bluuebunny/crossref_metadata_2025_split huggingface dataset:
PTC effect and structure of polymer composites based on polyethylene/polyoxymethylene blend filled with dispersed iron
Authors: Mamunya Y.P. , Muzychenko Y.V. , Lebedev E.V. , Boiteux G. , Seytre G. , Boullanger C. , Pissis P. 
Published: December 2006

AbstractThe temperature dependence of resistivity, structure, and thermal expansion of composites based on polyethylene/polyoxymethylene (PE/POM) blends filled with dispersed iron (Fe) have been studied. The dependence of conductivity on filler content shows percolation behavior, with the values of the percolation thresholds equal to 21 vol% for PE‐Fe, 24 vol% for POM‐Fe, and 9 vol% for the filled blend PE/POM‐Fe, with two‐step character of the conductivity curve. The evolution of structure of the composite PE/POM‐Fe demonstrates transition from polymer matrix POM‐Fe, with inclusions of PE through cocontinuous phases of both POM‐Fe and PE, to PE matrix, with inclusions of POM‐Fe. Such a structure occurs due to localization of the filler only in one of the polymer phases, namely in POM. Measurements of the coefficient of thermal expansion α show the presence of two values of α: higher value (equal to α of PE) and lower value (equal to α of POM‐Fe), the transition between them corresponding to the structure with cocontinuous phases. The PE/POM‐Fe composites demonstrate double‐positive temperature coefficient (PTC) effect, with the presence of two transitions and a plateau between them. In such a system, two contributions to the PTC effect coexist: the first contribution originates from the thermal expansion of the nonconductive PE phase with higher value of the coefficient α, which leads to the break of the continuity of the conductive POM‐Fe phase; the second contribution originates from the break of the conductive structure of the filler inside the POM‐Fe phase because of the morphological changes in the vicinity of the melting temperature of POM. The double PTC effect is explained in terms of these two processes (thermal expansion and melting). POLYM. ENG. SCI., 47:34–42, 2007. © 2006 Society of Plastics Engineers
Preparation and properties of electrospun poly(vinyl alcohol)/silver fiber web as wound dressings
Authors: Hong Kyung Hwa 
Published: December 2006

AbstractA novel wound dressing material was prepared by electrospinning poly(vinyl alcohol) (PVA)/AgNO3 aqueous solution into nonwoven webs and then treating the webs by heat or UV radiation. Through SEM, TEM, and XPS analyses, it was observed that the silver (Ag) nanoparticles were generated and existed in the near surface of the electrospun nanofibers. It was found that heat treatment as well as UV radiation reduced the Ag+++ ions in the electrospun PVA/AgNO3 fiber web into the Ag nanoparticles. Also the heat treatment improved the crystallinity of the electrospun PVA fiber web and so it made the web unsolved in moisture environment. Therefore, it was concluded that the only heat treated electrospun PVA/AgNO3 fiber web was a good material as wound dressings because it had structural stability in moisture environment as well as excellent antimicrobial ability and, quick and continuous release of the effectiveness. POLYM. ENG. SCI., 47:43–49, 2007. © 2006 Society of Plastics Engineers
Morphology development of PC/PE blends during compounding in a twin‐screw extruder
Authors: Yin Bo , Zhao Yin , Yu Run‐Ze , An Hai‐Ning , Yang Ming‐Bo 
Published: December 2006

AbstractThe morphological development of a polycarbonate/polyethylene (PC/PE) blend in a twin‐screw extruder was studied using a scanning electron microscope (SEM). The effects of extrusion temperature, viscosity ratio (the ratio of the viscosity of the dispersed phase to that of the matrix), and the screw configuration on the morphology of the PC/PE blend during the extrusion were discussed in detail. It was found that the morphology of the dispersed particles and the interfacial adhesion between the dispersed phase and matrix were both influenced by the extrusion temperature. The dispersed phase had a spheroidal shape and a small size during the high temperature processing, and an irregular shape and a large size when it was processed at low temperature. The PC phase with a lower viscosity was easier to disperse and also to coalesce. Therefore, the deformation of the low‐viscosity dispersed phase during the processing was more intense than that of the high‐viscosity dispersed phase. By comparing the effects of the different screw configurations on the morphology development of the PC/PE blend, it was found that the melting and breaking up of the dispersed phase were mainly affected in the initial blending stages by the number of the kneading blocks. While a kneading block with a 90 degree staggering angle was used, the size of the dispersed particles decreased and the long fibers were shortened, the large particles were drawn by the additional kneading zone. Finally, all of these structures were completely changed to the short fibers. POLYM. ENG. SCI., 47:14–25, 2007. © 2006 Society of Plastics Engineers
Efficient dispersion of multi‐walled carbon nanotubes by in situ polymerization
Authors: Hu Nantao , Zhou Hongwei , Dang Guodong , Rao Xianhua , Chen Chunhai , Zhang Wanjin 
Published: December 2006

AbstractMulti‐walled carbon nanotube (MWNT)‐reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers in the presence of acylated MWNTs. The acyl groups associated with the MWNTs participated in the reaction through the formation of amide bonds. This process enabled uniform dispersion of MWNT bundles in the polymer matrix. The resultant MWNT–polyimide nanocomposite films were optically transparent with significant mechanical enhancement at a very low loading (0.5 wt%). Evidence has been obtained for improved interactions between the nanotubes and the matrix polymer. Copyright © 2006 Society of Chemical Industry
Preparation of superabsorbent slow release nitrogen fertilizer by inverse suspension polymerization
Authors: Liu Mingzhu , Liang Rui , Zhan Falu , Liu Zhen , Niu Aizhen 
Published: December 2006

AbstractA superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (Mc) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g−1 in distilled water and 185 g g−1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry
Effect of cationic surfactant on homogenization and polymerization of methyl methacrylate miniemulsion modified by chitosan
Authors: Jeng Jauder , Dai Chi‐An , Chiu Wen‐Yen , Young Pin‐Yen 
Published: December 2006

AbstractHomogenization of monomer droplets and polymerization of methyl methacrylate (MMA) miniemulsion, stabilized by a combination of cationic surfactants including different amounts of n‐hexadecyltrimethylammonium chloride (HTMA) and chitosan 100, were investigated. With increasing HTMA concentration or decreasing concentration of chitosan 100, the required ultrasonication time for the miniemulsion to reach a critically stabilized state is reduced. After polymerization, for higher HTMA concentrations, droplet nucleation dominates because of higher surface coverage of HTMA on the droplets. However, for lower HTMA concentrations, the size distributions (SDs) of final latex particles are different from those of the droplets. Because surface coverage of HTMA on the droplets is lower in this condition, both droplet nucleation and homogeneous and/or micellar nucleation occur simultaneously in the miniemulsion polymerization. On increasing the concentration of chitosan 100 in the system, the SD of the final latex particles is far different from that of the droplets. This is due to a decrease of the effective surface coverage of chitosan 100 and HTMA on the droplets. Consequently, the opportunity of collision coalescence of the droplets increases, and MMA molecules can diffuse out more easily into the aqueous phase. Droplet nucleation is, therefore, no longer the major source for the latex particles. Copyright © 2006 Society of Chemical Industry
Understanding surfaces and buried interfaces of polymer materials at the molecular level using sum frequency generation vibrational spectroscopy
Authors: Chen Zhan 
Published: December 2006

AbstractThis paper reviews recent progress in the studies on polymer surfaces/interfaces using sum frequency generation (SFG) vibrational spectroscopy. SFG theory, technique, and some experimental details have been presented. The review is focused on the SFG studies on buried interfaces involving polymer materials, such as polymer–water interfaces and polymer–polymer interfaces. Molecular interactions between polymer surfaces and adhesion promoters as well as biological molecules such as proteins and peptides have also been elucidated using SFG. This review demonstrates that SFG is a powerful technique to characterize molecular level structural information of complicated polymer surfaces and interfaces in situ. Copyright © 2006 Society of Chemical Industry
Thermomechanical properties and shape memory effect of epoxidized natural rubber crosslinked by 3‐amino‐1,2,4‐triazole
Authors: Chang Young‐Wook , Mishra Joy K , Cheong Jong‐Hoon , Kim Dong‐Kook 
Published: December 2006

AbstractA thermally induced shape memory polymer based on epoxidized natural rubber (ENR) was produced by curing the ENR with 3‐amino‐1,2,4‐triazole as a crosslinker in the presence of bisphenol‐A as a catalyst. Dynamic mechanical and tensile analysis was conducted to examine the variation of glass transition temperature, stiffness, and extensibility of the vulcanizates with the amount of curatives. Shape memory properties of the ENR vulcanizates were characterized by shape retention and shape recovery. It was revealed that the glass transition temperature of the ENR vulcanizates could be tuned well above room temperature by increasing the amount of curing agents. Also, ENR vulcanizates with Tg higher than ambient temperature showed good shape memory effects under 100% elongation, and the response temperatures of the recovery were well matched with Tg of the samples. Copyright © 2006 Society of Chemical Industry
Copolymers of N‐methylpyrrole and 3,4‐ethylenedioxythiophene: structural, physical and electronic properties
Authors: Ocampo Cintia , Alemán Carlos , Oliver Ramón , Arnedillo M Luisa , Ruiz Oriol , Estrany Francesc 
Published: December 2006

AbstractThe structural, electric and electronic properties of copolymers derived from mixtures of N‐methylpyrrole and 3,4‐ethylenedioxythiophene (EDOT) with various concentration ratios have been investigated and, additionally, compared with those of the corresponding homopolymers. The electropolymerization kinetics of all the generated copolymers and the homopolymers was examined in terms of current productivity using chronoamperometry. The chemical structure of the linkages between adjacent monomers and the microstructure of the chains were investigated using Fourier transform infrared spectroscopy and quantum mechanical calculations, respectively. The results indicate that the linkages between monomeric units formed during the anodic copolymerization are of the α–α type, while the microstructure of the copolymers depends on the EDOT content. Theoretical calculations were also used to examine the electronic properties of the systems under study, while the conductivity and the electrical stability were studied using the sheet‐resistance method. Interestingly, the electric properties are consistent with the random and block microstructures predicted for the copolymers with low and high EDOT content, respectively. Copyright © 2006 Society of Chemical Industry
The Decomposition of some RDX and HMX Based Materials in the One‐Dimensional Time to Explosion Apparatus. Part 1. Time to Explosion and Apparent Activation Energy
Authors: Williams Michael Robert , Matei Mariana Violetta 
Published: December 2006

AbstractA One‐Dimensional Time to Explosion (ODTX) apparatus has been used to study the times to explosion of a number of compositions based on RDX and HMX over a range of contact temperatures. The times to explosion at any given temperature tend to increase from RDX to HMX and with the proportion of HMX in the composition. Thermal ignition theory has been applied to time to explosion data to calculate kinetic parameters. The apparent activation energy for all of the compositions lay between 127 kJ mol−1 and 146 kJ mol−1. There were big differences in the pre‐exponential factor and this controlled the time to explosion rather than the activation energy for the process.
Preparation of Cu/CNT Composite Particles and Catalytic Performance on Thermal Decomposition of Ammonium Perchlorate
Authors: Ping Cui , Li Fengsheng , Jian Zhou , Wei Jiang 
Published: December 2006

AbstractComposite particles of carbon nanotubes (CNTs) and Cu were prepared by a chemical reduction method. Characterization of Cu/CNT composite particles was performed by TEM, SEM, FT‐IR, XRD, XPS, AAS, DTA and EDS. The results show that the surface of CNTs is covered by Cu particles, and that the diameter of Cu/CNT composite particles gets larger than that of CNTs. Furthermore, in the presence of Cu/CNT composite particles, the peak temperature of the high‐temperature decomposition of ammonium perchlorate (AP) decreased by 126.3 °C, and the peak of the low‐temperature decomposition disappeared. Compared with a sample of simply mixed Cu and CNTs, the peak temperature of the high‐temperature decomposition of AP‐Cu/CNTs composite particles decreased by 11.4 °C. Compared with Cu, the peak temperature of the high‐temperature decomposition of AP‐Cu/CNT composite particles decreased by 20.9 °C. This work shows that the catalytic performance of Cu on the thermal decomposition of AP can be improved by compounding with CNTs.
Effects of Twin‐Screw Extrusion Processing on the Burning Rate of Composite Propellants
Authors: Gallant Frederick M. , Bruck Hugh A. , Prickett Suzanne E. 
Published: December 2006

AbstractA new process for continuous manufacturing of composite propellants has been developed using Twin Screw Extrusion (TSE). The effects of TSE‐processing on the burning rates of an ammonium perchlorate (AP)‐based composite propellant have been characterized over a wide composition range (79 to 87 wt. % AP) and a wide range of screw speeds (45 to 85 RPM) using a quadratic model for an experimental Response Surface Analysis (RSA) based on the Kowalski, Cornell, and Vining (KCV) algorithm. Using Student‘s T‐test, it was determined that burning rates obtained from strand‐burning rate tests at 3.5 MPa, 7.0 MPa, and 10.5 MPa are affected only by the individual ingredients, the interaction between the coarse AP particles and the binder, and the screw speed. Measured burning rates were found to be 40% to 100% higher than Petite Ensemble Model (PEM) predictions, which was accounted for by modifying the PEM through a power law relationship with pressure that includes a rule‐of‐mixtures dependence of the exponent and coefficient on the weight fraction of coarse and fine AP particles. The resulting modified PEM reduced differences between the predictions and experimental data by 79% at 3.5 MPa, 83% at 7.0 MPa, and 78% at 10.5 MPa.
Antibody array profiling reveals serum TSP‐1 as a marker to distinguish benign from malignant prostatic disease
Authors: Shafer Michael W. , Mangold Leslie , Partin Alan W. , Haab Brian B. 
Published: December 2006

AbstractBACKGROUNDBlood protein markers that provide more accurate or earlier diagnosis of prostate cancer should have a positive impact on prostate cancer treatment and management.METHODSSerum samples from control subjects and patients with benign or malignant prostatic disease were analyzed on antibody arrays targeting multiple candidate prostate cancer markers and detected with two‐color, rolling‐circle amplification (TC‐RCA). The measurements of certain antibodies were validated using immunoblots, immunoprecipitation/mass spectrometry, and sandwich immunoassays.RESULTSSeveral potential disease‐associated protein alterations were uncovered. The most significant was thrombospondin‐1, which was strongly elevated in patients with benign prostatic disease and repressed in patients with prostate cancer. Thrombospondin‐1 levels did not correlate with prostate‐specific antigen (PSA) levels and differentiated benign from malignant disease with 79% sensitivity and 81% specificity.CONCLUSIONSThe measurement of thrombospondin‐1 could be used to assist the decision to obtain a biopsy in men with suspected prostate cancer, which could lead to a reduction in the number of unnecessary prostatic biopsies. Prostate 67:255–267, 2007. © 2006 Wiley‐Liss, Inc.
Changes in steroid receptors and proteoglycan expression in the guinea pig prostate stroma during puberty and hormone manipulation
Authors: Sakko Andrew J. , Ricciardelli Carmela , Mayne Keiko , Dours‐Zimmermann Maria T. , Zimmermann Dieter R. , Neufing Petra , Tilley Wayne D. , Marshall Villis R. , Horsfall David J. 
Published: December 2006

AbstractBackgroundProteoglycans are structural and informational molecules important during embryogenesis and organ maturation. Maturation of the prostate is influenced by androgens and estrogens, but changes in the relative spatiotemporal expression of steroid receptors and proteoglycans during hormonal change are unexplored.MethodsGuinea pig prostate was used to define hormone‐induced changes in the expression of androgen (AR) and estrogen (ERα) receptors, chondroitin sulfate (CS) glycosaminoglycan and core proteins of versican and syndecan‐1. Tissue locations of AR, ERα, CS and the proteoglycans versican and syndecan‐1 were determined by immunohistochemistry. Cellular content of ERα and syndecan‐1 was assessed visually. Versican, CS56 epitope, and AR were quantified by image analysis.ResultsAR expression within prostate epithelial and stromal cell nuclei decreased following castration and increased following treatment of castrate animals with dihydrotestosterone (DHT). ERα expression was restricted to prostate stromal cell nuclei and decreased during puberty, and following treatment of castrate animals with DHT. Versican was present in periacinar stroma immediately peripheral to basal epithelial cells, fibromuscular stromal tissue bands surrounding acinar units, and loose fibrovascular connective tissue interspersed between individual acini. Versican and native CS expression decreased (>10‐fold) in periacinar stroma during puberty and following administration of DHT to castrated animals. Expression of syndecan‐1 was restricted to fibromuscular cells of prostate stroma, and remained constant during puberty and hormone manipulation.ConclusionsERα, versican core protein and CS side chain epitopes are negatively regulated in prostate stromal tissue by DHT, whilst AR levels are positively regulated. Prostate 67:288–300, 2007. © 2006 Wiley‐Liss, Inc.
Allelopathy in crop/weed interactions — an update
Authors: Belz Regina G 
Published: December 2006

AbstractSince varietal differences in allelopathy of crops against weeds were discovered in the 1970s, much research has documented the potential that allelopathic crops offer for integrated weed management with substantially reduced herbicide rates. Research groups worldwide have identified several crop species possessing potent allelopathic interference mediated by root exudation of allelochemicals. Rice, wheat, barley and sorghum have attracted most attention. Past research focused on germplasm screening for elite allelopathic cultivars and the identification of the allelochemicals involved. Based on this, traditional breeding efforts were initiated in rice and wheat to breed agronomically acceptable, weed‐suppressive cultivars with improved allelopathic interference. Promising suppressive crosses are under investigation. Molecular approaches have elucidated the genetics of allelopathy by QTL mapping which associated the trait in rice and wheat with several chromosomes and suggested the involvement of several allelochemicals. Potentially important compounds that are constitutively secreted from roots have been identified in all crop species under investigation. Biosynthesis and exudation of these metabolites follow a distinct temporal pattern and can be induced by biotic and abiotic factors. The current state of knowledge suggests that allelopathy involves fluctuating mixtures of allelochemicals and their metabolites as regulated by genotype and developmental stage of the producing plant, environment, cultivation and signalling effects, as well as the chemical or microbial turnover of compounds in the rhizosphere. Functional genomics is being applied to identify genes involved in biosynthesis of several identified allelochemicals, providing the potential to improve allelopathy by molecular breeding. The dynamics of crop allelopathy, inducible processes and plant signalling is gaining growing attention; however, future research should also consider allelochemical release mechanisms, persistence, selectivity and modes of action, as well as consequences of improved crop allelopathy on plant physiology, the environment and management strategies. Creation of weed‐suppressive cultivars with improved allelopathic interference is still a challenge, but traditional breeding or biotechnology should pave the way. Copyright © 2006 Society of Chemical Industry
Equation of state of nanocrystalline BaTiO3 up to 52 GPa at room temperature
Authors: Kumar Ravhi S. , Cornelius Andrew L. , Nicol Malcolm F. 
Published: December 2006

AbstractWe have performed in situ high pressure X‐ray powder diffraction experiments on nanocrystalline BaTiO3 (average particle size 40 nm) up to 52 GPa using synchrotron X‐rays in the angle dispersive geometry with a diamond anvil cell. In order to understand the grain size effect on the tetragonal (P4mm) to cubic (Pm3m) phase transition and the compressibility, experiments were also carried out on bulkBaTiO3 up to 36 GPa. The results show nanoBaTiO3 is less compressible than the bulkBaTiO3 and the phase transition pressure is found to be 1.9 GPa higher for nanoBaTiO3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)