bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal‐shrinkage investigation of the chemical reaction during the stabilization of polyacrylonitrile fibers
Authors: Hou Yongping , Sun Tongqing , Wang Haojing , Wu Dong 
Published: August 2009

AbstractIt has been proposed that during the stabilization of polyacrylonitrile fibers, the reaction is initiated in the amorphous region and then propagates to the ordered region. However, the evidence is unsatisfactory, and some is quite controversial. It has been confirmed in this study through an examination of the shrinkage behavior and properties of stabilized polyacrylonitrile fibers that the cyclization reaction is initiated at 160°C in the amorphous region and that it propagates to the ordered region at about 200°C. Most of the nitriles can be transferred to a ladder polymer structure when the stabilization temperature is beyond 240°C, and the key temperature during stabilization is 240°C. For a higher degree of cyclization, the stabilization temperature should not be below 240°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Impact resistant polymeric glasses using compressive pre‐stress
Authors: Archer Jared S. , Lesser Alan J. 
Published: August 2009

AbstractThe application of an externally applied pre‐stress on impact properties is studied on polymethyl methacrylate (PMMA) organic glass. Samples are tested under equi‐biaxial compression, simple shear and a combination of biaxial compression and shear. Equi‐biaxial compression is shown to increase the threshold stress level for projectile penetration whereas shear pre‐stress has a large effect on the overall energy absorbed during an impact. There is also an apparent interaction observed between compression and shear to dramatically increase the threshold stress. Pre‐stressed laminates show an increase in damage area because of the unique formation of a secondary cone. Higher levels of compressive equi‐biaxial pre‐stress significantly increase the stress relaxation time because of the corresponding increase in hydrostatic stress. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Covalent immobilization of α‐amylase onto UV‐curable coating
Authors: Yarar Ümran , Kahraman Memet Vezir 
Published: August 2009

AbstractA UV‐curable N‐(4‐sodiumsulfophenyl)‐maleimide monomer was synthesized, and its potential for enzyme binding was investigated. The bromine, which is used to activate the synthesized monomer for covalent attachments, has the advantage of giving reaction with the surface groups of enzyme under very mild conditions (0°C, 30 min). In this procedure, sulfonyl bromide pendant monomer reacted with amino groups of the protein to form sulfonamide bonds. Polymeric support was prepaped by UV‐curing technique. The water adsorption value was found to be less than 1%. The enzyme‐bounding yield was found to be 68.18 ± 4.20 mg/g monomer. The maximum activity was observed at pH 6.5. Immobilization did not change the pH‐dependency of the enzyme activity. It was found that the optimum temperature for the free enzyme was ∼ 30°C, whereas it shifted to nearly 50°C for the immobilized enzyme. Free enzyme lost its activity completely within 15 days. Immobilized enzyme lost only 30% of its activity in 30 days. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Study on morphology and viscoelastic properties of PP/PET/SEBS ternary blend and their fibers
Authors: Mostofi N. , Nazockdast H. , Mohammadigoushki H. 
Published: August 2009

AbstractThe morphology development of polypropylene (PP)/polyethylene terephthalate (PET)/styrene‐ethylene‐butylene‐styrene (SEBS) ternary blends and their fibers were studied by means of scanning electron microscopy (SEM) in conjunction with the melt linear viscoelastic measurements. The morphology of the blends was also predicted by using Harkin's spreading coefficient approach. The samples varying in composition with PP as the major phase and PET and SEBS as the minor phases were considered. Although SEM of the binary blends showed matrix‐dispersed type morphology, the ternary blend samples exhibited a morphological feature in which the dispersed phase formed aggregates consisting of both PET and SEBS particles distributed in the PP matrix. The SEM of the blend samples containing 30 and 40 wt % of total dispersed phase showed an agglomerated structure formed between the aggregates. The SEM of the PP/PET binary fiber blends showed long well‐oriented microfibrils of PET whereas in the ternary blends, the microfibrils were found to have lower aspect ratio with a fraction of the SEBS stuck on the microfibril fracture surfaces. These results were attributed to a core‐shell type morphology in which the PET and SEBS formed the core‐shells distributed in the matrix. The melt viscoelastic behavior of the ternary blends containing less than 30 wt % of the total dispersed phase was found to be similar to the matrix and binary blend samples whereas the samples containing 30 and 40 wt % of dispersed phases exhibited a pronounced viscosity upturn and nonterminal storage modulus in low frequency range. These results were found to be in good agreement with the morphological results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A novel nonviral gene delivery vector: Low‐molecular‐weight polyethylenimine‐graft‐ovalbumin
Authors: Chen Dan , Liu Yang , Lehtinen Anna , Jiang Qiying , Liu Jun , Zhou Jun , Huang Hongliang , Wang Qingqing , Tang Guping , Shi Pei Hua 
Published: August 2009

AbstractA novel vector for gene delivery was synthesized. Here the ovalbumin (OVA) acts as a core and low‐molecular‐weight PEI600 was grafted to its surface. The finally product was characterized (1H‐NMR, UV, and TGA) and its biophysical properties such as DNA condensing, particle size, and zeta potential were determined. The agarose gel assay indicated that OVA‐PEI600 could efficiently condense plasmid DNA. Its particle size was about 150 nm and zeta potential was around +20 mV. The MTT assay showed that the cytotoxicity of OVA‐PEI600 was less than PEI25 kDa. Its transfection efficiency in SKOV‐3 and HepG2 cell lines was higher than that of PEI600 and comparable to PEI25 kDa. In vivo, luciferase activity could be tested in liver, spleen, kidney, lung, and blood serum, respectively, in mice. The core‐shell structure of OVA‐PEI600 provided a novel strategy for nonviral gene delivery. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Properties of isocyanate‐reactive waterborne polyurethane adhesives: Effect of cure reaction with various polyol and chain extender content
Authors: Rahman Mohammad Mizanur , Lee Won‐Ki 
Published: August 2009

AbstractThree series of isocyanate‐reactive waterborne polyurethane adhesives were prepared with various contents of chain extender (4.25/8.25/12.50 mol %) and polyol (20.75/16.75/12.50 mol %). Each series had a fixed amount of excess (residual) NCO group (0.50–2.00 mol %). FTIR and 1H‐NMR spectroscopy identified the formation of urea crosslink structure mainly above 80°C of various cure temperatures (20–120°C) with excess diisocyanate. The molecular weight, tensile strength, Young's modulus, and adhesive strength depend on excess NCO content and cure temperature and also varied with polyol and chain extender content. The optimum cure temperature was 100°C for all the samples. The tensile strength, Young's modulus, and adhesive strength increased with increasing cure temperature above 60°C up to the optimum temperature) (100°C) and then almost leveled off. Among all the samples, the maximum values of tensile strength, Young's modulus, and adhesive strength were found with 63.22 wt % polyol, 0.93 wt % chain extender, and 1.50 mol % excess (residual) NCO content at 100°C optimum cure temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Evaluating fouling‐resistance and fouling‐release performance of smart polyurethane surfaces: An outlook for efficient and environmentally benign marine coatings
Authors: Joshi Ravi G. , Goel Achin , Mannari Vijay M. , Finlay John A. , Callow Maureen E. , Callow James A. 
Published: August 2009

AbstractVarious environmentally friendly approaches have been studied in recent years for effectively controlling biofouling on marine structures. Among these, two distinct and successful approaches are (1) the use of hydrophilic surfaces that control biofouling by resisting the adhesion of fouling organisms and (2) the use of hydrophobic elastomeric surfaces that function by facilitating their easy removal. In this study, we attempted to investigate amphiphilic surfaces for their effectiveness in controlling marine biofouling. Polyurethane surfaces containing tethered hydrophilic, hydrophobic, and amphiphilic moieties were designed and synthesized. The wetting behaviors of these surfaces, as a function of the external environment, were studied by dynamic contact angle (DCA) measurements and their morphologies by atomic force microscopy (AFM). The results from DCA measurements and AFM postulate interesting characteristics of the amphiphilic surfaces. Bioassays with the green fouling alga Ulva showed that the amphiphilic surfaces had fouling‐resistance and fouling‐release potential and provide an insight into the scope of the development of smart marine coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Empirical models for end‐use properties prediction: Application to injection molding of some polyethylene resins
Authors: Costa M. C. B. , Jardini A. L. , Lima N. M. N. , Embiruçu M. , Maciel M. R. Wolf , Filho R. Maciel 
Published: August 2009

AbstractA great challenge related to polymers research has been the development of reliable models enabling prediction of polymer end‐use properties according to the initial operational conditions—either during the polymerization process or the transformation process phases. These models can be utilized to produce final devices with specified properties in a more economic and faster way. The first step for building up such kind of model is the information about the relationship between the intrinsic properties, which is a convenient way to develop the models. The intention is to optimize the operational conditions of transformation systems, resulting in better products with lower costs. Empirical models are suitable workable solutions to represent complex systems in which it is difficult and expensive or too time‐consuming to develop a detailed deterministic model. Bearing this in mind, this article aims to build‐up empirical models relating intrinsic and end‐use properties of polymers, which can be applied in the injection plastic molding. The development was carried out through resins characterizations together with the impact quantification of process operating variables including their interactions. Polyethylene resins produced in a second generation petrochemical industry were used as a case study. The first generation industries include the production of basic products from naphtha, whereas the second generation involves the transformation of basic petrochemicals, such as ethane and propane, into thermoplastic resins, polyethylene, and polypropylene. The developed models were compared to experimental data and good predictions were obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Carbohydrate‐based poly(ester‐urethane)s: A comparative study regarding cyclic alditols extenders and polymerization procedures
Authors: Marín Romina , Muñoz‐Guerra Sebastián 
Published: August 2009

AbstractA set of segmented poly(ester‐urethane)s were prepared from diisocyanates HDI or MDI and using 1,4‐butanediol and D‐glucose‐derived cyclic diols (1,4 : 3,6‐dianhydro‐D‐glucitol (isosorbide) or 2,4;3,5‐di‐O‐methylidene‐D‐glucitol (gludioxol) or mixtures of them) as extenders. Hydroxyl end‐capped polycaprolactone with a molecular weight of 3000 g·mol−1 was used as soft segment. Two polymerization methods, in solution and in bulk, were applied for the synthesis of these poly(ester‐urethane)s. The influence of the preparation procedure and composition in cyclic extender on synthesis results, structure, and properties of the novel poly(ester‐urethane)s was comparatively evaluated and discussed. The effect of replacement of 1,4‐butanediol by isosorbide or gludioxol on hydrodegradability was also assessed; the hydrolysis rate increased noticeably with the presence of glucitol derived units, although degradation of the polymers took place essentially by hydrolysis of the polyester soft segment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Tensile testing of individual ultrathin electrospun poly(L‐lactic acid) fibers
Authors: Jaeger Dominik , Schischka Jan , Bagdahn Jörg , Jaeger Raimund 
Published: August 2009

AbstractThe mechanical properties of ultrathin electrospun poly(L‐lactic acid) (PLLA) fibers were studied by performing tensile tests on individual fibers. The tests were carried out on microelectronic mechanical systems (MEMSs) which were developed for characterizing the mechanical properties of thin polymer fibers. Force–displacement curves were obtained from video recordings of the experiments which were carried out in a scanning electron microscope. Each video was processed with an image processing routine to determine the elongation of the fiber and the elastic deformation of a component of the MEMS which yielded the force acting on the specimen. PLLA fibers with diameters ranging from 150 nm to 2 μm were tested. The elastic modulus and the ultimate tensile strength of the fibers increased significantly for fiber diameters below 1 μm. This indicates a higher degree of orientation of the polymer chains in ultrathin fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A thermal and rheological investigation during the complex cure of a two‐component thermoset polyurethane
Authors: Papadopoulos Eleni , Ginic‐Markovic Milena , Clarke Stephen 
Published: August 2009

AbstractThe complex cure kinetics of the reaction between oligomeric diphenylmethane diisocyanate (PMDI) and glycerol was characterized through thermal and rheological techniques. Isoconversional analysis of Differential scanning calorimetry (DSC) data resulted in the activation energy varying with conversion. Isothermal analysis gave activation energies ranging from 5 kJ/mol to 33.7 kJ/ mol, whereas nonisothermal data gave values for the activation energy ranging from 49.5 to 55 kJ/mol. Incomplete cure was evident in isothermal DSC, becoming diffusion controlled in the final stages of cure. DMA analysis on the cured material gave a glass transition temperature of 104 ± 3°C, which was evidence for vitrification of the curing system. The primary and secondary hydroxyl group reactivity was dependant on the isothermal cure temperature. Rheological studies of viscosity increase and tan δ changes with time revealed a complex cure process, with primary and secondary hydroxyl reactivity also showing dependence on isothermal cure temperatures, reflecting similar results obtained from isothermal DSC studies. The independence of tan δ on frequency was used to determine the point where the polymer formed an infinite network and was no longer able to flow, providing an overall activation energy attained at the gel point of 77.4 ± 4.4 kJ/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Stress–strain curve modeling and length effect of polymer concrete subjected to flexural compressive stress
Authors: Yeon Kyu‐Seok 
Published: August 2009

AbstractStress–strain relation, stress‐block parameters, and length effect of polymer concrete flexural compression members were experimentally investigated. For these purposes, a series of C‐shaped polymer concrete specimens subjected to a flexural compressive load were tested. On the basis of the test results, we proposed an equation to predict stress–strain relation of polymer concrete. In this model, we took account of the slope of descending branch beyond the peak stress point of a single curve. The proposed equation was numerically integrated to compute the rectangular stress‐block parameters. Computed β1 was greater than the values prescribed in ACI 318 Code for cement concrete, and α1 was about 0.85 that is similar to the value regulated in ACI. A series of C‐shaped specimens were also tested to study the length effect. The test results were curve fitted to obtain parameters for the existing length effect equation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A new methodology in the study of PVAc‐based adhesive formulations
Authors: Salvini A. , Saija L. M. , Finocchiaro S. , Gianni G. , Giannelli C. , Tondi G. 
Published: August 2009

AbstractThe role of the main components of a PVAc‐based wood adhesive formulation in the formation and performance of the adhesive joint was investigated. A new analytical methodology was applied to carry out the chemical separation and characterization of the adhesive components present in the bond line. By using extraction techniques on the wet and dry glues it was possible to observe the variation in the solubility of the adhesive components, for different glue formulations. The swollen‐state NMR technique proved to be a very useful tool to characterize the insoluble parts present in the adhesive films. These findings, when put into relation to some specific properties of the adhesive joints, contribute to the understanding of the mechanisms involved in the adhesion process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and characterization of colloidal carbon sphere/rigid polyurethane foam composites
Authors: Zhuang Zhe‐Hui , Yang Zhen‐Guo 
Published: August 2009

AbstractSucrose decomposed under hydrothermal conditions, generating colloidal carbon spheres (CCSs) with a perfectly spherical morphology. X‐ray diffraction indicated that the main component of the CCSs was disordered carbon, and massive hydroxyl groups existed on the surface, as confirmed by Fourier transform infrared spectroscopy. CCSs were first introduced into polyurethane foams (PUFs), and CCS‐reinforced PUF (PUF/CCS) composites were synthesized. The introduction of CCSs did not increase the viscosity of polyol/CCS blends significantly. The good dispersion of CCSs and the compatibility between CCSs and polyurethane were confirmed by transmission electron microscopy measurements. The results of mechanical testing showed that PUF/CCS composites exhibited greatly improved mechanical properties in comparison with neat PUFs, and this could be ascribed to the finer cell structure of the PUF/CCS composites, which was inspected with scanning electron microscopy. Thermogravimetric analysis indicated that the effects of CCSs on the thermal stability of the foams were slight. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Perspectives on social tagging
Authors: Ding Ying , Jacob Elin K. , Zhang Zhixiong , Foo Schubert , Yan Erjia , George Nicolas L. , Guo Lijiang 
Published: August 2009

AbstractSocial tagging is one of the major phenomena transforming the World Wide Web from a static platform into an actively shared information space. This paper addresses various aspects of social tagging, including different views on the nature of social tagging, how to make use of social tags, and how to bridge social tagging with other Web functionalities; it discusses the use of facets to facilitate browsing and searching of tagging data; and it presents an analogy between bibliometrics and tagometrics, arguing that established bibliometric methodologies can be applied to analyze tagging behavior on the Web. Based on the Upper Tag Ontology (UTO), a Web crawler was built to harvest tag data from Delicious, Flickr, and YouTube in September 2007. In total, 1.8 million objects, including bookmarks, photos, and videos, 3.1 million taggers, and 12.1 million tags were collected and analyzed. Some tagging patterns and variations are identified and discussed.
Supramolecular Surface Modification and Solubilization of Single‐Walled Carbon Nanotubes with Cyclodextrin Complexation
Authors: Zu Sheng‐Zhen , Sun Xu‐Xia , Liu Yuanqin , Han Bao‐Hang 
Published: August 2009

AbstractA novel approach to solubilize single‐walled carbon nanotubes (SWCNTs) in the aqueous phase is described by employing supramolecular surface modification. We use cyclodextrin complexes of synthetic molecules that contain a planar pyrene moiety or a bent, shape‐fitted triptycene moiety as a binding group connected through a spacer to an adamantane moiety that is accommodated in the cyclodextrin cavity. The binding groups attach to the sidewalls of SWCNTs through a π–π stacking interaction to yield a supramolecular system that allows the SWCNTs to dissolve in the aqueous phase through the formed hydrophilic cyclodextrin shell. The black aqueous SWCNT solutions obtained are stable over a period of months. They are characterized through absorbance, static, and time‐resolved fluorescence spectroscopy as well as Raman spectroscopy, TEM, and fluorescence‐decay measurements. Furthermore, the shape‐fitted triptycene‐based system shows a pronounced selectivity for SWCNTs with a diameter of 1.0 nm.
Lewis Acid‐Assisted Ene Cyclization of 2‐Azetidinone‐Tethered Enals: Synthesis of Enantiopure Carbacepham Derivatives
Authors: Alcaide Benito , Almendros Pedro , Pardo Carmen , Rodríguez‐Ranera Carolina , Rodríguez‐Vicente Alberto 
Published: August 2009

AbstractDiastereocontrolled Lewis acid‐catalyzed preparation of enantiopure carbacepham derivatives have been developed starting from 2‐azetidinone‐tethered enals. The BF3⋅Et2O‐promoted reaction of alkenylaldehydes 1 and 16 is effective as carbocyclization protocol to afford 4‐substituted 5‐hydroxycarbacephams or 3‐substituted 4,5‐dihydroxycarbacephams, respectively, by a type I carbonyl‐ene reaction, while the BF3⋅Et2O or SnCl4‐mediated type II carbonyl‐ene cyclization of alkenylaldehydes 2 furnishes 3‐methylene 5‐hydroxycarbacephams along with the corresponding 3‐halo 5‐hydroxycarbacepham. The stereochemical outcome of these carbonyl‐ene cyclizations leading to carbacepham derivatives can be explained in terms of six‐membered, cyclic chair‐like transition‐state models. The formation of halocarbacepham derivatives is proposed to proceed by a stepwise mechanism.
Untersuchungen zum vertikalen Tragverhalten von Spundwänden
Authors: Grabe Jürgen , Schallück Christoph , Kinzler Steffen 
Published: August 2009

AbstractSpundwände werden im Wesentlichen auf Biegung infolge einer Belastung durch Erd‐ und Wasserdrücke beansprucht. Sie können aber auch zum Abtrag von Vertikallasten dienen. Das Tragverhalten von Spundwänden ist bei genauer Betrachtung äußerst komplex, da diesem eine räumlich und zeitlich gekoppelte Boden‐Bauwerk‐Interaktion zugrunde liegt. Für die praktische Bemessung muss das Tragverhalten daher stark idealisiert werden. Die Rechtfertigung der dafür notwendigen Modellvorstellungen sowie deren Vereinfachungen und Annnahmen sind, wie häufig in der Geotechnik, hauptsächlich durch Erfahrung begründet.Researching the vertical load bearing behaviour of sheet piles.Sheet pile walls are mainly used to carry loads caused by earth and water pressure via bending. In special cases these walls can be used to transfer vertical loads to the subsoil. The complex load bearing behaviour of sheet pile walls is caused by the sterical and temporal coupled soil structure interaction. For practical design the load bearing behaviour needs to be idealised. The apologies used to explain the model conceptions as well as their simplifications are, as usual in geotechnics, mainly motivated by operating experience.