric field. BN nanosheets assumed anisotrophic alignment under the electric field, without requiring surface coating with metallic nano particles despite the wide band gap. BN was dispersed by sonication in a pre-polymer polysiloxane mixture. The homogeneous suspension was cast on a glass spacer and subjected to either a DC electric field or a nanopulse-width electric field before the mixture was cured through polymerization. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that BN nanosheets in the polysiloxane matrix were aligned with high anisotropy to the electric field direction, which was perpendicular to the film plane. The transmittance of the film samples, measured by UV–visible spectrometry, indicated that the composite, prepared using a nanopulse-width electric field manifested a significantly improved transmittance, compared with composites prepared without using the electric field.     

Hepatocellular carcinoma in an orthotopic mouse model metastasizes intrahepatically in cirrhotic but not in normal liver

Prognosis of hepatocellular carcinoma (HCC) still remains poor mainly because of intrahepatic metastasis. In the majority of cases, HCC is found in conjunction with liver cirrhosis. It is, therefore, of great importance to investigate the invasive and metastatic behavior of HCC in cirrhotic liver. To examine this, a liver cirrhosis model was produced by injecting thioacetamide i.p. into mice. Murine HCC cells were labeled with the fluorescent carbocyanine dye, DiI, and implanted directly under the capsule of cirrhotic and normal livers of syngeneic mice. DiI-labeled HCC cells in the liver were observed under fluorescent and confocal microscopy. Histological analysis of cirrhotic and normal livers revealed that implanted HCC cells migrated to and invaded the adjacent periportal regions, but not the adjacent centrolobular areas. This characteristic behavior of HCC was more evident in cirrhotic liver than in normal liver. Furthermore, intrahepatic metastasis to unimplanted hepatic lobes was observed in cirrhotic liver as early as 7 days after implantation, while it was not detected in normal liver even 4 weeks later. Thus, an orthotopic animal model for HCC with cirrhosis described here may be suitable for investigating the invasive and metastatic behavior of HCC. Importantly, labeling tumor cells with a fluorescent dye before orthotopic implantation may be a convenient and useful method to investigate the invasive and metastatic behavior of various types of cancer.