bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of nano-Fe on the electromagnetic shielding properties of nano-Fe/carbon fiber/LDPE composites
Authors: Na Xie , Qingjie Jiao , Chongguang Zang , Chenglong Wang 
Published: August 2014

AbstractNano-Fe/carbon fiber/ Low-density polyethylene (LDPE) composites were prepared by melt compounding. The electromagnetic shielding properties of nano-Fe/CF/LDPE composites as a function of nano-Fe mass content were investigated. The data of DC electrical conductivity evidence percolation behavior of the composites, and percolation threshold descends with the increase of nano- Fe. When the CF/LDPE composites reach the percolation threshold (pCF=0.10), “double percolation” appears in the nano-Fe/ CF/LDPE composites as continuously adding nano-Fe into the CF/LDPE composites, and the percolation threshold of the “double percolation” is 0.10 mass fraction of CF and 0.08 mass fraction of nano-Fe, which result in at least 103 orders of magnitude greater than that of CF/LDPE composites. The data of Initial DC permeability μr, coercivity Hc, saturation magnetization Ms and residual magnetization Mr of nano-Fe/CF/LDPE composites at the magnetic field intensity between -2500 G and 2500 G enhance with increasing addition of nano-Fe. The value of relative permeability decreases as the loading of nano-Fe is increased from 0.04 to 0.19 mass fraction in frequency ranges of 300 KHz-100 MHz. The EMI SE in frequency ranges of 300KHz-100MHz increase with the addition of nano-Fe, and mechanism of electromagnetic shield for nano-Fe/CF/LDPE composites is compound shielding mechanism with reflection loss R and absorption loss A. Absorption loss A increases significantly with increasing addition of nano-Fe from 0.04 to 0.19 mass fraction, and increasing trend of reflection loss R slow down as mass fraction of the fillers reach percolation threshold.
Coagulation studies of cellulose/NaOH/thiourea/urea/H2O fiber spinning system
Authors: Zhang Shuai , Li Fa-xue , Yu Jian-yong , Gu Li-xia 
Published: August 2014

AbstractThe coagulation properties of cellulose from cellulose//NaOH/thiourea/ urea/H2O solutions were investigated with the goal of determining the optimal coagulation conditions for the spinning of cellulose fibers. The present study was concentrated on the effect of the coagulation variables upon the coagulation process. It was observed that at the start of the process, the thickness of the solidified layer ε was proportional to the square root of time. Model experiments were performed on gelled solutions of cellulose/NaOH/thiourea/urea/H2O in a coagulation bath to determine the coagulation rate,e / t , and mass transfer rate difference between the solvent and the coagulant, Dk . The influence of coagulant compositions, coagulation time and temperature, and cellulose concentrations on coagulation rate and mass transfer rate difference performed on cellulose samples had been demonstrated by microscopic observations, which was important for understanding and controlling the process of cellulose shaping from NaOH/thiourea/urea/H2O solutions. The data were analyzed by means of the diffusion model based on Fick's law, thereby depicting the mechanism of the coagulation process, which could be described as a two-phase separation, namely a cellulose-rich phase in the coagulated layer and a cellulose-poor phase in uncoagulated layer.
Internally gelled W/O and W/O/W double emulsions
Authors: Iancu Mihaela-Nicoleta , Chevalie Yves , Popa Marcel , Hamaide Thierry 
Published: August 2014

AbstractWater-in-oil emulsions having their aqueous internal phase gelled with starch were prepared and investigated. They were the primary emulsions required for the preparation of double w/o/w emulsions that could encapsulate hydrophilic materials inside the internal aqueous gel. The emulsification could be achieved at high temperature in spite of the high viscosity of the aqueous phase; the internal phase gelled upon cooling to room temperature. The high viscosity of the aqueous phase limited the possible concentration range of starch in the aqueous phase. The presence of starch made the surfactant demand larger for both the emulsification and the stabilization of the w/o emulsions. The larger the starch content, the larger the amount of required surfactant. One reason for the high surfactant demand was the high viscosity of the aqueous phase containing starch. Another cause of high surfactant demand was disclosed and it appeared that predominantly the interactions of the nonionic surfactants with starch retained the former inside the aqueous phase. The immobilized amount of surfactant had to be compensated by a supplementary concentration. Experimental evidence of the interactions between starch and the nonionic surfactants was given by interfacial tension measurements. Lastly, w/o/w double emulsions were prepared using the gelled w/o emulsions and a model hydrophilic molecule (caffeine) was encapsulated inside the internal gelled aqueous phase. The release rate of caffeine from the internally gelled double emulsions was slower than for the non-gelled emulsions, demonstrating the efficiency of the encapsulation and the possible control of the delivery.
Novel way of making high refractive index plastics; metal containing polymers for optical applications
Authors: Tyagi Mukti , Suri Gunjan , Chhabra Pranshu , Seshadri Geetha , Malik Amita , Aggarwal Saroj , Khandal Rakesh Kumar 
Published: August 2014

AbstractPlastics are being preferred in almost all possible applications of materials. Several new applications including optical devices are being developed using plastics replacing conventional materials like inorganic glass etc. For the optical applications, the most important properties of plastics essential for their desired performance include refractive index, Abbe number, optical clarity, etc. The biggest challenge in developing suitable materials for optical applications has always been to meet the criteria of high refractive index along with a high Abbe number. Normally, if the refractive index increases, the Abbe number automatically decreases. The researchers have tried several approaches to deal with this typical challenge without which it is not possible to develop novel optical plastics. Presently the most popularly known optical plastics includes polymers such as polymethacrylates, polyurethanes, polycarbonates, polystyrene and diethylene glycol bis allyl carbonate. The latest material of high refractive index plastics with a refractive index of 1.67 belongs to the polythiourethanes chemistry. Several approaches are being tried world over, to develop materials of high refractive index. One of the approaches being pursued for enhancement of refractive index of existing monomers pertain to the incorporation of metals or metal salts in the matrices. The other commonly tried but difficult to achieve approaches pertain to the preparation of nanoparticles or nanocomposites.
Graft copolymerization of acrylonitrile onto Saccharum cilliari fiber
Authors: Singha A.S. , Shama Anjali , Thakur Vijay Kumar 
Published: August 2014

AbstractThe present paper deals with the graft copolymerization of acrylonitrile (AN) onto Saccharum cilliare fiber in air in the presence of ferrous ammonium sulfate - potassium persulphate (FAS - KPS) as redox initiator. Various reaction parameters such as solvent, time, temperature, pH and concentration of monomer and initiator were optimized in order to get maximum graft yield (69 %). Raw fiber and its graft copolymers with AN were then subjected for evaluation of different properties. Characterization of the graft copolymers was carried out with Scanning electron microscope, Fourier transform infrared spectrophotometer and X-ray diffraction studies (X-RD).
Study of dielectric behavior in PVDF/clay nanocomposites
Authors: Chanmal C.V. , Jog J.P. 
Published: August 2014

AbstractA high dielectric permittivity nanocomposite based on poly(vinylidene fluoride) (PVDF) and organically modified clay is reported. The present work aims to study the effect of clay on dielectric behavior of PVDF. The dielectric permittivity study shows a remarkable enhancement in the permittivity of nanocomposites in the low frequency region. The obtained permittivity values fits quite well to the prediction of dielectric permittivity from Vo-Shi model, which takes contribution of interface to permittivity into account. This enhanced permittivity in nanocomposites is attributed to the presence of interfacial polarization. The interface effect is further studied with cole-cole plot analysis. The dielectric loss study of pristine PVDF shows two relaxations associated with segmental (glass transition relaxation) and crystalline chain relaxation. However in the PVDF/Clay nanocomposites crystalline relaxation peak disappears which is attributed to the formation of the β phase in PVDF/clay nanocomposites.
Surface charges of anionic and cationic polyelectrolytes and their effects on the nucleation and the growth of CaCO3 crystals
Authors: Jada Amane , Verraes Arnaud , Aue Alexandrine , Ducroquetz Céline 
Published: August 2014

AbstractStreaming Induced Potential (SIP) of polystyrene sulfonate, PSS, and poly(ethylenimine), PEI, in the presence of monovalent (NaCl) and divalent (CaCl2) electrolytes, were measured at ambient temperature. The data indicate that screening of polyelectrolyte surface charge, i.e. the reduction of SIP amplitude, is more efficient by divalent CaCl2, as compared to monovalent NaCl electrolytes. The screening of polyelectrolyte surface charge leads to reduction of the mutual repulsion between the polyelectrolyte segments. In the case of CaCl2 electrolyte, since PSS and PEI are, respectively, negatively and positively charged, sequestration of calcium ions by the polyelectrolyte leads to strong reduction of the free calcium ions concentration in the medium in the presence of the PSS when compared to the PEI. Further, the preparation of CaCO3 particles through a precipitation reaction, at room temperature, by using PSS and PEI polyelectrolytes as crystal modifiers were investigated. The final CaCO3 particles are found to result from the aggregation of nanocrystals, and have various shapes and sizes depending on polymer concentration and structure. It comes out that the properties of CaCO3 particles prepared in the presence of the polymer are function of the interaction efficiency between the polymer-repeating units and the calcium ions. Such interaction is found to affect the free calcium ions concentration in the medium.
Silane grafting of polyethylene: effect of molecular structure, physical form, blending, and antioxidants
Authors: Morshedian Jalil , Hoseinpour Pegah Mohammad 
Published: August 2014

AbstractCrosslinking of polyethylene would improve and modify its properties. A preferred method of crosslinking is via its silane grafting, initiated by peroxide. In this study, the grafting reactions of different types of low density (LDPE), linear low density (LLDPE) and high density polyethylene (HDPE) were studied and compared in efficiency, all in a fixed amount of silane (vinyltrimethoxysilane) and peroxide (dicumyl peroxide). Processing for silane grafting was carried out in an internal mixer for 15 minutes at 190 oC, and the silane grafting efficiency was determined through the corresponding peaks in their FTIR spectra. The effect of polymer physical form (powder versus granule) and premixing (the polymer with silane-DCP solution) prior to processing was also determined. In case of LDPE and LLDPE, three types of antioxidants (Irganox 1010, Irganox 1076, and KV10) were incorporated into the reaction mixture to assess their probable interference and effectiveness in grafting reaction. Finally, LDPE was melt blended with ethylene vinyl acetate (EVA) and once again with ethylene propylene diene monomer (EPDM) to investigate their effect on silane grafting efficiency. Amongst different grades of polyethylene, LLDPE had a better efficiency in silane grafting with regard to LDPE and HDPE. Furthermore, the lower molecular weight of polyethylene with narrower molecular weight distribution resulted in the more efficient silane grafting. In case of incorporating antioxidant, Irganox 1010 followed by Irganox 1076 had the best performance for LDPE, however, KV10 turned out to be more suitable for LLDPE. Finally, higher silane grafting efficiency was gained through blending polyethylene with EVA and EPDM.
Poly(amide) oligomers with silarylene and/or germarylene units – synthesis, characterization and thermal studies
Authors: Tagle Luis H. , Terraza Claudio A. , Leiva Angel , Alvarez Patricia 
Published: August 2014

AbstractTen poly(amide) oligomers were prepared from four acid dichlorides and two full-aromatic diamines, the latter containing silicon or germanium in their structure. The polymers, which contain Et/Me, Et/Et and nBu/nBu combinations on heteroatom of the acid dichloride moiety, were characterized by spectroscopic techniques, including 29Si NMR. The yields obtained and the ηιnh values established were low, indicating the low molecular weight nature of the polymers. Thermal stability was also evaluated by TG and DSC techniques. When a methyl group was replaced by a Et, the Tg of the poly(amides) (PAs) was increased in accordance with the gain in the flexibility of the chain. However and in general terms, the PAs with nBu groups show the inverse effect. Probably, the possibility of an effective interaction between these side chains affects negatively the flexibility of the main chain. On the other hand, PAs that contain single silicon in their structure show lower Tg values than the Ge-containing PAs. For the other heteroatom combinations, similar results were obtained. This fact does not agree with the lower size of silicon atom which should increase the molecular rigidity and therefore their Tg values. Probably, the influence of the side groups is decisive in hindering the chain rotation. The thermal degradation temperature (TDT) changed in agreement with the packing factor of the chains which was depending on the size of substitute groups. So, when Et group was replaced by nBu as lateral group, lower TDT were recovered. With respect to the heteroatoms used in the main chain, the TDT values do not show a clear tendency.
Crystallite dimensions - characterization of ethene-/ɑ-olefin Copolymers with various comonomers and comonomer Ccontents measured by small- and wide angle X-ray scattering
Authors: Stadler Florian J. , Takahashi Tatsuhiro , Yonetake Koichiro 
Published: August 2014

AbstractEthene-/ɑ-olefin copolymers having a wide range of comonomer contents and comonomers between 4 and 26 carbon atoms in length were characterized by wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). The data was evaluated with respect to the crystallite size. The half-width of the main crystallite peaks was transformed into the crystallite size s110 and s200 using the Scherrer equation. It was found to decrease with increasing comonomer content. The crystal lamella thickness was determined from the long period and the crystallinity of the samples. The crystal lamella thickness was found to decrease with decreasing crystallinity following a 3rd order polynomial. This means that the introduction of SCBs leads to a decrease of the crystallite size. A higher Mwleads to an increase of the lamella size in comparison to lower molecular samples with the same crystallinity. The lamella thickness is limited by the average distance between two short-chain branches which is dependent on the comonomer content.
Soluble, thermally stable poly(amide-ester)s containing pyridine pendent group
Authors: Mehdipour-Ataei Shahram , Mosslemin Mohammad Hossein , Kholghi Shahram , Mohaghegh S. Mohammad Seyed 
Published: August 2014

AbstractThe nitro group of 4-(p-nitrobenzyl)pyridine was converted to amino group and 4-(p-aminobenzyl)pyridine was prepared by catalytic hydrogenation using hydrazine hydrate/Pd-C systemReaction of 4-(p-aminobenzyl)pyridine with 1,3,5-benzenetricarboxylic acid under appropriate conditions yielded a new diacid containing amide group and pyridine unit. The prepared substances were characterized using FT-IR, H-NMR, and mass spectroscopy and also elemental analysis. Polycondensation reactions of the diacid with different commercially available diols in the presence of benzenesulfonyl chloride afforded new types of poly(amide-ester)s. All the polymers were characterized and their physical and thermal properties were studied. The polymers showed high thermal stability and also enhanced solubility in polar aprotic solvents.
On the determination of the ratios of the propagation rate constants on the basis of the MWD of copolymer chains: A new Monte Carlo algorithm
Authors: Szymanski Ryszard 
Published: August 2014

AbstractPossibility of determination of the relations among homo- and crosspropagation rate constants on the basis of analysis of the detailed distribution of copolymer chain lengths is presented. Importance of application of correct computation algorithms in Monte Carlo modelling of copolymerization is indicated. A new algorithm for Monte Carlo modelling of polymerization processes is proposed.
Influence of the lignin on thermal degradation and melting behaviour of poly(ethylene terephthalate) based composites
Authors: Canetti Maurizio , Bertini Fabio 
Published: August 2014

AbstractPoly(ethylene terephthalate) (PET) has been compounded with lignin (L) by a single-screw extruder. The influence of L presence and its content on the thermal stability of PET has been studied by using thermogravimetric analysis. The experiments carried out in oxidative conditions evidenced the barrier effect of L that interferes to the diffusion of the volatile degradation products to the gas phase and at the same time to the diffusion of the oxygen from the gas phase to the PET matrix. The influence of L on the melting behaviour of PET has been investigated on samples submitted to subsequent annealing steps procedure. X-ray techniques were employed to investigate crystallinity and crystal dimensions of pure PET and PET/L composites. Considering the supermolecular and crystal structure of the annealed samples, their melting behaviour was explained assuming small changes in the melting entropy.
Modelling the yield stress and the Poisson’s ratio of glassy polymers
Authors: D’Amore Alberto , Grassia Luigi , Acierno Domenico 
Published: August 2014

AbstractWe have recently reported that the volumetric as well as the viscoelastic intricacies of mechanically stimulated glasses can be predicted by coupling the structural relaxation kinetics and viscoelastic response [1, 2, 3].Here, it will be shown that our approach can be extended to predict the stressstrain behaviour of glassy polymers as function of temperature, strain rate and aging time. In particular, a linear dependence of yield stress on the logarithmic of the strain rate can be obtained, conforming to the classical Eyring-type behaviour. The Poisson’s ratio evolution was obtained from the volume relaxation behaviour highlighting an unexpected correlation between the yield point and the volumetric behaviour.
Reinforcement of diene elastomers by organically modified layered silicates
Authors: Galimberti Maurizio , Senatore Stanislao , Lostritto Angela , Giannini Luca , Conzatti Lucia , Costa Giovanna , Guerra Gaetano 
Published: August 2014

AbstractNanocomposites were prepared based on diene rubbers and layered clays modified with an alkyl quaternary ammonium cation (organoclay). A diene rubber, either polybutadiene, or synthetic or naturally occurring polyisoprene or styrene-butadiene copolymer, was melt blended with either a preformed organoclay or with a mixture of pristine clay and ammonium cation. Besides isolated lamellae, nanocomposites showed the presence of crystalline organoclays with intercalated organic layers made only by low molecular mass substances, essentially the ammonium cation, and no evidences for the intercalation of polymer chains were observed. Dynamic-mechanical properties of sulphur cured compounds with carbon black as the main filler and a minor amount of organoclay were investigated. The organoclay was found to bring about a reduction of Mooney viscosity, an increase of storage modulus at low temperature as well as an increase of thermoplasticity.
Bioresorbable electrospun nanofibrous scaffolds loaded with bioactive molecules
Authors: Gualandi Chiara , Wilczek Piotr , Focarete Maria Letizia , Pasquinelli Gianandrea , Kawalec Michal , Scandola Mariastella 
Published: August 2014

AbstractElectrospinning technology is used to fabricate sub-micrometric fiber mats made of a random equimolar poly(lactide-co-glycolide) copolymer (PLGA), whose in vitro hydrolytic degradation kinetics is investigated over a period of 49 days in phosphate buffer at 37 °C. The PLGA mats show a decrease of molecular weight (by GPC) from the very beginning of the experiment, whereas a macroscopic weight loss from the samples is appreciated (by gravimetry) only after 20 days of buffer exposure. The molar mass distribution curves remain monomodal during the degradation experiment suggesting that no acid auto-catalyzed hydrolysis, commonly observed in bulk specimens, occurs in sub-micrometric PLGA fibers. PLGA scaffolds containing Endothelial Growth Factor Supplement (ECGS) were also fabricated by electrospinning, from ECGS-containing polymer solutions. Mesenchymal cells derived from human bone marrow mononuclear cells were cultured in the presence of such ECGS-loaded PLGA scaffolds. Flow cytometry and Differential Interference Contrast microscopy were used to characterize the cell cultures over a 7 day period. The results of AnexinV/PI staining and of intranuclear Ki-67 protein expression show, together with concomitant cell morphology modifications, that growth factors released from the scaffolds support the survival, proliferation and growth of the mesenchymal cells. This result demonstrates that ECGS maintains its bioactivity upon release from the electrospun fibers and shows the versatility of the electrospinning technique.
Block copolymers as dispersants and migration inhibitors: incorporation of fluorescent dyes in polyethylene
Authors: Hariri Kamal , Ruch Thomas , Riess Gérard 
Published: August 2014

AbstractThe problem of dye migration in PE which is of importance for coating and packaging applications was examined with fluorescent colorant C.I. Solvent Yellow 43 as a model of fluorescent dye poorly soluble in PE. These types of dyes are soluble in the PE melt, they show however a strong tendency to crystallize on cooling and to migrate on the surface giving rise to the typical blooming effect. It could be demonstrated by different migration tests that on addition of P(EB)-b-PEO or SEBS block copolymers, having one sequence selectively miscible with PE, the other with the dye, prevent to a very large extent the dye migration and thus its surface crystallization (blooming). This improvement is attributed to the formation, in the PE amorphous phase, of PEO and PS microdomains respectively that are able to solubilize selectively the dye. By fluorescence spectroscopy it could be demonstrated that the dye is selectively solubilized in the PEO microdomains of the P(EB)-b-PEO block copolymer, as well for micelles formed in heptane, as for the blends with PE.