bluuebunny/crossref_metadata_2025_split huggingface dataset:
PAN monofilament in nanoscale: a novel approach
Authors: Sadrjahani M. , Hoseini S.A. , Mottaghitalab V. , Haghi A.K. 
Published: August 2014

AbstractA novel electrospinning setup was employed for producing aligned polyacrylonitrile (PAN) monofilament in nanoscale. Unlike conventional method, the PAN monofilaments is collected using a rotating drum with various linear speed from bulk of nanofibers. it originates from two syringe infusion pumps contain 14wt% PAN/DMF solution which passes through two separate high voltage electric field. Various collecting drum speed were examined to clarify its effect on degree of alignment, internal structure and mechanical properties. Image process technique used to illustrate the best degree of alignment for nano-monofilament collected at take up velocity of 59.5 m/min. The amount of Crystallization Index (C.I) and orientation parameter calculated respectively from FTIR spectra and Raman spectra also supports the results demonstrated by image processing techniques. The ultimate strength and elastic modulus of nano-monofilament bundles increase with increase of take up velocity. They approach respectively to a maximum of 73.7 MPa and 4.2 GPa at take up velocity of 59.5 m/min. Results acquired by differential scanning calorimetry (DSC) show no significant effect on glass transition temperature with increasing take up velocity. However, minimum value of evolved heat caused by chemical reaction was obtained at surface speed of 59.5 m/min.
Crystallization kinetics and miscibility of blends of polyhydroxybutyrate (PHB) with ethylene vinyl acetate copolymers (EVA)
Authors: El-Taweel S. H. , Stoll B. , Schick C. 
Published: August 2014

AbstractA series of ethylene vinyl acetate random copolymer EVA, with vinyl acetate (VA) varied from 9 to 91m%, was investigated by differential scanning calorimetry DSC and polarized optical microscopy. Biodegradable polymer blends of polyhydroxybutyrate PHB and EVA, having VA in EVA in range from 40m% till 91m%, were prepared by film casting from a chloroform solution. The miscibility and crystallization behavior of these blends were investigated. The isothermal crystallization behaviors of PHB and PHB/EVA blends are discussed in terms of the half time of crystallization t1/2. Experimental results indicated that blends of PHB/ EVA91 are completely miscible blend in the entire (0 to 100 m%) compositional ranges. Blends PHB/ EVA, for VA varied from 40 till 70 m% are immiscible as evidenced by the existence of unchanged composition independent glass transition temperatures (Tg), crystallization and melting behavior. The isothermal crystallization of PHB blends was investigated from room temperature till 130 °C. 80 °C was found to be the best temperature for comparison of different blends. At 80 °C t1/2 strongly depends on the content of VA in PHB/EVA blend, mainly due to differences in miscibility as well as due to differences in segmental mobility as identified by differences in glass transition temperature. Since both components in PHB/EVA80, pure PHB and pure EVA80, have glass transition temperatures close to 0 °C, it is difficult to decide its miscibility from Tg. However from the strong dependence of the value of crystallization half time t1/2 of PHB/EVA80 on blend composition, it was possible to reasonably infer that PHB/EVA80 is partially miscible.
Predicting the Young’s modulus of intercalated and exfoliated polymer/clay nanocomposites
Authors: Molajavadi Vadoud , Garmabi Hamid 
Published: August 2014

AbstractThe Halpin-Tsai equations were used for the composites with low level content of reinforcements, which contain lamellar shape, high modulus and high aspect ratio. These characteristics of reinforcements were taken into consideration to simplify the Halpin-Tsai equations. The effect of different parameters on the longitudinal Young’s modulus of well aligned polymer/clay nanocomposites was investigated for both exfoliated and intercalated microstructures. It was shown that the applied simplification had negligible effect on the prediction of the Halpin-Tsai model. For the intercalated structures with a high number of platelets per stack (n), increase in the gallery spacing did not influence the predicted modulus values. In an intercalated structure, the surface area of a stack, as the interface of fillermatrix, is n times lower than that of the exfoliated state. By considering the effect of the degree of exfoliation in the proposed model, a new equation was developed to predict the modulus enhancement in the nanocomposites filled with Montmorillonite (MMT). The theoretical predictions were supported by the experimental results.
Synthesis of polyetherols with 1,3-pyrimidine ring using 6-aminouracil, ethylene carbonate and propylene oxide
Authors: Chmiel-Szukiewicz Elżbieta 
Published: August 2014

AbstractNew method of synthesis of polyetherols with 1,3-pyrimidine ring by reactions of 6-aminouracil with ethylene carbonate and propylene oxide was described. The structure of products was analyzed using the IR, 1H-NMR and MALDI-TOF spectroscopies. Some physical properties and thermal stability of polyetherols were investigated. Initial tests on the foaming of polyurethanes obtained from the polyetherols were performed. Some properties of the foams such as apparent density, absorption of water, linear dimensions stability, thermal resistance and compression strength were investigated. Obtained foams show an improved thermal stability.
Characterization of nylon 6/11/montmorillonite nanocomposites prepared by in situ copolymerization
Authors: Zhang Yunsheng , Hu Guosheng , Wang Biaobing 
Published: August 2014

AbstractA novel nylon 6/11/montmorillonite nanocomposite was prepared by in situ copolymerization of prepolymer of caprolactam with aminoundecanoic acid in the presence of organoclay, and characterized in terms of Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), transmission electron micrograph (TEM), intrinsic viscosity as well as differential scanning calorimetry (DSC). It was found that the addition of organoclay had great influence on the intrinsic viscosity and melting behavior but not on the crystal transition of nylon 6/11 matrix. Intercalated/exfoliated and stacked silicates layers were observed for various nanocomposites.
Silica supported Schiff-base cobaltIII complex-Lewis base system: a highly selective catalyst for alternating copolymerization of CO2 and propylene oxide
Authors: Niu Yongsheng , Li Hongchun 
Published: August 2014

AbstractAn binary catalyst system of a silica supported Schiff-base cobalt complex SalenCoIII (OAC)-MCM-41 (Salen = 3-[N,N-bis-2-(3,5-di-tert-butylsalicylidenamino) ethyl] amine) was developed to generate the copolymerization of CO2 and propylene oxide in presence of (4-dimethylamino)-pyridine (DMAP). The influence of the molar ratio of catalyst components, the operating temperature, reaction time, and CO2 pressure on the yield as well as the molecular weight of polycarbonate was systematically investigated. The high selectivity of polycarbonate over cyclic carbonate at 40 °C was maintained after a longer reaction time to attain quantitative formation of the alternating copolymer. High molecular weight of 67 000 were achieved at an appropriate combination of all variables.
Preparation of poly(vinylidene fluoride)-silver nanoparticle composite using dimethylformide as both a solvent and a reductant
Authors: Chen Yingbo , Liu Lina , Zhang Yufeng 
Published: August 2014

AbstractPoly(vinylidene fluoride)-silver nanoparticle (PVDF-Ag) composites were synthesized by in situ reduction of silver salt using dimethylformide (DMF) as both a solvent and a reductant. The crystalline properties (e.g., crystallinity and the types of crystals) of the composites were characterized. It was shown that PVDF in the composites had a higher melting temperature than pure PVDF, and the α phase crystal in the composites became more stable with an increase in the amount of silver nanoparticles. The mechanical properties and morphologies of the composites were also investigated. It was noted that the PVDF-Ag composites have better mechanical properties when silver nanoparticles were added. The increase in toughness could be attributed to the formation of continuous structure between PVDF and silver particles.
Sulfur-containing polyurethanes as novel macro photoinitiators comprising in-chain benzophenone and coinitiator amine for photopolymerization
Authors: Wei Jun , Lu Rong , Qiu Jun , Liu Fang 
Published: August 2014

AbstractThree novel sulfur-containing polyurethanes (PUs) as macrophotoinitiators, hydroxyl-terminated PUa and PUb, and amino-terminated PUc, were synthesized through polycondensation of a novel diamine 4,4’-bis[(4- amino)thiophenyl]benzophenone (BATPBP), isophorone diisocyanate (IPDI) and N-methyldiethanolamine (MDEA). The beznophenone and coinitiator amine structures were successfully introduced into the backbones of PUs. FT-IR, 1H NMR, GPC and DSC analyses confirmed their structures and properties. UV-vis spectra indicate that the macromolecular structure nearly has no influence on their UV-vis absorptions. A trifunctional monomer of trimethylolpropane triacrylate (TMPTA), initiated by these macrophotoinitiators with a low-molecular-weight photoinitiator system (benzophenone/MDEA) as the reference, was studied through photo differential scanning calorimetry (photo-DSC). The results show PUa is the most efficient photoinitiator and the molar content of coinitiator amine in PUs has an important effect on their photoefficiency.
Carbohydrate-based polyurethanes: A comparative study of polymers made from isosorbide and 1,4-butanediol
Authors: Marín Romina , Alla Abdelilah , Ilarduya Antxon Martínez de , Muñoz- Guerra Sebastián 
Published: August 2014

AbstractA set of polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4-butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is2HDI and Is2MDI) as diols. The thermal properties and stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those of the polyurethane analogues entirely made of BD. Incorporation of isosorbide produced significant changes in Tg, Tm and Td but no noteworthy differences were found between copolymers made from Is or Is2 monomers. Degradation assays revealed that incorporation of Is units increased slightly the hydrolysis rate.
Influence of nanoparticles on the morphology, thermal stability and air permeability of electrospun polylactic-acid fibres
Authors: Alongi Jenny , Pošković Merima 
Published: August 2014

AbstractPolylactic-acid (PLA) and PLA-clay fibres have been produced from solution of 1,1,1,3,3,3-hexafluoro-2-propanol by electrospinning. Nanoclays having different aspect ratio, namely a montmorillonite and a sepiolite, have been added and dispersed within the polymer matrix in order to enhance the thermal stability and air permeability of PLA. The influence of the polymer molecular weight, the solution viscosity and conductivity on the morphology of the fibres has been investigated. Electron microscopy has shown that fibre diameter and the presence of beads defects in the fibres depend on the type of clay added to the polymer matrix. The thermal stability in nitrogen and in air has been drastically enhanced for the presence of the clays as compared with neat polymer. Finally, permeability tests performed on the electrospun condensed fibres pointed out that PLA-clay fibres exhibit a lower permeability to air (up to 90%) with respect to neat PLA fibres.
Use of crystal violet to prepare SBR-montmorillonite clay nanocomposites
Authors: Chakraborty Sugata , Kar Saptrashi , Dasgupta Saikat , Mukhopadhyay Rabindra , Bandyopadhyay Samar 
Published: August 2014

AbstractPresent study describes the preparation and characterization of crystal violet modified-montmorillonite clay nanocomposites by latex blending technique. Coagulation of the latex-clay slurry produced nanocomposites master batch. The master batch was compounded with Styrene Butadiene rubber (SBR). WAXD and TEM provided the evidences of formation of nanocomposite. Remarkable improvements in the mechanical properties were found by addition of small amount of modified clay.
Fabrication and electrochemical characterization of carbon nanofibers by electrospinning with various MnO2 contents
Authors: Chang Duk-Rye , Heo Gi-Seok 
Published: August 2014

AbstractCarbon nanofibers were fabricated by electrospinning with various concentrations of MnO2, carbonization and activation processing for supercapacitor applications. Microstructure and electrochemical properties were characterized by scanning electron microscopy (SEM), the 4-point probe method, and a battery cycler system. It was observed that 8-20 wt.% MnO2/PAN nanofibers had 190- 260 nm diameters. The diameter decreased with increasing MnO2 concentration, but it increased for concentrations greater than 16 wt.%. The 16 wt.% MnO2 solution produced the nanofibers with the smallest diameter. The nanofibers showed capacitor characteristics when fabricated into electrodes, and their electrical conductivity and capacitance increased with increasing MnO2 concentration. The 20 wt.% MnO2/PAN carbon nanofibers showed the highest electrical conductivity value (2.82×10-3 S/cm) and the highest capacitance value (186.28 F/g), which indicates their potential for development of supercapacitor electrodes.
correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP
Authors: Saengsuwan Sayant 
Published: August 2014

AbstractDrawn composite thin film based on thermotropic liquid crystalline polymer (TLCP) and polypropylene (PP) was annealed at 130 °C at different times. The influence of annealing time on microstructural and mechanical properties of the composite film has been studied. The correlation in mechanical properties and their microstructural parameters has also been investigated. X-Ray diffraction results reveal that the smectic mesophase transforms progressively into the monoclinic phase as annealing time is increased. Consequently, the true crystallinity (Xc), crystal thickness (L) as well as relative level of molecular orientation of PP crystalline phase in the annealed TLCP/PP films are increased significantly. Also, the TLCP fibrils have no influence on the microstructure of PP crystalline phase. The apparent crystallinity (Xc,a) of PP phase evaluated by DSC also increase significantly with annealing time. As a result, the increases of these microstructural parameters coupled with the reinforcement of TLCP fibrils could be contributed directly to the remarkable enhancement of mechanical properties of the annealed TLCP/PP film in both machine (MD) and transverse (TD) directions. The correlation of moduli with microstructural parameters (Xc, Xc,a and L) exhibits nonlinear relations. However, the relative level of molecular orientation is a more suitable parameter to correlate with the improvement of mechanical properties of the annealed TLCP/PP film. Finally, this work presents that the mechanical properties of the TLCP in situ reinforced thermoplastics can be significantly enhanced via a simple thermal treatment.
Polymerization of acrylamide inverse microemulsion initiated directly by UV radiation
Authors: Xie Long , Shao Ziqiang , Wang Huiqing , Lv Shaoyi 
Published: August 2014

AbstractCombining the microemulsion polymerization with UV direct initiation, an efficient method for polymerization of AM with high polymerization rate and conversion, low polymerization temperature, high purity of product and simple radiation equipment was developed. In the absence of initiator and under UV radiation, the polymerizations of AM inverse microemulsion system with high monomer content and low emulsifier content were successfully accomplished at low temperature (24~30 °C) and PAM with high purity and high limiting viscosity [η] was obtained. The polymerization rate was fast and the conversion reached to higher than 85% in 30 minutes. Based on the abundant experimental results, the reasonable polymerization mechanisms were proposed as follows: the AM participated in the initiation reaction and the main initiation locus was the emulsifier layer. Rp and [η] were weakly influenced by temperature due to the low apparent activation energy of the reaction (Ea = 12.98 kJ/mol). The polymerization kinetics of Rp was expressed as the following: Rp = [IUV]0.4972[M]1.5048[E]-0.5731. The Rp order with respect to [M] is equal 1.5048 which confirms the conclusion that the monomer participated in the initiation reaction.
Preparation of silk fibroin microspheres by emulsificationdiffusion method for controlled release drug delivery applications
Authors: Imsombut Thanonchat , Srisa-ard Mangkorn , Srihanam Prasong , Baimark Yodthong 
Published: August 2014

AbstractSilk fibroin (SF) microspheres containing a model drug were prepared by a simple water-in-oil emulsification-diffusion method. Aqueous SF solution and ethyl acetate were used as water and oil phases, respectively. Methylene Blue was used as a water-soluble model drug. Effect of drug content on microsphere characteristics, drug loading efficiency and drug release behavior was determined. Scanning electron microscopy revealed that drug-loaded SF microspheres were spherical in shape with a smooth surface. The SF microspheres showed predominant random coil SF conformation. All drug loading efficiencies were approximately 50%. An increase in drug/SF ratio could lead to an increase in %drug release and surface erosion after the drug release test. Drug release from SF microspheres is due to SF matrix swelling and surface erosion processes.
Preparation of polyethylene-g-(polyacrylic acid) and its sodium salt ionomer by in-situ chlorinating graft copolymerization
Authors: Zhao Zhi-Qiang , Wang Shuang-Shuang , Wang Na , Zhao Ji-Ruo , Feng Ying 
Published: August 2014

AbstractAcrylic acid (AA) was grafted firstly onto high density polyethylene (HDPE) by in-situ chlorinating graft copolymerization (ISCGC), so a graft copolymer composed of chlorinated polyethylene (CPE) as backbone and poly (acrylic acid) (PAA) as branched chains was synthesized. And subsequently the preparation of its carboxylated ionmers was studied. This work was focused on discussing the reaction process for grafting AA onto HDPE by ISCGC and the preparing of carboxylated ionmers of CPE. In this paper, the structure of graft copolymer and the ionomer were characterized mainly by FT-IR, gel permeation chromatography (GPC) and graft degree (GD). The influence factors which related to the main and side reactions, including the monomer concentration, chlorine contents of the product, and reaction temperature were investigated. Additionally, effects of these factors on reaction process controlling were described. The aim of above is to investigate how CPE-cg-PAA and its sodium-salt ionomer were prepared.
The miscibility estimation of some nanocomposites based on starch
Authors: Dimonie Doina , Radu Socoteanu , Doncea Sanda , Pop Florentina Simona , Petre Celina , Dumitriu Irina , Fierascu Radu 
Published: August 2014

AbstractBased on the FTIR spectral changes, the miscibility of some nanocomposites based on starch, polyvinyl alcohol and treated multilayered silicate, was qualitatively estimated. The FTIR spectroscopy provide evident gross/small spectral changes as well as appreciable spectral shifts mainly in those spectral range that defines hydroxyl O-H vibrations (3600- 3000 cm-1 ), water absorbtion (1800 - 1500 cm-1) , the morphological order degree and the interaction with multilayered silicate and (1192 - 950 cm-1). Based on the observed spectral modifications it can be estimate that high miscibility do exist between the components of the studied nanocomposites.
Effect of FeCl3 on the morphology, wetting behavior, and stabilization/carbonization of polyacrylonitrile nanofibers prepared by electrospinning
Authors: Cai Yibing , Xu Xiaolin , Wei Qufu , Ke Huizhen , Yao Wang , Qiao Hui , Lai Chuilin , He Guangfei , Zhao Yong , Fong Hao 
Published: August 2014

AbstractHerein we report that the neat polyacrylonitrile (PAN) nanofibers and PAN/FeCl3 composite nanofibers were prepared by the materials-processing technique of electrospinning. The effect of FeCl3 amount on the morphology and wetting behavior of the resulting composite nanofibers were studied by scanning electron microscopy (SEM) and drop shape analysis (DSA), respectively. The SEM images indicated that the diameters of composite nanofibers decreased with increase of FeCl3 amount, and this was probably due to the conductivity increase of spinning solutions. The results acquired from DSA measurement showed that the addition of FeCl3 increased the surface contact angle of water deposited on composite nanofibers, suggesting the higher hydrophobicity and the lower wetting behavior. Additionally, the effect of FeCl3 on stabilization and carbonization of the PAN composite nanofibers were investigated. The structural and morphological evolutions of the stabilized and carbonized nanofibers were studied by Fourier transfer infrared (FTIR) spectra and SEM. The FTIR spectra showed that the presence of FeCl3 in composite nanofibers considerably varied the mechanisms of thermo-chemical reactions during the heat treatments. The SEM images revealed that there were conglutinations of nanofibers after carbonization, while the degree of conglutination for the carbonized PAN composite nanofibers with FeCl3 was higher than that for the carbonized neat PAN nanofibers.
Synthesis of star hydrophobically-modified acrylamide copolymers and its some properties in brine
Authors: Duan Ming , Fang Shenwen , Zhang Liehui 
Published: August 2014

AbstractStar copolymers of acrylamide (AM) and N,N-dimethyl-Nvinylnonadecan- 1- aminium chloride (C18DMAAC) were synthesized by photopolymerization in water. Some properties of these star hydrophobically modified acrylamide copolymers (SHMPAM) with different C18DMAAC contents and the linear hydrophobically modified acrylamide copolymers (LHMPAM) in brine were characterized. The increase in C18DMAAC content resulted in decreased intrinsic viscosity and increased Huggins constant for SHMPAM. Similar results were observed for LHMPAM. With similar intrinsic viscosity and C18DMAAC content, the Huggins constant of SHMPAM was much higher than that of LHMPAM, which might be due to the fact that SHMPAM had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAM was increased with increasing C18DMAAC content, which was similar to that of LHMPAM. However SHMPAM exhibited higher apparent viscosity than LHMPAM because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the flowinduced scission experiment, SHMPAM exhibited superior shear stability in comparison with LHMPAM. When the extensional shear rate was ≈ 40000 s-1, the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were about 80%. In contrast, when the extensional shear rate was ≈20000 s-1, the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80%.