bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Ethylene Polymerization Kinetics over Ziegler-Natta Catalysts: Employing Moment Equation Modeling to Study the Effect of Different Active Centers on Homopolymerization Kinetics
Authors: Salami-Kalajahi Mehdi , Haddadi-Asl Vahid , Najafi Mohammad , Ghafelebashi Zarand Sayyed Mehdi
Published: August 2014

In the present work, ethylene polymerization kinetics was modeled using moment equations. According to the results obtained, the molecular weight distribution of each active center follows a Schultz-Flory distribution. However, the molecular weight distribution of polymer produced is much broader than a Schultz- Flory distribution. Besides, the order of polymerization with regard to monomer concentration is higher than unity. Moreover, the catalyst active centers deteriorate in the presence of hydrogen and consequently catalyst yield drops; nevertheless, polymerization kinetics is not mainly affected by hydrogen. Hydrogen also reduces polymer molecular weight since it is a strong transfer agent in olefin polymerizations. Notwithstanding, it does not affect polydispersity index. Last of all, although increasing cocatalyst concentration does not influence the activity of active centers, it lessens the molecular weight as a transfer agent
Novel poly(aryl ether ketone)s with anthracene in the backbone
Authors: Ying Na , Haibo Zhang , Yunhe Zhang , Yaming Niu , Sibo Jiang , Zhenhua Jiang
Published: August 2014

Two novel poly (aryl ether ketone)s with anthracene moieties in the backbone were synthesized through the conventional nucleophilic aromatic substitution polycondensation for the first time, by using a new bisfluoro monomer, 9,10-bis(4-fluorobenzoyl) anthracene (AnBF). The structures of obtained polymers were confirmed by NMR, IR and UV characterizations. The polymers have high molecular weight and show good solubility in common organic solvents. Differential Scanning Calorimetry (DSC) indicates that they are vitrified polymers with high glass transition temperatures above 188° Thermogravimetric analysis (TGA) shows that these polymers have good thermal stability in nitrogen atmosphere with a 5% weight loss (TGA-5%) above 465°.
Effect of Melting Conditions on Crystallization Behavior of Poly(trimethylene terephthalate)
Authors: Xu Yong , Jia Hong-bing , Ye Sheng-rong , Huang Jian
Published: August 2014

The effect of melting conditions on the crystallization kinetics of poly(trimethylene terephthalate)(PTT) was presented by means of depolarized light intensity (DLI) technique. The kinetics of PTT crystallization from melt depends on melting conditions and primarily upon the temperature of the melt. Higher melt temperature or longer time of melting may cause a reduction of crystallization rates at the melt temperature range from 506 to 531 K. Crystallization mechanism of PTT crystallizing from various melting conditions has been discussed according to Avrami kinetics parameters and morphology study. The reduction of the rate may result from two reasons: 1) the decrease of regularity such as residual nuclei in the PTT melt which lead to a reduction in the number of heterogeneous nuclei in the crystallization process; 2) the decreased spherulitic growth rate of PTT with higher melt temperature or longer residence time for melting
Effects of triethoxy and triphenylvinylsilanes on the porous structure of cross-linked poly(methyl methacrylate) beads
Authors: Naghash Hamid Javaherian , Fariba Dehghan , Ahmad Reza Massah
Published: August 2014

Novel microprous beads with the particle size of about 0.6-1.1 mm were prepared for the first time, from methylmethacrylate (MMA), ethyleneglycol dimethacrylate (EGDM), triethoxyvinylsilane (TEVS) and triphenylvinylsilane (TPVS) by suspension polymerization technique. In this study toluene was used as solvent. The swelling measurement results indicate that increasing silicone concentration increases the amount of pores and porosity percent, the weight swelling ratio, and particle sizes, but it has been observed that the apparent density decreases in the case of TEVS, and not in the case of TPVS. Also it has been demonstrated that the volume swelling ratio is independent of TEVS and increases by increasing TPVS concentration. The resulting copolymer beads were characterized by using swelling studies and Fourier transform infrared spectroscopy (FTIR). The morphology of copolymer beads were also investigated by scanning electron microscopy (SEM) and optical microscopy (OM).
Evaluation of mechanical, morphological and thermal properties of waste rubber tire powder/LLDPE blends
Authors: Zhang Zhen Xiu , Zhang Shu Ling , Kim Jin Kuk
Published: August 2014

Polymer blends of WRT (waste rubber tire) powder/LLDPE (linear low density polyethylene) have been attempted to prepare thermoplastic elastomers (TPEs). The effects of maleic anhydride-grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) and dicumyl peroxide (DCP) on mechanical, morphological and thermal properties of the blends were evaluated using universal testing machine (UTM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). It was found that combination of SEBS-g-MA and DCP could better enhance the mechanical properties of WRT powder/LLDPE blends compared to SEBS-g-MA or DCP alone. Better compatibility between WRT powder and LLDPE was responsible for the enhancement of mechanical properties, as supported by SEM. The incorporation of SEBS-g-MA and DCP with WRT powder/LLDPE blends reduced the crystallizable perfectness of the blends, but slightly increased the thermal stability of the blends, as shown from DSC and TGA results
Synthesis of soluble sulfonated polybenzimidazoles derived from 2-sulfonate terephthalic acid
Authors: Wu Qunying , Xiao Guyu , Yan Deyue
Published: August 2014

2-Sulfonate p-terephthalic acid (sTA) was synthesized, and sulfonated polybenzimidazoles (sPBI) were prepared by direct polycondensation of 3,3’- diaminobenzidine (DAB) and sTA with 4,4’-oxybis(benzoic acid) (OBBA) or 2,2’- bis(4-carboxylphenyl)-hexafluoropropane (BCHFP). Thus the ether groups and hexafluoroisopropylidene units were incorporated into the backbone of the sPBI in order to improve the flexibility and solubility. The sPBI based on OBBA showed poor solubility, while the sPBI containing hexafluoroisopropylidene units were soluble in common solvents. sPBI-20 ~ sPBI-60 could form tough and transparent membranes by solution casting. sPBI indicated high thermal stability, the 5% weight loss temperature (T5%) which was higher than 520°C, decreased with the increase of degree of sulfonation. sPBI-20 ~ sPBI-60 showed no glass transition at temperatures lower than 380°C. In addition, sPBI showed low water uptake, low swelling ratio as well as excellent resistance to oxidation. But sPBI exhibited low proton conductivity because of the strong acid-base interactions between basic benzimidazole and sulfonic acid groups.
Anti-reflection and anti-static (AR/AS) coatings made by TiO2 sol-gel process with poly(3,4-ethylenedioxy thiophene)
Authors: Kim Won Jung , Kim Tae Young , Park Chin Su , Kim Jong Eun , Lee Tae Hee , Yoon Ho Gyu , Suh Kwnag S.
Published: August 2014

In this study, we designed a two-layer hybrid Anti-Reflection/Anti-Static (AR/AS) thin film. Two kinds of UV-curable fluorinated compounds were synthesized as low refractive index materials, and a TiO2 sol combined with a conducting polymer, poly(3,4-ethylenedioxythiophene) was made by the sol-gel process for use as a high refractive index material as well as a conducting layer. In order to determine the most optimized AR/AS system, the spectral properties were simulated with the refractive index of each layer. According to the simulated results, a high refractive index layer was deposited on the hard coated poly(ethylene terephthalate) (PET) substrate by the spin coating technique, and a low refractive index layer was spin coated on the low refractive index layer. The reflectance and transmittance were measured by UV-VIS-NIR spectroscopy. It was found that the measured reflectance and the maximum transmittance of the AR/AS film were 0.71 %R at a wavelength of 550 nm and 93 %T in the wavelength range between 400 and 700 nm, respectively. The surface resistance of the AR/AS film was 108.6 ohms.
Crystalline form transformation of isotactic polypropylene induced by N,N’-diphenyl glutaramide
Authors: Lu Quliang , Dou Qiang
Published: August 2014

N,N’-Diphenyl glutaramide (DPG) is found to be an effective nucleating agent to induce the β-form of iPP. The results of wide angle X-ray diffraction, differential scanning calorimetry and polarized light microscopy indicate that 0.2 wt% of DPG can induce the maximum amount of β-form iPP, and the favorable crystallization temperature for the growth of β-form is 120 ˚C in this study. Analysis of the misfit factor between the cell parameters of DPG and β-iPP shows β-iPP can epitaxially crystallize on the bc face of DPG crystal well.
Electrical conduction of polyimide films prepared from polyamic acid (PAA) and pre-imidized polyimide (PI) solution
Authors: Kim T.Y. , Kim W.J. , Lee T.H. , Kim J.E. , Yoon H. G. , Suh K.S.
Published: August 2014

Electrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA) and pre-imidized polyimide (PI) solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.
Anomalous phase behavior in blends of -SO3H terminated polystyrene with poly(n-butyl acrylate) containing a small amount of tertiary amino groups
Authors: Yamamoto Kenji , Nanakno Ayumi , Masunaga Hiroyasu , Akiba Isamu
Published: August 2014

Abstract P

hase behavior in the blend of -SO3H terminated polystyrene (PSS) with poly(n-butyl acrylate-co-N,N-dimethylaminoethyl methacrylate) containing 6.0 mol% N,N-dimethylaminoethyl methacrylate (P1) is investigated by optical microscopy and small-angle X-ray scattering (SAXS). Comparing the miscibility of polystyrene/P1 blend, it is confirmed that the miscibility of the PSS/P1 blend is drastically improved by the hydrogen bonds between -SO3H and tertiary amino group. In addition, two-phase region of the PSS/P1 blend is split into two regions around the stoichiometric composition, in which the molar ratio of -SO3H to tertiary amino group is 1:1 stoichiometry. SAXS result shows that the PSS/P1 blend at stoichiometric composition forms a block copolymer-like aggregate and it takes a disorder state.
Preparation and Characterization of Novel Sulfonated Copolyimide Membranes
Authors: Mehdipour-Ataei Shahram , Banihashemi Ahmad , Yeganeh Hamid , Rabiee Ahmad
Published: August 2014

Nucleophilic substitution reaction of 5-amino-1-naphthol with disodium- 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone (SBCPS) in the presence of sodium hydroxide and subsequent acidification resulted in a new diamine monomer named as 3,3'-disulfonic acid-bis[4-(5-amino-1-naphthoxy)phenyl]sulfone (DANPS). This monomer containing ether, sulfone, and bulky naphthyl groups was used to prepare two series of new copolyimides via one step polycondensation reaction. This sulfonated diamine (DANPS) was polycondensed with two unsulfonated diamines, 4,4'-oxydianiline (ODA), and m-phenylenediamine (m-PDA) and 1,4,5,8- naphthalene tetracarboxylic dianhydride (NDA) to prepare copolyimides with controlled degrees of sulfonation. Monomers and polymers were fully characterized with common methods and the physical properties of the polymers including thermal behavior and stability, viscosity, and ion exchange capacity (IEC) as a criterion for evaluation of the performance in fuel cell membrane were investigated.
A simple route to high-strength hydrogel with an interpenetrating polymer network
Authors: Tang Qunwei , Sun Xiaoming , Li Qinghua , Wu Jihuai , Lin Jianming , Huang Miaoliang
Published: August 2014

Hydrogels have potential applications in many fields, but the poor mechanical strength has limited their further development. In this article, we designed a simple route to high-strength interpenetrating polymer network (IPN) hydrogel from polyacrylamide (PAAm) and poly(vinyl alcohol) (PVOH). The highest tensile strength and elongation were 2.4 Mpa and 4300 %, respectively. It was found that the hydrogel strength depended on the chemical crosslinking, physical entanglement and PVOH precipitates. Because of the hydrogen bonding interactions and self-crosslinking, the structure of PVOH transferred from crystal to amorphous. PVOH precipitates scattered in the crosslinked PAAm matrix which dispersed the stress and improved the hydrogel toughness. The simple method is versatile in synthesizing high-strength IPN hydrogels using many kinds of polymer species.
Cryogenic mechanical milling of high density polyethylene
Authors: Cysne Barbosa Ana Paula , Stranz Michael , Katzenberg Frank , Köster Uwe
Published: August 2014

HDPE was analyzed after being submitted to cryogenic mechanical milling (CMM) by X-ray diffraction (WAXS), polarized light microscopy and differential scanning calorimetry (DSC). After CMM, besides the known phase transformation of the orthorhombic PE crystals into the monoclinic modification, slight changes in the melting and crystallization behavior as well as an unexpected increase in crystallinity were observed. The observed results can be explained by assuming a solid/solid phase transition as the responsible mechanism.
Positive temperature coefficient effects of carbon blackfilled polytetrafluoroethylene composites
Authors: Zhou Dongxiang , Wang Fajun , Gong Shuping
Published: August 2014

Carbon black (CB)-filled polytetrafluoroethylene (PTFE) composites were prepared by compact molding of a dry-mixture of CB and polymer powders followed by a sintering technology. The composites show a very low percolation threshold about 5 vol. %, which can be attributed to the segregated distribution of CB in the interfacial regions of PTFE particles. The PTFE/CB composites exhibit a high PTC transition temperature (>300 0C), high PTC intensity (3.5) and no NTC effects. The absence of NTC effect of the composites was attributed to the extremely high viscosity of PTFE at temperatures above its melting point, which restricts the migration of CB particles and prevents the formation of new conductive networks.
Evaluation of morphological architecture of cellulose chains in grass during conversion from macro to nano dimensions
Authors: Pandey Jitendra K. , Kim Chung-Soo , Chu Won-Shik , Lee Caroline S. , Jang Dong-Young , Ahn Sung-Hoon
Published: August 2014

The cellulose nanowhiskers (CNW) are of imminent importance in the development of ecofriendly green material for environment. Morphological study of their structure was carried out after extraction from grass. The controlled alkali and acid hydrolysis after soxhlet extraction of bleached fiber in ethanol and water provided a mixture of micro/nano fiber which can be further converted into CNW by mechanical treatment. Width of obtained CNW were found to be ~10-65 nm with length of several nanometers as evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The changes in dimensions during alkali treatment, bleaching and acid hydrolysis of grass exhibited an interesting architecture and clarify the phenomenon of separation of nano level fibrils from the matrix of hemicellulose and lignin which starts after swelling of fibers and opening from middle followed by splitting from each other. The nanofibers were embedded in the matrix surrounded by amorphous layers. The size of fibers was directly associated with the extent of treatments. The crystalline part of fiber was intact during hydrolysis which must be attributed to easy removal of amorphous region by penetration of hydronum ions from acid. The results of SEM and TEM were correlated with the Scanning Ion Microscopy (SIM) which showed a direct evidence of breaking of thick fiber strands resulting in the formation of sharp edged crystalline entities composed of cellulose crystals.
PA6/NBR blends: improvement of processability and mechanical properties
Authors: Gomes Ana C. O. , Soares Bluma G. , Oliveira Marcia G. , Oliveira Marcelo F. L. , Paranhos Caio M.
Published: August 2014

This work deals with the study of the processability of blends based on PA6 and NBR. The aim is to achieve reduced PA 6 melting temperatures in order to avoid degradation of the NBR phase during processing. The effect of different additives in PA has been studied. For this purpose PA6 was blended with nonylphenol, EVA 18, EVA 33 and EVAMA. Among several masterbatches based on PA6; the sample containing 5% of EVAMA presented the best combination of processability and mechanical properties. The influence of additives in the processing behavior, crystallinity of the PA6 phase, mechanical and physicochemical properties are discussed in the present work.
Preparation and characterization of new thermally stable and optically active polyesters by direct polycondensation reaction promoted by Vilsmeier adduct
Authors: Mallakpour Shadpour , Tirgir Farhang
Published: August 2014

Highly soluble and optically active aromatic polyesters (PE)s containing phthalimide and flexible chiral groups were prepared with moderate molecular weights by step-growth polymerization of diacid monomer containing pendant 4- [(2L)-phthalimidylpropanoylamino)benzoyl group with several aromatic diols, in a system of tosyl chloride, pyridine (Py) and N,N-dimethylformamide (DMF) to give a series of new optically active PEs with good yield and moderate inherent viscosity ranging from 0.28 to 0.48 dL/g. The aim of this work was to obtain novel optically active PEs that was more soluble in common organic solvents while maintaining the high thermal stability. All polymers derived from such a diacid and aromatic diols were highly organosoluble in solvents like N-methyl-2-pyrrolidinone, N,Ndimethylacetamide, DMF, Py, dimethyl sulfoxide. Thermogravimetric analysis data showed that these PEs are thermally stable, with 10% weight loss being recorded above 400 °C and showed good thermal stability associated with high glasstransition temperatures above 200 °C as measured by differential scanning calorimetry. All of the above polymers were characterized by FT-IR and specific rotation techniques and some of them were also characterized by 1H-NMR and elemental analyses methods.
Compatibility and interactions in polyacrylonitrile/soy protein isolate/polyurethane blends
Authors: Xiao Ru , Yin Duan , Fan Wei , Sun Gang
Published: August 2014

Polyacrylonitrile/Soy protein isolate/polyurethane (PAN/SPI/PU) blends were prepared in dimethylsulfoxide (DMSO). The compatibility and interactive properties of PAN/SPI, SPI/PU, and PAN/PU blend systems were studied using dilute solution viscometry and phase contrast microscopy. It was found that PAN/SPI and PAN/PU were immiscible systems, but that there was an attractive interaction between them. However, the SPI/PU was an almost miscible system. To improve compatibility, the main product of graft copolymerization of acrylonitrile and SPI (AN-g-SPI) and the alkaline hydrolysis polyacrylonitrile (HPAN) were used as compatibilizers. The results showed that the mechanical properties of both the PAN/SPI and PAN/SPI/PU systems were significantly improved.
Electrospinning of polyaniline-polyacrylonitrile blend nanofibers
Authors: Raeesi Fatemeh , Nouri Mahdi , Haghi Akbar Khodaparast
Published: August 2014

Electrospinning of emeraldine base polyaniline/polyacrylonitrile (PANI/PAN) blends with different composition ratios were performed using Nmethyl- 2-pyrrolidone (NMP) as solvent. The blends were electrospun at various electrospinning temperature and electric fields. Morphology and fibers diameters were investigated by scanning electronic microscopy (SEM). The average diameter of nanofibers and their distributions were determined from 100 measurements of the random fibers with image analyzer software (manual microstructure distance measurement). Electrical conductivity of the prepared mats was characterized using standard four point probe method. The fibers with diameter ranging from 60 to 600 nm were obtained. The PANI/PAN blends containing up to the PANI content of 30% could be electrospun into the continuous fibrous structure, although pure PANI solution was not able to be electrospun into the fibrous structure. Average of fiber diameter decreased with increasing PANI content and electrospinning temperature. The electrospun PANI/PAN fibers at 50 °C and 75 °C showed smaller diameters with much better uniformity than those electrospun at 25 °C. The electrical conductivity of the mats increased with the increase of PANI content in the blend with percolation threshold of 0.5%.
Chain mobility in bulky carbosilane modified polymeric siloxane systems
Authors: Kowalewska Anna , Delczyk Bogumiła , Chruściel Jerzy
Published: August 2014

Hydrosilylation of bulky carbosilanes [CH2=CHRC(SiMe2R')3, R=CH2, (CH2)3 or SiMe2; R'=Me or Ph] with oligosiloxane precursors [M(D2DH)7D2M, M(D2DH 2)11D2M, PDMSx%-PMHS100-x% (x=85, 50, 30, 0)] was carried out. The relationship between the mobility of siloxane chain and the type of carbosilane moiety, as well as the type of distribution of carbosilane group along the polymer chain, was consecutively studied. Carbosilane substituents, due to their exceptional steric requirements, have been shown to strongly affect thermal properties of siloxane oligomers, implying a substantial change of the chain flexibility and free volume of modified oligomers.
Effect of boric acid on thermal stability of poly (acrylonitrile-methyl acrylate)
Authors: Han Na , Zhang Xingxiang
Published: August 2014

A series of acrylonitrile(AN)-methyl acrylate (MA) copolymers (AN/MA) with molar ratios of 100/0-70/30 were synthesized by water depositing polymerization. One to three percent of boric acid (BA) was adopted as a stabilizer to enhance the thermal stability of AN/MA. The copolymers and the mixtures of copolymers treated with BA were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (1H NMR), Gel Permeation Chromatography (GPC), Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), X-ray diffraction (XRD) and Optic Microscope. The results show that melting point (Tm), glass transition temperature (Tg) and crystallinity of the copolymer decreased while decomposition temperature (Td) increased with the increase of MA content. Tm of AN/MA dropped to 174 °C and Td rose up to 321 °C when 15 mol% MA was incorporated. It was worthy to note that Tm of the copolymers increased conspicuously after being treated with BA. Stability of AN/MA with a molar ratio of 85/15 containing 1 wt% BA improved remarkably. The mixture can be kept stable up to 30 min at 220 °C.
Preparation, characterization and properties of polymeric nanocomposites based on natural rubber and polybutadiene rubber blend
Authors: Kooshki Mehdi Mehrabi , Arani Azam Jalali
Published: August 2014

Nanocomposites based on natural rubber and polybutadiene rubber blend were prepared by employing different amounts of modified layered silicate. X-ray diffraction was used to determine the structure of prepared nanocomposites. The effects of incorporation of organically modified clays on vulcanization reactions of the rubber blend were analyzed by using oscillating disk rheometer. High reduction in scorch time and optimum cure time was observed when organoclay was added and this was attributed to the amine groups of the organic modifier. Tensile strength, modulus, abrasion resistance and tear strength improved significantly on adding organoclay and there was a good correlation between abrasion resistance and tear strength of the nanocomposites. Elongation at break decreased by using organoclay and increase in loading of organoclay up to 10 phr and further led to decrease in the rate of variation of tensile properties. Thermal stability of the blend was improved by using 5 phr organoclay.
Chitosan-poly(vinyl alcohol) blend nanofibers: Morphology, biological and antimicrobial properties
Authors: Gholipour. K A. , Bahrami S .H. , Nouri M.
Published: August 2014

Blend nanofibers from Chitosan (Cs) (Mw =1 X 106) in 2% acetic acid and poly(vinyl alcohol) (PVA) (Mw=72 X 103) in deionized water were produced in 10/90, 20/80, 25/75, 50/50 mass ratio of Cs/PVA. The effect of blend ratio on the fiber formation and fiber properties has been investigated. Nanofibers produced were characterized by SEM, FTIR and DSC. The diameter of fibers increased with increasing chitosan content in blends. However, fibers with lower diameter showed micro cracks on the surface. FTIR data show that these two polymers have intermolecular interaction. DSC data reveals that the exothermic peak at about 200 0C for PVA decreased to lower temperature with increasing Cs content. Chitosan (Cs) (Mw =1 X 106) was hydrolyzed and the molecular weight reduced to 6.219 X 105 then we could electrospin the pure chitosan in 90% acetic acid as solvent and the nanofibers with diameter in the range of 43 nm were produced. SEM results showed that although the chitosan nanofibers were produced, because of high viscosity of solution there are a lot of beads on their surface.

The cell culture result show excellent cell viability in this medium when the cells were exposed to chitosan/PVA nanofibers for 7 days in CO2 incubator, 99% RH and 37 °C. On the other hand the chitosan/PVA nanofibers in their antimicrobial experimentations showed efficient antimicrobial properties.
Swelling and network parameters of crosslinked porous octadecyl acrylate copolymers as oil spill sorbers
Authors: Abdel-Azim Abdel-Azim A. , Abdul-Raheim A. Mahmoud , Atta Ayman Mohamady , Brostow Witold , Datashvili Tea
Published: August 2014

In previous work crosslinked copolymers were prepared from cinnamoyloxy ethyl methacrylate (CEMA) and several monomers feed ratios of octadecyl acrylate (ODA). Networks so produced are both flexible and porous; we now report their swelling efficacies as a function of temperature in toluene and in crude petroleum. Network characteristics is presented including the polymer + solvent interaction parameter χ, effective crosslink density υe, equilibrium modulus of elasticity E, average molecular weight between crosslinks Mc and the theoretical crosslink density υt. These parameters are correlated with structures of the synthesized sorbers.
Studies on PEBAX/organoclay nanocomposites by meltintercalation process: Effect of organoclay surface
Authors: Mohamadi Somayeh , Sanjani Naser Sharifi
Published: August 2014

In this study, the polyetherblock amide (PEBAX)® nanocomposites with 2.5 % and 5 wt.% organoclay, based on Cloisite 30B (montmorillonite intercalated with dimethyl, 2-ethyl hexyl hydrogenated tallow alkyl ammonium cation), were prepared by the melt-intercalation process. The structural properties, thermal behaviors and the mechanical properties were characterized using the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), melt flow index (MFI), differential scanning calorimetry (DSC), thermogravimetry analyses (TGA), transition electron microscopy (TEM), scanning electron microscopy (SEM) and the tensile test. The XRD analysis indicated the formation of intercalated PEBAX nanocomposites. The TGA results revealed that the addition of 2.5 wt.% nanoclay improved the thermal properties, while the nanocomposite with 5 wt.% nanoclay did not enhance the thermal stability. The DSC analysis indicated that, in the case of PEBAX with 2.5 wt.% organoclay, each peak was related to the fusion of the crystalline fraction of the poly ether and poly amide affected blocks. On the contrary, regarding the PEBAX with 5 wt.% nanoclay, only the peak related to polyamide was changed. Interestingly, the tensile modulus increased with the incorporation of 2.5 wt.% clay, but it decreased in PEBA 5. The elongation at break reduced with the incorporation of the clay, attaining a minimum value at the clay concentration of 2.5 wt.%, and followed by an increase at the clay concentration of 5 wt.%.
Starch–metal complexes and their rheology
Authors: Ciesielski Wojciech , Krystyjan Magdalena
Published: August 2014

Changes in conductivity of 5 w/w% starch gels was studied on their titration with 0.1 M aqueous solutions of selected metal salts. Starch gels usually trapped around 10 mg metal ions per 1 g starch [Co(II), Cu(II), Fe(III), Ni(II)] and that value was only slightly dependent on starch origin (amaranthus, corn, potato, tapioca, waxy corn). Among salts studied (acetates, chlorides, nitrates) FeCl3 and NiCl2 were likely to be used because they hydrolyzed increasing conductivity of the solutions and formed micelles of corresponding hydroxides adhering to starch micelles and increasing amount of trapped metal. Addition of metal salts to starch gels had a devastating effect on pseudoplasticity and viscosity of starch gels and only potato starch gel was to a certain extent, exceptional in that respect.
FTIR Study of the retardation effect of boric acid on the cyclization reaction of polyacrylonitrile
Authors: Ouyang Qin , Cheng Lu , Wang Haojing , Li Kaixi
Published: August 2014

A retardation effect of boric acid on the cyclization reaction of polyacrylonitrile (PAN) was clearly observed by Fourier transform infrared spectroscopy. The Lewis acid nature of boric acid probably accounts for this retardation effect. A quantitative evaluation of this effect was also made, indicating two potential applications, i.e., high temperature stabilization and melt spinning, which are favourable for the cheap and fast fabrication of PAN-based carbon fibers.
New trends in polymer electrolytes: a review
Authors: Srivastava Neelam , Tiwari Tuhina
Published: August 2014

Since the work of Armand, polymer electrolytes have received great attention and lots of publication can be found in the literature. Each publication has its particular orientation and tries to emphasize only limited points to prove their system as the better one. But to really get some good fruitful material we need to look simultaneously for different aspects of the electrolyte such as good conductivity and mechanical property, understanding of interaction between the salt and other materials present in the system, nature of solid electrolyte/ electrode interface, electrochemical window, working temperature window etc. Hence a brief summary of the variety of polymer electrolytes is given in the paper with their advantages and disadvantages. Paper discusses polymer electrolytes starting from Dry SPE to the latest IL/Zwitterionic electrolytes and the behavior of the some devices using these materials.
Photoluminescence and electron migration characteristics of aromatic poly(amide-imide) containing 1-naphthaldehyde and 4,4′-diamino diphenyl ether
Authors: Khoee Sepideh , Zamani Somayeh
Published: August 2014

A new photoactive polymer poly(amide-imide), was fabricated by reacting two synthesized monomers, N,N'-(4,4'-oxy-bis(4,1-phenylene))-bis-(1,3- dioxo-1,3-dihydroisobenzofuran-5-carbox amide) and N-(4,6-diamino-1,3,5- triazine-2-yl)-1-naphthamide. Polycondensation reaction of the two monomers was performed under 10 min microwave irradiation in o-cresol as solvent for producing a photoactive poly(amide-imide) in a quantitative yield. The resulting polymer was characterized by FT-IR, 1H-NMR, TGA techniques and its solvatochromic and fluorescence properties were investigated in different solvents. The poly(amideimide) exhibit broad fluorescent band, and the fluorescence intensity is related to the intermolecular chain-chain or chain-solvent interaction. Also the self-quenching mechanism was studied according to the specific behavior of the polymer in different solvents and the self-quenching rate constant for the association reaction in the excited state (Kq) could be measured from the Stern-Volmer equation. This kind of fused system and diamines show various electron migration mechanisms and photoluminescent properties in the singlet excited states.
Morphology, thermal and mechanical properties of PVAc/ TiO2 hybrid nanofibers
Authors: Wu Ning , Wang Jiaxi , Wei Qufu , Cai Yibing , Lu Bing
Published: August 2014

Organic/inorganic hybrid was successfully prepared by sol-gel technique, which consisted of polyvinyl acetate (PVAc) as organic segment and titanium dioxide (TiO2) as inorganic part. The PVAc/ TiO2 hybrid nanofibers were fabricated by electrospinning. The structures and properties of the hybrid nanofibers were investigated by transmission electronic microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analyzer (TGA) and tensile testing. SEM observation revealed the fibrous structures of the hybrid nanofibers. AFM and TEM images indicated the surface morphology and inner structures of the hybrid nanofibers. It was found by TGA analysis that the thermal stability of pure PVAc nanofibers was enhanced by the increase of TiO2 phase. The breaking strength was increased while the breaking elongation was decreased as the TiO2 content increased.
Influence of the molecular weight distribution on the percolation threshold of carbon nanotube – polystyrene composites
Authors: Hermant Marie Claire , Smeets Niels M. B. , Hal Roger C. F. van , Meuldijk Jan , Heuts Hans P. A. , Klumperman Bert , Herk Alex M. van , Koning Cor E.
Published: August 2014

Carbon nanotubes were introduced into insulating polystyrene (PS) and poly(methyl methacrylate) (PMMA) by means of a latex-based technique. A systematic study of the effect of the polydispersity index, more particularly the presence of different amounts of low molar mass polymer, on the final composite conductivity was performed. Six latexes with varying molecular weight distributions were prepared by means of conventional free radical emulsion polymerization in the presence of different amounts of chain transfer agent, namely n-dodecyl mercaptan. Composites were prepared with both multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Shifts in the percolation threshold from 0.9 to 0.6 wt% for MWCNTs and from 0.7 to 0.4 wt% for SWCNTs were observed for PS matrix material, whereas for PMMA matrix material the percolation thresholds shifted from 0.6 to 0.3 wt% for MWCNTs and 0.35 to 0.2 wt% for SWCNTs upon increasing the amount of low molecular weight polymer in the polymer matrix.
Application of the Monte Carlo simulation method to the Investigation of the effect of chain-length-dependent bimolecular termination on ATRP
Authors: Najafi Mohammad , Haddadi-Asl Vahid , Salami-Kalajahi Mehdi , Mamaghani Hossein Roughani
Published: August 2014

An optimized and high-performance Monte Carlo simulation is developed to take thorough account of the influence of chain-length-dependent termination rate constant on polymer microstructure in ATRP. According to the simulation results, bimolecular termination rate constant sharply drops throughout the polymerization when chain length dependency is applied to the program. The dependence of on reaction time, as a common feature of ATRP, is almost linear. Moreover, the polymerization proceeds to higher conversion when the chain-length-dependent termination rate constant is applied to the simulation model. In addition, the plot of against reaction time is completely linear; also, the initiator is entirely decomposed at the early stages of the polymerization as the plot of CIagainst time shows. The concentration of the catalyst in lower oxidation state decreases first and then plateaus at higher conversion. Furthermore, the amount of Mtn Y/L used in the polymerization is lower when the chain-length-dependent termination rate constant is employed in the simulation. Finally, the peak of molecular weight distribution of polymer chains shifts toward higher molecular weight during the reaction. Besides, the molecular weight distribution broadens at higher conversion. However, the molecular weight distribution of polymer chains produced under conditions of applying chain-lengthdependent termination rate constant is narrower.
Thermal, mechanical and wettability properties of some branched polyetherurethane elastomers
Authors: Vlad Stelian , Spiridon Iuliana , Grigoras Cristian Vasile , Drobota Mioara , Nistor Alexandra
Published: August 2014

In this study three series of polyetherurethanes (PEU) based on Terathane ® (polytetramethyleneetherglycol - PTMEG, Mn 1400) as polyol; isophorone diisocyanate (IPDI), 4,4’-methylene-bis-(cyclohexyl-isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) as aliphatic diisocyanate components; 1,4- butanediol (BD) and glycerin (Gly) as chain extenders were synthesized. The glycerin as triol is responsible for the crosslinking structures. All polyether urethanes were synthesized by prepolymer method. The PTMEG was reacted with diisocyanate to realize a diisocyanate-terminated prepolymer, which in next step was extended with blend of the 1,4-butanediol (BD) and glycerin (Gly) in different proportion. The influence of the diisocyanate structure and chain extender functionality on the thermal, mechanical and wettability properties were the aim of this study. The physical, mechanical and wettability properties of these polymers were measured according to standard methods. All polymers were characterized by conventional characterization methods. Different methods of thermal analysis (TGA and DSC) were used for characterization. Wettability was estimated by determination of the dynamic contact angle. The structures were confirmed by FTIR and H-NMR analysis. The results show that the thermal stability, mechanical and wettability properties of the final products are influenced by the diisocyanate and chain extenders nature.
Coating of Al mould surfaces with polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA) and ethylene-tetrafluoroethylene (ETFE)
Authors: Akinci Akin , Cobanoglu Ebutalip
Published: August 2014

Because of low cost, easily productivity and high thermal conductivity, aluminum (Al) moulds are preferred in the production of the polyurethane (PUR) parts. In this study, adhesion behavior and surface properties of coated materials between mould used in the production of automotive seat and PUR materials were investigated. Four different polymer types were coated on Al mould and they were characterized using contact angle, surface roughness, coating thickness, adhesion, cross-cut and SEM test methods. It was found that, PFA has the least value of surface roughness and ETFE has the highest one in the four different coatings produced. After holding period in isocyanate, decrease were measured on the angle values of all coatings. In the contact angle measurements before and after isocyanate tests, PFA exhibited the highest contact angle value.
Synthesis, Characterization and Adsorption Performance of Semi-crystalline/Liquid Crystalline Polyether Chelating Resins
Authors: Zhang Shuangqing , Zhang Chaocan , He Changhai , Xu Jun
Published: August 2014

A series of polyether chelating resins with pendent biphenyl mesogenic groups were synthesized, and the chemical structure of monomers and polymers were confirmed by IR and 1H NMR detection. The thermal properties of resins were investigated by the Differential Scanning Calorimetry (DSC) and Polarizing Microscopy (POM), and the results showed that only the product of polyepichlorohydrin grafted with 4-cyano-4’-hydrobiphenyl, i.e., HPCN resin, was a kind of nematic liquid crystal polymer with typical schlieren texture (70-130 0C) and other resins were semi-crystalline. The results of adsorption experiments showed that all five resins exhibited a higher adsorption capacity (>1.0 mmol/g) for Cu (II) and Hg (II) and medium adsorption ability for Cd (II), Zn (II), Pb (II) and Co (II), however, a poor adsorption capacity (<0.3 mmol/g) for Mg (II), indicating that this type of polyether resins have a better selective adsorption for above metal ions. In addition, the adsorption capacity of HPnCP resins was generally higher than that of HPd and HPCN owing to the existence of terminal pyrrole coordination groups in HPnCP resins.
Photoinduced supramolecular chirality in glassy nematic linear and star shaped methacrylic azopolymers obtained by ATRP
Authors: Angiolini Luigi , Barberá Joaquín , Benelli Tiziana , Giorgini Loris , Paris Fabio , Salatelli Elisabetta , Tejedor Rosa M.
Published: August 2014

The induction of chirality in achiral liquid crystalline azoaromatic polymers with circularly polarized light (CPL) has been studied on well-defined macromolecular derivatives with different molecular structures, synthesized by atom transfer radical polymerization (ATRP). Two methacrylic homopolymers have been investigated: a linear and a three arms star polymer. Both the polymeric samples are featured by low polydispersity and similar average polymerization degree, so that structure-properties correlations are made possible. Irradiation with CPL of one handed rotation sense of casted films and a planar cell of these polymers in the glassy nematic phase allowed to ascertain by UV-Vis and CD spectroscopy the formation of a supramolecular chiral structure with high chirality induced into the material. The results are interpreted in terms of the structural features of the polymers.
Improved dispersion of multi-wall carbon nanotubes in poly(butylene terephthalate) using benzimidazolium surfactants
Authors: Colonna Martino , Berti Corrado , Binassi Enrico , Fiorini Maurizio , Acquasanta Francesco , Celli Annamaria
Published: August 2014

Multi-wall carbon nanotubes/poly(butylene terephthalate) nanocomposites have been prepared by in-situ polymerization. Benzimidazolium tetrafluoroborate salts improve the dispersion of carbon nanotubes in the polymer matrix due to the formation of “π-cation” interactions of the imidazolium salt with the surface of the carbon nanotubes. An improved dispersion of the nanotubes in butanediol was also observed using the benzimidazolium salt. The presence of the compatibilization agent gives rise to improved thermo-mechanical properties and electrical conductivity for the nanocomposite. The presence of the nanotubes also consistently increases the thermal stability and enhances the nucleation process on PBT crystallization.
Vitrification and devitrification of the rigid amorphous fraction in poly(ethylene terephthalate)
Authors: Righetti Maria Cristina , Di Lorenzo Maria Laura
Published: August 2014

Vitrification and devitrification of the rigid amorphous fraction (RAF) of poly(ethylene terephthalate) (PET), analyzed during development and disappearance of the three phase structure, are detailed in this contribution. Upon cooling from the melt at a constant rate, the rigid amorphous fraction starts to vitrify when the crystallization process is almost finished, and continues on further cooling. The rigid amorphous fraction is formed in the same temperature range of the secondary crystal growth. Analysis of the low melting endotherm that is observed in isothermally crystallized PET a few degrees above the crystallization temperature reveals a joint contribution of melting and devitrification of the rigid amorphous fraction. The results confirm a link between secondary crystallization and vitrification of the rigid amorphous fraction in semicrystalline polymers. Secondary crystallization takes place in geometrically restricted areas, in which the polymer chains undergo large constraints, so that the mobility of the amorphous chain portions coupled with the crystal phase is reduced. Similarly, the gain in mobility upon partial melting of thinner and/or more defective crystals allows an increase in mobility of the coupled amorphous regions, which results in concurrent mobilization of the rigid amorphous fraction.
The role of the matrix-filler affinity on morphology and properties of polyethylene/clay and polyethylene/ compatibilizer/clay nanocomposites drawn fibers
Authors: Dintcheva Nadka Tzankova , Marino Rosamaria , La Mantia Francesco Paolo
Published: August 2014

In this work the structural variations and mechanical performance of polyethylene/clay nanocomposite drawn fibres, also in the presence of compatibilizer, such as a commercial maleic anhydride grafted polyethylene, PEgMA, was studied. In the isotropic state both systems show intercalated morphology.

After spinning and cold drawing, by adding the nanoparticles, the tensile strength as a function of the draw ratio increases and this rise is more pronounced for the filled compatibilized system. The reduction of the elongation at break, on the contrary, is about the same for all the examined samples. The orientation of the macromolecules, evaluated by measurements of the birefringence and calorimetric analysis, is similar for all the samples, but the filled, drawn fibres show a higher level of intercalation and, in particular, some exfoliation, more and more pronounced with the draw ratio and in presence of compatibilizer, as a consequence of the application of the extensional (at low and high temperature) flow. For the three components system with greater affinity between the polymer matrix and clay, the extensional flow is more efficient. The initial intercalated morphology changes to some more intercalation and finally, at the highest anisotropic condition in the presence of the PEgMA, evolves to delaminated clay structure.
Modelling of mechanical behaviour of polyamide nanocomposite fibres using a three-phase Halpin-Tsai model
Authors: Garofalo Emilia , Russo Giovanna Maria , Di Maio Luciano , Incarnato Loredana
Published: August 2014

The aim of the present study is to correlate the features of the elongational flow-induced morphology to the mechanical properties of polyamide based nanocomposite fibres. Particular attention was paid to modelling the mechanical behaviour of the hybrids which were produced by fibre spinning technique and collected at different draw ratios.

Tensile properties of as-spun and stretched fibres were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspects of the hybrids morphology, such as X-Ray diffraction and TEM analysis. In particular, the TEM images of the nanocomposite systems showed intercalated/exfoliated morphology in all hybrids. For this reason, a three-phase Halpin-Tsai model, based on polyamide-6 matrix, exfoliated clay platelets and nanolayer intercalated clusters, was used to fit the experimental data.

This method was applied to calculate the Young’s modulus of nanocomposite fibres both as-spun and stretched ones. Moreover, the model was used for predicting the effect of various morphological parameters including the exfoliation degree, clay layer and cluster aspect ratio.
Synthesis and characterization of poly(4-oxyalkylenoxy benzoate)s of different chain length
Authors: Siracusa Valentina , Lotti Nadia , Puglisi Concetto , Samperi Filippo , Munari Andrea , Finelli Lara , Battiato Salvatore
Published: August 2014

Three different monomers starting from p-(4-hydroxy)benzoic acid and 3- chloro-1-propanol, 4-chloro-1-butanol and 6-chloro-1-hexanol, respectively, were synthesized and extensively characterized by means of 1H and 13C NMR, MALDITOF MS and elemental analysis. Subsequently, poly(4-oxyalkylenoxy benzoate)s polymers with different chain length were prepared in bulk starting from the mentioned above monomers, employing Ti(OBu)4 as catalyst, according to the usual two-stage polymerization procedure. The polymers were characterized in terms of chemical structure, molecular mass and thermal behaviour. Tg, Tm and the ability to crystallize were found to be affected by the number of methylene groups per repeat unit and the results were explained mainly on the basis of the increment of the chain flexibility.