bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scratch velocity and wear resistance
Authors: Bermúdez M. Dolores , Brostow Witold , Carrión-Vilches Francisco J. , Cervantes Juan J. , Damarla Gowrisankar , Perez Jose M. 
Published: August 2014

AbstractUsing a micro-scratch tester we have determined the influence of scratch velocity on the sliding wear resistance of several thermoplastics: polystyrene (PS), styrene-acrylonitrile, polyamide 6, polyethersulfone and polysulfone. Variable velocities (from 1 to 15 mm/min) were applied under two different load configurations: progressively increasing loads from 0.03 to 30 N and multiple scratching under constant loads from 2.5 to 10 N. Penetration and residual depth were measured along a 5 mm length. In the case of PS the scanning electron microscopy images of the progressive load scratch reveal a transition from shear yielding to crazing at low velocity. In multiple scratching tests the residual depths obtained at 1 mm/min are substantially higher than those at 15 mm/min for all thermoplastics tested. This result is explained by contact heating at higher speeds resulting in increased chain relaxation capability and thus more viscoelastic recovery. Scanning probe microscopy was used in order to observe surface damages. Except for PS, all other materials at all velocities exhibit asymptotic behaviour of the residual depth as a function of the number of tests.
Magnetic colloids: preparation and biomedical applications
Authors: Elaissari Abdelhamid 
Published: August 2014

AbstractIncreasing interest has been focused on the preparation of magnetic latex particles and their use in biomedical diagnostics. All elaborated magnetic colloidal particles or latexes are principally used as a solid support of biomolecules involved in the specific capture of targeted biomolecules such as antigens in immunoassays (i.e., ELISA) and nucleic acid detection in ELOSA. Nowadays, the main objective in biomedical diagnosis is to enhance the sensitivity and to accelerate the procedure by elaborating new magnetic colloidal particles and diagnostic methods. The general problem in this field is related to the limited sensitivity. One possibility to partially solve it is to increase the concentration of captured targets (antigens, nucleic acids, etc.) before the specific detection step. Thus, the use of appropriate magnetic colloidal particles and methods for extraction and concentration of biomolecules is of extreme interest.
Simulation of the shrinkage of dental polymeric composites
Authors: Boguszewski Tomasz , Swieszkowski Wojciech , Lewandowska Malgorzata , Kurzydlowski Krzysztof J. 
Published: August 2014

AbstractThe aim of this study was to investigate the influence of size and shape of ceramic filler in dental composites on polymerization shrinkage. Moreover, the influence of resin shrinkage itself on the whole composite shrinkage was investigated. In 3D linear elastic finite element analyses, the process of shrinkage of dental resin/ceramic composites during polymerization was simulated using the ANSYS software. Composites were modelled with volumetric content of ceramics ranging from 0 up to 45%. Aggregates with different shape and size were analysed. Quantitative estimates have been obtained of the reduction in composite shrinkage with increasing content of ceramic aggregate or decreasing shrinkage of the resin. It has been found that by adjusting aggregate size and resin shrinkage a lower shrinkage of the dental composite may be obtained.
Starch-based multiphase polymer materials
Authors: Kozłowska Anna , Kozłowski Marek , Iwańczuk Andrzej 
Published: August 2014

AbstractBiocomposites prepared by melt blending were investigated. The blends were composed of synthetic and natural macromolecules, including poly(vinyl alcohol), aliphatic-aromatic polyester and thermoplastic starch. Mechanical properties of the composites, their microstructure, melt rheology and thermal characteristics are presented. Influence of water on the properties as well as the degradation rate of the materials has been estimated as a function of their composition. Such materials may find applications for packaging as well as in medicine and biology as polymeric scaffolds, drug delivery systems etc.
Structural study of semi-crystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate) by means of linear correlation and interface distribution functions
Authors: Fatnassi Mohamed , Larbi Fadhel Ben Cheikh , Dubault André , Halary Jean Louis 
Published: August 2014

AbstractIn this article small-angle X-ray scattering (SAXS) is used to characterize the structural parameters of semi-crystalline blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate). Different blend compositions from 100 to 50 wt.-% of PVDF were investigated. The samples were considered to be isotropic. As two-dimensional SAXS patterns with cylindrical symmetry were examined, a single direction in the SAXS pattern plane was chosen to collect and plot absolute intensities versus the scattering vector. Using the one-dimensional (linear) electron density correlation and interface distribution functions obtained, respectively, from the Fourier-transformed Lorentz-corrected experimental scattering intensity and from the interference function, structural parameters such as the minimal value and the most probable value of the long period, the average lamellar thickness, and the volume crystallinity were determined.
Power-law distribution of molecular weights of nonlinear emulsion polymers
Authors: Tobita Hidetaka 
Published: August 2014

AbstractIt is shown that power-law distributed polymers can be synthesized via nonlinear emulsion polymerization. Theoretical simulation results demonstrate that emulsion polymers formed with polymer transfer reactions during interval II approach a power-law distribution as polymerization proceeds. The exponent α of the weight fraction distribution, W(M) ~ M -α, satisfies the simple relationship α = 1/Pb, where Pb is the probability that the chain end is connected to a backbone chain. This relationship can be used to estimate the polymer transfer constant on the basis of the measured molecular weight distribution. The branched polymer structure is significantly different from randomly branched polymers. The expected branching density of the large-polymer limit is equal to that for Pb = 1 of randomly branched polymers, irrespective of the magnitude of Pb in the emulsion polymers. A preliminary investigation shows that power-law distributed polymers can also be synthesized via crosslinking emulsion polymerization.
Synthesis and characterization of novel organosoluble aromatic copolyimides
Authors: Yang Jintian , Huang Wei , Zhou Yongfeng , Yan Deyue , Wang Xiaohang 
Published: August 2014

AbstractA series of novel aromatic copolyimides was synthesized from pyromellitic dianhydride with the commercial diamine 4,4’-methylenebisaniline (MBA) and the diamine 4,4’-methylenebis(2-tert-butylaniline) (MBTBA) specially designed by ourselves. The solubility of the copolyimides in conventional solvents decreased with the mole ratio of MBTBA to MBA. When MBTBA/MBA was larger than 8/2, the copolyimides are soluble in low boiling point solvents (such as chloroform and tetrahydrofuran) and can form a transparent, flexible, tough film by solution casting. When MBTBA/MBA was between 7/3 and 5/5, the copolyimides are only soluble in dipolar aprotic solvents (such as dimethylformamide and N-methyl-2-pyrrolidone) and form films, too. The copolyimide was precipitated in m-cresol in the polymerization process when MBTBA/MBA was lower than 5/5. The number-average molecular weights of the soluble copolyimides measured by gel permeation chromatography were larger than 5.0·104 and the polydispersity index was higher than 1.5. Only one glass transition of these copolyimides was detected at around 350°C. The copolyimides did not show appreciable decomposition up to 400°C under air and 550°C under nitrogen, and their thermal stability increased a little with the introduction of MBA into the polymer chains.
Adsorption of monodisperse polybutadienes on carbon black, 3 Displacement of pre-adsorbed molecules by the same polymer. Conformational and molecular weight effects
Authors: Vuillaume Kathy , Haidar Bassel , Vidal Alain 
Published: August 2014

AbstractDisplacement of pre-adsorbed macromolecules by the same polymer, polybutadiene, of the same or of different molecular weight was studied in solution and in the bulk. The effect of polymer concentration on pre-adsorption and displacement processes was determined. Displacement was investigated by gel permeation chromatography and by determination of the amount of bound polymer before and after displacement. A conformational factor was established as a major driving force - besides molecular weight - in the displacement process. Polymer chains adsorbed in flat conformation had the highest adsorption stability and could not be displaced by any other molecular weight of the same polymer.
Self-organization of poly(N-isopropylacrylamide)-carrying microspheres into two-dimensional colloidal thin films
Authors: Tsuji Sakiko , Kawaguchi Haruma 
Published: August 2014

AbstractA simple method to fabricate colloidal thin films with periodical structures was investigated. In this study, poly(N-isopropylacrylamide) (PNIPAM) microgel and polystyrene particles with PNIPAM chains on the surface (hairy particles) are used as components. Aqueous dispersions of these PNIPAM-carrying particles spontaneously form monolayers as water evaporates. After the medium is completely evaporated, periodical structures remain on the substrate. This paper focuses on the effect of graft chain density of the hairy particles on film formation.
Surface sulfate groups on poly(methyl methacrylate) and poly(vinyl acetate) particles from soap-free emulsion polymerization
Authors: Saiga Tadanobu , Suzuki Atsushi , Kikuchi Kenji , Okaya Takuji 
Published: August 2014

AbstractThe amounts of sulfate groups on the particle surfaces of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) obtained in soap-free emulsion polymerization were determined. Polymerization was carried out at low monomer concentration using ammonium persulfate as an initiator. After the ionexchange procedure, conductometric titration was carried out. Amounts of surface sulfate groups were lower and particle diameter was larger in the PMMA system compared with PVAc. A large and remarkable difference appeared in the ratio of surface sulfate groups to decomposed sulfate radicals, viz. 90% for the PVAc system and 50% for PMMA. The ratios of sulfate groups per polymer molecule on PMMA and PVAc particles (functionality) were calculated. The functionality of the PMMA system was 70% of the theoretical value, while it was close to 100% in the PVAc system. This large difference might arise from the weak reactivity of the sulfate radical with MMA compared with that of VAc, due to the strong electrophilic nature of the radical. A side reaction of the sulfate radical with MMA is assumed. On the basis of these experimental results, the instability of the emulsion polymerization of acrylic monomers using poly(vinyl alcohol) (PVA) as a protective colloid is discussed in terms of the instability of the soap-free particles formed after the consumption of free PVA in water by the grafting reaction.
Gelation of thermoplastic polyurethane/2-butanone solutions
Authors: Florez Sonia , Muñoz María Eugenia , Santamaría Anton 
Published: August 2014

AbstractNew features of thermoplastic polyurethane (PUR)/2-butanone gels are investigated, using dynamic viscoelastic measurements and differential scanning calorimetry. The work is focused on the effect of the hard-segments content on the gelation process. In the case of PUR with the highest hard-segment fraction (30%), soft segments are not able to crystallize on cooling from solution; consequently, gels are not formed. The copolymer with the lowest hard-segment content (12%) gives the shortest gel times. This is attributed to the low solution viscosity of this copolymer, which enhances the crystallization rate. All gels melt at 7°C, giving rise to a viscoelastic solution in a thermoreversible process. The critical gelation concentration is below the critical concentration for polymer chain entanglements.
Thermal Oligomerisation of Cardanol
Authors: Rodrigues Francisco Helder A. , Souza José Roberto R. , França Francisco Célio F. , Ricardo Nágila M. P. S. , Feitosa Judith P. A. 
Published: August 2014

AbstractCardanol was extracted from technical Cashew Nut Shell Liquid (CNSL), a naturally occurring meta-substituted long chain phenol and oligomerized by heating at 140 °C. Products were characterized by rheology, infrared and 1H NMR spectroscopy and thermogravimetric analysis (TGA). Increase in viscosity and the flow activation energy was found with increasing time of heating. The relative absorbance of double bond of the hydrocarbon chain decreased with time of heating and indicated that the oligomerization is taking place through the unsaturation of the side chain. Decrease in internal double bond as well as in vinyl bond, observed by 1H NMR, pointed out to the participation of these two kinds of unsaturation as well as monoene, diene and triene. The oligomerization is a slow process. With 40 h of heating, the average molecular weight increases only by 46%. Great differences were found in TGA curves of cardanol with different times of oligomerization. Thermal stability increases with time of heating. The degree of oligomerization could be determined from relative mass loss of the first event of TG, or from flow activation energy.
Synthesis and Characterization of a Novel Triblock Copolymer Containing Double-hydrophilic Blocks and Poly(fluoroalkyl methacrylate) Block via Oxyanioninitiated Polymerization
Authors: Xu Jie , Ni Peihong , Mao Jiang 
Published: August 2014

AbstractA new triblock copolymer consisted of a double-hydrophilic diblock and a fluorinated block, namely poly(ethylene glycol)-b-poly[2-(dimethyl amino)-ethylmethacrylate]-b-poly(2,2,3,3,4,4,5,5-octafluoropentylmeth acrylate) (MePEG-b-PDMAEMA-b-POFPMA), was synthesized via oxyanioninitiated copolymerization. The hydroxyl group of poly(ethylene glycol) monomethyl ether (MePEG) reacted with potassium methylsulfinyl carbanion (DMSO-K+) and converted into a potassium alcoholate macroinitiator (MePEG-K). It could initiate DMAEMA monomer to yield a hydrophilichydrophilic diblock copolymer. If not quenched, the living chain could be subsequently used to initiate a second fed monomer such as OFPMA to produce a new triblock copolymer MePEG-b-PDMAEMA-b-POFPMA. As a comparison, the analogous triblock copolymers with different lengths of PDMAEMA and identical length of POFPMA were prepared. These copolymers were characterized by the measurements of 1H NMR, 19F NMR, and gel permeation chromatography (GPC). The results indicated that they had relatively low polydispersities (Mw/Mn̅ :1.25 −1.27) . The comparison of the critical aggregation concentration (CAC) of diblock copolymer MePEG-b- PDMAEMA and triblock copolymer MePEG-b-PDMAEMA-b-POFPMA has been investigated by measurements of surface tension and electrical conductivity. It was also found that the lower critical solution temperatures (LCSTs) of the di- and triblock copolymers varied with different factors, including the chemical structure, the length of DMAEMA block, and the concentration of the aqueous solution.
Molecular weight and contraction factors of hyperbranched poly(urea-urethane)s
Authors: Lederer Albena , Elrehim Mona Abd , Schallausky Falko , Voigt Dieter , Voit Brigitte 
Published: August 2014

AbstractElution fractionations of broadly molar mass-distributed, hyperbranched poly(urea-urethane)s with OH- and Ph- end groups were carried out to obtain a number of macromolecular samples possessing different molar masses at the same chemical structure. The characterization of the polymers was performed by SEC, MALLS, 1H-NMR, MALDI-TOF-MS and viscosity measurements. Modifications of the OH-end groups of the polymers were carried out. We observed a strong influence of the end groups on the solution behaviour of the hyperbranched samples. The molecular shape of the hyperbranched polymers in solution was compared to their linear analogue using the Kuhn-Mark-Houwink- Sakurada relationship. The calculated contraction factors between 0,15 and 0,7 depending on the molar masses correspond to a very compact structure of the modified branched polymers at high molar masses.
Dynamic Dilution Effects in Polymeric Networks
Authors: Larsen Anne Ladegaard , Sommer-Larsen Peter , Hassager Ole 
Published: August 2014

AbstractThe relaxation processes occurring in slightly and well-entangled polydimetylsiloxane (PDMS) networks are investigated. Swelling experiments are performed in order to determine the sol fractions. The low-frequency linear rheology of the two types of networks reveal two significant relaxation processes, namely the reptation of linear species within the network and the arm withdrawal process of star arms in the sol fraction and of dangling single-chain ends attached to the network. The relaxation spectra are influenced by the stoichiometry to a large extent due to dynamic dilution effects caused by the change in the amount of dangling arms and solubles with stoichiometry. The star arm relaxation is suppressed by washing out the sol fraction which is seen as a clear example of the dynamic dilution effect arising from the small amount of non-reactive PDMS.
Synthesis and characterization of hyperbranched poly (sulfone-amine) modified β-cyclodextrin
Authors: Chen Liang , He Peng , Jia Zhifeng , Zhu Xinyuan , Yan Deyue 
Published: August 2014

AbstractAn economical strategy to prepare hyperbranched poly(sulfone-amine) modified β-cyclodextrins (HPSA-m-CDs) from natural β-cyclodextrin (β-CD) and other commercially available materials has been reported. The final product has many good properties of hyperbranched poly(sulfone-amine)s (good solubility, low viscosity etc.), while its inclusion ability can also be well kept. It is a feasible approach to prepare functionalized modified cyclodextrin at very low cost, and may have potential applications in the fields of catalysis, drug delivery, food additives, etc.
Fractional isolation and structural characterisation of hemicellulosic polymers from delignified and ultrasonic irradiated sugarcane bagasse
Authors: Ren Jui-Li , Geng Zeng-Chao , Liu Chan-Fu , Xu Feng , Sun Jin-Xia , Sun Run-Cang 
Published: August 2014

AbstractHemicellulose-type polysaccharides were isolated from the delignified and ultrasonic irradiated sugarcane bagasse by a sequential two-step alkaline extraction. It was found that the successive extractions with 15% and 18% KOH for 2 h, 15% and 18% NaOH for 2 h, 8% and 10% KOH for 15 h, and with 8% and 10% NaOH for 15 h resulted in a total dissolution of 89.6%, 92.8%, 94.9%, and 97.3% of the original hemicelluloses, respectively. Sugar analysis revealed that xylose was the predominant sugar composition of all the hemicelluloses, comprising 57.4- 68.6% of the total sugars. Arabinose (12.3-18.4%) and glucose (10.8- 14.6%) appeared as the second and third major sugar constituents. Galactose (3.9-8.7%), uronic acids, mainly 4-O-methyl-glucuronic acid (2.7-5.8%), rhamnose (1.2-2.6%), and mannose (0.2-1.3%) were observed as minor constituents. The structural studies by 13C-NMR spectroscopy showed that L-arabino (4-O-methyl-D-glucurono) xylans were the major constituents of the hemicellulosic polymers. Furthermore, the current results also showed that the four alkali-soluble hemicellulosic fractions, isolated during the first step treatment with relatively lower concentrations of alkalis, were more branched and acidic, and had larger molecular weights (Mw, 23100-34500), but lower thermal stability than the other four alkali-soluble hemicellulosic preparations (Mw, 21700-28700), extracted during the second stage treatment with relatively higher concentrations of alkalis.
Preparation and characterization of sulfone-based polyimide nanofoams grafted with poly(propylene glycol)
Authors: Mehdipour-Ataei Shahram , Saidi Samaneh 
Published: August 2014

AbstractA route to thermally stable polyimide nanofoams was developed. Nanofoams were prepared from graft copolymers consisting of thermally stable and thermally labile blocks as continuous and disperse phase, respectively. The copolymers were synthesized via reaction of sulfone-based diamines with aromatic dianhydrides through the poly (amic acid) precursor, followed by thermal imidization. Foam formation was achieved by thermolysis of thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Polyimide precursors and nanofoams were subjected to a variety of characterization including FT-IR, thermal gravimetric analysis (TGA), dielectric constant, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The nanofoams showed good processability, high thermal stability, and low dielectric constant which are prerequisites for application in electronic industry.
A New Accurate Neural Network Quantitative Structure- Property Relationship for Prediction of θ (Lower Critical Solution Temperature) of Polymer Solutions
Authors: Gharagheizi Farhad 
Published: August 2014

Abstract In this study, a new neural network quantitative structure-property relationship model for prediction of θ (LCST ) of polymer solutions is presented. The parameters of this model are eight molecular descriptors which are calculated only from the chemical structure of polymer and solvent. These eight molecular descriptors were selected from 3328 molecular descriptors of polymer and solvent available in polymer solution by genetic algorithm-based multivariate linear regression (GA-MLR) technique. The obtained neural network model can predict the θ (LCST ) of 169 polymer solutions with mean relative error of 1.67% and squared correlation coefficient of 0.9736.
Preparation, Characterization and Swelling Behaviours of a Novel Multifunctional Superabsorbent Composite Based on Ca-Montmorillonite and Sodium Humate
Authors: Zheng Yian , Wang Aiqin 
Published: August 2014

AbstractIn this work, a novel water-managing superabsorbent composite was prepared by graft copolymerization reaction using acrylic acid (AA) and acrylamide (AM) as the monomers, calcium montmorillonite (Ca-MMT) as an inorganic component and sodium humate (SH) as fertilizer, and well characterized by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effects of the reaction temperature, neutralization degree of AA, amount of crosslinker, initiator, Ca-MMT and SH on water absorbencies were systematically investigated. The water absorbencies of the superabsorbent composite synthesized under optimal conditions with a Ca-MMT content of 20 wt% and an SH content of 30 wt% are 615 g g-1 and 45 g g-1 in distilled water and in 0.9 wt% NaCl solution, respectively. The swelling behaviours of the superabsorbent composite in various cationic salt solutions (NaCl, CaCl2 and FeCl3) were also investigated and it was found that at the same saline concentration (> 0.1 mmol L-1), the effect of three cationic salt solutions on the swelling capability has the following order: NaCl < CaCl2 < FeCl3. Here, it is worthy to point out that the water absorbency and swelling behaviours of the developed composite were improved by introducing simultaneously Ca-MMT and SH into PAA-AM network in comparison with that of incorporated single with Ca-MMT or SH.