bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of butyl acrylate grafted polypropylene fibre and its applications on oil-adsorption in floating water
Authors: Yuan Feng , Wei Jun-fu , Tang En-qi , Zhao Kongyin
Published: August 2014

Polypropylene oil-absorption fibre (PP-g-BA) was prepared by radiationinduced graft polymerization of butyl acrylate (BA) onto polypropylene (PP) using divinylbenzene (DVB) as cross-linking agent. The original and grafted PP fibres were characterized by Fourier transform infrared (FT-IR) spectrometer and Scanning Electron Microscopy (SEM), and the result indicated that butyl acrylate was successfully grafted onto PP fibre. The factors that influenced the grafting degree of PP were discussed, such as the concentration of monomer and crosslinking agent. When the concentration of DVB was 2% and the concentration of BA was 10%, the maximum grafting degree reached 20.53%. The oil absorption properties of PP and PP-g-BA fibre were investigated and the results showed that the maximum adsorption capacity of PP-g-BA reached 19.74 g/g for toluene and 18.8 g/g for kerosene. Simulating absorption in the oil floating on the surface of water showed that the oil could be absorbed quickly and completely in three minutes. PP-g-BA exhibited quicker adsorption rate and higher adsorption capacity than PP fibre did.
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

Nano-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

The 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

Water-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

Plastics 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

The 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

A 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

Streaming 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

Crosslinking 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

Ten 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

Ethene-/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

The 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

Possibility 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

Poly(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

We 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

Nanocomposites 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

Electrospinning 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

The 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.
Modification of porous PVC particles with polyacrylate elastomers using a surfactant-free aqueous dispersion polymerization technique
Authors: Hammer Shir , Tzur Aliza , Cohen Yachin , Narkis Moshe
Published: August 2014

The modification of porous suspension-type polyvinyl chloride (PVC) particles by an in-situ stabilizer-free polymerization/crosslinking of a monomer solution absorbed within the PVC particles is presented. The modifying polymers are polybutyl acrylate (PBA) and polyethylhexyl acrylate (PEHA) crosslinked with ethylene glycol dimethacrylate (EGDMA). The effect of the unique blending procedure on the physical and mechanical properties of PVC has been investigated. The modified PVC characterizations includes polymerization yield, transparency, fracture surface morphology, thermal stability, dynamic mechanical properties, tensile properties, impact resistance and melt rheology. The polymer chains formed are dispersed as a separate phase as observed by scanning electron microscopy (SEM), and two separate glass transitions are observed by dynamic mechanical thermal analysis (DMTA) system, typical of immiscible polymer blends. Mechanical properties of PVC/PEHA blends reveal a substantial increase in impact strength particularly when the blend is crosslinked; however, there is a decrease in the yield stress and elastic modulus. A shift from brittle failure to ductility has been observed in blends of PVC on incorporation of PEHA. SEM studies have been carried out to support these observations.
Non-isothermal degradation kinetics for polycarbonate/ polymethylphenylsilsesquioxane composites
Authors: Wang Jiangbo , Xin Zhong
Published: August 2014

The thermal degradation behaviors of PC/PMPSQ (polymethylphenylsilsesquioxane) systems were investigated by thermogravimetric analysis (TGA) under non-isothermal conditions in nitrogen atmosphere. During non-isothermal degradation, Kissinger and Flynn-Wall-Ozawa methods were used to analyze the thermal degradation process. The results showed that a remarkable decrease in activation energy ( E ) was observed in the early and middle stages of thermal degradation in the presence of PMPSQ, which indicated that the addition of PMPSQ promoted the thermal degradation of PC. Flynn-Wall-Ozawa method further revealed that PMPSQ significantly increased the activation energy of PC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of PC in the final period of thermal degradation process
Microstructures of fiber suspensions in complex geometry
Authors: Ruan Chunlei , Ouyang Jie
Published: August 2014

Evolutions of molecular conformation and fiber orientation in fiber suspensions are investigated by collocated finite volume method on unstructured triangular meshes. FENE-P (Finite Extensible Nonlinear Elastic Dumbbell model with Peterlin’s approximation) model which is microstructure-based is chosen to describe the polymeric matrix and TIF (transversely isotropic fluid) model is used to calculate the fiber contribution in order to realize the coupling of flow and fiber orientation. Microstructures of molecule and fiber are obtained by analyzing the information of molecular conformation tensor and second-order fiber orientation tensor respectively. Two numerical examples are considered, namely, a planar contraction flow and a planar flow past a confined cylinder. Present results are hoping to give more insight into the microscopic details of complex flows and thus be more helpful for industrial application.
Surface and electrical properties of high density polyethylene + carbon black composites near the percolation threshold
Authors: Vigueras-Santiago Enrique , Hernández-López Susana , Brostow Witold , Olea-Mejia Oscar , Lara-Sanjuan Omar
Published: August 2014

We have studied friction, scratch resistance and electrical resistivity in high density polyethylene (HDPE) + carbon black (CB) composites in relation to electric resistivity percolation threshold. Below the threshold, CB addition lowers dynamic friction by providing a smaller surface area of contact of the composites with the pin surface; the effect is stronger at higher loads. Above the percolation concentration, an increase in friction is seen due to formation of CB agglomerates and thus an increase in the area of contact. The recovery depth in scratch testing behaves similarly as dynamic friction and for the same reasons, particularly so at high loads, with a minimum at the percolation threshold. Thus, at the threshold we have simultaneously superior scratch resistance, low dynamic friction and low electric resistivity.
Influence of silica content in sulfonated polysulfone/ phosphotungstic acid hybrid membranes on properties for fuel cell application
Authors: Zhang Jian , Fei Guoping , Liang Yile , Zhang Youwei , Zhao Jiongxin
Published: August 2014

The sulfonated polysulfone (SPSU)/phosphotungstic acid (PWA)/silica (SiO2) hybrid membranes were researched for proton exchange membranes. The influence of silica content on the properties of composite membranes was studied in detail. The study displays that inorganic silica particles have a great influence on membrane properties, such as membrane durability, PWA extraction, proton and methanol transport behavior, thermal stability and water uptake. Interestingly, the hybrid membrane with 2 wt.% silica content showed the best results: low PWA extraction, long membrane life time under oxidative condition, high proton conductivity, and low methanol permeability. However, excessive silica content caused a large aggregation of SiO2 particles, leading to the deterioration of membrane properties.
Synthesis and characterization of organogel from poly(acrylic acid) with cellulose acetate
Authors: Rivas-Orta Valeria , Antonio-Cruz Rocío , Rivera-Armenta José Luis , Mendoza-Martínez Ana , Ramírez-Mesa Roberto
Published: August 2014

In the last decade, the interest in physical organogels has grown rapidly with the discovery and synthesis of a very large number of diverse molecules, which used organic solvents at low concentrations. New organogels based on poly (acrylic acid) (PAA) and cellulose acetate (CA) were prepared as thin films to study properties and swelling behavior. In organogels synthesis different crosslinking agent and initiator concentrations were studied. The swelling for PAA/CA organogels was carried out with acetone at 3 different temperatures (30°, 40° and 50 °C) and pH of 6.5 (pHacetone= 6.5). The higher swelling for PAA/CA organogels was 770% for 25PAA/75CA composition ratio with 3%wt N,N´-methylene-bis acrylamide (MBA) and 1%wt potassium persulphate (KPS) at 30 °C. The films were analyzed by FTIR and the presence of functional groups of each polymer was confirmed without secondary reactions. The DSC analysis indicated two glass transition temperatures (Tg); at 106 °C corresponding to PAA and 86 °C, corresponding to CA, respectively, indicative of phase separation, characteristic of gels. Surface morphology was analyzed by Scanning electron microscopy (SEM) showing smooth surface and small crystal forms.
Preparation and mechanical properties of PCL-based polyurethanes as potential biomaterials for short-term applications
Authors: Sobczak Marcin , Dębek Cezary , Goś Piotr
Published: August 2014

A series of polyurethanes (PURs) were prepared by metal-free method, containing polycaprolactone (PCL) as the soft segment with molecular weights of 1600, 2400 and 2600. PCL was obtained by the ring-opening polymerization of ε- caprolactone in the presence L-alanine and L-phenyloalanine. The structure of synthesized oligoesters and PURs were spectroscopically confirmed. The molecular weights, mechanical and thermal properties of the obtained materials were reported.
Nucleation loci in the ring-opening polymerization of octamethyl- cyclo-tetrasiloxane in Winsor I system with dodecylbenzene sulfonic acid sodium salt and sulfuric acid
Authors: Suzuki Kiyoshi , Andoh Daisuke , Hyodoh Akira , Satoh Shuzaemon , Nomura Mamoru
Published: August 2014

The ring-opening polymerization of octamethylcyclotetrasiloxane (OTS) was carried out in an Winsor I system with dodecylbenzene sulfonic acid, sodium salt (DBSNa) as emulsifier and sulfuric acid as initiator, to clarify the mechanism of the polymerization, especially focusing on the nucleation loci, the rate of generation of nonvolatile molecules and the average diameter of generated polymer droplets. In the system where DBSNa concentration is higher than the critical micellar concentration (CMC), nonvolatile molecules were generated in the aqueous phase and their generation rate became higher with an increase in DBSNa concentration, while nonvolatile molecules were not generated at emulsifier concentrations lower than the CMC. These experimental results support that nucleation did not take place in the true aqueous phase, but originated from the micelles.
Study of polyamide-6 hollow fiber membranes prepared via a thermally induced phase-separation method
Authors: Jiang Zhao-Hui , Xiao Chang-Fa , Hu Xiao-Yu
Published: August 2014

Hollow fiber membranes of polyamide-6(PA6) with porous structure were prepared by a thermally induced phase-separation method. N-Ethyl-o/p-toluene sulfonamide was chosen as diluent. On the basis of scanning electron microscopy (SEM) images, porosity, bubble point pore diameter and pure water flux, the influential factors including polymer concentration, coagulation bath temperature, post-stretching were investigated. The results indicate that with the increasing of PA6 concentration ‘slit-shaped’ pores in inner surfaces and cellular structure in cross-sections disappear, correspondingly, the properties of membranes such as porosity and pure water flux become poor. As the coagulation bath temperature varied from 20 °C to 50°C, the pure water flux of membranes is improved from 136 to 244 L·m-2·h-1. Post-stretching make the ‘interfacial micro-pores’ expand due to ‘stress concentration’ phenomenon, thus changing the structure and improving the properties of membranes. PA6 hollow fiber membranes with rational structure and high performance could be obtained by altering polymer concentration, coagulation bath temperature and post-stretching.
Hydrodegradation of starch incorporated polylactic acid with acrylic acid as interfacial linker
Authors: Xiao Yinghong , Che Jianfei , Bergeret Anne , Mao Chun , Shen Jian
Published: August 2014

Graft modification of polylactic acid (PLA) with acrylic acid (AA) using double initiators was studied. The composition of the graft copolymer (PLA-AA) was characterized with Fourier transform infrared (FTIR) spectroscopy and introduction of AA was demonstrated. Differential scanning calorimetry (DSC) analysis indicated that due to the increasing graft efficacy the modified PLA had better interfacial adhesion with starch compared to neat PLA. Fracture surfaces of starch/PLA and starch/PLA-AA were observed using scanning electron microscope (SEM) and the results also demonstrated the better interfacial adhesion of the latter composite. Graft modification of PLA matrix and introduction of starch played important roles in enhancing the mechanical properties (strength and modulus) while remaining good degradability of the composite.
Synthesis of conductive nanocomposites based on polyaniline/poly(styrene-alt-maleic anhydride)/polystyrene
Authors: Najafi Moghadam P , Nazarzadeh Zareh E
Published: August 2014

Conducting polyaniline (PANI) nano particles doped with HCl was synthesized by a sonochemical method. Polyaniline/poly(styrene-alt-maleic acid)/polystyrene composites with different polyaniline content were developed by solution-dispersion blending method. The influence of poly(styrene-alt-maleic acid) concentration in composite structure was also investigated. The composite dispersed solution in tetrahydrofuran (THF) was cast to fabricate conductive films with evaporation of the solvent. With only a mixing procedure and without any dispersant added, the PANI nanoparticles were well dispersed in the matrix polymer as indicated by scanning electron microscopy (SEM) images. The conductivity of obtained composites was measured with four probe technique. All of obtained composites have conductivity and between them, the maximum electrical conductivity was 2.4 S/cm. The obtained composites were characterized by FT-IR and UV-Vis spectroscopy.
Characterization of chitin and chitosan extracted from shrimp shells by two methods
Authors: Gartner Carmiña , Peláez Carlos Alberto , López Betty Lucy
Published: August 2014

Shrimp shells from Penaeus Vannamei species were hydrolyzed for chitin extraction by a chemical and a papain enzymatic method. Composition of shells was analyzed and their microstructure was characterized before and after hydrolysis by microscopy. Chitin fibers arrangement in the tissue was preserved after chemical extraction, but after papain hydrolysis the tissue presented structural disarrangement indicating that papain reacts indistinctly with peptidic and N-acetyl linkages. Although chemical purification is very effective, by-products are not recoverable. Conversely, papain hydrolysis yields partially purified chitosan but permits aminoacids isolation, which is important in food industry. This method has other advantages such as low cost and easy accessibility of papain. Chitin and chitosan were characterized by thermogravimetric analysis, infrared spectrophotometry and capillary electrophoresis. Degree of N-acetylation (DA) was determined by cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS 13CNMR) or potentiometry and crystallinity was measured by X ray diffraction.
Coalescence during annealing of quiescent immiscible polymer blends
Authors: Dimzoski Bojan , Fortelný Ivan , Šlouf Miroslav , Nevoralová Martina , Michálková Danuše , Mikešová Jana
Published: August 2014

Coalescence during annealing of quiescent immiscible polymer blends, containing polypropylene (PP) matrix and different amount of ethylene-propylene copolymer (EPR) as dispersed phase, was studied. Comparison of experimental results with available coalescence theories revealed that changes in the phase structure after 20 min annealing can be precisely estimated using the approximate theory of coalescence induced by van der Waals forces and considering drainage of the matrix film between spherical droplets. All results evidenced growth of the EPR droplet size with the annealing time and temperature; increase in the content of dispersed phase contributed to higher growth rate of the dispersed phase, more pronounced at the coalescence origin. Anisometry of the EPR droplets and droplet shape relaxation were perceived, both interfering the course of coalescence. Enhanced elasticity of examined blends at low frequencies and positive deviation of the complex viscosity from the linear mixing rules was observed.
Electrospinning technique in the nano-photocatalyst research
Authors: Li Cong-Ju , Xu Guo-Rong
Published: August 2014

Photocatalysts have attracted much scientific interest stemming from their high catalytic efficiency and environmental friendly properties. However, due to the development of nanosicence and nanotechnology, nano-photocatalysts have attracted more and more attention. Generally speaking, nano-photocatalyst indicates photocatalytic materials in nano size, including nanoparticles, nanofibers, nanowires, and so on. Electrospinning, used as a simple method to fabricate nanomaterials, is playing a very important role on nano-photocatalyst research, both on the production of novel nano-photocatalysts and on the study of innovative fabrication methods. The applications of electrospinning on nano-photocatalyst research are reviewed with an emphasis on fabrication of nano-photocatalysts and on the strategies that have been tried to improve nano-photocatalysts performance.
Phase transition behavior of silicone based liquid crystalline polymers
Authors: Jana R. N. , Bhunia H. , Im C.
Published: August 2014

Phase transition behavior of silicone based liquid crystalline (LC) polymers with variable isotropic transition temperatures (Ti), synthesized from poly(methyl hydrosiloxane), 10-undecenoic acid based crosslinking agent and cholesterol based side chain mesogen, was studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. The chemical structure of the mesogenic monomer and the LC polymers were confirmed by Fourier transform infra-red (FT-IR) spectroscopy and 1HNMR spectroscopy. DSC studies showed that the glass transition temperatures (Tg) and Ti of the LC polymers decreased with increasing proportion of mesogenic crosslinking agent at its low proportion and at its higher proportion Ti disappeared completely indicating that the polymeric chains had less chance to orient in the network structure. The results were consistent with the XRD and POM studies.
Quaternary ammonium salt substituted polyhedral oligosilsesquioxanes (POSSes) as structure directing agents in the generation of porous silica materials
Authors: Rózga-Wijas Krystyna , Fortuniak Witold , Chojnowski Julian
Published: August 2014

The sol-gel base catalysed hydrolytic polycondensations of tetramethoxysilane (TMOS) were studied in the presence of quaternary ammonium chloride substituted polyhedral oligosilsesquioxanes (POSSes): octa{3-[(2- hydroxyethyl)dimethylammonio]propyl chloride}octasilsesquioxane or octa[3-(noctyldimethylammonio) propyl chloride]octasilsesquioxane. Small amounts of these POSSes added to the sol-gel system markedly affected the morphology of the silica gel polycondensation products. The morphology was highly dependent on the POSS concentration. Amorphous mesoporous silica gels were obtained showing a high porosity and the surface area up to 615 m2g-1. Most of gels had a fairly large average pore diameters, 4-11 nm and pore volume 0.4-1.3 cm3g-1. TMOS having inserted hexamethyltrisiloxane chain, 1,1,1,7-tetramethoxyhexamethyltetra siloxane, (TMOSD3) in the mixture with TMOS was also used as the monomer in the sol-gel polycondensation; but obtained gels showed a low porosity.
Suzuki polycondensation: a simple way for synthesis of new polyazines containing thiophene and fluorene moieties
Authors: Mihai Iulia , Ivanoiu Maria , Vacareanu (Stafie) Loredana , Grigoras Mircea
Published: August 2014

Two novel polyazines were successfully synthesized via palladiumcatalyzed Suzuki coupling method of N,N'-bis(5-bromothiophene)-2-aldehyd azine with 2,5-thiophenediboronic acid and 9,9-dioctylfluorene-2,7-diboronic acid, respectively. The polymers were characterized by 1H-NMR, FT-IR and UV-VIS spectroscopy. The thermal properties of the polymers were investigated by TGA analysis. The semi-crystalline structure of these compounds was demonstrated by X-ray diffraction study.
Thermal characterization of novel aliphatic polyesters with ether and thioether linkages
Authors: Soccio M. , Lotti N. , Finelli L. , Munari A.
Published: August 2014

Several novel ether or thioether linkage containing aliphatic polyesters and poly(alkylene dicarboxylate)s for comparison were synthesized and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers showed a good thermal stability, even though lower for the ether or thioether linkage-containing polyesters. The decrement of the thermal stability appears to be more relevant in the case of presence of sulphur atoms. At room temperature the samples appeared semicrystalline, except PTTDG and PDEDG, which were viscous oils; the effect of the introduction of ether or thioether group was an increment of the Tg value, a decrement of the melting temperature and a significant decrease of the crystallization rate. The entity of the variations was found to be affected by the kind of group introduced, and the trend observed can be explained on the basis of atom electronegativity and dimensions.
Study on the coagulation process of cellulose nascent fibers with ionic liquid AMIMCl as a solvent during dry-wet spinning
Authors: Song Jun , Cheng Bowen , Jie Xiuji , Liang Yi , Lu Fei , Zhang Feining
Published: August 2014

The coagulation process of nascent fiber of cellulose with ionic liquid 1- allyl-3-methylimidazolium chloride (AMIMCI) as the solvent was studied during drywet spinning. The diffusion rate and the crystallization situation of nascent fiber were tested, its fracture morphology was observed, and the diffusion coefficient D of solvent and the crystallization degree of nascent fiber were calculated according to relevant equations. The diffusion rate and diffusion coefficient of ionic liquid decrease with cellulose concentration increasing in spinning solution and then remain almost the same when the cellulose mass fraction reaches 7%. With the increase of coagulation bath concentration, the diffusion rate and diffusion coefficient of the solvents increase first and then decrease. When the coagulation bath concentration reaches 5%, the diffusion rate and diffusion coefficient of the solvents are at their maximum. With the increase of coagulation bath temperature and the length of air gap, the diffusion rate and diffusion coefficient of ionic liquid increase slightly. The cellulose solution concentration and the spinning air gap have an influence on the crystallization degree of nascent fiber. With the increase of cellulose solution concentration and the spinning air gap, the crystallization degree of the produced nascent fiber increases slightly, but the coagulation bath temperature basically have no influence on the nascent fiber formation.
On the mechanism of conductivity enhancement in PEDOT/PSS film doped with sorbitol
Authors: Li Jiao , Liu Juncheng , Gao Congjie
Published: August 2014

The mechanism of conductivity enhancement in PEDOT/PSS film doped with sorbitol is investigated by X-ray diffraction (XRD), Fourier transform Raman spectroscopy (FT-RM), Atomic force microscopy (AFM), Scanning electron microscopy (SEM). The XRD show that the amorphous state of sorbitol-doped films is not changed and the FT-RM indicate that the main characteristic absorption peak of PEDOT shifts to red. These observations indicate that the increase in conductivity is not attributed to the crystallization behavior of PEDOT, but to the change of the resonant structure of PEDOT chain from a ‘benzoid’ to a ‘quinoid’ structure, which increase the rigidity of PEDOT chain. In addition, there is a conformational conversion of the PEDOT chains from the coil structure to expanded-coil or linear structure. These chains changes are helpful to charge transport through the PEDOT chains and conductivity enhancement of composite films. The increased inter-molecule interactions were investigated by the morphological changes of films as observed in AFM and SEM images, which further confirmed the change of the resonant structure of PEDOT chain.