bluuebunny/crossref_metadata_2025 huggingface dataset:
Conductivity and Thermal Analysis Studies of Solid Polymeric Electrolytes Based on Plasticized Hydroxyethyl Cellulose
Authors: Machado Gilmara O. , Prud’homme Robert E. , Pawlicka Agnieszka
Published: August 2014

Transparent film samples of hydroxyethyl cellulose (HEC) based on solid polymeric electrolytes (SPE) were prepared by the plasticization of HEC with glycerol and addition of lithium perchlorate salt. SPEs with different quantities of glycerol and LiClO4 were studied by electrochemical impedance spectroscopy (EIS), Dynamic Mechanical Thermal Analysis (DMTA), TGA (Thermogravimetric Analysis) and DSC (Differential Scanning Calorimetry). The ionic conductivity measurements revealed that the sample containing [O]/[Li]=8 and 48% of glycerol showed the conductivity value of almost 10-4 S/cm at room temperature. The TGA analysis of electrolytes with high plastizant and salt concentrations showed 25% weight loss after heating to 130 °C, which can be related to the liberation of absorbed water. Finally, DMTA measurements showed changes attributed to the glass transition (Tg) evidenced by the decrease in the elastic modulus value and peaks in the tanδ curves. These results demonstrated that HEC is a good material to be used as a matrix for new solid polymeric electrolytes.
Molecularly Imprinted Polymers for Selective Adsorption of Cholesterol from Aqueous Environment
Authors: Puoci Francesco , Iemma Francesca , Cirillo Giuseppe , Trombino Sonia , Cassano Roberta , Picci Nevio
Published: August 2014

In this work the preparation and evaluation of molecularly imprinted polymers (MIPs) based on 2-hydroxyethylmetacrylate (HEMA) for selective recovery of cholesterol from aqueous media are reported. HEMA was used as functional monomer in order to maximize the hydrogen bond forming both in prepolymerization complex and in rebinding experiments which were performed in polar solvents; in particular, an acetonitrile:water (7:3 v/v) mixture was employed. The templating effect is clearly seen in the capacity of the synthesized polymers to bind cholesterol, and their selectivity was evaluated using two steroids quite similar to cholesterol such as progesterone and hydrocortisone which are less effectively bound by the matrices.
Polypropylene/Waste Ground Rubber Tire Powder Foams: A Study of the Relationship Between Processing and Structure Using Supercritical Carbon Dioxide
Authors: Zhang Zhen Xiu , Zhang Shu Ling , Xin Zhen Xiang , Kim Jin Kuk
Published: August 2014

In this study, processing-structure relationships in polypropylene (PP)/waste ground rubber tire powder (WGRT) foams made using supercritical carbon dioxide as a physical blowing agent were investigated. In order to investigate the relationship between structure and properties of PP/WGRT foams, it was necessary to make samples with a wide range of controlled structures. For this reason, a systematic investigation of the relationship between processing conditions and structure was performed based on a statistical experimental design. Regression analysis was conducted on the data and expressions were developed to quantify the relationships between structural parameters and processing conditions. The samples were saturated with carbon dioxide at high temperature and high pressure and the saturated specimens were expanded during the pressure-quench process. The importance of the individual processing parameters was determined. Statistical analysis of data showed that saturation temperature was the most important factor determining cell size, cell density and relative density. By controlling the foaming conditions, PP/WGRT samples having the same foam density and different cell size or having the same cell size and different foam density were produced.
Radical copolymerization of styrene and acrylonitrile in the presence of oligooxyethylene azoester
Authors: Wiśniewska Ewa , Pabin–Szafko Barbara
Published: August 2014

Telechelic vinyl oligomers terminated with hydroxyl groups were prepared by free radical copolymerization of styrene (S) and acrylonitrile (AN), initiated by azoester-2,2’-azobis[2-methyl-ω-hydroxy-oligo(oxyethylene) propionate] [AIB-OOE(400)], carried out in N,N-dimethylformamide. The reactivity ratios rS=0,225 and rAN=0,722 for styrene and acrylonitrile, respectively, were evaluated by Kelen-Tüdős method. The glass transition temperatures (Tg) of the copolymers were determined by differential scanning calorimetry. Tg values varied with the copolymer composition in the range of 60-82 °C and the maximum Tg value was obtained for copolymer with 60 mol% AN.
Microwave-assisted solid-state sulphation of starch
Authors: Staroszczyk Hanna , Fiedorowicz Maciej , Zhong Wei , Janas Piotr , Tomasik Piotr
Published: August 2014

Starch 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

The 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

Polypropylene / 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

Semi-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

Phenol-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

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

Some 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

To 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

Poly(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

The 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

The 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

Quantitatively, 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

Conducting 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

The 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

Depolymerization 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

Biodegradable 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

Well-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

The 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

Magnetic 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

Ethylene-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.
Influence of annealing on microstructure & molecular orientation, thermal behaviour, mechanical properties and their correlations of uniaxially drawn iPP thin film
Authors: Saengsuwan Sayant
Published: August 2014

The influence of annealing on the microstructure and molecular orientation, thermal behaviour and mechanical properties of uniaxially drawn iPP thin film was studied by wide-angle X-ray diffraction, differential scanning calorimetry and tensile testing, respectively. The correlations of mechanical and microstructural properties of annealed films were also examined. The transformation of smectic phase of iPP to the α-form was more pronounced with increasing annealing time and temperature. The true and apparent crystallinities and crystal thickness were strongly enhanced with annealing time and temperature. The relative molecular orientation tended to increase with annealing time. These results caused the significant improvement of modulus and tensile strength of the annealed films in both machine (MD) and transverse (TD) directions. The increases in MD-Young’s modulus and MD-tensile strength were well correlated with the increase in true crystallinity obtained in equatorial scans. Some relationship between the increase in crystal thickness and the increase in Young’s modulus in both MD and TD directions was also found.
Mechanical properties and morphology of low density polyethylene/polydimethylsiloxane immiscible blends: modeling and influence of curing agent
Authors: Razavi-Nouri Mohammad , Morshedian Jalil , Ehsani Morteza , Faghihi Farhad
Published: August 2014

The tensile behavior of low density polyethylene/polydimethylsiloxane immiscible blends was investigated with respect to morphological variation of the blends. Experimental data of elastic modulus was compared with theoretical predictions of parallel model (mixing rule), as the upper bound of modulus, Halpin- Tsai model, and a two-parameter equivalent mechanical model proposed by Kolarik, which takes into account the continuity of minor phase. As the predictions of these models were not in good quantitative agreement with experiment, some modifications were made to the Kolarik model. Furthermore, a new approach for determining equivalent mechanical model parameters was proposed based on the calculation of phase continuity parameters as a function of composition. Using this approach, the values predicted for elastic modulus were found to be in good agreement with the experimental data. Moreover, the influence of a peroxide curing agent on the tensile properties of the blends was studied. The improvement of the tensile properties of the blends could have resulted from two contributions: the effect of curing reaction on the tensile properties of constituents and the better interfacial adhesion, because of possible interfacial reaction, as indicated by morphological observation.
Novel cross-linkable polyphosphazene with o-acetyl phenoxide as the pendant group
Authors: Huang Yawen , Tang Xiaozhen , Pan Yang , Fu Jianwei , Huang Xiaobin
Published: August 2014

A new polyphosphazene which bears o-acetylphenoxide group [NP(o- C6H4-COCH3)]n, PAOP was synthesized. PAOP can be efficiently thermally crosslinked at mild condition using p-phthalaldehyde as cross-linker and sodium hydroxide as catalyst both in solution and solid reaction. It was found that solid reaction gives more products with carbon-carbon double bond. The suggested process of cross-linking reaction was described based on the progress of small molecular reaction. Influence factors of cross-linking reaction including water and temperature were also discussed and it was concluded that water prevents crosslinking and higher temperature causes higher percent conversion. The photochemical reaction of cross-linked PAOP was simply studied using UV and it was demonstrated that carbon-carbon double bond decayed under UV irradiation and more complicated products were obtained.
Effect of glycidyl methacrylate (GMA) on the stability of acrylic latex
Authors: Wu Guangfeng , Tao Yue , Kang Hong , Zhang Huixuan
Published: August 2014

The stability of core-shell particles (CSPs) with butyl acrylate (BA) as the core and methyl methacrylate (MMA)/glycidyl methacrylate (GMA) mixture in various compositions as the shell was investigated by turbidity measurements. The experiments demonstrate that lower amount addition of GMA could not improve the latex stability. When the amount of GMA exceeded 2% of the total reactants, it began to improve the stability of the latex. With the increasing content of GMA, the latex became more and more stable. On the other hand, experimental data also show that the stability was improved by increasing the concentration of sodium dodecyl sulfate (SDS).
Morphology and properties of halloysite nanotubes reinforced polypropylene nanocomposites
Authors: Du Mingliang , Guo Baochun , Cai Xiaojia , Jia Zhixin , Liu Mingxian , Jia Demin
Published: August 2014

Halloysite nanotubes (HNTs) were utilized to prepare polypropylene (PP) nanocomposites by simple melt-compounding approach. Compared with other silicates such as montmorillonite and kaolinite, HNTs show much better dispersion property. The PP nanocomposites with HNTs exhibit concurrence increase in tensile and flexural strength, flexural modulus and impact toughness. Surface modification of HNTs lends the PP nanocomposites higher strength, modulus and lower toughness. The increase in mechanical properties is correlated with the well dispersion of the high aspect ratio HNTs and the orientation of HNTs in PP matrix. Morphology studies show that HNTs can be dispersed in PP uniformly at lower HNTs loading and excessive loading of HNTs causes a little aggregation. Surface modification of HNTs can alleviate the aggregation effectively. The storage modulus of the nanocomposites increases consistently with the HNTs concentration. The surface modification is beneficial to the further improvement in storage modulus. Similar to other silicates, HNTs facilitate the crystallization of PP due to the heterogeneous nucleation
Synthesis of antimicrobial polymer composition and in vitro drugs release study
Authors: Nita Tudorachi
Published: August 2014

The study presents a procedure to acquire a colloidal silver-based antimicrobial polymer composition. Carboxymethylstarch (CMS) as polymer matrix, and colloidal silver particles (Ag0) obtained by in situ synthesis with silver nitrate and sodium citrate as reducing agent, were used. In solution, the presence of COOH and OH groups in carboxymethylstarch directs to silver complexation and acquirement of a stable suspension of silver particles. Due to the presence of colloidal silver particles, the composition presents bacteriostatic activity and in association with some drugs (acetylsalicylic acid or diclofenac sodium) pharmaceutical compositions can be obtained, which are useful in the prevention and treatment of some infections or diseases. The compositions were characterized by FTIR spectroscopy, UV-vis spectrophotometry, particle size analysis and zeta potential measurements. Drug release tests were done in vitro in phosphate buffer solution (pH=7.4, at 37°C).
Synthesis and properties of a spinnable phase change material CDA-IPDI-MPEG
Authors: Cheng Shiliang , Chen Yanmo , Yu Hao , Zhu Meifang
Published: August 2014

A comb like phase change material (PCM) CDA-IPDI-MPEG, based on cellulose diacetate (CDA) as a backbone, with methoxy polyethylene glycol (MPEG) grafted onto it, was synthesized by a two-step reaction in the presence of dibutyltin dilaurate (DBTDL) catalyst system, using acetone as solvent and isophorone diisocyanate (IPDI) as crosslinking reagent. Size exclusion chromatography (SEC) was used to characterize the molecular weight distribution of each step reaction products. Back titration was utilized for determination of free isocyanate. The molecular structures were confirmed qualitatively using FTIR and H1-NMR measurements. Phase change properties were characterized by differential scanning calorimetry (DSC).
Synthesis of acrylated styrene-isoprene-styrene copolymer
Authors: Klinpituksa Pairote , Chaisuriyathepkul Anont , Phinyocheep Pranee , Nakason Charoen , Kittipoom Sumet
Published: August 2014

Vulcanization of polymer by ultraviolet irradiation has been playing an important role in the industrial sector especially for coating, ink and printing applications. Polymers used in this area are sensitive to ultraviolet (UV) radiation. Their final products have properties required for particular specifications. One of the methods to synthesize ultraviolet-sensitive polymers is the grafting of ultraviolet-sensitive units onto other polymer backbones. In this work, styreneisoprene- styrene copolymer (SIS) was selected as a polymer backbone whilst acrylic acid served as an ultraviolet sensitiser. The grafting reaction was carried out in a solution state of toluene through the ring-opening addition reaction of epoxidized SIS molecules. The results indicated that acrylic acid can be successfully grafted onto a previously epoxidized SIS backbone at a reaction temperature of 100°C. Furthermore, the acrylation yield increased with the increase of reaction time.
Alkoxymethylcyclosiloxanes - new efficient precursors of crystalline (CH3SiO3/2)8 silsesquioxane and polymethyl silsesquioxanes
Authors: Kowalewska Anna , Rózga-Wijas Krystyna , Handke Mirosław
Published: August 2014

A new, highly efficient and very simple method for the synthesis of pure octahedral methylsilsesquioxanes (CH3SiO3/2)8, from cyclic 2,4,6,8-tetraalkoxy- 2,4,6,8-tetramethylsiloxane, was developed. We have found that T8Me can be synthesized from a mixture of alkoxymethylcyclosiloxane isomers in the hydrolytic condensation process, utilizing an ionic catalyst - tetrabutylammonium fluoride (TBAF). The reaction was carried out under very mild conditions, at room temperature, in a variety of solvents of different polarity. A substantial solvent effect was observed. THF helped in the formation of pure T8Me, whereas in other solvents mixtures of T8Me and poly(methylsilsesquioxanes) (PMQS) of substantial degree of regularity, were obtained.
Effect of temperature on structure, morphology and crystallinity of PVDF nanofibers via electrospinning
Authors: Huang Fenglin , Wei Qufu , Wang Jiaxi , Cai Yibing , Huang Yubo
Published: August 2014

Abstract I

nfluence of temperature on morphology, structure and crystallinity of Poly (vinylidene fluoride) (PVDF) nanofibers was investigated in this study. The Wehilmy technique and viscosity testing apparatus were used to evaluate the surface tension and viscosity of electrospun solutions at various ambient temperatures. Surface morphologies and diameters of nanofibers were examined by Field-emission Scanning Electron Microscopy (FE-SEM) and atomic force microscopy (AFM). It was found that the surface morphologies were obviously affected by ambient temperature. This dependence was attributed to the change of the properties of Poly (vinylidence fluoride) solutions with temperature. The thermal properties and crystal structures of the PVDF nanofibers electrospun at different temperatures were also studied by differential scanning calorimetry (DSC), and Xray diffraction (XRD). The results revealed that the crystallinity and thermal properties were improved by increasing the ambient temperature during electrospinning
Controlled release of indomethacin from crosslinked alginate beads
Authors: Inal Murat , Yiğitoğlu Mustafa , Işiklan Nuran
Published: August 2014

Beads of the sodium alginate (NaAlg) were prepared by dropping aqueous sodium alginate (NaAlg) into glutaraldehyde (GA) as a crosslinker and HCl as a catalyst mixture solution. Beads prepared were used to deliver a model non-steroid, anti-inflammatory drug, indomethacin (IM). The beads were characterized with Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. SEM photograph indicated that alginate bead has spherical shape and rough surface. Preparation conditions of the beads were optimized by considering the percentage of entrapment efficiency, swelling capacity of the beads, particle size and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of variables such as, GA concentration, exposure time to GA, drug/polymer (d/p) ratio and percentage of HCl on the release of the IM were investigated. It was observed that, IM release from the beads decreased with increasing GA concentration, exposure time to GA, d/p ratio and percentage of HCl. The highest cumulative IM release obtained at the end of 6 h was 68% for alginate beads which were prepared with 0.5% HCl. On the other hand the least cumulative IM release obtained was to be 20 % for alginate beads which were prepared with 30 min exposure time to GA. In order to understand the crosslinking of the polymeric matrix, the molar mass between crosslinks were calculated using the swelling parameters. It was also found from the swelling experiments that swelling degree of the beads increases with increase in the temperature. The release data have been fitted to an empirical equation to estimate the kinetic parameters. The diffusion coefficient was also calculated for the transport of the drug through the polymeric beads. Values of these parameters were found to be consistent with the release data.
PAAm and PEDOT/PSS hydrogel as potential electroactive devices: evaluation of surface and hydrophilic properties
Authors: Aouada Fauze A. , de Moura Márcia R. , Radovanovic Eduardo , Girotto Emerson M. , Rubira Adley F. , Muniz Edvani C.
Published: August 2014

The aim of this work was to analyze the hydrophilic and surface properties of semi-IPN hydrogels with good electroactive properties based on poly (acrylamide) (PAAm) and conductive polymer poly(3,4-ethylene dioxythiophene)/ poly(styrenesulfonate) (PEDOT/PSS). The hydrogels properties were analyzed by degree of swelling (DS), drop water contact angle (DWCA) and atomic force microscopy (AFM). In addition, the state of water in the hydrogels was estimated by differential scanning calorimetry (DSC) analysis. Results revealed that the presence of PEDOT/PSS reduce the hydrophilicity of the network, mainly those prepared with lower cross-linking density, demonstrating that PEDOT/PSS chains (or their segments) are displayed in surface hydrogels. The possibility of producing PAAm-PEDOT/PSS hydrogels with controlled properties in a desired range of values is of key importance to optimize its use in several applications, mainly in optical devices, capacitors, artificial muscles, and rechargeable lithium batteries
In air synthesis of GA-cl-poly(MAA) hydrogel and study of its salt- resistant swelling behavior in different salts
Authors: Kaith B. S. , Ranjta Shabnam , Kumar Kiran
Published: August 2014

A novel hydrogel has been synthesized by grafting methacrylic acid (MAA) onto Gum arabic (GA) through free radical graft co-polymerization in the presence of potassium persulphate (KPS) as an initiator and hexamethylene tetramine (HMTA) as a cross-linker. Various reaction parameters like reaction temperature, reaction time, concentration of initiator, amount of solvent, pH, concentration of monomer and concentration of cross-linker were optimized. GAcl-poly(MAA) was characterized by FTIR spectroscopy, SEM and TGA-DTA techniques. Optimized polymer was studied for its salt-resistant swelling behavior in different solutions: NaCl, MgCl2, CaCl2, FeCl3, ZnCl2 and BaCl2 as a function of salt concentration, temperature and pH. It was observed that GA-cl-poly(MAA) exhibits following salt-resistant swelling trend in different salts: NaCl > ZnCl2 > MgCl2 > CaCl2 > BaCl2 > FeCl3
Synthesis, characterization and evaluation of poly [glucose acrylate-methacrylic acid] hydrogels for colon-specific drug delivery
Authors: Mahkam Mehrdad
Published: August 2014

New biodegradable polymeric hydrogels based on biocompatible materials, glucose acrylate (GA) and methacrylic acid (MAA) were designed and synthesized. In the first time, the glucose-6-acrylate-1,2,3,4-tetraacetate (GATA) monomer was prepared under mild conditions. The removal of protecting acetate groups from GATA will be carried out before the polymerization and then, the corresponding water soluble glycomonomer (GA) was obtained. This deprotected glycomonomer can be polymerized in aqueous media, which points to a way to obtain polymers with applications in biomedical and biochemical fields. Hydrogel synthesis was carried out by free-radical polymerization of the co-monomers using persulfate as an initiator and N,N′-methylenebisacrylamide as crosslinker. The hydrogels was characterized by FT-IR. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). The swelling behaviour of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in pH 1 or an increase in gel swelling in pH 7.4. Model drug, 5-aminosalicylic acid (5-ASA) was entrapped into these hydrogels and the in vitro release profile of this drug was established separately in both enzyme-free SGF and SIF. Based on the great difference in swelling ratio at pH 1 and 7.4 for these hydrogels, it appears to be good candidates for colon-specific drug delivery.
Preparation and characterization of thermoplastic elastomers (TPEs) based on waste polypropylene and waste ground rubber tire powder
Authors: Zhang Shu Ling , Zhang Zhen Xiu , Kang Dong jin , Bang Dae Suk , Kim Jin Kuk
Published: August 2014

In this article, the possibility of obtaining the recycled material based on waste polypropylene (WPP) and waste ground rubber tire powder (WGRT) has been studied. It has been proved that partially replacing WPP with PP-g-MA increased the elongation at break of WPP/WGRT blends, whereas decreased the thermal stability. The presence of compatibilizer increased the elongation at break and thermal stability of WPP/WGRT blends, whereas decreased the processing flowability, as revealed by using universal testing machine (UTM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and capillary rheometer. Moreover, the tendency of the change became more obvious with the content of PP-g-MA and compatibilizer or with the combination of PP-g-MA and compatibilizer. In addition, the improvement of the nonpolar compatibilizer (SEBS) in properties of WPP/WGRT blends was better than that of the polar compatibilizer (SEBS-g-MA).
Microstructure and properties of PET/EPDM, EPDM-g- MA/organoclay ternary hybrid nanocomposites: effect of blending sequence
Authors: Khatibi Morad Ali , Arefazar Ahmad , Esfandeh Masoud
Published: August 2014

Poly(ethylene terphthalate) (PET)/organomontmorilonite (OMMT)/maleic anhydride ethylene-propylene-diene rubber (EPDM-g-MA) nanocomposites were prepared via melt blending of the ingredients in a Haake Rheocord mixer. To make the hybrid composites, four different blending routes were examined: 1) preparing EPDM/EPDM-g-MA (EPMA)/organoclay nanocomposite and then blending it with PET, (S1), 2) dispersion of organoclay in PET and then blending it with EPMA, (S2), 3) blending PET with EPMA and then mixing it with organoclay, (S3), 4) blending PET, EPMA and organoclay in a single process, (S4). The microstructure of the PET/(EPMA)/organoclay ternary hybrids were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The result showed that the blending sequence greatly affects the dispersion of organoclay in the polymer matrix as well as the microstructure of the blends. Mechanical behavior of the blends including tensile and impact properties were also studied. Results revealed that PET/ (EPMA)/organoclay nanocomposites made by mixing sequence, S1, has the maximum tensile and impact strength among the others. This was attributed to its fine “Sea-Island” morphology and good dispersion of the organoclay in the continuous PET matrix.