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Selected AbstractsSynthesis of a magnesium/aluminum/iron layered double hydroxide and its flammability characteristics in halogen-free, flame-retardant ethylene/vinyl acetate copolymer compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Chuan-Mei Jiao Abstract Mg,Al,Fe ternary hydrotalcites were synthesized by a coprecipitation method and characterized with powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The flame-retardant effects of Mg/Al,CO3 layered double hydroxides (LDHs) and Mg/Al/Fe,CO3 LDHs in an ethylene/vinyl acetate copolymer (EVA) were studied with the limited oxygen index (LOI), the UL-94 test, and the cone calorimeter test (CCT), and the thermal degradation behavior of the composites was examined by thermogravimetric analysis. The results showed that the LOI values of the EVA/(Mg/Al/Fe,CO3 LDH) composites were basically higher than those of the EVA/(Mg/Al,CO3 LDH) composites at the same additive level. In the UL-94 test, there was no rating for the EVA/(Mg/Al,CO3 LDH) composite at the 50% additive level, and a dripping phenomenon occurred. However, the EVA/(Mg/Al/Fe,CO3 LDH) composites at the same loading level of LDHs containing a suitable amount of Fe3+ ion reached the V-0 rating, the dripping phenomenon disappearing. The CCTs indicated that the heat release rate (HRR) of the EVA composites with Mg/Al/Fe,CO3 LDHs containing a suitable amount of Fe3+ decreased greatly in comparison with that of the composites with Mg/Al,CO3 LDHs. The introduction of a given amount of Fe3+ ion into Mg/Al,CO3 LDHs resulted in an increase in the LOI, a decrease in the HRR, and the achievement of the UL-94 V-0 rating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of morphology on the electric conductivity of binary polymer blends filled with carbon blackJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Zhongbin Xu Abstract Several carbon black (CB)-filled binary polymer blends were prepared in Haake rheometer. Distribution states of CB and effect of morphology on the electric conductivity of different ternary composites were investigated. Under our experimental condition CB particles located preferentially at the interface between polymethyl methacrylate (PMMA) and polypropylene (PP) in PMMA/PP/CB composites, in high-density polyethylene (HDPE) phase in PP/HDPE/CB composites, and in Nylon6 (PA6) phase in polystyrene (PS)/PA6/CB, PP/PA6/CB, PMMA/PA6/CB, and polyacrylonitrile (PAN)/PA6/CB composites; the ternary composites in which CB particles locate at the interface of two polymer components have the highest electric conductivity when the mass ratio of the two polymers is near to 1 : 1. The ternary composites in which CB particles located preferentially in one polymer have the highest electric conductivity usually when the amount of the polymer component having CB particles is comparatively less than the amount of the polymer component not having CB particles; if the formulations of PS/PA6/CB, PP/PA6/CB, and PMMA/PA6/CB composites equaled and PA6/CB in them is in dispersed phase, PS/PA6/CB composites have the highest electric conductivity and PP/PA6/CB composites have the lowest electric conductivity; suitable amount of PS or PAN in PA6/CB composites increase the electric conductivity due in the formation of a parallel electrocircuit for electrons to transmit. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Microwave Dielectric Properties of SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Sherin Thomas The apatite type SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics have been prepared by the conventional solid-state ceramic route. The phase purity and surface morphology of the sintered ceramics were studied using X-ray diffraction and scanning electron microscopy methods. These materials showed poor sinterability and was improved by the addition of a small weight percentage of zinc borosilicate glass. The microwave dielectric properties of these materials were studied for the first time. SrRE4Si3O13 ceramics have a low relative permittivity (,r) in the range 9,16, a Q-factor (Qu×f) upto 26 000 GHz and a low temperature coefficient of resonant frequency (,f). The SrLa4Si3O13 ceramics possessed a high Qu×f of nearly 26 000 GHz but with a high negative ,f of ,46 ppm/°C. The ,f of SrLa4Si3O13 ceramics was tuned by the addition of suitable amount of TiO2. [source] Synthesis and Characterization of Amphiphilic Star-Shaped Polymers With Calix[6]arene CoresMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Weipu Zhu Abstract Summary: The syntheses and characterizations of well-defined star-shaped amphiphilic polymers containing a hydrophobic p - tert -butyl-calix[6]arene core and six hydrophilic PPO or PPO- b -PDTC arms are described. The average number of PO units in each arm could be adjusted by choosing a suitable amount of raw material. Schematic structure of the amphiphilic star-shaped block copolymer containing a hydrophobic p - tert -butyl-calix[6]arene core and six PPO- b -PDTC arms. [source] Searching for DNA in museum specimens: a comparison of sources in a mammal speciesMOLECULAR ECOLOGY RESOURCES, Issue 3 2010M. CASAS-MARCE Abstract The number of genetic studies that use preserved specimens as sources of DNA has been steadily increasing during the last few years. Therefore, selecting the sources that are more likely to provide a suitable amount of DNA of enough quality to be amplified and at the minimum cost to the original specimen is an important step for future research. We have compared different types of tissue (hides vs. bones) from museum specimens of Iberian lynx and multiple alternative sources within each type (skin, footpad, footpad powder, claw, diaphysis, maxilloturbinal bone, mastoid process and canine) for DNA yield and probability of amplification of both mitochondrial and nuclear targets. Our results show that bone samples yield more and better DNA than hides, particularly from sources from skull, such as mastoid process and canines. However, claws offer an amplification success as high as bone sources, which makes them the preferred DNA source when no skeletal pieces have been preserved. Most importantly, these recommended sources can be sampled incurring minimal damage to the specimens while amplifying at a high success rate for both mitochondrial and microsatellite markers. [source] Effects of poly(ethylene- co -propylene) elastomer on mechanical properties and combustion behaviour of flame retarded polyethylene/magnesium hydroxide compositesPOLYMER INTERNATIONAL, Issue 7 2002Zhengzhou Wang Abstract Magnesium hydroxide-based halogen-free flame retarded linear low density polyethylene composites containing poly(ethylene- co -propylene) elastomer were prepared in the melt process and subsequently vulcanized thermally. Influences of the elastomer on the mechanical properties, combustion characteristics and crystallization behaviour of polyethylene/magnesium hydroxide composites have been investigated. The results from the mechanical tests show that the incorporation of a suitable amount of elastomer into polyethylene/magnesium hydroxide composites after vulcanization can increase both the tensile strength and elongation greatly, compared with those of the composites without the elastomer. It has been found that the properties such as limiting oxygen index, UL-94 rating, the time to ignition and the rate of heat release of polyethylene/magnesium hydroxide/elastomer composites are all improved in comparison with polyethylene/magnesium hydroxide composites at the same retardant level. Scanning electron microscopy studies show that the incorporation of the elastomer into polyethylene/magnesium hydroxide composites improves the compatibility between the filler and the polymer substrate. The degrees of crystallinity of polyethylene/magnesium hydroxide/elastomer composites decrease with increasing the elastomer content. © 2002 Society of Chemical Industry [source] Asymmetric inducing synthesis of optically active tetrahedral cluster containing SMCOW coreCHINESE JOURNAL OF CHEMISTRY, Issue 7 2004Quan-Yi Zhao Abstract The chiral clusters (,3 -S)MCoW(CO)8[n5 -C5H4C(O)OCH3] =Ru (2), Fe (3)] were synthesized by asymmetric induction of N-benzylcinchonium chloride as phase-transfer catalyst (PTC). The most suitable amount of PTC is 70 mol%. Cluster 3 was determined by single crystal X-ray diffraction analysis. The best ee of the chiral cluster is over 20%. [source] Conductivity and Methanol Permeability of Nafion,Zirconium Phosphate Composite Membranes Containing High Aspect Ratio Filler Particles,FUEL CELLS, Issue 4 2009M. Casciola Abstract Gels of exfoliated ,-zirconium phosphate (ZrPexf) in dimethylformamide (DMF) were used to prepare Nafion/ZrPexf composite membranes with filler loadings up to 7,wt.-% by casting mixtures of Nafion 1100 solutions in DMF and suitable amounts of 2,wt.-% ZrP gels in DMF. TEM pictures showed that the ZrPexf particles had aspect ratio of at least 20. All samples were characterised by methanol permeability (P) and through-plane (,thp) and in-plane (,inp) conductivity measurements at 40,°C and 100% RH. The methanol permeability of Nafion membranes containing in situ grown ZrP particles with low aspect ratio (Nafion/ZrPisg) was also determined. The methanol permeability and the swelling behaviour of the composite membranes turned out to be strongly dependent on the filler morphology. As a general trend, both permeability and swelling decreased according to the sequence: Nafion/ZrPisg > Nafion > Nafion/ZrPexf. The maximum selectivity (,thp/P,=,1.4,×,105,S,cm,3,s) was found for the membrane filled with 1,wt.-% ZrPexf: this value is seven times higher than that of Nafion. For the Nafion/ZrPexf membranes, the ratio ,inp/,thp increases with the filler loading, thus indicating that the preferred orientation of the ZrP sheets is parallel to the membrane surface. [source] | |||||||||||||