bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of aspect ratio, surface modification and compatibilizer on the mechanical and thermal properties of ldpe-mwcnt nanocomposites
Authors: Abbasi Sarfraz H. , Al-Juhani Abdulhadi A. , Ul-Hamid Anwar , Hussein Ibnelwaleed A. 
Published: August 2014

AbstractIn this work, nanocomposites of low density polyethylene (LDPE) / multiwall carbon nanotubes (MWCNTs) were prepared using melt blending. The effects of CNT aspect ratio, CNT loading, CNT chemical modification and the presence of a compatibilizer (maleated polyethylene) on morphology, mechanical and thermal properties of the CNT/LDPE composites were studied. Different MWCNTs were used: long CNT (LCNT); COOH modified CNT (MCNT) and short CNT (SCNT). FE-SEM images of produced nanocomposites show agglomeration of the MWCNTs. Addition of compatibilizer to both LCNT and MCNT nanocomposites improved their dispersion in the LDPE matrix. Yield strength and modulus increased with loading of various MWCNTs. However, ultimate strength, percent elongation and toughness reduced significantly for CNT loadings of 2% CNT and higher. The addition of maleated PE resulted in improvements of Young’s modulus, yield strength and ultimate strength but no impact on elongation at break or toughness. Addition of compatibilizer did not affect the crystallinity of the produced nanocomposites. In general, the use of CNT with high aspect ratio and the addition of compatibilizer and chemical modification improved the dispersion of MWCNTs and consequently improved most of the mechanical properties except elongation at break and toughness.
SPPO/PEI-based acid-base blend membranes for direct methanol fuel cells
Authors: Tsen Wen-Chin , Chuang Fu-Sheng , Shu Yao-Chi , Chen Chien-Chung , Gong Chunli , Wen Sheng 
Published: August 2014

AbstractNew acid-base polymer blends based on sulfonated poly(phenylene oxide) (SPPO) as the proton-conducting component and poly(ether imide) (PEI) as the basic component were considered for use as proton-exchange membranes (PEM). The obtained blend membranes had a higher thermal stability and a higher glass transition temperature (Tg) than the pure SPPO, as revealed by TGA and DSC. The morphology of blend membranes indicated that PEI was highly compatible with SPPO polymers because of the formation of hydrogen bonds between the sulfonated acid and PEI. Although the blend membranes exhibited a lower water uptake and lower proton conductivity than the pure SPPO membrane, the PEI component improved the dimensional stability, mechanic properties, and especially inhibited methanol permeation. The methanol permeability coefficient of the blend membrane with 30 wt.% PEI content was 9.68×10-8 cm2/s, which is lower than that of the pure SPPO and just one tenth of that of Nafion® 112. This considerable reduction in methanol crossover revealed the feasibility of the blend membranes as promising electrolytes for direct methanol fuel cells.
Ring-opening polymerization of ethylene carbonate using ionic liquids as catalysts
Authors: Zhou Jiancheng , Cheng Ling , Wu Dongfang 
Published: August 2014

AbstractThe ring-opening polymerization of ethylene carbonate was examined using ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-3-methylimidazolium chlorozincate ([bmim]Cl-(ZnCl2)x), as polymerization catalysts. It was shown that the polymerization was accompanied with decarboxylation and chain cleavage reaction. As the reaction time increased, the monomer conversion increased and the content of ethylene carbonate units in the resultant polymer decreased, while the polymer molecular weight increased at first, reached a maximum and then decreased. It was also found that not only the polymerizing activity of the [bmim]Cl-(ZnCl2)x but also its performance for suppressing the decarboxylation and chain cleavage increased with the molar fraction of ZnCl2. It was deduced that the catalytic performance of ionic liquids mainly depended on their inorganic anions and that the larger the amount of these anions in the reaction system, the better the catalytic performance. The polymerizing activity of ionic liquids was much higher than conventional catalysts often used for the polymerization of ethylene carbonate.
Synthesis and magnetic properties of poly(amic acid) complexes containing 1,10-phenanthroline
Authors: Zheng Renhua , Jiang Huajiang , Guo Haichang , Sun Weilin 
Published: August 2014

AbstractA novel poly(amic acid) containing 1,10-phenanthroline (PPHPA) was first synthesized by the polycondensation of 4,4'-oxydiphthalic dianhydride (ODPA) with 5,6-diamine-1,10-phenanthroline (DAPH). Three polymeric complexes were first prepared by the reaction of polymer (PPHPA) with NiSO4, CuSO4, and NdCl3, respectively. The structures of the polymer and the complexes were characterized by IR, 1H-NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0-50 kOe) at 5 K and as a function of temperature (5-300 K) at a magnetic field strength of 30 kOe. The results show that PPHPA-Ni2+ and PPHPA-Nd3+ were soft ferromagnets, whereas PPHPA-Cu2+ exhibited the features of an antiferromagnet.
Toughening of glass fiber reinforced Nylon 66 with EPDMMAH: Dynamic mechanical, rheological, and morphological investigations
Authors: Soltani Iman , Zeynali Mohammad Ebrahim , Yousefi Ali Akbar 
Published: August 2014

AbstractIn this research the variation of mechanical and rheological properties of the composite as a function of different processing parameters and ethylene propylene diene monomer (EPDM) rubber content was studied. The optimum amount of dicumyl peroxide (DCP) to achieve the highest percentage of grafting of maleic anhydride to EPDM was obtained by Fourier transform infrared (FTIR) spectroscopy. In general, immiscibility between nylon 66 and EPDM, and their high interfacial tension makes their blending difficult. Maleic anhydride was grafted to EPDM to reduce interfacial tension between two phases. Also the blends were prepared at highest possible speed of mixing (screw speed in extrusion) and lowest temperature to reach a well mixed sample which can be seen in scanning electron microscopy (SEM) images and impact strength results. Dynamic mechanical thermal analysis (DMTA) tests were conducted to evaluate the miscibility of the components and to measure the glass transition temperature of the blends. Rheological measurement showed that the viscosities of the components of the blend getting closer to each other when EPDM content, time of mixing and shear rate increase.
Effect of clay modification on the dynamic mechanical and dielectric properties of PMMA nanocomposites via melt blending
Authors: Wang Yeh , Chen Wei-C. 
Published: August 2014

AbstractThe dynamic mechanical and dielectric properties of poly(methyl methacrylate)/ clay nanocomposites (PCNs) prepared with melt blending was studied in terms of clay modification and nanoscale dispersion. The pristine clay was modified via various routes, including PMMA concentrates from in situ polymerization and POP-diamine intercalation. Partially exfoliated clay layers were uniformly dispersed in the nanocomposites as evidenced from x-ray diffraction study. The subglass β relaxation, the segmental α relaxation, and the α β-merging process above Tg were observed in the nanocomposites from the dielectric analysis. Compared to neat PMMA, with only 5 wt% clay loading, the modified PCN materials exhibit higher glass-transition temperatures and higher dynamic storage moduli, which was attributed to the polymer chain tethering and confinement effect. Significant increase in dielectric permittivity’s and losses due to interfacial polarization and ionic conduction were observed for the PCNs. The intensity of the interfacial polarization process increases with the dispersion degree of clay layers and hence the relaxation process can be assigned to the space charge polarization of the ionic species in the clay intergalleries.
Properties and structural characterization of chitosan/poly(vinyl alcohol)/graphene oxide nano composites
Authors: Ma Jun , Liu Changhua , Li Rui , Wang Jia 
Published: August 2014

AbstractChitosan (CS)/poly(vinyl alcohol) (PVA)/graphene oxide (GO) nanocomposites in the form of films are prepared in a casting and solvent evaporation method. Fourier-transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing and moisture uptake were used to study the structure and properties of these chitosan/poly(vinyl alcohol) /graphene oxide (PCS/GO-n) nanocomposites. The result from tensile testing indicated that the nanocomposite containing 2 wt% GO exhibits high tensile strength (71.21 MPa) with a large elongation at break (51.8%). The high mechanical properties of the nanocomposite films are mainly due to uniform dispersion of GO sheets in the polymer matrix and strong interfacial interactions among components.
Morphology, thermal properties and mechanical relaxations of metallocene syndiotactic polypropylenes
Authors: Moya Ester López , Gómez-Elvira José M. , Benavente Rosario , Pérez Ernesto 
Published: August 2014

AbstractThe complex polymorphic behaviour of four syndiotactic polypropylene (sPP) samples have been analysed by means of DSC and WAXD techniques. Two samples (sPP1, sPP2) were synthesised via metallocene polymerization by using the ansa-zirconocene Ph2C(Cp)(9-Flu)ZrCl2 as catalyst. Finally, two additional specimens with different molar masses (sPP1-Fr1, sPP1-Fr2) were prepared from the most syndiotactic sPP1 sample by temperature gradient extraction. The WAXD analysis shows that together with the orthorhombic form I, form II can coexist in a variable but small proportion depending on both the chain features and the processing conditions. The relative contribution of the disordered and the ordered types of form I is also dictated by molar mass, configurational microstructure as well as processing conditions. The observed changes in the thermal properties as measured by DSC and in the mechanic-dynamical relaxations of the samples, on slowing the crystallisation rate down, can be rationalised in terms of two concurrent processes, namely the perfection undergone by the crystals and the segregation of the amorphous phase.
Preparation and properties of molecular-weight-controlled polyimide adhesive film
Authors: Huo Haitao , Mo Song , Sun Hongjie , Yang Shiyong , Fan Lin 
Published: August 2014

AbstractA series of molecular-weight-controlled aromatic polyimides based on 4,4’-oxydiphthalic anhydride (ODPA), 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene (6FAPB) and 4,4’-diaminodiphenylsulphone (4,4’-DDS) were synthesized in the presence of phthalic anhydride (PA) as end-capping agent. The effect of molecular weight on solubility, melt viscosity, thermal and mechanical properties of polyimides was investigated. Experimental results demonstrated that these polyimides have good solubility not only in most of polar aprotic solvents but also in some of common organic solvents, such as DMSO and THF. Homogeneous and stable polyimide solutions with solid content as high as 40-45 wt.% could be achieved. High-quality polyimide films could be obtained by casting the polyimide solutions onto glass plate followed by baking at a relatively low temperature. The polyimide films exhibited outstanding thermal and mechanical properties. The rheological behavior of these polyimides depends on their molecular weight. Adhesive properties of polyimide films bonded to stainless steel were evaluated by lap shear strength (LSS) test. The bonding conditions were optimized with respect to the melt temperature, bonding pressure and time, as well as thickness of the adhesive layer. It is found that the polyimides with moderate molecular weight exhibited better adhesive properties.
Tissue engineering scaffold electrospun from poly(ε- caprolactone)-b-poly(sulfobetaine methacrylate) block copolymers with improved hydrophilicity and good cytocompatibility
Authors: Li Qian , Wang Zhihong , Zhao Qiang , Wang Lianyong , Wang Shufang , Kong Deling 
Published: August 2014

AbstractAn amphiphilic block copolymer, poly(ε-caprolactone)-b-poly (sulfobetaine methacrylate), (PCL-b-PSBMA), which comprising of hydrophobic polyester segment and hydrophilic zwitterionic segment, was synthesized by ringopening polymerization (ROP) together with atom transfer radical polymerization (ATRP). The chemical structure and composition of the synthesized copolymers were first investigated by 1HNMR and GPC. The copolymers were further processed into non-woven fabrics by electrospinning. The surface chemical composition, fiber morphology, hydrophilic/hydrophobic property, and cell viability of the as-prepared scaffold were evaluated by X-ray photoelectron spectroscopy, SEM, water contact angle and uptake measurement, and MTT assay, respectively. All these results indicate that this kind of copolymers is a suitable candidate for the biomedical application.
ARGET ATRP of copolymerization of styrene and acrylonitrile with environmentally friendly catalyst and ligand
Authors: Wang Guoxiang , Lu Mang 
Published: August 2014

AbstractThe atom transfer radical polymerization of styrene and acrylonitrile using activators regenerated electron transfer (ARGET) has been carried out in N,N-dimethylformamide (DMF) at 90 °C in the presence of air with a catalyst system of FeCl3·6H2O/succinic acid using 2-bromoisobutyrate as the initiator and ascorbic acid as the reducing agent. The ARGET ATRP of styrene and acrylonitrile was proved a ‘living’/controlled polymerization such as a linear increase in molecular weights of polymers with monomer conversion and relatively narrow polydispersities (<1.25) when the conversion was beyond 20%. The chain extension experiment was carried out to confirm the controlled manner of the polymerization system. The resultant SAN was characterized by nuclear magnetic resonance and gel permeation chromatography.
Polymerization of 1,3-butadiene using (salen)Ni(II) and (salphen)Ni(II) complexes in combination with methylaluminoxane
Authors: Wang Baolin , Gong Dirong , Wu Guangfeng , Zhang Xuequan 
Published: August 2014

AbstractEight nickel complexes with various imino-backbones and substituents at ortho- and para-positions on the aromatic ring of the salicylaldehyde are prepared and characterized. Activated by MAO, the precursors have been investigated for 1,3-butadiene polymerization. All the complexes display high cis- 1,4 selectivity (cis-1,4 contents: 90.4 to 93.4 %), while the catalytic activity strongly depends on the position of bulky group located. Introduction of t-butyl at 3,3′- position on the aromatic ring of the ligands remarkably increases catalytic activity, while that at the 5,5′-position decreases the activity. Relatively, variation of iminobackbone shows little influence on catalytic performance. Effects of [Al]/[Ni] molar ratio and temperature on catalytic activity and stereo-selectivity are also investigated.
Effects of sterically hindered N-alkoxyamines on photooxidative stability of reinforced polypropylene
Authors: Enescu Daniela , Frache Alberto 
Published: August 2014

AbstractIn the present paper the influence of Flamestab® NORTM 116 (abbrev. FNOR), a sterically hindered N-alkoxyamine stabilizer, on the photo-oxidative stability of calcium carbonate reinforced polypropylene (abbrev. CCPP) used for production of plastic collars has been investigated. The samples, prepared by melt compounding, were exposed to artificial accelerated photo-ageing carried out at λ>300 nm and 45 °C in air. FT-IR and UV-VIS analysis revealed that the deterioration of neat CCPP takes place very rapidly in comparison with the composites containing FNOR. Hydroperoxides and various carbonyl species are formed as the main degradation products during the photo-oxidation process. Moreover, the intensity of the absorption bands grows with increasing of UV exposure time indicating that the material suffers a photo-oxidative degradation process. Indeed, addition of only 0.1 wt.-% FNOR did not significantly modify the length of the induction period of neat CCPP, but a strong efficiency was obtained by increasing the amount of FNOR (0.5 wt.-%) which shows an increase of eight times more as compared with neat CCPP. Therefore, it may be supposed that OIT is linked to the level of concentration of the stabilizer. This remarkable increase in composite stability demonstrated by a lengthening of OIT is typical for sterically hindered N-alkoxyamine stabilizers since they are very efficient at scavenging freeradicals formed as the polymer degrades. In other words, these UV stabilizers are converted to nitroxide radicals (see Scheme 1) which readily trap the polymer degradation species to produce alkoxyamines. Then, the formed alkoxyamines do subsequently react with peroxy radicals to regenerate the active nitroxide radical, thereby this process (called Denisov cycle) proceed in a regenerative cycle, thus retarding oxidative polymer degradation. The increase of absorbance in the carbonyl region as a function of irradiation time was used to determinate the photooxidation rate. It was found out that the photooxidation rate measured from the slope of linear part of the curves is significantly decreased for the CCPP/FNOR 0.5 composite compared to neat CCPP. In the light of the above mentioned findings, FNOR could be taken into consideration as an UV stabilizer for CCPP.
Influence of hydrophobe fraction content on the rheological properties of hydrosoluble associative polymers obtained by micellar polymerization
Authors: Jiménez-Regalado Enrique J. , Hernández-Flores Elva B. 
Published: August 2014

AbstractThe synthesis, characterization and rheological properties in aqueous solutions of water-soluble associative polymers (AP’s) are reported. Polymer chains consisting of water-soluble polyacrylamides, hydrophobically modified with low amounts of N,N-dihexylacrylamide (1, 2, 3 and 4 mol%) were prepared via free radical micellar polymerization. The properties of these polymers, with respect to the concentration of hydrophobic groups, using steady-flow and oscillatory experiments were compared. An increase of relaxation time (TR) and modulus plateau (G0) was observed in all samples studied. Two different regimes can be clearly distinguished: a first unentangled regime where the viscosity increase rate strongly depends on hydrophobic content and a second entangled regime where the viscosity follows a scaling behavior of the polymer concentration with an exponent close to 4.
Synthesis and characterization of salt resistance hydrogel microspheres by inverse suspension polymerization
Authors: Zhou Ming , Zhao Jinzhou , Pu Wanfen , Wang Xu , Yang Yan 
Published: August 2014

AbstractA series of novel salt-resistance hydrogel microspheres P(AM-co-AMPS) are synthesized by inverse suspension copolymerization using ammonium persulfate (APS) as the initiator and N,N-methylene bisacrylamide (MBA) as the crosslinker and polyvinyl alcohol (PVA) as disperse agent. Optimization syntheses condition of hydrogel microspheres copolymer P(AM-co-AMPS) SAPs is crosslinker content 0.01%, ratio of water to oil 4%, ratio of monomer to surfactant 30%, ratio of acrylamide to 2-acrylamido-2-methylpropane sulphonic acid 80:20 and initiator APS content 1.0%. Their effects on the salt absorbency of the synthesized hydrogel microspheres are investigated. FTIR indicates the two monomeric units of the acrylamide and 2-acrylamido-2-methylpropane sulphonic acid exists in copolymer backbone. SEM indicates that the number of the micropores largely decrease with the water/oil ratio increasing from 4% to 10%. Elemental analysis indicate that the measured values of carbon, sulfur, nitrogen, hydrogen four elements is very close to theoretical value. The experimental results of salt-resistance hydrogel microspheres show the salt absorbency decrease with the increase of salt concentration. The maximum salt absorbency is 132g/g within 75min in 0.9% sodium chloride solution and the effect of calcium ion on salt absorbency is much greater than that of sodium ion.
Erythrina lysistemon-derived flavonoids account only in part for the plant’s specific effects on rat uterus and vagina
Authors: Njamen Dieudonné , Mvondo Marie Alfrede , Gueyo Telesphore Nanbo , Zingue Stéphane , Fomum Stephen Tanee , Wandji Jean 
Published: August 2014

Abstract

Background: The stem bark ethyl acetate extract of Erythrina lysistemon was found to induce vaginal proliferation in ovariectomized rats orally treated. Alpinumisoflavone (AIF) and abyssinone V-4′-methyl-ether (AME), isolated as its major constituents, were reported to separately provoke uterine growth and/or vaginal proliferation. The present study aimed at evaluating the effects of the mixture of AIF and AME (51 mg/kg [AIF]+153 mg/kg [AME]) following their relative abundance in the extract, in order to compare these effects to those of E. lysistemon.

Methods: The study was performed in ovariectomized rats treated intraperitoneally for 3 days. Estradiol valerate (E2 V) and AME were used for positive controls. Morphological and histological changes of animals’ uterus and vagina were used as the hallmark of estrogenicity.

Results:
E. lysistemon extract induced estrogen-like effects only on the uterus and significantly increased uterine wet weight (p<0.01) and uterine epithelial height (p<0.01). These results suggest a tissue-selective action of E. lysistemon extract depending on the route of administration. The mixture of AIF and AME induced E. lysistemon-like effects only at a dose of 1 mg/kg BW/d (0.25 mg/kg+0.75 mg/kg), although these effects were lower in magnitude (p<0.05) compared to those induced by E. lysistemon extract.

Conclusions: Effects induced by the mixture of AIF and AME are analogous to those of E. lysistemon, but the low magnitude of these effects suggests that there are minor metabolites that interact with AIF and AME to provoke the specific effects of E. lysistemon.
Consumptive hypothyroidism associated with parotid infantile hemangioma
Authors: De Corti Federica , Crivellaro Carlo , Zanon Giovanni Franco , Luzzatto Claudia 
Published: August 2014

Abstract
Consumptive hypothyroidism is a rare condition usually described in association with diffuse infantile hemangioma of the liver, over-expressing type 3 iodothyronine-deiodinase. We report a case of acquired hypothyroidism associated with a parotid hemangioma in a male child, who was initially evaluated at 48 days of age due to persistent jaundice. Replacement hormonal therapy was promptly started, but resolution of the clinical and laboratory findings of hypothyroidism was only achieved at 3 months of age, when propranolol treatment was added to the therapeutic regimen. Our review of the literature retrieved only one case of proven consumptive hypothyroidism associated with a parotid infantile hemangioma, making a real incidence an underestimate: we believe one should consider this association a real possibility.