bluuebunny/crossref_metadata_2025 huggingface dataset:
Polypropylene + Polystyrene Blends with a Compatibilizer. Part I. Morphology and Thermophysical Properties
Authors: Brostow Witold , Holjevac Grguric Tamara , Olea-Mejia Oscar , Rek Vesna , Unni Jaykumar
Published: August 2014

Various concentrations of polypropylene (PP) and polystyrene (PS) blends were prepared with styrene-ethylene/butylene-styrene block copolymer (SEBS) added as a compatibilizer between the two main polymers. We have investigated the effect of SEBS on processing, morphology and thermophysical properties of the blends. The compatibilizing agent improves the blend morphology since smaller particles of the dispersed PS phase in the PP matrix blends are obtained; adding more than 5 % SEBS has no further effect on the blends. The presence of SEBS lowers the crystallinity of the PP-rich phase - as reflected in the enthalpy of fusion and also in the enthalpy of crystallization.
Characterization of acrylic copolymer latex modified by fluorine, silicon, and epoxy resin
Authors: Xiong Pingting , Guan Rong , Lu Deping , Chen Peizhi , Hongzhi Huang Ling Shen
Published: August 2014

The ever-increasing demand of waterborne heavy-duty coatings for high resistance to many aggressive environment factors and low-surface energy has spurred the ongoing development of acrylic latex modified by fluorine, silicon, and epoxy resin. The morphology of the latex particles were characterized by means of light scattering and transmission electron microscopy (TEM). The stability measurements of modified latex and films showed that the resultant acrylic copolymers containing fluorine, silicon and epoxy resin represented very good resistance to organic solvent, acid and base, water and heat. From contact angle measurements and atomic force microscopy (AFM), a dense and gradient film with surface energy as low as 16.1 mN/m was obtained.
High density polyethylene/boron carbide composites for neutron shielding
Authors: Yasin Tariq , Khan Muhammad Nasir
Published: August 2014

Composites of high density polyethylene with three different amounts of modified boron carbide namely: 7 phr (parts per hundred parts of resin), 15 phr and 24 phr have been prepared. These composites show excellent thermal neutron shielding properties which increase with the increase of boron content in the composites matrix. Moreover, the effects of boron carbide on the mechanical properties, the effect of thermal oxidative aging on mechanical properties and swelling of composites in different solvents have also been studied in these composites.
Review on the thermo-oxidative degradation of polymers during processing and in service
Authors: Gijsman Pieter
Published: August 2014

During processing as well as in service life, polymers degrade. For the majority of polymers this is due to oxidative processes. In this review the mechanism of the thermo-oxidative degradation of the most important (unstabilized) polymers as well as the factors determining the degradation rates are discussed.
The effect of extraction condition on gel spun super denier PVA fiber structure and properties
Authors: Yumin Xia , Zhixin Wang , Huigong Tang
Published: August 2014

This paper is directed towards PVA monofilament with good mechanical properties and super denier, which was produced with the gel spinning technique, first used by K. YAMAURA, used to strengthen the concrete. The structure and properties of PVA fiber were affected especially by extraction conditions, including the temperature, the solvent content and the duration of the extraction, all of which were studied and the optimum parameters were selected.
Biodegradable poly(vinyl alcohol-lactic acid-aspartic acid) copolymers
Authors: Tudorachi Nita , Lipsa Rodica
Published: August 2014

The aliphatic polyesters: polylactides (PLA), polyglycolides (PGA), poly( -caprolactone) (PCL) as well as their copolymers especially, poly(lactide-coglycolide) (PLGA), poly(vinyl alcohol) (PVA), chitosan, dextran and starch occupy first place among biodegradable, biocompatible and non-toxic polymers. PVA, with different molecular weights, hydrolysis degree, tacticity, crystallinity, and due to the abundance of pendant hydroxy groups in the backbone is capable of several grafting and cross-linking. The present study concerns the synthesis of graft copolymers poly(vinyl alcohol) with lactic acid (LA) and aspartic acid (Asp). The modification reaction of poly(vinyl alcohol) with lactic and aspartic acid was achieved by solution polycondensation using dioxane/water (3/1) as solvent mixture, different molar ratios PVA/LA/Asp and manganese acetate as catalyst: Mn(CH3COO)2 4H2O. The copolymers were characterized by FTIR, 1H-NMR, thermal stability (DSC, TG), elemental analysis, wide angle X-ray diffraction (WAXD). The average particle size and zeta potential for aqueous dispersions of copolymers, solubility in organic solvents and biodegradation testing on agar-agar medium inoculated with a fungus Chaetomium globosum class MO5 stock, were studied.
Thixotropy of aqueous solution of fluorocarbon-modified poly(acrylic acid)
Authors: Hu Hongqi , Li Lin , Chen Mingcai
Published: August 2014

The rheological properties of the aqueous solution of 1H,1H,11Hperfluoroundecyl acrylate -modified poly(acrylic acid) were studied. It was found that the solutions show different viscosity dependence on shear time at different pH and shear rates. At lower pH and moderate shear rates, the viscosity of the solutions shows a great increase with time. At pH 5.0 and above, it exhibits thixotropy at any shear rate, i.e., the viscosity decreases with time at constant shear rates. If the shearing stops, the viscosity of the solutions can be recovered to some extent. These phenomena are interpreted to be due to the intermolecular hydrophobic association: the construction of the association leads to an increase of the viscosity, the destroying of the association leads to a decrease of the viscosity. The pH-induced conformational change and the shearing-induced chain elongation jointly influence the intermolecular hydrophobic association.
Infrared study of the photochemical behaviour of aromatic poly(ether urethanes): effect of various stabilizers
Authors: Mendikute G. , Irusta L. , Fernández-Berridi M.J.
Published: August 2014

The influence of various additives on poly(ether-urethane) UV stability is evaluated. The extent of the photo degradation has been studied by FTIR spectroscopy. The photo-stabilizer 2-hydroxy-benzophenone decreases the photooxidation on both hard and soft segment, whereas the effect of the phenolic antioxidant 2,6-di-t-butyl-4-hydroxytoluene is more significant on the soft segment. However, the effect of the nickel chelate, 2,2’-thiobis(4-t-octylphenolate)-nbutylamine of nickel, depends on the polyurethane nature.
Effect of rosemary extract on the radiation stability of UHMWPE
Authors: Zaharescu Traian , Jipa Silviu , Artenie Mariş Dan , Mariş Maria , Kappel Wilhelm
Published: August 2014

This paper presents the assay on the radiochemical degradation of UHMWPE films containing rosemary. Three concentrations of natural polyphenolic extract were selected: 0, 0.25 and 0.50 % (w/w). FTIR and UV-VIS spectra were recorded and the variation in the characteristic bands was followed. The accumulation of carbonyl and hydroperoxyl structures was attempted for all samples including neat specimen. The contribution of additive to the protection of UHMWPE against oxidative degradation is discussed in relation with polyphenol concentration and irradiation dose. The spectral information is correlated with the results of chemiluminescence investigation. The increase in the additive concentration brings about significant longer induction times that are determined by the slower accumulation of primary intermediates, hydroperoxides. The antioxidant efficiency of rosemary extract is also revealed by the variation in carbonyl and hydroxyl indexes.
Fabrication and properties of PVDF/expanded graphite nanocomposites
Authors: Li Yuchao , Li R. K. Y. , Tjong S. C.
Published: August 2014

Poly(vinylidene fluoride) (PVDF) nanocomposites filled with various expanded graphite (EG) contents were prepared via melt-mixing followed by hotpressing. The structure, electrical, and thermal properties of resulting nanocomposites were investigated. X-ray diffraction results indicated that the EG additions do not lead to structural changes of PVDF. Differential thermal calorimetry measurements revealed that EG act as a nucleating agent for PVDF molecular chains. The crystallization temperature shifted to higher temperature with increasing EG content. DMA results showed that the storage modulus and glass transition temperature can be enhanced by adding EG. The nanocomposites were found to exhibit a small percolation threshold of 6.3 vol% due to the large aspect ratio of graphite nano-sheets. A great enhancement of dielectric constant is also found as EG concentration approaches percolation threshold. Both the electrical conductivity and dielectric constant of PVDF/EG nanocomposites can be well described by the percolation theory.
Preparation and characterization of carbamoylethyl hemicelluloses
Authors: Ren Jun-Li , Peng Feng , Sun Run-Cang , Zhang Xun-Li
Published: August 2014

The reaction of hemicelluloses, isolated from wheat straw, with acrylamide in alkaline aqueous solution was investigated. The degree of substitution (DS, up to 0.65) of the products could be obtained by adjusting the molar ratios of reagent to xylose unit in hemicelluloses (1.0-10.0) and the molar ratios of catalyst to xylose unit in hemicelluloses (0.5-1.6). Changes in the structure of hemicelluloses were verified by FT-IR and 1H and 13C NMR spectroscopies. The results showed that carbamoylethyl groups surely were grafted onto the main chain of hemicelluloses. Moreover, it was also found that the saponification of carbamoylethyl groups to carboxyl groups occurred in alkaline medium. The behavior of modified hemicelluloses was monitored by means of thermo gravimetry (TG) and differential thermal analysis (TGA). It was found that the products had a lower thermal stability than the native hemicelluloses.
Rheological properties of conductive polymer composite (CPC) filled with double percolated network of carbon nanoparticles and boron nitride powder
Authors: Droval Guillaume , Feller Jean-François , Salagnac Patrick , Glouannec Patrick
Published: August 2014

In this study, double percolated network of carbon nanoparticles and ceramics powder is used to uncouple electrical and thermal conductivity of polymer composite. The influence of ceramic powders on morphological properties of a biphasic conductive polymer composite (CPC) is investigated by means of rheological measurements. The biphasic materials studied are blends of a thermally conductive polymer phase (syndiotactic poly(styrene) (sPS) filled with boron nitride (BN)) with an electrically conductive polymer phase (high-density poly(ethylene) (hdPE) filled with nano-structured carbon black (NCB)) into a cocontinuous structure. The elastic modulus (with viscous modulus) was found to be the most sensitive rheological property to accurately detect the co-continuous morphology in our system. It was found to be at 40% v/v of hdPE-NCB, which can be interpreted as the phase inversion.
The thermal behaviors of Ag/polyamidoamine nanocomposites
Authors: Peng Zheng , Zhang Jianmin , Diao Jianzhi , Mei Shigang
Published: August 2014

Ag/polyamidoamine nanocomposites were produced by photoreduction of relevant metallic salts in polyamidoamine methanol solutions under room temperature and ambient pressure. The obtained products were characterized by FTIR, XRD, TEM, TGA and DSC techniques. The results showed that Ag nanoparticles were quite uniform in size with a diameter of about 15 nm, and the amount of Ag nanoparticles could well affect the thermal stability and the glass transition temperature of polyamidoamine. As the mass ratio of Ag nanoparticles to polyamidoamine increased, the glass transition temperatures were increased, while the weight loss ratios were decreased. TGA curves indicated that the loading of Ag nanoparticles mainly influences the high temperature thermal stability of polyamidoamine. Moreover, the multistage decomposition profile of DTG curves suggested that the Ag/polyamidoamine nanocomposites of higher silver loading might contain some intermediate Ag+/polyamidoamine type of composites.
The polymeric crystallinity effect on the responses of bone marrow stromal cells
Authors: Yi Qiangying , Wen Xiantao , Li Li , He Bin , Wu Yao , Nie Yu , Gu Zhongwei
Published: August 2014

The cell-material interaction is an important factor to be considered in the applications of biomaterials. The properties of biomaterials, for example crystallinity, would change the cell behaviors such as proliferation, differentiation, morphology and so on. In this article, the research was focused on the relationship between the crystallinity of polymeric substrates and the cell responses. Two kinds of biodegradable poly(L-lactide) (PLLA) films with different crystallinity were prepared and used as substrates for cell behavior study. The PLLA films were fabricated with crystallinity of 19% and 69% through solution casting and isothermal processing, respectively. The crystallinity of PLLA films was characterized by DSC and XRD. The surface morphologies of PLLA films with different crystallinity were observed by SEM. Bone marrow stromal cells (MSCs) isolated from the marrow of new born male Sprague Dawley rats were cultured on the films. The cell morphology, proliferation, total protein amount and alkaline phosphatase (ALP) activities were tested. The results showed that the crystallinity of PLLA films affected the behavior of MSCs greatly.
One pot synthesis and characterization of industrially important graft copolymer (GOH-g-ACM) by using peroxymonosulphate/ mercaptosuccinic acid redox pair
Authors: Srivastava Arti , Mishra Vivek , Kumar Singh Shailendra , Kumar Rajesh
Published: August 2014

Guar gum-g-polyacrylamide is a graft copolymer which is used for many industrial applications. This paper outlines the details of synthesis of guar gum -gacrylamide by using potassium peroxymonosulphate/ mercaptosuccinic acid redox pair in an inert atmosphere and their characterization by infrared spectroscopy, UV analysis and study of swelling and thermal properties. Grafting characteristics: %G, %E, %C, %A and %H were determined by using Fanta’s definition; rate of grafting was also calculated. On studying the effect of reaction conditions on grafting characteristics, it was found that the optimum concentration of peroxymonosulphate, mercaptosuccinic acid, hydrogen ion, acrylamide and guar gum for maximum % of grafting were 8.0×10-3, 3.2×10-3, 8.0×10-3, 16.0×10-2 mol dm-3 and 60.0×10-2 g dm-3 respectively. The optimum time duration and temperature of reaction were found to be 120 min and 40 °C respectively. During the study [H+] variation showed prompt changes on grafting characteristics. It was found that after 310 °C the polyacrylamide grafted guar gum was thermally more stable than pure guar gum.
Barrier and physical properties of polypropylene/highbarrier ethylene vinyl alcohol copolymer blends compatibilized with a sodium ionomer
Authors: Ares Ana , Abad María J , Barral Luis , García-Garabal Sandra
Published: August 2014

The aim of this work is to investigate the properties of the PP/EVOH films for their potential use in the packaging industry. Besides, the barrier properties, the mechanical parameters and the morphology of the PP/EVOH films have been studied as function of their composition and the processing technique used for their manufacture. In these applications, the package is frequently in contact with humidity environments and for this, it is necessary to know how environments with different humidity contents, affect the O2 permeability of the polymer material. For these reasons, the influence of the moisture in the values of permeability was evaluated too. The data showed that the oxygen transmission rate (O2TR) decreased with the amount of EVOH, and if the copolymer mass is maintained constant, the O2TR diminished with the quantity of the ionomer in the compositions. Besides, the films obtained by extrusion and following unidirectional stretching, presented better barrier properties to the oxygen molecules than the compression moulded films. When the ionomer is added to the compositions the permeability is reduced even for the films maintained in wet atmosphere. The micrographs obtained by SEM showed that the films have a biphasic structure, where the EVOH particles are dispersed in the PP matrix.
Toughening of PBT/PC blends with epoxy functionalized core-shell modifiers
Authors: Zhang Fangfang , Sun Shulin , Liu Xiaoyun , Zhang Lixia , Zhang Huixuan
Published: August 2014

Core-shell modifiers of MB-g-GMA have been synthesized by emulsion polymerization technique. For these modifiers, the core is made up of the crosslinked poly(butadiene) and the shell is methyl methacrylate (MMA) and glycidyl methacrylate (GMA) copolymer. These modifiers were used to toughen poly(butylene terephthalate) (PBT)/bisphenol A polycarbonate (PC) blends. The mechanical properties showed that the addition of 15% MB-g-GMA had a very good influence on the notched Izod impact strength and elongation at break of the PBT/PC blends. DMA results showed PBT was partially miscible with PC and the addition of MB-g-GMA further improved the miscibility of PBT and PC. DSC tests further testified the introduction of MB-g-GMA improved miscibility between PBT and PC. Scanning electron microscopy (SEM) displayed a very good dispersion of MB-g-GMA particles in PBT/PC blend. Transmission electron microscopy (TEM) proved MB-g-GMA particles were enveloped by a thin layer of PC, PBT and PC showed co-continuous structure or dispersed phase which depended on the content of MB-g-GMA. SEM results showed shear yielding of the matrix and cavitation of rubber particles were the major toughening mechanisms.
Selective recognition of methotrexate by molecularly imprinted polymers
Authors: Curcio Manuela , Parisi Ortensia Ilaria , Cirillo Giuseppe , Spizzirri Umile Gianfranco , Puoci Francesco , Iemma Francesca , Picci Nevio
Published: August 2014

The aim of this study is the preparation of molecularly imprinted polymers with high selectivity for metotrexate (MTX), a useful antineoplastic drug widely employed in clinical trials. Methacrylic acid, 2-(dimethylamino)ethyl methacrylate and a mixture of them were tested as functional monomers in order to optimize the performance of imprinted materials. The specificity and the selectivity of imprinted polymers was tested by performing rebinding experiments in water at pH 7.4. The best results were obtained by employing both functional monomers in the polymeric feed. In this way, each monomer interacts with complementary functionalities on template molecule, stabilizing the prepolymerization complex and minimizing the repulsive effects (due to the ionization of functional groups) in the rebinding media.
Piezoresistive polymer composites based on EPDM and MWNTs for strain sensing applications
Authors: Ciselli Paola , Lu Lan , Busfield James J.C. , Peijs Ton
Published: August 2014

Elastomeric composites based on Ethylene-Propylene-Diene-Monomer (EPDM) filled with multi-wall carbon nanotubes (MWNTs) have been prepared, showing improved mechanical properties as compared to the pure EPDM matrix. The results have been discussed using the Guth model. The main focus of the study was on the electrical behavior of these conductive polymer composites (CPCs), in view of possible sensor applications. A linear relation has been found between conductivity and deformations up to 10% strain, which means that such materials could be used for applications such as strain or pressure sensors. Cyclic experiments were conducted to establish whether the linear relation was reversible, which is an important requirement for sensor materials.
Second harmonic generation and photochromic grating in guest-host polymer system containing azo amide chromophores
Authors: K. Marański , S. Kucharski , E Ortyl , R. Janik , J.-M. Nunzi , S. Ahmadi-Kandjani , R. Barille
Published: August 2014

The azo sulfonamide chromophores containing long aliphatic chain were used as active nonlinear optical (NLO) materials in films prepared by spin-coating on glass surfaces. The sulfonamides were: N-{4-[{4-[(pyrimidin-2-ylamino)sulfonyl]phenyl}diazenyl]phenyl} decanamide (Amid P); N-{4-[{4-[(1,3-thiazol-2-ylamino)-sulfonyl]phenyl}diazenyl]phenyl} decanamide (Amid T) and N-{4-[(4-nitrophenyl)-diazenyl]-phenyl}undec-10-enamide (Amid N). The host matrix was a copolymer of methyl and butyl methacrylate. The formation of diffraction grating by the guest-host system was successful only in the case of Amid N. The pitch and amplitude of the grating was 930 nm and ca. 45 nm, respectively. Quantum chemical calculations revealed that the chromophores were moderate NLO-fores showing static β values of ca. 110-130 m4/V. Two procedures were involved to align chromophores to determine first order NLO susceptibility: a) corona poling, and b) all-optical poling. The NLO coefficient d33 determined in corona poled film was 25.2, 28.6 and 93.2 pm/V for Amid P, T and N, respectively.
L-Lactide polymerization by calix[4]arene-titanium (IV) complex using conventional heating and microwave irradiation
Authors: Frediani Marco , Sémeril David , Matt Dominique , Rizzolo Fabio , Papini Anna Maria , Frediani Piero , Rosi Luca , Santella Marco , Giachi Guido
Published: August 2014

Since the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called “microwave effect” and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment.
Preparation and properties of polyurethane foams from hydroxypropoxy derivatives of urea and isocyanates
Authors: Zarzyka-Niemiec Iwona , Rydel Katarzyna
Published: August 2014

The products of hydroxyalkylation of N,N’-bis(2-hydroxypropyl)urea (BHPU) with large molar excess of propylene carbonate (PC) posses enhanced thermal stability. These products and 4,4’-diphenylmethane diisocyanate were used as substrates for obtaining rigid polyurethane foams, which had high thermal stability and low water uptake.
Charge storage and mechanical properties of porous PTFE and composite PTFE/COC electrets
Authors: Ko Wen-Ching , Tseng Chien-Kai , Wu Wen-Jong , Lee Chih-Kung
Published: August 2014

Recent futuristic applications of flexible electret loudspeakers have garnered much interest for these novel loudspeakers. To increase the loudspeaker properties, a processing method was developed to improve the electret and mechanical properties of porous PTFE film. Taking a thin porous PTFE film as the base material, a cyclic olefin copolymer (COC) was coated to a base material to form a PTFE/COC composite film. Results show that the composite material improves the advantageous characteristics when used as an electret diaphragm for loudspeakers. By measuring the surface potential decay and the elastic modulus, properties of a standard porous PTFE film were compared to an improved composite PTFE/COC film. Experimental results showed that the composite PTFE/COC possess the following advantages: (1) 80% higher surface potential after 10 days at room temperature, (2) a better thermal resistance of charge storage, and (3) a 643% higher elastic modulus. Therefore, our novel composite material can be used to create a much improved electret diaphragm for flexible electret loudspeakers.
Optimization of chitosan-polyvinylalcohol electrospinning process by response surface methodology (RSM)
Authors: Gholipour A. , Bahrami S. H. , Nouri M.
Published: August 2014

Response Surface Methodology (RSM) is a collection of statistical and mathematical techniques useful for developing, improving, and optimizing processes. RSM was used to model and optimize the electrospinning parameters for the spinning of blend CS/PVA nanofibers. In this study, chitosan (CS)/polyvinyl alcohol (PVA) blend solutions (CS (Mw =1 X 106) in 2% acetic acid and PVA (Mw=12 X 103) in deionized water) with different blend ratio ranging from 10/90 to 50/50 were electrospun. CS/PVA (25/75) blend ratio was chosen as base and optimum ratio due to its suitable morphological properties and diameter. In a constant ratio of blend SEM analysis shows that the diameter of nanofibers changed by varying the voltage and extrusion rate in the electrospinning process. Voltage (10-25 KV) and polymer solutions extrusion rate of (0.2-1 ml/hr) from the nozzle were chosen as variables to control the fiber diameter at similar spinning distances (10 cm). Fiber diameter was correlated to production variables by using a second order polynomial function. The predicted fiber diameters were in good agreement with the experimental results.
Poly(ethylene terephthalate)-carbon nanofiber nano composite for fiber spinning; properties and combustion behavior
Authors: Alongi Jenny , Frache Alberto
Published: August 2014

Carbon nanofiber (CNF)-polyethylene terephthalate (PET) blends were previously prepared by melt blending and, subsequently, melt spun in order to obtain nanostructured fibers characterized by high flame retardant properties and resistance to the combustion. The morphological analysis showed that CNFs are homogeneously distributed and finely dispersed within PET matrix. The mechanical properties in tensile testing of the fibers change in the presence of CNFs: the elongation at break increases, whereas the tenacity and the tensile strength decrease. The combustion tests by cone calorimetry reveal a relevant decrease of heat release rate, total heat evolved and total smokes released by the nanocomposites as compared to neat PET.
Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization
Authors: John Joseph , Sivaraman Sajeev , Jaylekshmi S.
Published: August 2014

Polypyrrole is a widely studied conducting polymer with excellent optical and electrical properties. Polypyrrole thin films in the pristine and iodine doped forms have been prepared by ac plasma polymerization. The in situ doping of iodine during the process of plasma polymerization modified the optical absorption behaviour of the thin films due to the incorporation of charged defects in the film structure. Optical band gap and related constants are estimated from optical absorption studies. The Urbach tail analysis of the pristine and doped thin films shows that more defect levels are created, when the polymerization was carried out in the iodine atmosphere. The electrical properties of these thin films were estimated from the conductivity measurements. It is found that in the case of iodine doped films, the optical band gap decreased and electrical conductivity enhanced when compared to the pristine ones. The results are correlated with the structural differences of the pristine and doped thin films with the help of Fourier Transform Infrared Spectroscopy (FTIR) analysis.
Preparation and properties of fluorosilicone and fluorosilicone elastomer with various contents of trifluoropropyl groups
Authors: Cui Yan , Jiang Wenge , Li Dongmei , Niu Chengqun ,   Jiezhang, Feng Shengyu
Published: August 2014

Poly(dimethyl-methyltrifluoropropyl-methylvinyl)siloxanes (PFMVS) with various contents of trifluoropropyl groups were prepared by ring-opening copolymerization of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (D3F), octamethylcyclotetrasiloxane (D4) and 1,3,5,7-tetramethyl tetravinylcyclotetrasiloxane (D4Vi). All the polymers were characterized by IR, 1HNMR, 29SiNMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The results show that methyltrifluoropropyl-siloxane units in the copolymer can disrupt the molecular regularity and lead to noncrystalline copolymers with low glasstransition temperatures. Moreover, the onset temperatures of thermal degradation and the glass transition temperatures of polymers decrease gradually with the content of trifluoropropyl groups increasing. Then the thermal stability and solvent resistance of elastomers based on PFMVSs were measured. The data of TGA indicate that the thermal stability of fluorosilicone elastomers are less than conventional methyl vinyl silicone rubber (MVQ), but the fluorosilicone elastomers have outstanding solvent resistance. The content of the trifluoropropyl groups influences the performances of elastomer to a certain degree.
Polymer composites as sensing materials for liquid organic solvents – preliminary results
Authors: Frackowiak Stanislaw , Maciejewska Monika , Szczurek Andrzej , Kozlowski Marek
Published: August 2014

Carbon black-filled polymer composites were investigated as sensing materials for organic liquids. Polypropylene and polystyrene which were selected as matrices and various amounts of carbon black were considered as the main factors influencing sensitivity of the composites in view of the percolation theory. Disposable filaments were produced of these materials. Change in their electrical resistivity was measured upon immersion in benzene, toluene, xylene, ethylbenzene and their mixtures. It has been found that studied materials were sensitive to the composition of liquid mixtures of organic solvent. Relationships between the filament response and volumetric fraction of the components were presented. The studied materials have shown promising sensing properties, which suggest their applicability for identification and quantification of multicomponent organic liquids.
Synthesis of thermotropic polyurethanes containing ester mesogen units and their mesophase behavior
Authors: Ban Jian-Feng , Lu Shao-Rong , Zhang Chenxi , Liu Ting , Huang Zhiyi
Published: August 2014

A series of novel thermotropic liquid crystalline was synthesized from bi(p-hydroxyl benzoic acid)hydroquinone ester (PHQ), triethylene glycol and 2,4- toluenediisocyanate (2,4-TDI) by altering the molar ratio of PHQ and diol, and PHQ was prepared by using hydroquinone and p-hydroxybenzoic acid as raw materials. The thermotropic mesophase behavior, the melting point temperature (Tm) and the isotropization temperature (Ti) of the synthesized polyurethanes were characterized by FT-IR, DSC and POM. It showed that all of the polyurethane polymers exhibited nematic textures at temperature of 110~230 °C. The shift of the melting and isotropization temperature (Tm, Ti) to lower temperature is discussed to be a consequence of the increasing amount of diol content.
Preparation of polyacrylonitrile via AGET ATRP initiated by CCl4
Authors: Ma Jing , Chen Hou , Zong Guangxi , Wang Chunhua , Liu Delong
Published: August 2014

A commercially available alkyl halide carbon tetrachloride (CCl4) was used as the initiator for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of acrylonitrile (AN) in N,N-dimethyl formamide (DMF). Environmentally benign ascorbic acid (VC) was chosen as the reducing agent and copper bromide (CuBr2) as the catalyst precursor together with iminodiacetic acid (IDA) as the ligand. The polymerization proceeded in a controlled manner as evidenced by kinetic of AGET ATRP of AN, a linear increase of number-average molecular weight (Mn) with monomer conversion and low polydispersity index (PDI) throughout the reactions. The monomer (AN) conversion increased with the increase of VC and CCl4. The value of PDI increased with the increase in concentration of VC. For an increase of CCl4, the value of PDI decreased first and then increased. 1H-NMR spectrum of PAN further confirmed the “living”/controlled feature of AGET ATRP of AN.
Modification and shaping of carbon nanotubes with an electron beam
Authors: Xu Zhiwei , Wang Rui , Wang Chunhong , Liu Liangsen , Chen Lei , Chen Guangwei
Published: August 2014

The paper reviews the modification and shaping of electron beam irradiation on carbon nanotubes (CNTs), as well as how this could be potentially useful for electron beam modification of nanotubes. The influence of irradiation on the mechanical property, electrical property and field effect of CNTs is discussed. Several examples are given with particular emphasis on the cutting, shaping and welding of CNTs by the electron beam in an electron microscope. It is shown that the change of incident electron energy and ambient temperature will lead to the different irradiation results. It is expected that electron irradiation studies will continue to play an important role in the research on CNTs.
Thermal stability, crystallization and mechanical properties of nylon11/montmorillonite nanocomposites
Authors: Li Yingchun , Hu Guosheng , He Bin
Published: August 2014

Nylon 11 nanocomposites with different montmorillonite loadings were successfully prepared by melt compounding. XRD and TEM show the exfoliated nanocomposites are formed at low montmorillonite concentration (less than 2 wt%) and the intercalated nanocomposites are obtained at higher montmorillonite contents. TGA shows that the thermal stability of the nanocomposites is improved by 27 °C when the montmorillonite content is only 2wt%. At the same time, The crystallization behavior of nylon11/montmorillonite nanocomposites has been studied by means of XRD, DSC.The Avrami equation described well the isothermal crystallization behavior of nylon11 and nylon11/montmorillonite nanocomposites. The results showed that the montmorillonite acted as the nucleating agent and facilitated the crystal growth rate of nylon 11 matrix. The incorporation of montmorillonite did not change the crystal morphology of nylon 11 but increased the crystallization temperature and decreased the crystallization activation energy, which lead to a easy crystallization of nylon11. Mechanical testing shows that the Izod impact strength of all nanocomposites are higher than that of the neat nylon 11, but the tensile strength of the nanocomposites decrease at low nanofiller concentrations (less than 8wt%) and then increased, when the montmorillonite content is 10wt% ,the tensile strength of the nanocomposite is 5% improved than neat nylon 11. This is may be due to the strong interaction between the nylon 11 matrix and the montmorillonite interface.
Tribological behavior of an ultrahigh molecular weight polyethylene in lubricated environments
Authors: Kahyaoglu O. K. , Unal H , Mimaroglu A , Yetgin S.H.
Published: August 2014

The wear and friction performance of GUR 1020 grade ultrahigh molecular weight polyethylene (UHMWPE) polymer was studied in distilled water, HASS (Hank’s balanced salt solution) and several protein lubrication environments. Wear tests were carried out using polymer pin -on AISI 304L stainless steel disc apparatus. Tests conditions were room temperature, 40N, 80N and 120N applied loads and 0.5 m/s sliding speed. For the range of load and speed value of this work, the coefficient of friction and wear rate for UHMWPE polymer decreases with the increase in applied load values. The coefficient of friction is highest and the specific wear rate values is lowest under HASS +HA solution lubricant. The average specific wear rate values for UHMWPE polymer under distilled water and HASS+HA (Hank’s balanced salt solution with Hyaluronic acid) lubrication conditions are in the order of 9x10-15 m2/N and 3x10-15 m2/N respectively. The wear mechanism includes abrasion and adhesive processes.
Copolymerization of acenaphthylene with methacrylic monomers
Authors: Navarro L. , Bilbao E. , Laza J.M. , Vilas J.L. , Garay M.T. , Rodríguez M. , León L.M.
Published: August 2014

The copolymerization of acenaphthylene with methylmethacrylate, ethylmethacrylate, butylmethacrylete, iso-butylmethacrylate and cyclohexylmethacrylate has been carried out in tetrahydrofuran at 323 K and the composition of the copolymers has been determined by size exclusion chromatography using a double RI-UV detector system. Several methods have been applied to obtain the reactivity ratios of the copolymerization process. The glass transition temperature of the copolymers has been obtained by DSC and the thermal stability has been studied by thermogravimetry. Analysis of the degradation volatile products reveals that copolymers degrade mainly by depolymerization.
Hypercrosslinked polystyrene microspheres by suspension and dispersion polymerization
Authors: Šálek Petr , Horák Daniel
Published: August 2014

To determine the influence of particle size on the specific surface area of hypercrosslinked poly(styrene-co-divinylbenzene) (PS) microspheres, two methods were chosen for preparation of particles, suspension and dispersion polymerization. While the former method produced hundred micrometer-sized PS-S microspheres, the latter yielded PS-D particles of ca. 1-μm size. Dispersion copolymerization of styrene (St) and divinylbenzene (DVB) in ethanol was stabilized by (hydroxypropyl)cellulose (HPC) and initiated with dibenzoyl peroxide (BPO). Monodisperse 1.4-μm PS-D microspheres were prepared only in the presence of 3.6 wt% HPC. All microspheres were chloromethylated with chloromethyl methyl ether (CMME), chloromethyl ethyl ether (CMEE) or chloromethyl octyl ether (CMOE) to investigate the effect of the chloromethylation agent on the specific surface area of microspheres. Chloromethylated microspheres were hypercrosslinked in 1,2-dichloroethane (DCE) in the presence of a Lewis acid (SnCl4). The effects of the crosslinker (DVB) and DCE/microsphere ratio on properties of the product were studied. The specific surface area, pore volume and pore size distribution of the microspheres were analyzed by dynamic desorption of nitrogen, cyclohexane regain and mercury porosimetry.
Synthesis, characterization and properties of novel thermally stable copoly(amide-imide)s containing dimethylsilane moieties
Authors: Kolahdoozan Majid , Ghoreishi Monir S.
Published: August 2014

New type of poly(amide-imide)s were prepared based on novel diacid monomer containing softening siloxane groups. Bis(p-aminophenoxy) dimethyl silane (3) was prepared by the reaction of dimethyl dichlorosilane with paminophenol in toluene. N,N'-Bis(4-trimellitimidophenoxy) dimethylsilane (5) as a novel aromatic dicarboxylic acid containing silicone moiety was synthesized by condensation of bis(p-aminophenoxy) dimethylsilane with trimelitic anhydride in acetic acid. The structure of diacid 5 was confirmed using various spectroscopy methods. The direct polycondensation technique was used for the polyamidation of monomer 5 with several aromatic diamines using pyridine / 2-methylpyrrolidone / triphenyl phosphite / CaCl2 as condensing agent. The resulting novel poly(amideimide- siloxane)s were obtained in high yields and inherent viscosities. These polymers were characterized using FT-IR, 1H-NMR, thermogravimetric and elemental analysis techniques. The results show that silicone modified poly(amideimide) s show high solubility and excellent thermal stability.
A predictive model for the synthesis of polylactide from lactic acid by response surface methodology
Authors: Agarwal P. , Mondal A. , Mishra P.K. , Srivastava P.
Published: August 2014

The present work describes the statistical process optimization of a lowcost production process of PLA using organometallic (stannous octoate) compounds. The process optimization for both lactide and polylactide, was developed by factorial design and response surface methodology. The influence of different experimental parameters such as reaction temperature, time, concentration of catalyst and co-initiator concentration on the yield of lactide and polylactide has been evaluated. There are many studies reported on the synthesis of polylactide but no earlier study exists for the application of statistical analysis in determining the interactions among the process variables for lactide and polylactide production. Central composite experimental design with multiple linear regression has been used to estimate the coefficients of the polynomial model equation for the yield(s) of both lactide and polylactide. The statistical significance of polynomial model equation was validated by F test (ANOVA). Determination coefficient (R2) values found to be 0.913 and 0.958 for lactide and polylactide respectively, states that predicted values were in good agreement with the experimental values. Results of the statistical analysis showed that the model fits in all cases. Above synthesised polymer was characterized by FT-IR, 1H-NMR, DSC and GPC to confirm the polymer structure and properties.
Preparation and characterization of poly(acryl amide-coacrylic acid)/nay and Clinoptilolite nanocomposites with improved methylene blue dye removal behavior from aqueous solution
Authors: Zendehdel M. , Barati A. , Alikhani H.
Published: August 2014

The nanocomposites of poly(acryl amide-co-acrylic acid) with NaY and Clinoptilolite were prepared using ammonium persulfate as an initiator and N,N′- methylene bis acryl amide as the cross-linker. The morphology was characterized by SEM and the structure of nanocomposite materials was studied with XRD and FT-IR that showed the interaction between porous materials and poly(AAm-co- AAc). Thermo gravimetric analyzer (TGA) curve shows that all the chain-extended poly(AAm-co-AAc) are stable up to 250 °C and maximum weight loss occurs at 890 °C. The TGA results indicated higher stability for poly(acryl amide-co-acrylic acid)/NaY and Clinoptilolite composites than poly(AAm-co-AAc). The adsorption and desorption behavior of methylene blue were investigated for nanocomposites. It was shown that poly(AAm-co-AAc)/NaY and Clinoptilolite nanocomposites have higher adsorption than NaY, Clinoptilolite and poly(AAm-co-AAc) alone. This effect was attributed to good interaction between the hydroxyl group in porous materials and carboxylic group in poly(AAm-co-AAc) with methylene blue.
Shear degradation resistance of star poly(ethyleneimine) - polyacrylamides during elongational flow
Authors: Duan Ming , Fang Shenwen , Zhang Liehui , Wang Fuxiao , Zhang Peng , Zhang Jian
Published: August 2014

An experimental study of the flow-induced scission behaviour of four star hydrolyzed polyacrylamides (HPMA) with different arms during planar elongational flow in a cross-slot flow cell is described. The results showed that the shear stability of linear HPAM in distilled water was not essentially different from star HPAM. Polymer scission was not observed in either system in a shear rate range from 20,000 to 100,000s-1, which can be attributed to the strong polyelectrolyte behaviour of HPAM in distilled water. However, at the same shear rate, the star HPAMs exhibited superior shear stability in comparison to the linear HPAMs in aqueous solutions containing NaCl (CNaCl=0.2-1.0%wt) and, in particular, the initial reduction rate of relative viscosity (R) decreased with the degree of branching of the HPAMs. In addition, it was found that the R of five HPAMs in NaCl aqueous solutions exhibited an exponential dependence on shear rate, in which the coefficient C1 can be used to quantitatively evaluate shear stability. In star HPAM NaCl aqueous solutions, the increase of R with shear rate is very likely due to the decrease of the hydrodynamic radius (Rh) of these HPAMs, while the increase of R with NaCl concentrations can be attributed to the relatively low viscosity of these polymers at high NaCl concentrations.
Fractional isolation and structural characterization of hemicellulosic polymers from Caragana sinica
Authors: Xiao Ling-Ping , Xu Feng , Sun Run-Cang
Published: August 2014

The cell wall material of Caragana sinica was fractionated by successive extractions with distilled water at 80 °C for 2 h, 70% ethanol, 70% ethanol containing 1% NaOH, 1 M KOH, 1 M NaOH, 3 M KOH, and 3 M NaOH at 75 °C for 3 h. The sequential treatments resulted in a total dissolution of 86.7% of the original hemicelluloses and 80.1% of the original lignin from dewaxed C. sinica. The current results showed that the four alkali-soluble hemicellulosic preparations, comprising almost 80% xylose of the total neutral sugars, were more linear and acidic, but lower molecular weights (Mw, 28420-55140 g/mol) than the other two organosolv-soluble hemicelluloses (Mw, 57930-96470 g/mol). The 1 M KOH-soluble hemicellulosic fraction was characterized by sugar analysis and 1D, 2D NMR spectroscopy and was found to be composed of a linear (1→4)-β-D-xylopyranosyl main chain with a 4 Omethylglucuronic acid substituting the C-2 position of approximately every eight xylose unit, which is typical of a hardwood acidic 4-O-methylglucuronoxylan (MGX).
Percipitation copolymerization of acrylamide and acrylic acid: Determination of reactivity ratio by various methods
Authors: Nazaripour Sedigheh , Rafizadeh Mehdi , Bouhendi Hosein
Published: August 2014

Copolymers of acrylamide ( AM ) and acrylic acid ( AA) were prepared by precipitation polymerization method at 65 °C in the ethyl acetate as solvent. Copolymer composition was determined by elemental analysis. Monomer reactivity ratios were determined in low conversions. Mayo-Lewis, Finemann-Ross, Inverted Finemann-Ross, Ezrielev-Brokhina-Roskin, Kelen-Tudos, Extended Kelen-Tudos and Mao-Huglin methods, as linear methods, and Tidwell-Mortimer, as nonlinear method, were applied to calculate rAM and rAA r reactivity ratios. Monomer reactivity ratios of AM and AA were obtained 0.46 and 0.28, respectively. Comparing of reactivity ratios of AM and AA in this work by other solvents showed that hydrogen bonding and ionic strength are important parameters that can affect the reactivity ratios of monomers. Moreover, microstructure of copolymers was determined using reactivity ratios and conditional probability based on the kinetic model for free-radical polymerization.
Synthesis of artificial opals with core-shell morphology via emulsion polymerization technique
Authors: Shaghaghi Mehri , Yousefi Aliakbar , Pishvaei Maliheh
Published: August 2014

Colloidal crystals with a refractive index varying periodically on the scale of the light wavelengths have been prepared by various methods. These photonic crystals reflect light and exhibit, at sufficiently strong contrast, even a complete band-gap in which light cannot propagate in any direction. In this study we first synthesize the latex spheres with a hard, crosslinked core and a grafted-on elastomeric shell that flows at elevated temperatures under uniaxial compression much like other polymer melts. However, the spheres start crystallizing at the plates of the press, whereupon the crystalline order grows, layer by layer, into the flowing melt. The process is fast and yields large area films, thin or thick, in which the latex spheres are crystallized. The refractive index contrast of these purely polymeric films is too small for a complete band-gap photonic crystal, but the films are attractive color materials showing wavelength and angle dependent reflection colors.