bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(methyl methacrylate)-block-polystyrene and polystyrene-block-poly(n-butyl acrylate) as compatibilizers in PMMA/PnBA blends
Authors: Stenert Michael , Döring Andreas , Bandermann Friedhelm 
Published: August 2014

Abstract The influence of the addition of poly(methyl methacrylate)-blockpolystyrene (PMMA-b-PS) and PS-b-poly(n-butyl acrylate) (PS-b-PnBA) diblock copolymers on the structure and the mechanical properties of PMMA/PnBA polymer blends was investigated. In binary polymer blends of PMMA and PS, and PS and PnBA, and in the ternary system the corresponding diblock copolymers caused a significantly higher distribution of the dispersed phase and an appreciable narrowing of the particle size distribution as shown by scanning force microscopy using the pulsed force mode technique. Transmission electron microscopy images proved that in the ternary system the two diblock copolymers formed no own separate phase but are arranged as a ring layer at the interface between the two homopolymers PMMA and PnBA. Charpy tests demonstrated that the impact strength of the ternary blends is increased by the two diblock copolymers even at low amounts of the latter. The influence on mechanical properties like Young’s modulus, yield stress, and tensile strength at break was less marked as strainstress measurements showed. The major effect seems to be exerted on the elongation at break.
Nafion-layered silicate nanocomposite membrane for fuel cell application
Authors: Thomassin Jean-Michel , Pagnoulle Christophe , Bizzari Didier , Caldarella Giuseppe , Germain Albert , Jérôme Robert 
Published: August 2014

Abstract Direct methanol fuel cells (DMFCs) using a proton exchange membrane as electrolyte is an attractive option for electricity generation. The most widely used membrane in the DMFC system is based on a perfluorinated polymer bearing sulfonic acid functions like Nafion ®. The latter combines chemical, mechanical and thermal stability and high protonic conductivity but shows elevated methanol permeability. We propose the preparation of a novel type of hybrid membranes to tentatively solve this problem. This innovative material results from the homogeneous dispersion of a nano-scaled inorganic filler within Nafion. The filler consists of stacks of negatively charged alumino-silicate layers (Cloisite), with a positive counter-ion in the interlamellar space. The purpose of the addition of this filler is to decrease methanol diffusion through the polymer membrane without decreasing too much the ionic conductivity.
Plasticizing of isotactic polypropylene upon addition of hydrocarbon oils
Authors: Nitta Koh-hei , Ando Hidetaka , Asami Takuo 
Published: August 2014

Abstract The effect of the addition of hydrocarbon oil on the mechanical behaviour of isotactic polypropylenes (iPPs) was examined. It was found that the oil molecules are completely dissolved in the amorphous region of iPP so that the blending lowers the glass transition temperature, Tg, of iPP. As a result, Young’s modulus of iPP/oil blends is dominated by the difference between the measurement temperature and Tg (ΔTg = T - Tg), independent of the oil content. The elongation at break is proportional to ΔTg, while the strength at break increases linearly with increasing tie-molecule fraction (which increases with decreasing oil content), being independent of ΔTg.
Kinetic considerations on the mechanical behaviour of polypropylene + wood flour and polypropylene + sisal fibre blends
Authors: Albano Carmen , Poleo Rebeca , Reyes Jacobo , Ichazo Miren , González Jeanette , Brito María 
Published: August 2014

Abstract This work is aimed at analyzing by means of simple mathematical models the effect of different integral doses of γ-irradiation on the mechanical properties and concentration of radicals of the blends of polypropylene (PP) + wood flour and PP + sisal fibre. The analysis of the results permits inferring that the kinetic behaviour of the mechanical properties and the concentration of radicals at low integral doses (≤ 10 KGy) are indicative of a complex degradation process, implying the possibility of cross-linking and chain scission reactions both in the polymer as well as in the filler. Consequently, it can be concluded that cross-linking reactions are predominant. The behaviour observed at higher irradiation doses means that both reactions (cross-linking and chain scission) occur, the breaking reactions being the prevailing ones. This study of the kinetic analysis of the tensile properties is based on the behaviour detected for the melt-flow index.
Room temperature Monte Carlo study of the mechanical properties of thermoplastic polymers
Authors: Ospina Silvio A. , Hess Michael , López Betty L. 
Published: August 2014

Abstract The effect of the tensile test rate upon the mechanical properties of semicrystalline high-density polyethylene (HDPE) is studied by the Monte Carlo method. A two-dimensional lattice model is used, which considers first and second neighbour’s interactions between CH2-CH2 groups. Metropolis dynamics is implemented as energy minimization tool. Results reveal the existence of two distinguishable regions in the stress-strain curves. One of them is characterized by an elastic and linear behaviour below 0.27% of deformation where the elastic modulus is practically insensitive to the number of Monte Carlo steps, whereas at higher deformation the system exhibits a non-linear behaviour ascribed to the viscoelastic character of the material endorsed by a clear dependence of the relaxation modulus as a function of the strain rate. The relaxation behaviour of HDPE obtained in our simulation shows an exponential decrease of the stress as time increases, which agrees with experimental data.
Investigation of the effects of the types of food waste utilized as carbon source on the molecular weight distributions and thermal properties of polyhydroxybutyrate produced by two strains of microorganisms
Authors: A. L. Wong Phoeby , Cheung Man Ken , Lo Wai-Hung , Chua Hong , Yu Peter Hoi Fu 
Published: August 2014

Abstract The average molecular weight and molecular weight distribution of polyhydroxybutyrate can be affected by different bacterial strains, different cultivation time and also different carbon sources. Food waste was proven to have a high potential in the induction of biosynthesis of polyhydroxybutyrate with different production yields and physical properties. A specific culture of Alcaligenes latus DSM 1124 and Staphylococcus epidermidis, which was isolated from sesame oil, were selected to ferment several types of food wastes as nutrients, including malt waste, soy waste, confectionery waste, milk waste, vinegar waste and sesame oil, into polyhydroxybutyrate in this study. Average molecular weight and molecular weight distribution of polyhydroxybutyrate were measured by gel permeation chromatography. By comparing the results with those obtained using sucrose as a carbon source, the average molecular weight of polyhydroxybutyrate produced from food wastes was increased for Alcaligenes latus; however, it was decreased for S. epidermidis. Thermal analyses of the biopolymer produced by S. epidermidis indicated that the melting point of the polymer produced from sesame oil as carbon source was 188°C, the highest temperature among those polymers produced by using ice cream, malt, and soya wastes.
Silane pre-treatment of calcium carbonate nanofillers for polyurethane composites
Authors: Lučić Blagojević Sanja , Kovačević Vera , Leskovac Mirela , Vrsaljko Domagoj , Volovšek Vesna , Nover Christoph 
Published: August 2014

Abstract In this work we have investigated the effects of CaCO3 nanofiller pretreatment on the properties of polyurethane (PU) composites prepared by a mixing procedure. The aim was to enhance interactions at the matrix/filler interface and to improve the distribution of the filler in the polyurethane matrix. CaCO3 nanofiller was treated with two different functional trialkoxysilanes, viz. γ-aminopropyltriethoxysilane (AMPTES) and γ-glycidoxypropyltrimethoxysilane (GPTMS). Fourier transform IR spectroscopy of the pre-treated CaCO3 surface indicates that AMPTES formed a high-molecular-weight ladder-type structure on the CaCO3 surface, while GPTMS was adsorbed in the form of a lower-molecular-weight oligomeric structure. Increased ultimate tensile strength and elongation were obtained for PU + CaCO3 nanocomposites with silane pre-treated filler. This can be explained as the consequence of better stress transfer through the composite, observed on scanning electron micrographs, due to an improved adhesion between PU matrix and silane-treated fillers. The reinforcement effect is more pronounced for PU composites with aminosilane-treated CaCO3 filler in comparison to filler treated with glycidoxysilane.
N-Alkylacrylamide copolymers with (meth)acrylamide derivatives of cholic acid: Solution properties and aggregation
Authors: Avoce Damien , Baille Wilms E. , Zhu X. X. 
Published: August 2014

Abstract Solution properties of a series of thermosensitive copolymers based on acrylamide and methacrylamide derivatives of cholic acid and N-alkylacrylamides such as N,N-diethylacrylamide, N-ethylacrylamide, and N-isopropylacrylamide have been studied by various techniques including fluorescence and turbidimetry. These copolymers contained 1 - 5 mol-% of the (meth)acrylamide derivatives of cholic acid as determined by NMR spectroscopy. A two-stage aggregation process was observed for the copolymers of N-isopropylacrylamide when the number of cholic acid residues was sufficiently high. The presence of the copolymers lowered the critical micellar concentration of sodium dodecyl sulfate but had little effect on the micellization of sodium cholate. The critical micellar concentration of these copolymers decreased with increasing content of cholic acid residues in the polymers.
On the durability of low-density polyethylene nanocomposites
Authors: Pandey Jitendra K. , Singh Raj Pal 
Published: August 2014

Abstract Low-density polyethylene (PE) containing nano-particulate clay was prepared after functionalization with maleic anhydride (MA) by reactive grafting in the presence of peroxide followed by blending of maleated PE with neat polymer in different concentrations. Four classes of composites were obtained: (i) exfoliated, (ii) intercalated, (iii) microcomposites, and (iv) intermediate of intercalated and microcomposites, as evidenced by wide-angle X-ray diffraction. All samples were kept for artificial UV irradiation (λ ≥ 290 nm) and for composting to study their photo- and bio-durability. Fourier-transform IR spectroscopy (FT-IR) and scanning electron microscopy were used to monitor the functional group and morphological changes, respectively, whereas biodurability was evaluated by measuring the weight loss. MA functionalization and nature of composites have detrimental effects on the overall durability of composites. Nanocomposites showed higher resistance than microcomposites during initial weathering and composting with a long induction period. The stability of nanocomposites decreases with time and overall durability was worse than of pristine polymer in both environments. It was concluded that the initial protection is due to the filler-generated long diffusion path, which decreases the oxygen diffusion through the matrix. The bio-durability of composites decreased with oxo-degradation. Biodegradation of PE nanocomposites during composting follows the mechanism described by Albertsson et al. as evidenced by FT-IR spectroscopy.
Magnetic hydrogel beads based on chitosan
Authors: Paneva Dilyana , Stoilova Olya , Manolova Nevena , Rashkov Iliya 
Published: August 2014

Abstract A novel effective route for incorporating magnetic material in chitosan beads by capillary extrusion is proposed. Magnetic material (Fe3O4) with particle size 2 μm and 10 nm was used. The weight ratio chitosan : Fe3O4 was varied in the range from 4:1 to 1:1. The obtained magnetic beads were modified by physical crosslinking with CuSO4, chemical crosslinking with epichlorohydrin, or were coated with a polyelectrolyte complex chitosan/poly(2-acryloylamido-2-methylpropanesulfonic acid). The morphology and the magnetic properties of the beads were studied by optical and scanning electron microscopy, and magnetometry. The magnetisation values of the beads increased on increasing the proportion of Fe3O4. A magnetic field intensity of 6 kOe was completely enough to reach orientation of all dipole moments of the incorporated Fe3O4. The magnetic beads completely sorbed a model dye - reactive red - from its aqueous solution, thus implying that such materials might be used for wastewater treatment in textile industry.
Degradation of networks composed of chitosan and polyacrylamide by a crude enzyme complex from Bacillus subtilis
Authors: Bonina Petranka , Petrova Tsvetanka , Manolova Nevena , Rashkov Iliya 
Published: August 2014

Abstract The degradation of semi-interpenetrating and interpenetrating networks of chitosan and polyacrylamide - net-PAAm-sipn-chitosan, net-chitosan-sipn- PAAm and net-chitosan-net-PAAm, by a crude enzyme complex produced by the beneficial soil microorganism Bacillus subtilis was studied. The effect of the degree of crosslinking was examined under otherwise invariable conditions (pH 6, ionic strength I = 0.1, and 35°C). It was found that the lower the degree of crosslinking, the faster the enzymatic hydrolysis. Degradation of the three types of networks proceeded faster under the action of the enzyme complex from B. subtilis than by the enzymes from T. viride.
Synthesis and characterization of novel polyamides based on tridecanedioic acid: Nylons 3 13, 5 13, 6 13, 7 13, 9 13, 10 13, 11 13
Authors: Cui Xiaowen , Yan Deyue , Xiao Dan 
Published: August 2014

Abstract Linear polyamides with high aliphatic content were prepared through step-heating melt polycondensation of tridecanedioic acid with various diamines. The synthesized polyamides were characterized comprehensively by means of IR, NMR and Raman spectroscopy. In addition, thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis were used to investigate thermal properties of the obtained polyamides. It was found that melting and crystallization temperatures decrease as the aliphatic content increases. X-ray diffraction was applied to determine the crystal structures of the polyamides.
The role of flow-induced crystallisation in melt spinning
Authors: Ziabicki Andrzej , Jarecki Leszek , Sorrentino Andrea 
Published: August 2014

Abstract Flow-induced crystallisation in the course of melt spinning changes properties of as-spun fibres and modifies dynamics of the process. Velocity, stress and temperature profiles depend on the speed of on-line crystallisation. Very important but little studied is coupling between crystallinity and rheological properties of the polymer melt. Effects of crystallisation on the dynamics of melt spinning and on the rheological behaviour have been discussed and compared with model calculations and available experimental data.
Dynamic mechanical study of thermoplastic polyurethane/ polypropylene blends
Authors: Bajsić Emi Govorčin , Rek Vesna 
Published: August 2014

Abstract Thermoplastic polyurethanes (TPU) are an important class of elastomers that found many novel and specialized applications where high mechanical and chemical performances are prerequisites. They are known for their good mechanical strength, wear and tear resistance, and low-temperature elasticity. The aim of this work is to study the viscoelastic behaviour of TPU, polypropylene (PP) and their blends using dynamic mechanical analysis. Blends of TPU+PP as well as samples of pure TPU and PP were prepared using a laboratory twin-screw extruder. Primary and secondary viscoelastic functions were determined. Primary viscoelastic functions, viz. storage modulus, loss modulus and loss tangent, were evaluated in the temperature range -100 to 250°C. The secondary viscoelastic functions creep, recovery and creep modulus were investigated in the creepfatigue regime at 25 - 65°C. A master curve at the reference temperature 25°C for the creep modulus of TPU, PP and TPU+PP blends was created by applying the time-temperature correspondence principle. The obtained results are discussed.
Properties of epoxy nanocomposites filled with carbon nanomaterials
Authors: Song Young Seok , Youn Jae Ryoun 
Published: August 2014

Abstract Rheological, mechanical, electrical, and thermal properties of epoxy nanocomposites containing carbon nanomaterials (CNMs) were investigated with different loading. Two kinds of CNMs - multiwalled carbon nanotubes (MWNTs) and carbon blacks (CBs) - were selected to examine the effect of their geometrical structure on various properties. Under sonication, MWNTs and CBs (0.5, 1.0, and 1.5 wt.-%) were mixed with the epoxy resin by using a solvent. Dispersion of the CNMs in the epoxy nanocomposites was characterized by means of transmission electron microscopy and field emission scanning electron microscopy. Carbon nanotubes (CNTs)/epoxy composites show significant differences from the CBs/ epoxy composites due to their high aspect ratio. It was found that the CNTs/epoxy composites exhibit non-Newtonian rheological behaviour, while the CBs/epoxy composites with the same weight content show Newtonian behaviour. The CNTs/ epoxy composites have better mechanical and thermal properties than the CBs/ epoxy composites. In the CNTs nanocomposites, the percolation threshold of electrical conductivity is found to be less than 0.5 wt.-%, which is too low to be obtained by using other carbon materials such as carbon fibre in polymer composites. Effects of CNM content on the various properties were also examined. As loading of the CNMs increased, improved results were obtained.
Porous polymeric scaffolds for bone regeneration
Authors: Filipczak Katarzyna , Janik Ireneusz , Kozicki Marek , Ulanski Piotr , Rosiak Janusz M. , Pajewski Leonardo A. , Olkowski Radoslaw , Wozniak Piotr , Chroscicka Anna , Lewandowska-Szumiel Malgorzata 
Published: August 2014

AbstractSolvent casting/particulate leaching has been used to synthesize highly porous polymeric scaffolds of controlled pore size, based on poly(methyl methacrylate) (PMMA) and poly(ε-caprolactone) (PCL). Obtained structures have a total porosity of c. 60%, with good interconnections between the pores. Porous scaffolds prepared using the greatest size of NaCl particles have the best mechanical properties. Both PMMA- and PCL-based materials can be sterilized by ionizing radiation. In the case of PCL-based scaffolds, irradiation causes cross-linking of polymer chains, which leads to an improvement of the mechanical properties of the scaffold. The compressive elastic modulus for non-porous samples increases with irradiation dose from 1.5 MPa for 0 kGy to 1.9 MPa for 280 kGy. Preliminary in vitro studies indicate good biocompatibility of both materials.
In vivo wear of polyethylene glenoid components in total shoulder arthroplasty
Authors: Swieszkowski Wojciech , Frankle Mark , Bersee Harald E. N. , Kurzydlowski Krzysztof J. 
Published: August 2014

AbstractLoosening of the glenoid component after a total shoulder arthroplasty, leading to pain and the need for a revision operation, accounts for one third of all shoulder replacement complications. It has been shown that glenoid loosening could be a result of osteolysis of periprosthetic bone induced by polymeric wear debris. The aim of this study was to determine the amount and pattern of in vivo wear of polyethylene glenoid components by examining a set of so-called retrievals. Six glenoid components were retrieved and examined (5 all-polyethylene and 1 metal-backed). The average time of functioning of these components in human bodies was 10 years with the shortest time of 7 and longest 14 years. Four components were scanned using a laser scanner. The results of measurements have been used to generate geometrical models of the retrievals using CAD software. These models have been subsequently used to determine the maximum depth and volumetric wear rate for each component. All six retrievals were examined using scanning electron microscopy (SEM). The maximum volumetric wear rate and wear depth for the analyzed retrievals was 30 mm3/year and 0.2 mm/year, respectively. From SEM analysis of the retrievals it was found that at macroscopic level the worn surfaces consist of (a) polished and (b) scratched regions. Intensive wear areas and fine multidirectional scratches were dominant in all retrievals. Random scratches were also observed, most probably due to third body wear (cement particles). In two implants pitting areas and surface micro-cracks have been observed, which most likely result from subsurface fatigue.
Radical crosslinking during polyhydrosilylation between fluorinated and silicone molecules: a model study
Authors: Longuet Claire , Ratsimihety Amédée , Guida-Pietrasanta Francine , Ganachaud François , Boutevin Bernard 
Published: August 2014

AbstractThe present study deals with an explanation for crosslinking reactions that occur during the polyhydrosilylation of telechelic Si-H silicones with divinylperfluoro molecules. For a better understanding of the chemical process, a model reaction was performed and characterized by a full battery of techniques, including the different nuclei NMR analyses. Even if hydrosilylation occurs, side methyl groups on the silicon atoms also react with tert-butoxy radicals. Abstraction of a hydrogen radical from the methyl side group of the silicone chains allows the vinyl fluorinated molecules to add on polydimethylsiloxane and to bridge chains together.
Synthesis, characterization and ring-closing depolymerization of furanic polyesters
Authors: Kamoun Wided , Salhi Slim , Abid Souhir , Tessier Martine , Gharbi Rachid El , Fradet Alain 
Published: August 2014

AbstractFuranic polyesters were prepared by the bulk polycondensation of 5,5'- isopropylidene-bis(2-furoic acid) with 1,2-ethanediol, 1,4-propanediol and 1,6- hexanediol, and were characterized by size exclusion chromatography, NMR and MALDI-TOF MS. The ring-closing depolymerization of these polyesters was then investigated at 10 g/L concentration in 1-methylnaphthalene at 130 - 240°C. Chain flexibility, the use of zinc diacetate catalyst and, particularly, the presence of hydroxy end-groups were found to be favourable factors for the formation of high yields of cyclic oligoesters. A side reaction leading to the formation of non-reactive furyl-terminated species took place when the reactions were carried out at high temperature (240°C), limiting the yield of cyclic oligoesters.
Rheological characterization of polymer-based nanocomposites with different nanoscale dispersions
Authors: Seong Dong Gi , Kang Tae Jin , Youn Jae Ryoun 
Published: August 2014

AbstractPolyamide 6 - clay nanocomposites with different nanoscale dispersions were prepared by melt compounding via twin-screw extrusion and their internal structures were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The rheological behaviour of these nanocomposites in shear and extensional flow were investigated using an Advanced Rheometric Expansion System and an Elongational Melts Rheometer in connection with the analysis by XRD and TEM. Nanocomposites with fully exfoliated structure and with poorly dispersed structure showed very different rheological behaviour. In general, addition of clay increased the viscosity and the storage modulus of nanocomposites, but different rheological behaviours were observed depending upon the degree of clay dispersion in the polymer matrix. In shear flow, only the exfoliated nanocomposite showed solid-like plateau behaviour in storage modulus and strong shear-thinning behaviour in shear viscosity. In extensional flow, only fully exfoliated nanocomposites showed strain-hardening behaviour, which is caused by the interaction between nanoparticles as well as between polymer molecules and nanoparticles.