bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microwave-assisted solid-state sulphation of starch
Authors: Staroszczyk Hanna , Fiedorowicz Maciej , Zhong Wei , Janas Piotr , Tomasik Piotr 
Published: August 2014

AbstractStarch was sulphated with pyridine.SO3 complex in the microwaveassisted solid state processes in multimodal microwave oven and, for comparison, also on convectional heating blends of solid reagents. Starch was less hydrolysed in microwave-assisted reactions. The degree of the esterification of the sulphuric acid anhydride depended to a lesser extent on the reaction time and the power applied, and more essentially on the reagent ratio, that is, dose of the sulphating agent. Its higher doses favoured depolymerization and esterification leading to diesters, that is, crosslinking.
Effect of Vibration on Drawing and Annealing of High- Speed Spun Poly(trimethylene terephthalate) Fiber
Authors: Kim Kyoung Hou , Lee Yang Hun , Cho Hyun Hok , Kikutani Takeshi 
Published: August 2014

AbstractThe physical properties of poly(trimethylene terephthalate) (PTT) fibres were improved by means of vibration in the hot-drawing and annealing, which may be caused by the developed molecular packing. For high-speed spun PTT fibers, it was not until at the take-up speed of 3~4 km/min that the orientation induced crystallization started to emerge due to extensional stress occurred in spin line; confirmed from the results of WAXD and DSC. The PTT fibers obtained at the take-up speeds of 2~3 km/min and then drawn and annealed with vibration possessed low density and weight-crystallinity, but their birefringence was especially high. Moreover, the estimation of both refractive index parallel and normal directions to fiber axis using the interference microscopy showed that the refractive index parallel to the fiber axis was very high, which enhanced the mechanical properties of PTT fiber. Accordingly, the well-oriented chains along the fiber axis allow the PTT fiber to have better physical property such as elastic recovery although the PTT fiber has low density and crystallinity compared to PET and PBT. In effect, the PTT fiber possesses lower birefringence of over 10 times than those of PET and PBT due to its chain conformational characteristics. Therefore, we do suggest that the structural assessment against the subsequent mechanical properties according to various processes in the PTT fiber is preferred to be estimated through the respective refractive indices of parallel and normal to the fiber axis rather than conventional methods such as birefringence, crystallinity, and crystalline orientation.
Polypropylene/montmorillonite Nanocomposites for Food Packaging
Authors: Sirousazar Mohammad , Yari Mortaza , Achachlouei Bahram Fathi , Arsalani Jalal , Mansoori Yagoub 
Published: August 2014

AbstractPolypropylene / organically modified montmorillonite nanocomposites were prepared using polypropylene-graft-maleic anhydride as compatibilizer by the melt blending method. The structural, mechanical and gas barrier properties of the prepared nanocomposites containing various amounts of organoclay (i.e. 0, 2, 5, 7 and 10 wt%) were investigated to evaluate their potential as food packaging materials. The X-ray diffraction (XRD) profiles of the nanocomposites and the transmission electron microscopy (TEM) micrograph showed that polypropylene chains have intercalated between silicate layers of organoclay. The mechanical properties tests showed that the tensile modulus and strength of the nanocomposites increased on increasing the clay loading, while the strain at the break decreased. The gas permeability tests demonstrated that adding organoclay into polypropylene matrix enhances the barrier property of the matrix against O2 , CO2 and water vapour.
Plasticity of semi-crystalline polymers: crystal slip versus melting-recrystallization
Authors: Séguéla Roland 
Published: August 2014

AbstractSemi-crystalline polymers can be drawn up to very high draw ratios that involve a complete molecular rearrangement of the chain-folded lamellar morphology into a more or less chain-unfolded fibrillar microstructure. This metamorphosis is likely to take place through an intermediate state of high molecular disorder at a local scale. This is the reason why some authors talk of a strain-induced melting-recrystallization process. In contrast, several structural features occurring at moderate plastic strains are relevant to strictly crystallographic processes. A critical discussion of experimental findings and theoretical approaches is made for pointing out the strength or the deficiency of the different author argumentations. No doubt that both phenomena can occur: crystallographic processes are active at all strain levels whereas meltingrecrystallization is restricted to the post-yield stage accompanied with chain unfolding. Melting-recrystallization is rather a corollary of chain unfolding than a basic mechanism of the plastic deformation. Besides, it may concern only a part of the crystalline phase and can be inhibited under adequate deformation conditions.
Improvements in Essential Electrical and Physical Properties of Phenol Formaldehyde Resin by Incorporation of Modified Coal Tar Pitch
Authors: Kaushik Sapana , Raina Rajesh Kumar , Verma Gurucharan Lal , Bhatia Gopal , Khandal Rakesh Kumar 
Published: August 2014

AbstractPhenol-formaldehyde (PF) resin is used here for making thermosetting composites along with environmentally friendly coal tar pitch(CTP). These PF-CTP composites are made with dual objectives of using environment-friendly CTP to improve the electrical and physical properties of PF resin and to reduce cost of PF resin for final applications. The composites are prepared by a two-step method using standard compression molding technique. Comparing the properties of the samples containing varying amount of CTP with pure PF resin as the reference sample, significant improvements in electrical properties like surface resistivity, volume resistivity and dielectric strength are observed with the increase in amount of CTP. The waterproofing tendency also improved as the amount of CTP is increased. The best properties are observed for the thermosetting composition with 40 phr of CTP.
Electrical Behavior of High Density Polyethylene/ZnO Nano-composites
Authors: Tjong Sie Chin , Liang Guodong 
Published: August 2014

Abstract High density polyethylene (HDPE)/ZnO composites containing a wide range of ZnO content (1-60 vol%) were prepared by melt compounding. ZnO powders with sizes of ~ 200 nm and ~ 2 μm were employed as reinforcing fillers. The effects of the size and filler particle content as well as annealing treatment on the dielectric and conducting properties of the HDPE/ZnO composites were examined. The results showed that the dielectric constant of HDPE/ZnO composites increased gradually with an increase of the ZnO content. The resistivity of HDPE/ZnO composites can be described satisfactorily by the interparticle distance of filled particles. This behavior is interpreted in terms of tunneling of the electrons through the insulating layer of polymer separating two neighboring ZnO fillers. The correlation between the structure and electrical property of the composites is discussed.
The effect of aliphatic chain length on thermal properties of poly(alkylene dicarboxylate)s
Authors: Berti Corrado , Celli Annamaria , Marchese Paola , Marianucci Elisabetta , Barbiroli Giancarlo , Credico Francesco Di 
Published: August 2014

AbstractSome poly(alkylene dicarboxylate)s, derived from ethanediol or 1,4- butanediol and different diacids, have been synthesized and analyzed by DSC to determine the correlations existing between the thermal properties and the length of the aliphatic chain. The polymers show crystallization and melting temperatures and enthalpies which increase as the polymethylene segments lengthen, due to the formation of more stable crystals. The samples derived from ethanediol are peculiar; they show reorganization processes during the melting and the melting temperatures are notably higher with respect to those of the other polyesters. This behavior is discussed. Isothermal analysis highlights that poly(alkylene dicarboxylate)s are fast crystallizing polymers. The Avrami analysis suggests a crystallization mechanism characterized by heterogeneous nucleation and three dimensional growth; secondary crystallizations is present only in the samples characterized by short -(CH2)- sequences, due to the reorganization of less perfect crystalline forms. A comparative study between the crystallization rates as a function of the undercooling is reported.
Preparation and characterization of sugarcane bagasse hemicellulosic derivatives containing quaternary ammonium groups in various media
Authors: Jun-Li Ren , Chuan-Fu Liu , Run-Cang Sun , Diao She , Jian-Chao Liu 
Published: August 2014

AbstractTo increase the solubility and produce cationic or ampholytic polymers as beater additives in papermaking from native hemicelluloses, quaternization of hemicelluloses were performed by reacting hemicelluloses with 3-chloro-2- hydroxypropyltrimethylammonium chloride (CHMAC) and preferably with 2,3- epoxypropyltrimethylammonium chloride (ETA) in aqueous sodium hydroxide, homogenously in dimethyl sulfoxide (DMSO), and completely heterogeneously in ethanol/water, respectively. The extent of modification was measured by degree of substitution (DS), and its value of up to 0.55 can be controlled by adjusting the molar ratio of reagent to hydroxyl functionality in hemicelluloses and the concentration of sodium hydroxide. The characterization of hemicellulosic derivatives was performed by elemental analysis, GPC, FT-IR and 13C NMR spectroscopy as well as thermal analysis. It was found that hemicellulosic polymer was significantly degraded in aqueous sodium hydroxide solution compared with in dimethyl sulfoxide and in ethanol/water systems under the conditions given. The thermal stability of modified hemicelluloses decreased after chemical modification, corresponding to the decreasing Mw of hemicelluloses derivatives.
Charge transport and conductivity measurement in polyaniline-poly(vinyl acetate) blends
Authors: Kanhegaokar Shivkalyan.A. 
Published: August 2014

AbstractPoly(vinyl acetate) (PVAc) is used extensively in coatings, adhesives and films. The carbonyl group (C=O) in the structure of PVAc forms hydrogen bonding with amine and hydroxyl groups and this may also enhance miscibility with polyaniline. Hence, PVAc has been chosen for blending with PANI. Further, PVAc can be used in moisture sensors and after blending with PANI its conductivity would be in semi conducting range with moisture response, which will be suitable for easy measurement. It was expected that, the given blend may give higher conductivity because 1) PVAc and PANI solubility parameter values match closely: the Hilde Brand solubility parameter (δ) of aniline is 21.1 Mpa1/2 and PVAc is found to be 20 Mpa1/2, 2) Its miscibility also increases due to H-bonding forces of attraction observed in amine group of PANI and ‘CO’ group of PVAc. 3) PVAc has excellent sticking properties to different substrates which makes it useful as an adhesive and 4) Work function values of PANI as well as PVAc match closely. It is interesting to mention that PVAc has a low Tg (28 °C) and thus may serve as a polymeric plasticizer for PANI, which would help to improve processability and/or film formation. There are many methods of blending polymers but only limited techniques can be applicable for conducting polymers. PVAc is soluble in high dielectric constant solvent such as methanol. However, PANI is not soluble in this solvent even after modification with suitable dopants. Hence, a new method has been adopted for blending these two components; i.e. the in situ blending method. This system also explains ex-situ blending method, electrical properties and charge transport processes in the blend.
Polymerization of acrylic and methacrylic monomers using CF3OC(O)OO(O)COCF3 as radical initiator
Authors: Bierbrauer Karina L. , Argüello Gustavo A. , Strumia Miriam C. 
Published: August 2014

AbstractThe study of CF3OC(O)OO(O)COCF3as radical initiator in polymerization of acrylic and methacrylic monomers as acrylic acid (AA), acrylonitrile (AN), 2-hydroxyethyl methacrylate, (HEMA), and methyl methacrylate (MMA), is presented. The reactions were carried out under different conditions in order to explore the efficiency of the initiator. The results demonstrated that the yield and the type of the products (soluble or non-soluble) is dependent on the reactivity and the solubility of the initiator in the monomers, constituting a heterogeneous system influenced by hydrophobic-hydrophilic balance of the species involved.
Precipitation and surface polymerizations of aniline at different aniline:oxidizer molar ratios
Authors: Mascaro Lucia Helena , Gonçalves Débora 
Published: August 2014

AbstractThe oxidative polymerization of aniline was monitored by means of open-circuit potential (OCP) measurements of Pt electrodes immersed in an aqueous acidic medium containing different aniline:oxidizer (ammonium persulfate) molar ratios. Thin polyaniline (PANI) films were formed on the Pt electrode surfaces during the OCP measurements, and they were studied by SEM and cyclic voltammetry in a monomer-free solution at different reaction times. A precipitate also obtained during the polymerization process was analyzed by UV-VIS spectroscopy in 1-methyl-2-pyrrolidinone. It is observed that aniline or short oligomeric species are necessary to initiate the growth of a PANI film, which takes place at the first few minutes of the reaction.
On heat regimes of anion-activated polymerization of ε- caprolactam
Authors: Davtyan Sevan , Zakaryan Hayk , Tonoyan Anahit , Varderesyan Gagik 
Published: August 2014

AbstractQuantitatively, the Semenov diagram of heat generation-temperature relationship is analyzed. Critical transitions of heat regimes during anion-activated polymerization of ε-caprolactam are investigated. Various outcomes as compared with classic cases already discussed by Semenov are observed for the polymerization and crystallization processes running sequentially. It was shown that the critical Semenov parameter holds even for the weak-exothermal polymerization reaction when steep transition from quasi-thermal-low temperature to quasi-adiabatic-high temperature heat regime takes place.
The synthesis and capacitive properties of poly(3,4- ethylene dioxythiophene)/poly(styrene-sulfonate) and poly (acrylamide) conducting hydrogels
Authors: Aouada Fauze A. , Moura Márcia R. de , Girotto Emerson M. , Rubira Adley F. , Muniz Edvani C. 
Published: August 2014

AbstractConducting hydrogels, consisting of conductive polymer poly(3,4- ethylene dioxythiophene)/poly(styrene-sulfonate) (PEDOT/PSS) entangled in the polyacrylamide (PAAm) network, were synthesized by UV using potassium periodate as photo-sensitizer initiator. Electrochemical properties of conducting hydrogels were evaluated by cyclic voltammetry measurements at room temperature. Electrochemical tests indicated the rectangular shape of voltammograms. In addition, the charge/discharge time obtained was very short. Both are characteristic of capacitive materials. Additionally, the conducting hydrogels presented practically the same electrochemical behavior and coulombic efficiency (η) of around 100% after 1,000 charge/discharge cycles. This shows that from the electrochemical perspective, the redox processes involved are reversible, even after several charge/discharge cycles, which is indicative of a material with excellent electrochemical properties.
Interpretation of experimental IR spectra of (z)-4-(2- (acryloyloxy)ethoxy)-4-oxobut-2-enoic acid and its polymers
Authors: Song Chen , Li Xiaoyu 
Published: August 2014

AbstractThe solid phase FTIR spectra of (z)-4-(2-(acryloyloxy)ethoxy)-4-oxobut- 2-enoic acid (cis-AEOEA) and its polymers have been recorded in the regions 3500~500 cm-1, respectively. The IR spectra of cis-AEOEA was interpreted with the aid of normal coordinated analysis following full structure optimization and force field calculation based on density functional theory (DFT). Standard scaling factor was used to afford better correspondence between the calculated and experimental wavenumbers for the separation and unambiguous identification of observed IR spectra of cis-AEOEA, especially for C=C double bonds. The characteristic absorption bands of C=C are used for identifying the kind of C=C double bonds in cis-AEOEA’s polymers.
Study of PET depolymerization during recycling
Authors: Kratofil Krehula Ljerka , Hrnjak-Murgić Zlata , Andričić Branka , Jelenčić Jasenka 
Published: August 2014

AbstractDepolymerization of poly(ethylene-terephthalate) (PET) in PET/HDPE blends, obtained from virgin polymers during mechanical recycling was studied. Extrusion of PET/HDPE blends was simulation of the first cycle of recycling and extrusion of the blends with EPDM/HDPE (E-M) masterbatch and HDPE/EPDM (PEM) masterbatch the second cycle. After that the samples were additionally treated to examine their thermooxidative stability. Blends were characterized by determination of the concentration of carboxyl groups by Pohl titration, by FTIR spectroscopy and differential scanning calorimetry (DSC) to determine crystallization (Tc) and melting (Tm) temperatures. The concentration of determinated carboxyl end groups in blends indicate presence of formed polymer radicals with hydroxyl-carboxyl end groups as the result of depolymerization of PET. Presence of characteristic groups was also confirmed by FTIR. DSC results indicate the influence of HDPE on crystallization temperature of PET and points to the fact that even degraded samples maintain the chemical structure of PET. From the results it can be seen that addition of the particular modifier can reduce and even prevent the depolymerization during the recycling process.
Mechanical properties and hydrolytic degradation of methoxy poly(ethylene glycol)-b-poly(DL-lactide-coglycolide- co-ε-caprolactone) diblock copolymer films
Authors: Morakot Nongnit , Threeprom Jirasak , Baimark Yodthong 
Published: August 2014

AbstractBiodegradable films of methoxy poly(ethylene glycol)-b-poly(DL-lactideco- glycolide-co-ε-caprolactone) diblock copolymers (MPEG-b-PDLLGCL) were prepared by solution casting method. Effects of MPEG block length and DLL:G:CL ratio of the MPEG-b-PDLLGCL films on their mechanical properties and hydrolytic degradation were studied and discussed. It was found that the mechanical properties of films were strongly dependent on glass transition temperatures (Tg) of the diblock copolymers. The hydrolytic degradation was investigated in phosphatebuffered solution at 37°C. The degraded films were characterized using gravimetry (%water uptake and %weight loss), 1H-NMR spectroscopy, differential scanning calorimetry and size exclusion chromatography. The %weight loss of the degraded films increased and molecular weight decreased on increasing the MPEG block length and incorporating the G and CL units, according to their %water uptakes. The MPEG content of the degraded film decreased and the Tg increased with hydrolytic degradation time.
Synthesis of poly(styrene-block-ethylene oxide) copolymers by anionic polymerization and acid cleavage into its constituent homopolymers for the formation of ordered nanoporous thin films
Authors: Varshney Sunil K. , Zhang Jian-Xin , Ahmed Jasim , Song Zhengji , Klep Viktor , Luzinov Igor 
Published: August 2014

AbstractWell-defined cleavable poly(styrene-block-ethylene oxide) polymers were prepared by living anioinc polymerization, using cumyl potassium as the initiator. These polymers contained an acid cleavable moiety, such as diphenyl methyl or anthracenyl methyl ether linkage, between polystyrene and poly ethylene oxide block. Atomic force microscopy (AFM) studies on the thin films illustrate the formation of nanoporous architecture due to acid cleavage of the polyethylene oxide fraction.
A Study of Crystallinity of Graft Copolymers of Flax Fiber with Binary Vinyl Monomers
Authors: Kaith B.S. , Kalia Susheel 
Published: August 2014

AbstractThe present paper deals with graft copolymerization of binary vinyl monomer mixtures onto flax fiber. Maximum grafting (86.02 %) has been found with MMA+EA binary mixture. Percentage crystallinity and crystallinity index of graft copolymers were measured with X-ray diffraction (XRD) technique. Crystallinity of flax decreases on grafting with binary vinyl monomer mixtures. Flax showed the highest value of percentage crystallinity (76.96 %) and crystallinity index (0.7005) in comparison to Flax-g-copolymers.
Encapsulation of ferromagnetic iron oxide particles by polyester resin
Authors: Baharvand H. 
Published: August 2014

AbstractMagnetic iron oxide (maghemite, Fe3O4) particles were encapsulated with polyester resin. The resulting magnetic powders were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fritsch particle sizer, scanning electron microscopy (SEM), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM) measurements. FTIR and XRD confirmed the presence of iron oxide in polymer phase. The TGA and DSC measurements indicated the magnetic polymer particles have more than 50% iron oxide content and high thermal stability. SEM revealed that all maghemite particles were embedded in the polymer phase. The size distribution analysis of prepared magnetic particles has shown that the mean diameter of the bare iron oxide particles slightly increased with encapsulation. According to our magnetometry data, shape of the loops evidences the ferromagnetic character of the material and no evidence of superparamagnetism was seen.
Synthesis and characterization of poly(ethylene-vinyl alcohol)-g-poly(butyl acrylate) copolymers
Authors: Azam M. , Dawkins John V. 
Published: August 2014

AbstractEthylene-vinyl alcohol (EVOH) copolymers with different vinyl alcohol (VOH) mole % have been grafted by the carboxyl terminated poly(butyl acrylate) (PBA) prepolymers by the grafting-onto method. The carboxyl terminated PBA were synthesised by solution radical polymerization using 4,4 azobis(cyanovaleric acid) (ACVA) as initiator and thioglycolic acid (TGA) as matched chain transfer agent and then converting carboxyl groups into acid chloride terminated prepolymer by reacting with oxalyl chloride. The acid chloride terminated prepolymers were reacted with EVOH copolymer backbone to synthesize graft copolymers. The graft copolymers were characterized by the Size Exclusion Chromatography (SEC), Fourier Transfer Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Results from these analyses confirmed the grafting of PBA side chain on to EVOH backbone. Differential Scanning Calorimetery (DSC), Dynamic Mechanical Thermal Analysis (DMTA) and x-ray diffraction studies of graft copolymers showed that the morphology of crystalline EVOH polymers has been disrupted due to grafting of amorphous PBA chains.