Ultrahigh molecular mass polyethylene (UHMMPE) is filled with carbon nano-tubes (CNTs) by solution in the presence of maleic
anhydride grafted styrene-(ethylene-co-butylene)-styrene copolymer (MA-SEBS) as a compatibilizer. The UHMMPE/CNT composites
crystallized from melt were prepared at a cooling rate of 20C min-1. The melting and crystallization behaviors of UHMMPE/ CNT composites were investigated by differential scanning calorimetry.
The results showed that onset melting temperature (Tm) and degree of crystallinity (Xc) of UHMMPE/CNT composites crystallized from solution are higher than those from melt due to the larger crystalline lamellar
thickness. The onset crystallization temperature (Tc) of UHMMPE/CNT composites tends to shift to higher temperature region with increasing CNT content in the composites. Tm and
Tc of UHMMPE phase in UHMMPE/CNT composites decrease with the addition of MA-SEBS. Moreover, the crystallization rate of UHMMPE
phase in UHMMPE/CNT composite is increased due to the introduction of CNTs. MA-SEBS acts as compatilizer, enhances the dispersion
of CNTs in the UHMMPE matrix. Thereby, the crystallization rate of UHMMPE phase in UHMMPE/CNT composite is further increased
with the addition of MA-SEBS.
Authors:J. Ying, S. Liu, F. Guo, X. Zhou, and X. Xie
Polypropylene (PP) /ethylene-octene copolymer (POE) blends with different content of POE were prepared by mixing chamber of
a Haake torque rheometer. The crystallization behaviors and crystal structure of PP/POE blends were systematically investigated
by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The
results showed that PP spherulites became defective and the crystallization behavior was influenced intensely with the introduction
of POE. At the low content of POE, the addition of POE decreases the apparent incubation period (Δti) and the apparent total crystallization period (Δtc) of PP in blends due to the heterogeneous nucleation of POE, and small amount of β-form PP crystals form because of the existence
of POE. However, at high content of POE, the addition of POE decreases the mobility of PP segments due to their strong intermolecular
interaction and chain entanglements, resulting in retarding the crystallization of PP, decreasing in the amount of β-form
PP crystals, and increasing in Δti and Δtc of PP in blends.
Authors:Z. Chen, F. Xie, X. Wang, Y. Chang, and Z. Zhang
A method of efficiency calibration for the measurement of 88Kr and 138Xe by HPGe γ-spectrometer is proposed in the present paper. The question for the efficient calibration is, how to achieve
homogeneous sources of 88Kr-88Rb and 138Xe-138Cs. The fission product gases were obtained by irradiating a precisely measured amount of U3O8 (90% 235U) filled in a quartz glass ampoule. Source cell was first filled up with stearic acid, and then the fission product gases
were charged into it. Xenon and krypton are not adsorbed on stearic acid, therefore, homogeneous sources of 88Kr-88Rb and 138Xe-138Cs can be prepared. The results of the experiment demonstrate that the method is feasible and successful.
Lanzou Alkaline Stretched Noodles (LASN) was a traditional staple food in northwest China for nearly 90 years. LASN specialty wheat breeding has become an important target since 1990s. In order to discover the LASN specialty wheat quality requirement for allelic variations at
of northwest China spring wheats. Two northwest China spring wheat cultivars and 39 elite F6 breeding lines were adopted to determine the low-molecular-weight glutenin subunits (LMW-GS) composition by one step one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) basing on the protocol of Singh et al. (1991). The results showed that
were correlated to high protein content, high volume of SDS-sediment and super dough strength (W). While
was bad to dry gluten content and SDS-sediment as well as dough properties such as dough strength (W) and dough tenacity (P). Moreover,
has not significant influence on flour quality, but it has the negative effect on dough strength (W) and dough extensibility (L). As for LASN quality,
were beneficial alleles and
was unbeneficial alleles for LASN quality.
Authors:W.-Y. Liu, Sh.-L. Xie, X.-Zh. Xu, Ch.-Y. Wu, and F. Feng
Oroxylin A (5,7-dihydroxy-6-methoxyflavone), which has showed multiple pharmacological effects, was semi-synthesized chemically as a pharmaceutical agent. Its impurities, degradation products and their formation pathways remain unknown. In the present study, two impurities (5,6,7-trihydroxyflavone, 5-hydroxy-6,7-dimethoxytlavone) and a degradation product (5,7-dihydroxy-8-methoxyflavone) in Oroxylin A bulk drug substance were identified, and their formation pathways were proposed. A reversed phase liquid chromatographic method for the simultaneous determination of Oroxylin A and the three compounds was developed on a C18 column using methanol-acetonitrile-0.1% acetic acid (54:23:23, v/v/v) as the mobile phase. The detection was performed at 271 nm. The method was validated to be robust, precise, specific and linear between 4 and 40 μg mL−1; the limits of detection and quantification of Oroxylin A were 0.01 and 0.04 μg mL−1, respectively. The developed method was found to be suitable to check the quality of bulk samples of Oroxylin A at the time of batch release and also during its stability studies (long term and accelerated stability).
Authors:W.-Y. Liu, M.-L. Wei, C.-Y. Wu, H.-Y. Zhu, F. Feng, and N. Xie
Patrinia scabra Bunge has long been used in clinic as a traditional Chinese medicine for treating leukemia and cancer and regulating host immune response. Despite their wide use in China, no report on system analysis on their chemical constituents is available so far. The current study was designed to profile the fingerprint of ethyl acetate extract of it, and in addition, to characterize the major fingerprint peaks and determine their quantity. Therefore, a detailed gradient high-performance liquid chromatography was described to separate more than 30 compounds with satisfactory resolution in P. scabra Bunge. Based on the chromatograms of 10 batches samples, a typical high-performance liquid chromatographic (HPLC) fingerprint was established with 23 chromatographic peaks being assigned as common fingerprint peaks. Furthermore, a quadrupole time of flight mass spectrometry (Q-TOF/MS) was coupled for the characterization of major compound. As (+)-nortrachelogenin was the most predominant compound in P. scabra Bunge, the quantification on it was also carried out with the method being validated. As a result, (+)-nortrachelogenin was found to be from 1.33 to 2.21 mg g−1 in this plant material. This rapid and effective analytical method could be employed for quality assessment of P. scabra Bunge, as well as pharmaceutical products containing this herbal material.
Authors:D.-Y. Yang, Q.-X. Liu, X.-L. Xie, and F.-D. Zeng
The exfoliated poly(vinyl chloride) (PVC)/montmorillonite
(MMT) nanocomposites were synthesized by in situ intercalated polymerization
of vinyl chloride (VC) in the presence of organic-intercalated montmorillonite
(OMMT). Their structures and thermal properties were characterized. The results
showed that layered silicates are well exfoliated and uniformly distributed
in PVC matrix during in situ intercalated polymerization of VC in the presence
of OMMT. The glass transition temperatures of PVC phases in the PVC/MMT nanocomposites
are all lower than that of pristine PVC due to the incorporation of the exfoliated
silicate layers in PVC matrix. The 5% mass loss temperature (T5%),
the dehydrochlorination temperature (Tmax1)
of the PVC matrix decreased due to the free and interlayer water in MMT, the
low thermal stability, and the enhanced dehydrochlorination of the PVC matrix
by alkyl ammonium pre-treated MMT. However, the thermal decomposition temperature
of the dehydrochlorinated PVC (Tmax2)
and char at 600C are slightly increased in the presence of silicate layers.