bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of two algorithms for calculation of the apparent rate constant in the kinetic modelling of diallyl terephthalate bulk polymerization
Authors: Hace Iztok 
Published: August 2014

AbstractIn the present study a comparison was made of two most frequently used algorithms for calculation of the apparent rate constant in the kinetic modelling of bulk cross-linking diallyl terephthalate (DAT) polymerization with four different peroxide initiators, bis(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, benzoyl peroxide and dicumyl peroxide, in the temperature range from 50 to 150°C and at three different initiator loadings. The first algorithm is the CCS algorithm developed by Chiu, Carratt and Soong and the second is the S algorithm developed by Smoluchowski. Only two kinetic parameters had to be found by fitting a previously proposed kinetic model for bulk DAT polymerization, developed by Hace et al., to measured conversion points. Conversions and other necessary physico-chemical properties used for kinetic modelling were obtained from our previous kinetic studies on DAT polymerization.
High-throughput screening of the chemical composition distribution of random styrene-butyl acrylate copolymers
Authors: Romero Iván García , Pasch Harald 
Published: August 2014

AbstractThe development of high-throughput liquid chromatographic techniques for the analysis of styrene-butyl acrylate (SBA) copolymers is discussed. The analysis time in size-exclusion chromatography (SEC) can be reduced to about 3 min per sample when high-throughput SEC columns and high flow rates are used. In gradient HPLC, small columns with improved separation efficiencies can be applied. The time requirements can be decreased to less than 2 min per sample. Using the high-throughput HPLC technique, the chemical composition distribution of high-conversion SBA copolymers can be analyzed in a fast and efficient way. The calibration of HPLC separation is conducted by coupling the HPLC system with FTIR through the LC-transform interface. A comparison of the chemical compositions of the copolymers obtained by 1H NMR, off-line FTIR and coupled HPLCFTIR verifies the accuracy of the high-throughput copolymer analysis approach.
Influence of adding poly(vinyl alcohol) fibres to poly(methyl methacrylate) matrix on the fracture behaviour of fibrereinforced composites
Authors: Pavelka Vladimir , Jancar Josef , Nezbedova Eva 
Published: August 2014

AbstractThis paper reports on the relationship between structure and mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with randomly oriented short poly(vinyl alcohol) (PVA) fibres. Special focus was on the effect of fibre content on the impact resistance of PMMA/PVA composites. Instrumented Charpy impact tests were carried out to characterize the impact resistance of PMMA/PVA composites. Linear elastics fracture mechanics was used to determine the dynamic critical strain energy release rate (GId) and the critical stress intensity factor (KId). Fracture surfaces were observed using scanning electron microscopy (SEM). Dynamic mechanical analysis was carried out to describe the viscoelastic response of the material. Finally, the behaviour of PMMA/PVA composites was interpreted using current short-fibre composite models. It was shown that a small amount of added PVA fibres (0.42 - 1.68 vol.-%) led to an increase of elastic modulus and yield stress under impact conditions. GId was also slightly increased, but KId remained unchanged. Good agreement was found between SEM observations and fracture toughness measured under impact loading.
Three-dimensional numerical simulation of viscoelastic flow through an abrupt contraction geometry
Authors: Kwon Young Il , Seo Dongjin , Youn Jae Ryoun 
Published: August 2014

AbstractA numerical scheme for simulating three-dimensional viscoelastic flow was developed. The three-dimensional finite volume method (FVM) based on a non-staggered grid and the semi-implicit method for pressure-linked equations (SIMPLE) were adopted to solve the continuity and momentum equations. As we used a non-staggered grid, the momentum interpolation method (MIM) was employed to avoid checkerboard type pressure fields. Viscoelastic properties of the fluid were described by the Phan-Thien and Tanner (PTT) model, which was treated by the compressive interface capturing scheme for arbitrary meshes (CICSAM). The elastic viscous split stress scheme (EVSS) was used to decouple the velocity and the stress fields. Algebraic equations obtained by the above schemes were handled by an iterative solver and a multi-grid method was applied to accelerate convergence. In order to verify the scheme developed in this study, Newtonian flow in a rectangular duct was studied and the resulting velocity fields were compared with the analytical flow fields. Then viscoelastic flow in 4:1 contraction geometry, one of the most frequently used benchmarking problems, was predicted by applying the fully three-dimensional finite volume method.
Structure and thermodynamic modelling of Pluronic L64 solutions
Authors: Ghaouar Naoufel , Aschi Adel , Jebari Mohamed Mondher , Gharbi Abedelhafidh 
Published: August 2014

AbstractThe aim of the present work is to model structure and thermodynamic properties of Pluronic L64 solutions (triblock copolymer with hydrophilic ends and a hydrophobic middle). We first determined the micelle size by dynamic light scattering at various temperatures. This helps to understand the particle formation mechanism in solution and the interparticle interactions by following the virial coefficient as well as its temperature dependence. Two semi-empirical intermolecular potentials were tested to predict sample properties. First, we used a pure Lennard- Jones pair potential and then we introduced the Lu and Marlow (LM) contribution in its repulsive part. All quantities of interest were computed using the integral equation scheme with hybridized mean spherical approximation. We found that the LM contribution corrects structure and thermodynamic properties of the system by taking into account the effect of particle size.
COPOINT – a simple computer program to determine copolymerization parameters by numerical integration
Authors: Beginn Uwe 
Published: August 2014

AbstractA computer program is introduced that evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data as obtained from polymerization experiments with finite monomer conversion. The program numerically integrates a given copolymerization equation in its differential form and can be applied to a broad variety of functions. Copolymerization parameters are obtained by minimizing the sum of square differences between measured and calculated polymer compositions with respect to the copolymerization parameters. Errors of the fitted parameters are estimated from the statistical error of the sum of square differences, as well as from a quadratic approximation of this sum in the vicinity of the optimized values of the copolymerization parameters.
Surface functionalization by smart binary polymer brushes to tune physico-chemical characteristics at biointerfaces
Authors: Uhlmann Petra , Houbenov Nikolay , Minko Sergiy , Stamm Manfred 
Published: August 2014

AbstractPolymer brushes consist of an assembly of polymer chains that are attached by one end to the surface with sufficient grafting density. Binary brushes constituted from two incompatible polymers can be used in the form of ultrathin polymeric layers as a versatile tool for surface engineering to tune physicochemical surface characteristics as wettability, surface charge, chemical composition or morphology, and furthermore to create responsive surface properties. It is also possible to fix surface structures obtained in this way by (photo)crosslinking of the layers. Mixed brushes of oppositely charged polyelectrolytes are representing a special case of responding surfaces, which are sensitive to changes of the pH in aqueous environment. It is shown that structural changes occur in the plateau region of the adsorption isotherm of a model protein and that changes of the pH also cause changes in the structure of the adsorbed protein layer.
Bis(vinylcyclopropane) and bis(methacrylate) monomers with cholesteryl group for dental composites
Authors: Choi SooWhan , Hessamian Anahita , Tabatabai Monir , Fischer Urs Karl , Moszner Norbert , Ritter Helmut 
Published: August 2014

AbstractNovel bis(vinylcyclopropane)-based monomers with cholesteryl group and high molecular weight were prepared. The phase behaviour of the synthesized monomers was investigated. The obtained macromonomers showed a polymerisation shrinkage that was significantly lower compared to dimethacrylates used in dental composites.
Synthesis and characterization of 4- and 6-arm star-shaped poly(ε-caprolactone)s
Authors: Meier Michael A. R. , Schubert Ulrich S. 
Published: August 2014

AbstractStar-shaped poly(ε-caprolactone) (PCL) polymers were synthesized and fully characterized by gel permeation chromatography, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) as well as 1H NMR spectroscopy. First a series of four-armed PCLs with different molecular weights was prepared and analyzed with the mentioned analytical techniques revealing that the applied ring-opening polymerization was controlled and defined star-shaped polymers could be synthesized. Subsequently, also the synthesis of six-armed PCL polymers was investigated with the conclusion that also these starshaped polymers could be prepared in a controlled fashion.
Characterisation of ‘wet’ polymer surfaces for tissue engineering applications: Are flat surfaces a suitable model for complex structures?
Authors: Safinia Laleh , Blaker Jonny J. , Maquet Véronique , Boccaccini Aldo R. , Mantalaris Athanassios , Bismarck Alexander 
Published: August 2014

AbstractTissue engineering scaffolds are 3D constructs that simulate the growth environment in vivo. The present work aims to address the question of whether thin films, i.e., flat surfaces, are a suitable model for more complex 3D structures? With this in mind a complete study of the morphology and surface chemistry of poly(D,Llactide) (PDLLA) substrates, fabricated into two different structures, is presented. The polymer structures studied include a 3D, porous, foam-like scaffold prepared by the thermally induced phase separation (TIPS) method and flat polymer thin films made by solvent casting. Based on the maximum bubble point test, a new method to assess the wettability of wet pore wall surfaces inside highly porous 3D structures was developed and tested. The maximum pore diameter determined using the maximum bubble point test for the total wetting liquids was confirmed through image analysis of scanning electron micrographs. The method allows the determination of the contact angle between the wet pore wall and a contacting liquid. The captive bubble method was employed to characterise the wettability of flat polymer films in contact with water. Both structures were further characterised using zeta- (ζ-) potential measurements to assess the surface chemistry of the polymer. The results demonstrate that PDLLA contains acidic functional groups and is hydrophobic. In order to evaluate the sensitivity of the test methods, the polymer surfaces were modified by protein adsorption using fibronectin and collagen. ζ-Potential and wettability measurements show that proteins indeed adsorb on virgin PDLLA surfaces. Protein adsorption causes the wettability of the PDLLA for water to improve. Our results strongly indicate that flat surfaces are not a suitable model for surfaces in complex 3D structures such as highly porous tissue engineering scaffolds. Such scaffolds must be characterised as a 3D system.
Preparation and release behavior of pH and ionic sensitive chitosan/poly(vinylpyrrolidone) semi-IPN beads for coenzyme A
Authors: Guo Baolin , Yuan Jinfang , Gao Qingyu 
Published: August 2014

AbstractA series of pH- and ionic sensitive semi-interpenetrating polymer network (semi-IPN) beads of chitosan (CS) and poly(vinyl pyrrolidone) (PVP) were prepared using glutaraldehyde as crosslinking agent and characterized for the release of coenzyme A (Co A). The swelling behavior of the semi-IPN beads and the influential factors, such as the component ratio of CS and PVP, the loaded amount of Co A, the pH and ionic strength of the release medium on Co A release were studied. The results showed that within 48 h the cumulative release rate of Co A decreased with Co A loading content, ionic strength increase or crosslinking time increase; when the weight ratios of CS to PVP in the drug-loaded beads were 100:0, 80:20, 60:40, 50:50, 40:60 and 20:80, the cumulative release rates of Co A at pH 2.1 solution were 95.2, 72.1, 73.2, 74.2, 86.5 and 80.1%, respectively, and they were 22.7, 30.1, 28.0, 33.1, 38.4 and 35.2% at pH 7.4 solution, respectively. All the results indicated that the CS/PVP semi-IPN beads were suitable for drug delivery systems.
Characterization of polydimethylsiloxane rubber upon photochemical, thermal, salt-fog ageings and exposure to acid vapours
Authors: Delor-Jestin F. , Tomer N. S. , Singh R.P. , Lacoste J. 
Published: August 2014

AbstractThe changes in the chemical structure and the physical properties of a filled crosslinked polydimethylsiloxane rubber were monitored as a function of various ageing factors. The variables included photochemical, thermal, salt-fog ageings and exposure to acid vapours. Unaged and aged samples were studied by IR spectroscopy, hardness measurements, Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) coupled with IR spectroscopy. No significant oxidation was detected after all ageings, except for nitric acid treatment. The presence of aluminium trihydrate was clearly identified as responsible for the observed chemical changes. Then an important vulnerability of this filled silicone rubber towards the cross-linking reactions provoked by usual ageings was also detected. The DSC-thermoporosimetry measurements of the mesh size distribution gave a comparison of cross-linking densities for each ageing. The complementary analysis with TGAIR allowed us to differenciate the thermal stability of the formulation after various ageings and to acquire new knowledge about thermal decomposition.
Polyketone Nanocomposites by Palladium-Catalyzed Ethylene-Carbon Monoxide-(Propene) Co(Ter)polymerization Inside an Unmodified Layered Silicate
Authors: Miller Hamish A. , Moneti Simonetta , Vizza Francesco , Passaglia Elisa , Bianchini Claudio , Bronco Simona , Ceriegi Silvia , Sulcis Roberta , Frediani Marco , Ciardelli Francesco , Costa Giovanna 
Published: August 2014

AbstractComposites from Na-montmorillonite with a content in inorganic material ranging from 3 to 98 wt % were prepared in situ either by copolymerization of ethylene and CO or by terpolymerization of ethylene, propene and CO using a palladium(II) catalyst modified with 1,3-bis(diphenylphosphino)propane. This catalytic system is active in polar media and allowed to produce nanocomposites starting from unmodified Na-montmorillonite in water-methanol solutions. The morphological analysis, performed on samples with less than 40 wt % silicate by XRD and TEM, showed the formation of either intercalated or exfoliated (nanocomposite) structures, depending on the initial amount of the layered silicate in the reactor as well as the presence of propene as comonomer. Improved thermal stability of the hybrid materials, as compared to the corresponding organic polymers, was shown by TGA. A preliminary study of the blending of some polyketone nanocomposites with polyamide (nylon-6) was carried out by melt mixing at high temperature in a Brabender mixer.
Synthesis of cationic flocculants based on acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride co polymers by semicontinuous inverse microemulsion co polymerization. Part I: Criteria for selection of comonomer formulation
Authors: Ochoa G. José R. , Río Francisca , Sasia Pedro M. , Katime Issa A. , Escudero Francisco Javier , Díaz de Apodaca Elena , Mestre Javier Nieto 
Published: August 2014

AbstractThe influence of surfactant blend composition, organic solvent (oil) structure and cationic charge density (CCD) on stability of comonomer inverse microemulsions of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride has been studied in order to obtain criteria for selecting comonomer inverse microemulsions before copolymerization resulting in copolymer inverse microemulsion useful as flocculants. Results show that optimum HLB can be explained by cohesive energy ratio theory and it increases with CCD; the higher the hydrophobic chain length of surfactants in surfactant blend, the lower the minimum surfactant blend concentrations (SBCm) needed to obtain stable inverse microemulsions; and linear organic solvents allow a decrease of the SBCm required for stabilizing comonomer inverse microemulsions.
Removal of Pentachlorophenol from Water Using Novel Smart Hydrogel Microspheres
Authors: Szczubiałka Krzysztof , Karewicz Anna , Moczek Łukasz , Zomerska Karolina , Nowakowska Maria 
Published: August 2014

AbstractThe thermoresponsive hydrogel microspheres were obtained by copolymerization of N-isopropylacrylamide (NIPAM) and 2-hydroxyethyl methacrylate (HEMA) crosslinked with N,N’-methylenebisacrylamide (BIS). The hydrogel was then functionalized using 1-naphthyl glycidyl ether (NGE) to attach naphthyl chromophores, which absorb UV light and act as photosensitizers. The ability of the functionalized microspheres to photosensitize dechlorination reactions was confirmed using pentachlorophenol (PCP) as a model compound.
Synthesis and characterization of glycosylated nano particles
Authors: Lepoittevin Bénédicte , Masson Sébastien , Huc Vincent , Haut Christian , Roger Philippe 
Published: August 2014

AbstractFunctionalized polymer nanoparticles have been synthesized by emulsifier-free emulsion polymerization of styrene with amino-functionalized monomers. Two monomers were used: the well-known 2- aminoethylmethacrylate and a new monomer with a styrenic polymerizable function, 4-(2-aminoethylthio)methylstyrene. The latexes were characterized by gravimetry, dynamic light scattering and colorimetric titration in order to obtain the styrene conversion, the hydrodynamic diameter, the particle size distribution and the concentration of surface amino groups, respectively. Then, glycosydic molecules such as maltose, lactose, maltotriose and galactopyranosylethanal were covalently grafted to the nanoparticles by amidation or reductive amination.
Impact Modification of Polyoxymethylene (POM)
Authors: Uthaman Nalini , Majeed Abdul ,   Pandurangan
Published: August 2014

AbstractPolyoxymethylene (POM) was blended with various weight percentages of ethylene propylene diene terpolymer (EPDM) and ethylene vinyl acetate copolymer (EVA) separately in a twin screw extruder under optimum conditions. The mechanical properties of the blends such as tensile strength, impact strength and % elongation were measured. Increasing content of EPDM and EVA up to 7.5% increases the impact strength of POM. Addition of elastomer beyond 7.5% decreases the impact strength due to the poor adhesion between plastic and elastomer phase. POM/EPDM blends compatibilised with EVA showed improved impact strength. The present study reveals that the impact strength of POM can be improved by blending with EPDM and EVA. The incorporation of EVA as compatibiliser into POM/EPDM causes significant improvement in impact strength. Scanning electron microscopy (SEM) reveals enhanced adhesion of POM and EPDM in the presence of EVA up to the extent 5 parts per hundred of resin (phr) resulting in improved dispersion of the elastomer in the plastic matrix.
Studies on the Odd-Even Effect of Methylene Spacers in Bismaleimides
Authors: Feng J. L. , Yue C. Y. , Chian K. S. 
Published: August 2014

AbstractThe synthesis of a series of bismaleimides based on diamines containing flexible units of variable length is presented. These structures were characterized by FTIR and NMR. The changes in spectra are dominated by the CH2 stretching and deformation vibrational bands. The wavenumber of methylene provides a sensitive measure for the chain packing geometry. An attempt has been made to explain the odd-even effects at the molecular level on the basis of the article results. DSC was used to monitor the thermal properties of the samples. The melting points of the bismaleamic acids and bismaleimides are affected by odd-even effect. The reactivity of maleimide group was analyzed. Positions of signals in FTIR and NMR spectra show that BMI should be more stable as the chain length increase.
Synthesis and evaluation of pH-sensitive glycopolymers for oral drug delivery systems
Authors: Mahkam Mehrdad , Mohammadi Reihaneh , Ranaei Siadat Seyed Omid , Ranaei-siadat Seyed Ehsan 
Published: August 2014

AbstractSucrose esters (SE) are surfactants with potential pharmaceutical applications because of their low toxicity, biocompatibility, and excellent biodegradability. Biodegradable and biocompatible copolymeric hydrogels based on glucose-6-acrylate-1, 2, 3, 4-tetraacetate (GATA) and methacrylic acid (MAA) were designed and synthesized. Because of the growing importance of sugar-based hydrogels as drug delivery systems, these new pH-responsive glucose-containing copolymeric hydrogels were investigated for oral drug delivery. The GATA monomer was synthesized and characterized. The copolymeric hydrogel was synthesized by free-radical polymerization. Azobisisobutyronitrile (AIBN) was the free-radical initiator employed and Cubane-1, 4-dicarboxylic acid (CDA) linked to two 2-hydroxyethyl methacrylate (HEMA) group was the crosslinking agent (CA) used for hydrogel preparations. The hydrogels were characterized by differential scanning calorimetry and FT-IR. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). A model drug, olsalazine [3, 3-َazobis (6-hydroxy benzoic acid)] (OSZ) an azo derivative of 5-aminosalicylic acid (5-ASA), was entrapped in these gels and the in vitro release profiles were established separately in both enzyme-free SGF and SIF. The drug release was found to be faster in SIF. The drug-release profiles indicated that amount of drug release depends on their degree of swelling and crosslinking.
Synthesis and Characterization of the Bismaleimides Containing Aliphatic-ether Chain for Microelectronics Application
Authors: Feng J. L. , Yue C. Y. , Chian K. S. 
Published: August 2014

AbstractThis project aims to develop and characterize a series of bismaleimide (BMI) polymers based on maleic anhydride and aliphatic-ether diamines. The effects of varying the chain length of aliphatic-ether diamines on the resultant bismaleimide systems were evaluated so that their suitability for microelectronics applications could be evaluated. The synthetic reaction and properties of the bismaleimide materials were investigated using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermo- Gravimetric Analysis (TGA), Dielectric Thermal Analysis (DEA) and rheometry. Results showed that thermal, dielectric and rheological properties were all affected by the main chain length of BMI. The magnitude of the dielectric constant at 100 kHz increases with the increasing chain length. The curing peak temperature, curing heat and degradation temperature of BMI, all decrease with the increasing chain length.