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.     

Absolute quantitation of quercetin and the glycosides in natural food additives by quantitative NMR

We are developing a simple absolute quantitation method for organic compounds, by means of quantitative nuclear magnetic resonance (qNMR), with traceability to the International System of Units (SI units). The qNMR method was applied to the absolute quantitation of rutin, isoquercitrin and quercetin in natural food additives, rutin (extract), enzymatically decomposed rutin extract and quercetin, and those compounds as commercial reagents. In this study, 1,4-bis-(trimethylsilyl)benzene-d(4) (1,4-BTMSB-d(4)) whose purity was precisely evaluated on the basis of metrology, was newly used as a qNMR reference material, to be added to the sample solution as an internal standard. The contents of quercetin and quercetin glycosides were calculated from the ratio of the signal intensities of each aromatic proton at the 2' position of the three compounds (these are observed at different chemical shifts) to the eighteen protons of the six methyl groups on 1,4-BTMSB-d(4) used as a qNMR reference material. Rapid and simple qNMR method with only one step process was carried by using 1,4-BTMSB-d(4). It was demonstrated that the purities of rutin, isoquercitrin and quercetin can be separately determined by qNMR without the need for a separation process or reference materials for all the target compounds.     

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.     

Studies on heterogeneous degradation of polypropylene/talc composite: Effect of iron impurity on the degradation behavior

In this study, an effect of iron oxide (Fe₂O₃) impurity in talc on degradation behavior of polypropylene (PP)/talc composite was studied using a PP/Fe₂O₃ model composite sample. The thermal oxidative degradation was performed at 100°C. Although the degradation of a pure PP sample hardly occurred at such temperature, the existence of Fe₂O₃ induced the PP degradation. The degraded PP part was formed around the Fe₂O₃ grain in the PP/Fe₂O₃ sample. It was found from the optical microscope observation that the degraded PP was able to diffuse only within the PP amorphous part. The analysis of the oxidation distribution on the degraded PP surface was performed employing a scanning electron microscope/electron dispersive spectrometer. The result showed that the PP spots in the vicinity of the Fe₂O₃ grain were unoxidized during the initial degradation process, and the oxidized PP spots were located at around 6 μm distance from the Fe₂O₃ grain. It was concluded that the degradation was initiated microscopically away from the Fe₂O₃ grain so that the Fe₂O₃ had both the abilities to accelerate the decomposition of PP hydroperoxide compounds and to reduce the produced radical species into nonradical products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructural Cause of the Peak Effect in Superconducting Y-Ba-Cu-O Melt-Grown Bulks

Superconducting Y-Ba-Cu-O bulks with J _c as high as 30 kA /cm ² (at 77 K and 1 T) containing both Y-123 and Y-211 phases were utilized in the present work . With different post-annealings, we obtained samples with different degrees of peak effect in the J _c -vs- H characteristics. Using specimens with TEM observable areas as wide as 20 × 20 (m) ² , large-area high-resolution transmission-electron-microscopic (LA-HRTEM) observations were made for the samples with different degrees of peak effect. Statistical analyses were made for the size of Y-211 particles and the distance between adjacent twin boundaries. It is revealed that (1) Y-211 particles including those of very small diameters have nothing to do with-the peak effect, while (2) the inter-twin-boundary distance is undoubtully correlated with the degree of peak effect. Further investigation on the twin boundary structure indicates that lower T _c regions may be formed in the vicinity of twin boundaries to provide fluxons with mesoscopically distributed weak pinning centers.     

Diffusion of platinum, vanadium and manganese in Ni3Al phase under high pressure

Diffusion of platinum, vanadium, and manganese in the Ni₃Al phase is investigated under high pressure. Platinum atoms occupy cubic face centred sites (α) in the L1₂ ordering structure. Vanadium atoms occupy cubic corner sites (β). Manganese atoms occupy both sites. Activation volumes ΔV for diffusion of these diffusing atoms to the molar volume of the Ni₃Al phase V₀ are as follows:

Additive effects of tripalmitin and low-density polyethylene on morphologies and tensile properties of polybutene-1/micro fibrous cellulose composite

Effects of tripalmitin (TP) and low-density polyethylene (LDPE) loading on morphologies and tensile properties of polybutene-1 (PB)/micro fibrous cellulose (MFC)/composite were studied. The scanning electron microscope (SEM) observation showed that the 10 % TP loading brought about good dispersity of the MFC in PB matrix. The TP worked as a good compatibilizer for the composite. The Young’s moduli of the PB/TP (10 %)/MFC (10 and 20 %) content were slightly lower than those of the corresponding PB/MFC under 0, 48 and 96 h aging treatments at r. t., and that of the PB/TP (10 %)/MFC (50 %) specifically decreased up to 73 %. The TP loading increased the PB crystal phase transformation rate, and its behavior suggested that there existed TP in the interface between the PB and MFC. The elongation at break values increased up to 281 % of the corresponding PB/MFC ones. The 30 % TP loading little improved the tensile properties of the composite as compared with the 10 % one. The 10 % LDPE loading brought about 5–51 % higher Young’s moduli than those of the corresponding PB/MFC without the aging treatment although the composite rapidly became embrittlement by the higher MFC content and aging. It was found that the LDPE loading highly improved the interface strength, in particular, without the aging treatment.