bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and swelling behaviour of fast-swelling superabsorbent composites
Authors: Zhang Fen , Liu Mingzhu , Qi Xiaohua , Chen Zhenbin 
Published: August 2014

AbstractFast-swelling porous superabsorbent composites with high water absorbency in 0.9 wt% NaCl solution both at atmospheric pressure and under certain load (p ≈ 2×103 pa) were synthesized by a rapid solution polymerization of concentrated sodium acrylate, acrylamide and 2-hydroxypropyl acrylate. The porosity was induced through foaming conducted in the course of polymerization using acetone as porosity generator. The copolymerization and surface morphology of the porous copolymers were characterized by FTIR and SEM. To improve other properties of swollen hydrogel such as strength, resilience and dispersion, the copolymers were modified with inorganic salts after surfacecrosslinking by trihydroxymethyl propane glycidol ether. The influences of various experimental conditions, such as neutralization degree of acrylic acid, amount of initiator and crosslinker on the water absorbent capacity in 0.9 wt% NaCl solution were investigated. The resulting products under optimum conditions possessed the water absorbency of 65 g g-1 and 10 g g-1 in 0.9 wt% NaCl solution at atmosphere pressure and under load, respectively. The results of swelling kinetics measurement in 0.9 wt% NaCl solution showed that the composites had very fast swelling rate (they can reach swelling equilibrium in minutes). In addition, the effect of amount of acetone on swelling rate of the composites was examined in detail. It was shown that appropriate amount of acetone caused products with high porosity, which led to large swelling rate. Moreover, the swollen hydrogel exhibited excellent strength, better resilience and dispersion.
Sulfur containing optical plastics and its ophthalmic lenses applications
Authors: Jha G. S. , Seshadri G. , Mohan A. , Khandal R. K. 
Published: August 2014

AbstractPlastics produced from the sulfur-based monomer are excellent materials with many optical applications such as ophthalmic lenses, fiber optics and non- linear optics. High refractive index plastic materials are able to reduce the curvature, edge and center thickness of lenses. Sulfur containing plastics such as sulfide, polysulfide, and sulfur containing vinyl compound, thioacrylate, polythiol and isocyanate/isothiocyanate based monomers have demonstrated high refractive index, high Abbe number, good impact strength, excellent machinability, good tintability and good transmittance. In the present article, various sulfur containing plastics with different types of monomers for ophthalmic lens applications are reviewed.
Using dioxane and water as mixed solvents to prepare pH and temperature dual responsive poly(N-isopropyl acrylamide-co-itaconic acid) hydrogels
Authors: Ling Youdao , Lu Mangeng 
Published: August 2014

AbstractpH and temperature dual responsive hydrogels based on itaconic acid (IA) and N-isopropylacrylamide (NIPAAm) were prepared by means of water and dioxane as mixed solvents. The chemical compositions, structures and morphologies of these hydrogels were characterized by FTIR, TGA and SEM, and their pH and temperature responsive behaviours were investigated through equilibrium swelling ratios, deswelling and reswelling kinetics. The results showed the hydrogels fabricated in this condition had expanded chain conformations and macroporous network structures, and exhibited the larger swelling ratios as well as improved deswelling/reswelling dynamics.
Impedance analysis and electromagnetic interference shielding effectiveness of vapor grown carbon nanofiber reinforced chlorobutyl rubber composites
Authors: Sridhar V. , Xu Deng , Tripathy D.K. , Kim Jin Kuk 
Published: August 2014

AbstractThe effect of processing variables (filler loadings) and operating variables (frequency) on the impedance and electromagnetic interference shielding effectiveness of vapor grown carbon nanofiber (VGCNF) reinforced chlorobutyl vulcanizates has been investigated. The dispersion and morphology of the VGCNF in the polymer matrix has been studied by scanning electron microscopy and Raman spectra. Addtionally, the utility of EPMA (Electron probe microanalyzer) as a tool to study the dispersion of nano fibers in polymer matrix has been explored for the first time. With increase in frequency and VGCNF loadings the composites showed a decrease in real part of complex impedance for increasing VGCNF loadings whereas the imaginary part showed a slight peak in the range of 9-10 GHz followed by a subsequent decrease. The measured impedance values were plotted as Nyquist plots (Argand diagrams) and a Resistor-Capacitance model was assumed. The EMI shielding effectiveness increased monotonically with filler loading and showed a maximum of around 55 dB at 12 phr loadings, thus making them suitable for EMI shielding applications.
A review on aromatic poly(ester-carbonate)s and transesterification resistant polyesters
Authors: Montaudo Maurizio S. 
Published: August 2014

AbstractThe review discusses poly(ester-carbonate)s (PECAs for brief), their production, characterization and their use. Great emphasis is on their production via ester-carbonate exchange and in particular on the copolymer obtained when mixing and heating poly(butylene terephthalate) (PBT for brief) or poly(ethyylene terephthalate) (PET for brief) together with poly(bisphenol A carbonate) (PC for brief). Some notes are added on PECAs with long polyester and /or long polycarbonate blocks and for the case of "transesterification resistant" polymers i.e. when the production of random copolymers via ester-carbonate exchange is impossible under ordinary conditions.
The use of crude tall oil as feed-stock for alkyd resins
Authors: Suarez Paulo A. Z. , Einloft Sandra , de S. Basso Nara R. , Fernandes Jonas A. , da Motta Ladimir , do Amaral Lisandra C. , Lima Daniella G. 
Published: August 2014

AbstractThe synthesis of modified alkyd resins using a crude tall oil with a content of rosin acids of 39.8 % is described. This material has the composition of fatty acids close to soybean oil, has low cost and is widely available being a forest product industrial residue. The synthetic route includes the reaction of tall oil and maleic anhydride, in the presence of the catalyst (LiOH), followed by polyesterification reaction steps, resulting in an alkyd resin with interesting properties. The acid value (AN) and viscosity were used to follow the reaction, and it appears to be dependent upon the polyalcohol used in the polyesterification step. A period of 15 hours was needed to yield a tack-free coating.
Synthesis and characterization of new disilane -containing arylacetylene resin
Authors: Yin Guoguang , Zhang Jian , Wang Canfeng , Huang Farong , Du Lei 
Published: August 2014

AbstractA novel disilane-containing arylacetylene resin, abbreviated as DSA resin, was synthesized from diethynylbenzene and halogenated disilane by Grignard reaction. The obtained resin was a viscous liquid and soluble in a variety of common solvents. The structures and properties of the resin, cured resin and sintered resin were characterized by FT-IR, 1H-NMR, DSC, TGA and XRD techniques. The results showed that the DSA resin could cure at temperatures lower than 200°C and the cured resin exhibited high temperature resistance and good ceramic formability.
Structural and dielectric properties of some epiclon-based polyimide films
Authors: Cosutchi Andreea Irina , Hulubei Camelia , Stoica Iuliana , Dobromir Marius , Ioan Silvia 
Published: August 2014

AbstractSurface and electrical properties of two flexible and cross-linked epiclon based polyimide films were investigated. Surface tension measurements indicate an increased hydrophobicity due to both isothermal treatment - which induces imidization and cross-linking - and to the chemical structure, characterized by the different number of ether linkages in the polyimide backbone. Morphology of film surfaces, modified by plasma treatment, shows high roughness and, implicitly, improved adhesion, as required in electronics. The studied polyimides exhibit low dielectric constants and dielectric losses, comparatively to conventional aromatic polyimides. The electrical conductance and resistivity characteristics of these polymers recommend them as good insulators for dielectric layers in microelectronic applications.
Poly(4-methyl-1-pentene)/MWNT nanocomposites
Authors: Patil Prashant A , Wanjale Santosh D , Jog Jyoti P. 
Published: August 2014

AbstractNanocomposites of poly(4-methyl-1-pentene) (PMP) with various weight fractions of multiwall carbon nanotubes (MWNT’s) were prepared by melt compounding. The nanocomposites are characterized for structure using scanning electron microscopy. The viscoelastic behavior of the nanocomposites is investigated in solid as well as melt state. The study reveals a significant increase in storage modulus especially in the rubbery regime of the polymer matrix and reduced tan δ. Rheological properties in melt show that the complex viscosity and shear storage modulus are increased as a result of incorporation of MWNT. A systematic decrease in the cross over frequency is noted which is attributed to the increased relaxation time. In dielectric analysis, composition dependent enhanced permittivity and conductivity are observed. The thermal stability of the polymer is found to be significantly improved in presence of MWNT’s.
Thermal stability, mechanical and adsorption resistant properties of HDPE/PEG/Clay nanocomposites on exposure to electron beam
Authors: Mohaddespour Ahmad , Javad Ahmadi Seyed , Abolghasemi Hossein , Jafarinejad Shahryar 
Published: August 2014

AbstractThe Influence of electron beam on behaviors of high density polyethylene/poly(ethylene glycol)/organoclay nanocomposites has been studied. Nanocomposite compounds were prepared by melt intercalation method. X-ray diffraction (XRD) and transition electron microscopy (TEM) revealed the combination of nanocomposite morphology. Thermal and mechanical properties of nanocomposites were studied by using Thermogravimetric analysis (TGA), Young's modulus, tensile strength and hardness tests. The results show that at 500 KGy dose of irradiation the Young’s modulus and tensile strength values have been enhanced in comparison with pure blend by cross-linking and the surface hardness of samples raises by increasing the clay content The samples with the clay content of 5 wt% in the matrix with 500KGy dose of irradiation have shown satisfactory thermal resistance.The irradiation at high levels has degraded the nanocomposites and an optimum dose must be employed to enhance their properties. The presence of poly(ethylene glycol) as a compatibilizer has improved the dispersion of clay layers into the matrix and has enhanced the mechanical properties and thermal resistance of nanocomposites. The presence of the clay in the matrix has increased the adsorption amount of xylene and toluene into the bulk of nanocomposites and the irradiation has decreased this capacity by the dose level.
Characterization of the surface and mechanical behavior of polyurethane microporous films doped with silver nanoparticles
Authors: Ciobanu Liana Cătălina , Ciobanu Constantin 
Published: August 2014

AbstractThe aim of this study was to investigate the effects of silver nanoparticles (Ag-NPs) concentration on surface of polyurethane microporous films. The Ag-NPs have a diameter between 1.74-10 nm and were synthesized in the polymer matrix. The effects of Ag-NPs at the surface of polyurethane (PU) microporous films were investigated by means of attenuated total reflection Fourier infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM) and contact angle measurements. The mechanical behavior of PU films vs Ag-NPs concentration was also studied. The Ag-NPs induce changes in the PU surface structure, wettability properties, topography and mechanical properties. These phenomena may be due to interactions between Ag-NPs and urethane groups which form new structure urethane-silver-urethane with a specific morphology and the nanostructuring of the surface by means of metallic nanoparticles.
Study of thermal properties of difunctional benzoxazines
Authors: Zhao Chun’e , Xu Guoliang , Zeng Ke , Miao Peikai , Zhou Hongfei , Wang Yipeng , Liu Tao , Yang Gang 
Published: August 2014

AbstractThree difunctional benzoxazine monomers bis (3,4-dihydro-2H-3-phenyl- 1,3-benzoxazinyl) methane, (abbreviated as BF-a), bis (3,4-dihydro-2H-3-phenyl-1, 3-benzoxazinyl) isopropane, (abbreviated as BA-a), bis (3,4-dihydro-2H-3-phenyl- 1,3-benzoxazinyl) biphenyl, (abbreviated as BP-a) were successfully synthesized via phenol (bisphenol A, 4,4’-Biphenol, bisphenol F), aniline and paraformaldehyde. Their structures were identified by 1H NMR and FT-IR. The monomers were thermally treated at 200 oC for 2 h in nitrogen to give corresponding prepolymers. The thermal properties of the monomers were investigated by TGA under nitrogen atmosphere. The thermal properties of the prepolymers were investigated by TGA under nitrogen and air atmosphere. It was found that the monomers of BF-a and BA-a showed lower melting points and exhibited wider processing windows than BP-a. The prepolymer from BP-a showed good thermal stabilities, compared with the prepolymers from BF-a and BA-a.
Effects of feed rate and solution conductivity on jet current and fiber diameter in electrospinning of polyacrylonitrile solutions
Authors: Fallahi Delaram , Rafizadeh Mehdi , Mohammadi Naser , Vahidi Behrooz 
Published: August 2014

AbstractElectrospinning of solutions of polyacrylonitrile in dimethylformamide (PAN/DMF) were performed under different voltages at different constant feed rates and the jet electric current was measured. The effects of applied voltage, feed rate and solution conductivity on jet electric current and fiber diameter were investigated. The results showed that the feed rate had no effect on jet current and fiber diameter, whereas by increasing the applied voltage and solution conductivity, both the jet current and fiber diameter were increased.
Accuracy in locating glass transitions: aging and gamma sterilization of vulcanized thermoplastic elastomers
Authors: Brostow Witold , Deshpande Sameer , Pietkiewicz Dorota , Wisner Steven R. 
Published: August 2014

AbstractWe have studied nine thermoplastic vulcanizate elastomers (TPVs) in four series: as made, after accelerated aging, after γ irradiation, after both irradiation and aging. The materials exhibit two glass transitions, one seen in crosslinked regions and the other in un-crosslinked amorphous regions. Three techniques of determination of glass transitions have been used and the results compared, all three based on dynamic mechanical analysis (DMA): as a peak in the loss modulus E’’; as a peak in tan δ; and as the midpoint of the rapid decrease in the storage modulus E’. We recommend the last method for both fundamental and practical reasons.
Effectiveness of heat protection of fabrics loaded with phase change materials
Authors: Fallahi Elham , Barmar Mohammad , Kish Mohammad Haghighat 
Published: August 2014

AbstractAmong different natural and non-corrosive products paraffin wax and camel fat are selected as phase change materials (PCM). These PCMs are applied to glass, polyester/viscose and wool/polyester woven fabrics. To examine their efficacy, their thermal behavior in a condition similar to the actual end uses is measured. Chemical nature and thermal properties of the PCMs are measured by Fourier transform infrared spectroscope and differential scanning calorimeter. A relation based on the principle of heat transfer is used to determine the temperature of a thermometer covered by fabrics loaded with PCMs. A simple exponential relation explains the experimental results. For glass and polyester/viscose fabrics use of these PCMs leads to substantial delays in the temperature changes. The important parameters for the evaluation of the products are discussed.
Thermal decomposition studies of highly alternating CO2- cyclohexene oxide copolymer
Authors: Jianxin Luo , Min Zhang , Zhiqiang Zou , Baohua Liu , Liban Chen 
Published: August 2014

AbstractHighly alternating CO2-cyclohexene oxide copolymer, namely poly(cyclohexene carbonate) (PCHC), considered potentially to be microelectronic sacrificial material, was successfully synthesized by copolymerization of cyclohexene oxide and CO2 in the presence of SalenAl(OiPr) catalyst. The obtained highly alternating PCHC copolymer were determined and proven to have superior thermal decomposition properties decomposing completely at 350 oC by thermogravimetric (TG) analysis under dynamic conditions. The thermal decomposition kinetics of the obtained PCHC was investigated by a different kinetic method using data from TG analysis. Based on the analytical, kinetic parameters were calculated and kinetic model of pyrolysis was proposed. TG-IR, Py-GC/MS, IR and 1H NMR techniques were applied to investigate the decomposition process. Based on Py-GC/MS and TG-IR techniques, carbon dioxide, 1,3-cyclohexadiene, cyclopentanecarboxaldehyde, cyclohexene oxide, cyclohexanone and trans-1,2- carbonyldioxycyclohexane were identified as thermal decomposition products of PCHC. The solid residues of the PCHC with 25% ether linkages decomposed at 200, 250, 300, 350 oC as determined by IR and 1H NMR. The results demonstrated that the carbonate content of the solid residues decreased gradually at elevated heat-temperatures and at 350 oC only few polyether linkages were observed.
Extremely high photocatalytic activity of polymer nanospheres embedded with CdS nanoparticles prepared by a novel method
Authors: Wu Yuanpeng , Gao Yongyi , Ding Xiaobin , Zheng Zhaohui , Peng Yuxing 
Published: August 2014

AbstractA novel, practicable and convenient route has been developed to prepare polymer nanospheres embedded with CdS nanoparticles which show an extremely high photocatalytic activity compared with other photocatalysts. In this method, polymer nanospheres were fabricated through the polymerization of cadmium dimethacrylate which was introduced into self-assembly system of chitosan and 3-mercaptopropionic acid. Then CdS nanoparticles were prepared insitu by inflating H2S into the polymer nanospheres.
Polyamide/layered silicate nanocomposites: A correlation between fracture toughness and molecular mobility
Authors: Kotek Jiří , Kelnar Ivan , Brus Jiří , Urbanová Martina 
Published: August 2014

AbstractThis study correlates toughness of polyamide nanocomposites with the molecular mobility of polymer segments in the amorphous phase. Two nanocomposite systems prepared by melt-compounding of polyamide-6 with sodium montmorillonite or organophilized montmorillonite were compared. They differed in the extent of silicate dispersion. While sodium montmorillonite formed intercalated nanocomposites, the organophilization promoted full exfoliation of the silicate layers in the matrix. The different morphology was imprinted in fracture behaviour, toughness of exfoliated nanocomposites was markedly lower that that of their intercalated counterparts. To explain this difference, a solid-state NMR was used as a selective tool for providing information about nanocomposites structure and, primarily, about dynamics of polymer segments. Comparison of NMR spinrelaxation behavior with fracture mechanics experiments revealed a close correlation between fracture toughness and the intensity of rapidly relaxing component of the amorphous phase.
Effect of calcium neutralization on elastic and swelling properties of crosslinked poly(acrylic acid) - correlation to inhomogeneities and phase behaviour
Authors: Larsson Mikael , Gustafsson Stefan , Olsson Eva , Larsson Anette 
Published: August 2014

AbstractCrosslinked hydrogels of poly(acrylic acid) neutralized with calcium hydroxide were synthesized using free radical co-polymerization. The effects of the amount added calcium on the elastic modulus and swelling properties of the gels and the correlation to phase behaviour and structural changes within the gels were studied using texture analysis, gravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and atomic force microscopy (AFM). It was found that the elastic modulus decreased nonlinearly with increasing amount of added calcium and that the swelling’s dependence on the amount of added calcium was complicated. The maximum swelling increased with increasing amount of added calcium until a critical calcium content was reached, upon which the gels phase separated, with a strong decrease in swelling as a result. The changes in properties are explained by the fact that calcium affects the structure of the polymer network during synthesis and by the phase behaviour of the gels. Changes in the gel structure with the addition of calcium were detected with AFM. Furthermore, AFM revealed different phases on the nanometre scale for the sample with a calcium content around which phase separation is macroscopically observed. Finally, it was shown that the sulphur from the initiator potassium persulfate formed crystal like regions with high sulphur and calcium content upon drying of the hydrogels.
Effects of polypropylene-g-dibutyl maleate on mechanical and rheological properties of PP/PA6 blends
Authors: Li Duxin , Ou Baoli , Jia Demin 
Published: August 2014

AbstractThe effects of polypropylene-grafted-dibutyl maleate (PP-g-DBM) used as compatibilizer on mechanical, rheological and morphological properties of polypropylene (PP) and nylon 6 (PA6) blends was systematically investigated in this paper. The results of Molau test, solvent extraction and differential scanning calorimetry (DSC) indicated the formation of PP-g-PA6 in vicinity of interfaces during melting extrusion. Owing to the reaction between the reactive groups of PPg- DBM and amine (-NH2) end groups of PA6, the tensile and impact strength of the PP-g-DBM compatibilized PP/PA6 blends were much higher than that of the uncompatibilized PP/PA6 blends. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the domain sizes of the dispersed phase in the compatibilized PP/PA6 blends decreased and the interfaces become more indistinct, which indicated a clear compatibiliting effect was induced by the PP-g-DBM in the immiscible PP/PA6 blends, i.e. the PP-g-DBM was an effective compatibilizer for the PP/PA6 blends. In addition, the rheological measurements showed the PP-g-DBM compatibilized PP/PA6 blends possessed higher pseudo plasticity, melt viscosity and flow activation energy.
Kinetics of suspended emulsion copolymerization of acrylonitrile with itaconic acid
Authors: Yu Mengmeng , Chen Hou , Liang Ying , Cui Hengli , Zhou Wenying , Li Dongmei , Cui Xianqiang 
Published: August 2014

AbstractAcrylonitrile(AN) was successfully used to copolymerize with itaconic acid (IA) by suspension emulsion polymerization at 70 ˚C under N2 atmosphere for the first time. Porous AN/IA copolymers were prepared by using potassium peroxydisulphate (KPS) as initiator, poly(vinyl alcohol) (PVA) as dispersant and Span60 as emulsifier. Kinetics of suspension emulsion copolymerization of AN with IA were studied. Effects of various mass ratios of water/monomer, initiator concentrations, emulsifier concentrations and dispersant concentrations on AN/IA copolymerization rate and changes of particle size and size distribution with the extension of polymerization time were investigated. It was found that the copolymerization rate increased with water/monomer mass ratio and KPS concentration. Span60 concentration and PVA concentration had no obvious effect on the polymerization rate. Finally, a suspension emulsion polymerization mechanism for AN and IA was proposed.