bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical and conductivity studies of Pseudo‐doped chitin‐polyaniline blend
Authors: Rao Vijayalakshmi , Ramaprasad A. T.
Published: June 2007

In this article, we report the preparation and characterization of self‐doped conducting chitin, polyaniline blends by solution blending method. The characterization of the blends was done by UV–vis absorption spectrum, FTIR, and conductivity studies. Conductivity of the self doped blends increases from less than ∼10−7 S/cm to 2.15 × 10−5 S/cm, depending on the percentage of polyaniline in the blend. Spectroscopic analysis shows interaction between chitin and polyaniline and the electronic states are similar to those of the emeraldine and protonically doped forms of polyaniline. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Dielectric properties of thermosetting material nanocomposites
Authors: Luiz Dias Filho Newton , Adolfo de Aquino Hermes , Souza Pereira Denise , Rosa André H.
Published: June 2007

The dieletric relaxation properties of thermosetting material nanocomposites based on spherosilicate nanoplatforms were studied from room temperature to 170°C, varying the frequency from 10 to 1000 KHz. Permittivity (ε′), dielectric loss (ε″), and activation energy (Ea) were calculated. The results of dielectric relaxation were confirmed by those of the final properties. The dielectric loss amplitude decreases with increasing ODPG content until about 70–73 wt % and slightly increases at higher ODPG content. This means that the increasing of the ODPG content in the composite samples decreases the number of pendants groups and/or increases crosslink density, causing decreased motion of organic tethers, and subsequently decreasing of the dipolar mobility. The results of apparent activation energy, fracture toughness and tensile modulus mechanical properties show the same profile with respect to ODPG content, in the sense that they exhibit maxima around 70 wt % ODPG. For the ODPG/MDA composites, this formulation of 70 wt % ODPG containing excess of amine is not composition where the highest crosslinked density is reached. This implies that the best mechanical properties and Ea are provided by some degree of chain flexibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Recognition properties of poly(vinylidene fluoride) hollow‐fiber membranes modified by levofloxacin‐imprinted polymers
Authors: Bing Nai‐Ci , Xu Zhen‐Liang , Wang Xue‐Jun , Yang Zuo‐Guo , Yang Hu
Published: June 2007

Through the use of thermal polymerization, poly(vinylidene fluoride) (PVDF) hollow‐fiber membranes modified by a thin layer of molecularly imprinted polymers (MIPs) were developed for the selective separation of levofloxacin. To demonstrate the changes induced by thermal polymerization, PVDF hollow‐fiber membranes with different modification degrees by repeated polymerization were weighed. The total weight of the imprinted membranes increased by 14 μg/cm2 after a five‐cycle polymerization. An increase in the membrane weight indicated the deposition of an MIP layer on the external surface of PVDF hollow‐fiber membranes during each polymerization cycle, which was also characterized by scanning electron microscopy. MIP membranes with different degrees of surface modification provided highly selective binding of levofloxacin. Both hollow‐fiber MIP membranes and nonimprinted membranes showed enhanced adsorption of levofloxacin and ofloxacin gradually with an increase in the modification degrees of PVDF hollow‐fiber membranes to a maximum value followed by a decrease. These results indicate that thermal polymerization indeed produces an MIP layer on the external surface of PVDF hollow‐fiber membranes and that it is feasible to control the permeability by repeated polymerization cycles. Different solvent systems in the permeation experiments were used to understand the hydrophobic interaction as one of the results of the binding specificity of MIP membranes. Selective separation was obtained by multisite binding to the template via ionic, hydrogen‐bond, and hydrophobic interactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Use of poly(o‐toluidine)/ZrO2 nanocomposite coatings for the corrosion protection of mild steel
Authors: Chaudhari Sudeshna , Patil P. P. , Mandale A. B. , Patil K. R. , Sainkar S. R.
Published: June 2007

This study explored the possibility of using poly(o‐toluidine) (POT)/ZrO2 nanocomposite coatings for the corrosion protection of mild steel in a chloride environment. POT/ZrO2 nanocomposite coatings were synthesized on steel substrates through an electrochemical route. These coatings were characterized with cyclic voltammetry, ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The performance of POT/ZrO2 nanocomposites as protective coatings against the corrosion of mild steel in aqueous 3 wt % NaCl was evaluated with the potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results of this study demonstrate that POT/ZrO2 nanocomposite coatings provide better protection for mild steel against corrosion than pure POT coatings. The corrosion potential was about 0.312 V versus a saturated calomel electrode, more positive in aqueous 3 wt % NaCl for the nanocomposite‐coated steel than the uncoated steel, and the corrosion rate of steel was reduced by a factor of almost 51. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Phase morphology and mechanical properties of a poly(ether sulfone)‐modified bismaleimide resin
Authors: Liu Xiao Yun , Zhan Guo Zhu , Han Zhe Wen , Li Shan Jun , Yu Ying Feng
Published: June 2007

The polymerization‐induced phase‐separation behavior of a thermoplastic [poly(ether sulfone) (PES)]‐ modified thermosetting bismaleimide resin during isothermal curing was investigated with differential scanning calorimetry, time‐resolved light scattering, and scanning electron microscopy with various contents and molecular weights of PES. The results suggested that the phase structure changed from a dispersed structure to a bicontinuous structure to phase inversion with an increase in the PES content. Three kinds of PES with different molecular weights were used to study the effects of the molecular weight on the phase structure and mechanical properties of modified systems. With higher molecular weight PES, a phase‐inversion morphology could be obtained at lower PES contents. The curing conversion of bismaleimide was affected by the composition of the blend. The curing rate decreased with an increase in the PES content. A blend with 15 wt % PES of a suitable molecular weight had a higher tensile strength and elongation at break than that without PES. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Acid‐dye‐dyeable polyacrylonitrile/ poly(N,N‐dilkylaminoethylacrylate) acrylic blend fiber
Authors: Wang Ya‐Zhen , Du Shu‐Ping , Shen Xin‐Yuan , Zhu Li‐Wu , Gong Zhen‐Ping
Published: June 2007

An acid‐dye‐dyeable polyacrylonitrile/poly (N,N‐dilkylaminoethylacrylate) blend fiber was prepared. On the basis of research for the dye uptake, color strength, tensile strength, and breaking elongation of the polyacrylonitrile/poly (N,N‐dilkylaminoethylacrylate) blend fiber, it was found that the blend fiber and its fabrics for acid dyes possessed favorable dyeability and mechanical properties. The effect of the polyacrylonitrile ratio on the blend fiber was examined. The optimum dyeing‐process parameters were determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Cationic water‐soluble polymers with the ability to remove arsenate through an ultrafiltration technique
Authors: Rivas Bernabé L. , del Carmen Aguirre María , Pereira Eduardo
Published: June 2007

Different cationic water‐soluble polymers with (R)4N+X− groups and pyridinium groups were prepared, and their arsenate retention performance was investigated with the liquid‐phase polymer‐based retention technique. Poly[3‐(methacryloylamino)propyl]trimethylammonium chloride, poly[2‐(acryloyloxy)ethyl]trimethylammonium chloride, poly(ar‐vinylbenzyl)trimethylammonium chloride, poly[2‐(acryloyloxy)ethyl]trimethylammonium methyl sulfate, poly(4‐vinyl‐1‐methyl pyridinium)bromide, and poly[3‐(methacryloylamino)propyl]dimethyl(3‐sulfopropyl)ammonium hydroxide were prepared. The synthesis of the polymers by solution radical polymerization produced a yield higher than 77%. Structural analyses were performed with Fourier transform infrared and 1H‐NMR spectroscopy and thermogravimetry/differential scanning calorimetry. Commercial poly(4‐vinyl‐1‐methyl pyridinium)bromide and poly(ar‐vinylbenzyl)trimethylammonium chloride were also used. The liquid‐phase polymer‐based retention technique was employed to study the retention of arsenate species. The polymer structure and exchange groups, such as methyl sulfate, chloride, bromide, and hydroxide, presented different properties for removing arsenate anions from aqueous solutions. The type of voluminous quaternary ammonium group present influenced arsenic retention. All the polymers could bind HAsO42− species from an aqueous solution more selectively at pHs 8 and 6 than at pH 4. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Hyperbranched aromatic polyamines with s‐triazine rings
Authors: Mahapatra Sibdas Singha , Karak Niranjan
Published: June 2007

Two aromatic hyperbranched polyamines with s‐triazine rings were synthesized from A2 (4,4′‐sulfonyl dianiline or 4,4′‐methylene dianiline) and B3 (2,4,6‐trichloro‐s‐triazine) types of monomers by a single‐step nucleophilic displacement polymerization technique in the presence of diisopropyl ethyl amine as the base. The hyperbranched polyamines were obtained in high yields (∼ 82–90%) with this technique. The polymers were characterized through solubility testing, measurements of the inherent viscosity, Fourier transform infrared, ultraviolet, 1H‐NMR, and 13C‐NMR spectroscopy, and X‐ray diffraction studies. The inherent viscosities of the polymers were in the range of 0.23–0.42 dL/g in 0.5% (w/v) N,N′‐dimethylacetamide at 27 ± 0.1°C. They were soluble only in highly polar solvents such as N,N′‐dimethylacetamide, dimethylformamide, dimethyl sulfoxide, and N‐methylpyrrolidone. The thermal behavior of the polymers was investigated with thermogravimetric analysis and differential scanning calorimetry studies. The flame‐retardant characteristics of the polymers were tested through the measurement of the limiting oxygen index. In the thermogravimetric analysis of these hyperbranched polyamines, no weight loss was observed below 250°C under a nitrogen atmosphere, whereas differential scanning calorimetry showed that the glass‐transition temperatures were about 240 and 230°C for the polymers with sulfonyl and methylene groups, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Styrene–butadiene block copolymer with high cis‐1,4 microstructure
Authors: Zhu Han , Wu Yi‐Xian , Zhao Jiang‐Wei , Guo Qing‐Lei , Huang Qi‐gu , Wu Guan‐Ying
Published: June 2007

The sequential block copolymerization of styrene (St) and butadiene (Bd) was carried out with an activated rare earth catalyst composed of catalyst neodymium tricarboxylate (Nd), cocatalyst Al(i‐Bu)3 (Al), and chlorinating agent (Cl). The microstructure, composition, and morphology of the copolymer were characterized by FTIR, 1H NMR, 13C NMR, and TEM. The results show that styrene–butadiene diblock copolymer with high cis‐1,4 microstructure of butadiene units (∼ 97 mol %) was synthesized. The cis‐selectivity for Bd units was almost independent on the content of styrene units in the copolymer ranging from 18.1 mol % to 29.8 mol %. The phase‐separated morphology of polystyrene (PS) domains of about 40 nm tethered by the elastomeric polybutadiene (PB) segments is observed. The PS‐b‐cis‐PB copolymer could be used as an effective compatilizer for noncompatilized binary PS/cis‐PB blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis, characterization, and acoustic properties of new soluble polyurethanes based on 2,2′‐[1,4‐phenylenebis(nitrilomethylylidene)diphenol and 2,2′‐[4,4′‐methylene‐di‐2‐methylphenylene‐1,1′‐bis(nitrilomethylylidene)]diphenol
Authors: Raghu A. V. , Gadaginamath G. S. , Mathew N. , Halligudi S. B. , Aminabhavi T. M.
Published: June 2007

Eight novel polyurethanes based on 2,2′‐[1,4‐phenylenebis(nitrilomethylylidene)]diphenol and 2,2′‐[4,4′‐methylene‐di‐2‐methylphenylene‐1,1′‐bis(nitrilomethylylidene)]diphenol acting as hard segments with two aromatic and two aliphatic diisocyanates (4,4′‐diphenylmethane diisocyanate, toluene 2,4‐diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate) were prepared and characterized with Fourier transform infrared, UV spectrophotometry, fluorescence spectroscopy, 1H‐NMR and 13C‐NMR spectroscopy, thermogravimetric analysis, and differential thermal analysis. All the polyurethanes contained domains of semicrystalline and amorphous structures, as indicated by X‐ray diffraction. The acoustic properties and solubility parameters were calculated with the group contribution method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Electrical behavior of polyurethane composites with acid treatment‐induced damage to multiwalled carbon nanotubes
Authors: Jang Pill Gyu , Suh Kwang S. , Park Min , Kim Jun Kyung , Kim Woo Nyon , Gyu Yoon Ho
Published: June 2007

We have studied the electrical conductivity and percolation threshold of polyurethane (PU) composites filled with multiwalled carbon nanotubes (MWCNT) purified by increasing immersion time in aqueous solutions of either nitric acid or a mixture of nitric and sulfuric acids at 80°C. The MWCNT crystallinity peaks after 2 h of treatment, which enables the PU composites to enhance the percolation threshold and electrical conductivity in the conductive network formation region. MWCNT treated under either a milder or severer acidic condition deteriorate the electrical behavior of the composites, since MWCNT are poorly dispersed in the PU matrix in the former condition, but lost their intrinsic electrical conductivity due to the partial destruction of their crystalline structure in the latter. Therefore, the acid treatment needs to be carefully controlled to effectively purify the MWCNT, maintain the crystalline structure without further damage, and thereby improve the electrical behavior of PU/MWCNT composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Kinetics for chlorination of maleic anhydride grafted polypropylene
Authors: Fu He‐Qing , Huang Hong , Zhang Xin‐Ya , Ye Dai‐Yong , Chen Huan‐Qin
Published: June 2007

Preparation of Chlorinated maleic anhydride grafted polypropylene (Cl‐PP‐g‐MAH) by free radical process was carried out using carbon tetrachloride (CCl4) as the solvent and benzoperoxide (BPO) as the initiator. Effects of reaction temperature, concentrations of PP‐g‐MAH and BPO on the rate of chlorination were studied. The experimental results showed the actual rate constant for chlorination of maleic anhydride grafted polypropylene followed the Arrhenius law and the total apparent activation energy was 19.7 kJ mol−1. The kinetic model for chlorination of maleic anhydride grafted polypropylene was found to be R = K[BPO]0.53[C]0.93. The properties of chlorination of maleic anhydride grafted polypropylene were better than those of maleic anhydride grafted polypropylene. The products were characterized by Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and properties of EPDM/TiO2 composites
Authors: Haitao Shan , Juqing Cui , Qiang Zhang , Wei Zhuang , Qihui He , Baixing Hu , Jian Shen
Published: June 2007

Composites of EPDM/TiO2 in which TiO2 particles were surface modified with γ‐methacryloxypropyl trimethoxysilane (MPS) and preultrasonically dispersed, and EPDM was grafted with maleic anhydride (MA) were successfully prepared. FTIR analysis showed that the modification of TiO2 and the grafting of EPDM had taken place. The uniform dispersion of TiO2 particles in EPDM matrix as well as good interfacial compatibility was observed from scanning electron microscopy (SEM) images. The tensile strength and elongation at break were greatly improved and reached the maximum as the content of TiO2 in the composite reached 7.5% wt. The result of swell and solution test indicated that the composites were evidently crosslinked. Thermogravimetric analysis (TGA) indicated that the decomposition temperature of the composite was increased about 20°C. This work provides a potential way for crosslinking EPDM matrix with inorganic filler in a convenient method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effect of the structure on sorption and diffusion processes in polyamide 6, part 1: Activation energy and thermodynamic parameters of water desorption in oriented and unoriented polyamide 6
Authors: Avramova Nadka
Published: June 2007

Effect of the structure on desorption of water in polyamide 6 is studied by differential scanning calorimetry and thermogravimetry. Oriented and unoriented polyamide 6 fibers annealed in water at 100°C for different times (2 s up to 1 h) are characterized by their structure and transport properties. It is found that water treatment leads to substantial change in the polymer structure (including phase transition even at room temperature). Activation energy and enthalpy of water desorption are determined, and their high values (Ea = 60–130 kJ/mol; ΔHd = 950–1360 J/g) are attributed to the formation of strong sorbent–sorbat bonds. Both parameters are influensed substantially by the polymer structure (degree of crystallinity and orientation). Besides, it is found that the temperature of water desorption (Td) is also very sensitive to the structure. The Td‐values increase sharply with rise of degree of crystallinity, being always considerably lower for oriented fibers. This quite unexpected result is also confirmed and further interpreted in the next parts of the article. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and thermal property of hybrid nanocomposites by free radical copolymerization of styrene with octavinyl polyhedral oligomeric silsesquioxane
Authors: Yang Benhong , Xu Hongyao , Wang Jiafeng , Gang Shanyi , Li Cun
Published: June 2007

The poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution 1H NMR, 29Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the 1H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic Tg and Tdec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Influence of different amides as plasticizer on the properties of soy protein plastics
Authors: Liu Dagang , Tian Huafeng , Zhang Lina
Published: June 2007

A series of amide‐plasticized soy protein isolate materials were prepared by hot compression‐molding techniques at 140°C and 20 MPa. The plasticizing efficiency of amides was in the order of formamide > acetamide > acrylamide resulting from scanning electron microscopy, optical transmittance and differential scanning calorimetry. The results from torque rheology indicated that flowability and processability could be improved by adding amide as plasticizers. All of the sheets showed single glass transition temperature obtained by differential scanning calorimetry, indicating good compatibility between amide and soy protein. The water uptake of the plastics sheets and effects of moisture content on the thermal and mechanical properties were also investigated. The glass transition temperature and tensile strength decreased with an increase of moisture content in sheets. Formamide was considered as the best plasticizer of three amides because of the higher plasticizing efficiency and water resistance of SFm sheets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Degradation and in situ reaction of polyolefin elastomers in the melt state induced by ultrasonic irradiation
Authors: Chen Jinyao , Li Huilin , Lai Shih‐Yaw , Jow Jinder
Published: June 2007

The degradation and in situ reaction with polystyrene (PS) of polyolefin elastomers in the melt state induced through high intensity ultrasonic wave were investigated. The effects of initial molecular weight of polyolefin elastomers, irradiation time, ultrasonic intensity, as well as reaction temperature on the ultrasonic degradation of polyolefin elastomers melt were studied using a “static” ultrasonic vibration system. The results show that the degradation occurs mostly at the tip of the ultrasonic probe, and little or no degradation was observed at the distance of 5 mm or greater from the tip of the probe. The intrinsic viscosity [η] of polyolefin elastomers near the tip of ultrasound probe significantly decreases with irradiation time in the first 100 s and tends toward a limiting value for all samples. The degradation rates increased with an increase in ultrasonic intensity and decrease in reaction temperature. The ultrasonic degradation kinetics of polyolefin elastomers in melt state follows the equation: [η]t = [η]∞ + Ae−kt. The fitting results by this equation accord well with the experimental data. The feasible ultrasonic degradation mechanism is proposed based on the viscoelastic characteristic of polymer melt. FTIR analysis confirms that the copolymer forms under ultrasonic irradiation for PS/POE mixtures and in situ reaction of polymer in melt state can be induced by ultrasonic irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Structure and properties of collagen‐konjac glucomannan‐sodium alginate blend films
Authors: Wang Bi , Jia Dong‐Ying , Ruan Shang‐Quan , Qin Song
Published: June 2007

A new kind of blend film was made by mixing the solutions of collagen, konjac glucommnnan (KGM), and sodium alginate. The structure of the blend film was characterized by FTIR, XRD, atomic absorption spectrophotometer, and SEM, respectively. The effects of weight ratio between the polymers on light transmittance, tensile strength, elongation at break, water permeability, and water absorption of the film were studied. The results showed that there were strong interactions and good compatibility between collagen, KGM, and sodium alginate in the film. The film possesses good mechanical properties. Therefore, it can be applied in biomedicine as a new type of biomaterial. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
PVDF‐PZT‐5H composites prepared by hot press and tape casting techniques
Authors: Seema A. , Dayas K. R. , Varghese Justin M.
Published: June 2007

Piezoelectric polymer–ceramic composites are promising materials for transducer applications, and they are widely used in underwater hydrophones, biomedical imaging with ultrasound, and nondestructive testing applications. The critical factor in the 0–3 composite is to ensure homogeneous distribution of the filler in the matrix. To ensure this objective, PVDF‐PZT composite was prepared by two different routes: hot press and tape casting techniques. Loss on ignition and scanning electron microscopy studies were conducted to find out the uniformity of the composites prepared. It is found that hot press technique gives better uniformity compared to tape casting technique. PZT concentration was varied from 20 to 60 vol %. Physical and dielectric properties were studied. FT‐IR, DSC, and XRD characterization studies of PVDF were also recorded. Density of the composites was 2.74 to 5.13 g/cm3 as PZT concentration increased from 20 to 60 volume fractions. The dielectric constant of composites at 1 MHz varied from 16.74 to 98.48 as PZT concentration increased from 20 to 60 volume fractions. Hot press technique that combines solution and melt processing was found to be the better method for the preparation of 0–3 composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Flame retardancy and thermomechanical properties of the poly‐(glycidyloxypropyl) phenyl silsesquioxane/layered titanate nanocomposites
Authors: Harada Miyuki , Minamigawa Shuichi , Tachibana Kumiko , Ochi Mitsukazu
Published: June 2007

Poly‐(glycidyloxypropyl) phenyl silsesquioxane (PGPSQ) was combined with an organo‐layered titanate filler. The phase structure of the obtained composite was evaluated by XRD and TEM observations. Moreover, a burning test was carried out according to the UL‐94 test method. The extinguishing time of the nanocomposites was classified V‐0 even for the 1 wt % layered titanate content. Based on the results, it was clarified that the frame retardancy of the PGPSQ/organo‐layered titanate system was superior to the poly‐(glycidyloxypropyl) silsesquioxane (PGSQ)/organo‐layered titanate system, which was reported in a previous paper. In addition, the layered titanate as a filler also improved the ductility of the PGPSQ. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Styrene maleic anhydride copolymer mediated dispersion of single wall carbon nanotubes in polyamide 12: Crystallization behavior and morphology
Authors: Bhattacharyya Arup R. , Bose Suryasarathi , Kulkarni Ajit R. , Pötschke Petra , Häuβler Liane , Fischer Dieter , Jehnichen Dieter
Published: June 2007

Melt mixed composites based on polyamide 12 (PA12) were prepared using single wall carbon nanotubes (SWNT), which were encapsulated by styrene maleic anhydride copolymer (SMA). The aim was to achieve a reactive coupling between the maleic anhydride functionality of SMA at the surface of the SWNT and the amine end groups of PA12 during the melt mixing. The reaction could be proven by infrared spectroscopy. The modified nanocomposites exhibited a better SWNT dispersion. An enhanced interfacial adhesion between PA12 and SWNT was detected from SEM investigations of tensile fractured surfaces of the SMA encapsulated PA12/SWNT composites. Electrical conductivity measurements revealed the formation of “network‐like” structure formation at 6 wt % SWNT content in PA12/SWNT composites, however, PA12/SWNT + SMA composites showed insulating behavior due to encapsulating SMA layer on SWNT surface. Studies on crystallization behavior indicated the nucleating action of unmodified and SMA encapsulated SWNT in the respective composites as found in the increase of crystallization temperature and the change in the crystalline morphology of PA12 as observed from DSC, WAXD, and SAXS. However, the degree of crystallinity of PA12 increased only marginally on incorporation of either unmodified or SMA encapsulated SWNT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
A comparative study of fracture behavior between carbon black/poly(ethylene terephthalate) and multiwalled carbon nanotube/poly(ethylene terephthalate) composite films
Authors: Kobayashi Haruki , Shioya Masatoshi , Tanaka Tomoya , Irisawa Toshihira , Sakurai Shinichi , Yamamoto Katsuhiro
Published: June 2007

Fracture behavior of amorphous poly(ethylene terephthalate) (PET) films added multiwalled carbon nanotube (MWCNT) has been compared with that of the PET films added with carbon black (CB) to elucidate the effects of the large aspect ratio of MWCNT. Fracture toughness has been evaluated using the essential work of fracture tests. Evolution of the crazes has been analyzed by conducting time‐resolved small‐angle X‐ray scattering measurements during tensile deformation of the films at room temperature using synchrotron radiation. CB and MWCNT increased the fracture toughness of the PET film by increasing the plastic work of fracture. This resulted from the effects of the fillers to prevent the localization of deformation upon the crazes formed at earlier stages of tensile deformation and to retard the growth of the fibrils in the crazes to a critical length. The CB particles provided a number of sites where the crazes were preferably formed due to stress concentration. In the case of MWCNT, on the other hand, the widening of the crazes formed at earlier stages was suppressed due to the bridging effect arising from the large aspect ratio of MWCNT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Investigations of the initial state polymerization of propylene with Ziegler–Natta catalysts in slurry
Authors: Heuvelsland Albert , Wichmann Silke , Schellenberg Jürgen
Published: June 2007

The initial state polymerization of propylene with Ziegler–Natta catalysts has been investigated and discussed at very low polymerization yields under adiabatic industrial prepolymerization conditions in diluted slurry regarding the effects of significant process parameters like monomer pressure, aluminum alkyl, and donor kind and concentration including the morphology of the catalyst/polymer particles formed. A sharp temperature increase in the first minutes of the initial state polymerization is followed by a temperature maximum and a slow decrease. With cocatalyst triethyl aluminum (TEAL), high prepolymerization yields were already achieved at a molar ratio TEAL/Ti of 3.0, remaining about constant until ratios of at least 300. The external donor dicyclopentyl dimethoxy silane leads to higher polymerization yields than the donor cyclohexyl dimethoxymethyl silane in the initial state polymerization too; however, both show a remarkable decreasing effect on polymerization yield above a specific molar ratio donor/Ti obviously correlated with the bulkiness of the alkyl groups. The particle size of the catalyst and the catalyst/prepolymer particles is increasing with polymerization yield until about 22 g PP/g Cat with particles almost perfectly spherical. The particle size distribution is rather broad at lower prepolymerization stages but unifying with lower polymerization rates at higher polymerization times. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis and characterization of poly(L‐lactic acid)‐b‐poly(ethylene terephthalate‐co‐sebacate)‐b‐poly(L‐lactic acid) copolyesters
Authors: Hui Zhao Yun , Zhao Yun , Yuan Xu‐Bo , Sheng Jing
Published: June 2007

Random copolyester namely, poly(ethylene terephthalate‐co‐sebacate) (PETS), with relatively lower molecular weight was first synthesized, and then it was used as a macromonomer to initiate ring‐opening polymerization of l‐lactide. 1H NMR quantified composition and structure of triblock copolyesters [poly(l‐lactic acid)‐b‐poly(ethylene terephthalate‐co‐sebacate)‐b‐poly(l‐lactic acid)] (PLLA‐PETS‐PLLA). Molecular weights of copolyesters were also estimated from NMR spectra, and confirmed by GPC. Copolyesters exhibited different solubilities according to the actual content of PLLA units in the main chain. Copolymerization effected melting behaviors significantly because of the incorporation of PETS and PLLA blocks. Crystalline morphology showed a special pattern for specimen with certain composition. It was obvious that copolyesters with more content of aromatic units of PET exhibited increased values in both of stress and modulus in tensile test. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Removal of Cd(II), Hg(II), and Pb(II) ions from aqueous solution using p(HEMA/chitosan) membranes
Authors: Bayramoglu Gulay , Yakup Arica M. , Bektas Sema
Published: June 2007

An interpenetration network (IPN) was synthesized from 2‐hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV‐initiated photo‐polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane–metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second‐order kinetic equations and the Langmuir isotherm model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Simultaneous Inference for Ratios of Linear Combinations of General Linear Model Parameters
Authors: Hare David R. , Spurrier John D.
Published: June 2007

Consider a general linear model with p ‐dimensional parameter vector β and i.i.d. normal errors. Let K1, …, Kk , and L be linearly independent vectors of constants such that LT β ≠ 0. We describe exact simultaneous tests for hypotheses that K$ _i ^T $β/LT β equal specified constants using one‐sided and two‐sided alternatives, and describe exact simultaneous confidence intervals for these ratios. In the case where the confidence set is a single bounded contiguous set, we describe what we claim are the best possible conservative simultaneous confidence intervals for these ratios – best in that they form the minimum k ‐dimensional hypercube enclosing the exact simultaneous confidence set. We show that in the case of k = 2, this “box” is defined by the minimum and maximum values for the two ratios in the simultaneous confidence set and that these values are obtained via one of two sources: either from the solutions to each of four systems of equations or at points along the boundary of the simultaneous confidence set where the correlation between two t variables is zero. We then verify that these intervals are narrower than those previously presented in the literature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Residual Analysis for Linear Mixed Models
Authors: Santos Nobre Juvêncio , da Motta Singer Julio
Published: June 2007

Residuals are frequently used to evaluate the validity of the assumptions of statistical models and may also be employed as tools for model selection. For standard (normal) linear models, for example, residuals are used to verify homoscedasticity, linearity of effects, presence of outliers, normality and independence of the errors. Similar uses may be envisaged for three types of residuals that emerge from the fitting of linear mixed models. We review some of the residual analysis techniques that have been used in this context and propose a standardization of the conditional residual useful to identify outlying observations and clusters. We illustrate the procedures with a practical example. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Random Time Interval Approach for Analysing the Impact of a Possible Intermediate Event on a Terminal Event
Authors: Beyersmann Jan
Published: June 2007

We consider the impact of a possible intermediate event on a terminal event in an illness‐death model with states ‘initial’, ‘intermediate’ and ‘terminal’. One aim is to unambiguously describe the occurrence of the intermediate event in terms of the observable data, the problem being that the intermediate event may not occur. We propose to consider a random time interval, whose length is the time spent in the intermediate state. We derive an estimator of the joint distribution of the left and right limit of the random time interval from the Aalen‐Johansen estimator of the matrix of transition probabilities and study its asymptotic properties. We apply our approach to hospital infection data. Estimating the distribution of the random time interval will usually be only a first step of an analysis. We illustrate this by analysing change in length of hospital stay following an infection and derive the large sample properties of the respective estimator. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
REML Estimation of Variance Parameters in Nonlinear Mixed Effects Models Using the SAEM Algorithm
Authors: Meza Cristian , Jaffrézic Florence , Foulley Jean‐Louis
Published: June 2007

Nonlinear mixed effects models are now widely used in biometrical studies, especially in pharmacokinetic research or for the analysis of growth traits for agricultural and laboratory species. Most of these studies, however, are often based on ML estimation procedures, which are known to be biased downwards. A few REML extensions have been proposed, but only for approximated methods. The aim of this paper is to present a REML implementation for nonlinear mixed effects models within an exact estimation scheme, based on an integration of the fixed effects and a stochastic estimation procedure. This method was implemented via a stochastic EM, namely the SAEM algorithm. The simulation study showed that the proposed REML estimation procedure considerably reduced the bias observed with the ML estimation, as well as the residual mean squared error of the variance parameter estimations, especially in the unbalanced cases. ML and REML based estimators of fixed effects were also compared via simulation. Although the two kinds of estimates were very close in terms of bias and mean square error, predictions of individual profiles were clearly improved when using REML vs. ML. An application of this estimation procedure is presented for the modelling of growth in lines of chicken. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional fibrous PLGA/HAp composite scaffold for BMP‐2 delivery
Authors: Nie Hemin , Soh Beng Wee , Fu Yin‐Chih , Wang Chi‐Hwa
Published: June 2007

A protein loaded three‐dimensional scaffold can be used for protein delivery and bone tissue regeneration. The main objective of this project was to develop recombinant human bone morphogenetic protein‐2 (rhBMP‐2) loaded poly(D,L‐lactide‐co‐glycolide)/hydroxylapatite (PLGA/HAp) composite fibrous scaffolds through a promising fabrication technique, electrospinning. In vitro release of BMP‐2 from these scaffolds, and the attachment ability and viability of marrow derived messenchymal stem cells (MSCs) in the presence of the scaffolds were investigated. The PLGA/HAp composite scaffolds developed in this study exhibit good morphology and it was observed that HAp nanoparticles were homogeneously dispersed inside PLGA matrix within the scaffold. The composite scaffolds allowed sustained (2–8 weeks) release of BMP‐2 whose release rate was accelerated with increasing HAp content. It was also shown that BMP‐2 protein successfully maintained its integrity and natural conformations after undergoing the process of electrospinning. Cell culture experiments showed that the encapsulation of HAp could enhance cell attachment to scaffolds and lower cytotoxicity. Biotechnol. Bioeng. 2008;99: 223–234. © 2007 Wiley Periodicals, Inc.
Structures of ionic liquids dictate the conversion and selectivity of enzymatic glycerolysis: Theoretical characterization by COSMO‐RS
Authors: Chen Biqiang , Guo Zheng , Tan Tianwei , Xu Xuebing
Published: June 2007

Lipase‐catalyzed glycerolysis of triolein has been examined using a group of tetraammonium‐based ionic liquids (ILs) as media, specifically with functional groups in cation part. The results demonstrated that the reaction evolution and profile specificity of respective IL system could be quantitatively associated with the structural characteristics of the IL by means of quantum chemical and COSMO‐RS calculation. Misfit interaction, Van der Waals interaction and chemical potential, etc. derived from COSMO‐RS calculation are shown to be effective measures to delineate multiple interactions of ILs and then can be used to understand the effects of ILs on reactions. The hydrophobic substituents in the cation are found to contribute to the increase of triolein solubility and enhancement of initial reaction rate; while strong polar anion and polyethoxyl and free hydroxyl groups in the cation part dictate improved product selectivity through reducing activity coefficients of monoglycerides. Integration of these structures into the same molecule constitutes a promising group of ILs that could produce over 90% monoglyceride with almost 100% triglyceride conversion, as well as bulky productivity, of particular potential for industrial applications. Overall, this work has presented a first attempt to characterize the IL structure‐dependency of reaction specificity by associating structural variations of ILs with thermodynamic property changes of resided compounds and subsequent effects on reaction specificity. This might be of general value to help to understand the multiple solvation interaction among IL reaction systems at molecular level and promote the application of IL‐mediated reactions to practical interests. Biotechnol. Bioeng. 2008;99: 18–29. © 2007 Wiley Periodicals, Inc.
Use of a whole‐cell biosensor to assess the bioavailability enhancement of aromatic hydrocarbon compounds by nonionic surfactants
Authors: Keane Angela , Lau Peter C.K. , Ghoshal Subhasis
Published: June 2007

The whole‐cell bioluminescent biosensor Pseudomonas putida F1G4 (PpF1G4), which contains a chromosomally‐based sep‐lux transcriptional fusion, was used as a tool for direct measurement of the bioavailability of hydrophobic organic compounds (HOCs) partitioned into surfactant micelles. The increased bioluminescent response of PpF1G4 in micellar solutions (up to 10 times the critical micellar concentration) of Triton X‐100 and Brij 35 indicated higher intracellular concentrations of the test compounds, toluene, naphthalene, and phenanthrene, compared to control systems with no surfactants present. In contrast, Brij 30 caused a decrease in the bioluminescent response to the test compounds in single‐solute systems, without adversely affecting cell growth. The decrease in bioluminescent response in the presence of Brij 30 did not occur in the presence of multiple HOCs extracted into the surfactant solutions from crude oil and creosote. The effect of the micellar solutions on the toluene biodegradation rate was consistent with the bioluminescent response in single‐solute systems. None of the surfactants were toxic to PpF1G4 at the doses employed in this study, and PpF1G4 did not produce a bioluminescent response to the surfactants nor utilize them as growth substrates. TEM images suggest that the surfactants did not rupture the cell membranes. The results demonstrate that for Pseudomonas putida F1, nonionic surfactants such as Triton X‐100 and Brij 35, at doses between 2 and 10 CMC, may increase the bioavailability and direct uptake of micellar phase HOCs that are common pollutants at contaminated sites. Biotechnol. Bioeng. 2008;99: 86–98. © 2007 Wiley Periodicals, Inc.
A continuous multicolumn countercurrent solvent gradient purification (MCSGP) process
Authors: Aumann Lars , Morbidelli Massimo
Published: June 2007

Biomolecules are often purified via solvent gradient batch chromatography. Typically suitable smooth linear solvent gradients are applied to obtain the separation between the desired component and hundreds of impurities. The desired product is usually intermediate between weakly and strongly adsorbing impurities, and therefore a central cut is required to get the desired pure product. The stationary phases used for preparative and industrial separations have a low efficiency due to strong axial dispersion and strong mass transfer resistances. Therefore a satisfactory purification often cannot be achieved in a single chromatographic step. For large scale productions and for very valuable molecules, countercurrent operation such as the well known SMB process, is needed in order to increase separation efficiency, yield and productivity. In this work a novel multicolumn solvent gradient purification process (MCSGP‐process) is introduced, which combines two chromatographic separation techniques, which are solvent gradient batch and continuous countercurrent SMB. The process consists of several chromatographic columns, which are switched in position opposite to the flow direction. Most of the columns are equipped with a gradient pump to adjust the modifier concentration at the column inlet. Some columns are interconnected, so that non pure product streams are internally, countercurrently recycled. Other columns are short circuited and operate in batch mode. As a working example the purification of an industrial stream containing 46% of the hormone Calcitonin is considered. It is found that for the required purity the MCSGP unit achieves a yield close to 100% compared to a maximum value of a single column batch chromatography of 66%. Biotechnol. Bioeng. 2007;98: 1043–1055. © 2007 Wiley Periodicals, Inc.
Study of pellet formation of filamentous fungi Rhizopus oryzae using a multiple logistic regression model
Authors: Liu Yan , Liao Wei , Chen Shulin
Published: June 2007

Fungal pellet formation is an important topic of fermentation research. It has been reported that many factors such as agitation, medium nutrients, pH, polymer additives, and inoculum size influence the formation of fungal pellets. However, a few studies on the effects of all of these factors on fungal pellet formation have been reported. This paper conducted a comprehensive investigation using a completely randomized design (CRD) on a filamentous fungus, Rhizopus oryzae NRRL 395, in order to discover the effects of the above factors on fungal pellet formation. In addition, other factors, such as addition of biodegradable polymers and spore storage time that have not been reportedly studied were examined and their effects on pellet formation were investigated. A multiple logistic regression model was established to predict the probability of pellet formation using the above factors and their interactions as predictor variables. Model building and diagnostics were obtained using the Statistical Analysis System (SAS 9.0) program. The model developed in this study can be used to predict the pellet formation of other R. oryzae strains as well. Biotechnol. Bioeng. 2008;99: 117–128. © 2007 Wiley Periodicals, Inc.