bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization behavior and mechanical properties of polypropylene copolymer by in situ copolymerization with a nucleating agent and/or nano‐calcium carbonate
Authors: Zhu Weiping , Zhang Guangping , Yu Jianyong , Dai Gance 
Published: November 2003

AbstractThe crystallization behavior of polypropylene (PP) copolymer obtained by in situ reactor copolymerization with or without a nucleating agent and/or nano‐CaCO3 particles was investigated both by thermal analysis and by polarized light microscopy. The Avrami model is successfully used to describe the crystallization kinetics of the studied copolymer. The results of the investigation show that a dramatic decrease of the half‐time of crystallization t1/2, as well as a significant increase of the overall crystallization rate, are observed in the presence of the nucleating agent. These effects are further promoted in the presence of the nano‐CaCO3 particles. The incorporation of the nucleating agent and nano‐CaCO3 particles into PP copolymer remarkably improved the mechanical properties and heat distortion temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 431–438, 2004
Synthesis and properties of polystyrene–montmorillonite nanocomposites by suspension polymerization
Authors: Hwu Jyh Ming , Ko Tzu Heng , Yang Wei‐Ta , Lin Jui Chi , Jiang George J. , Xie Wei , Pan Wei Ping 
Published: November 2003

AbstractOrganophilic montmorillonite was prepared using ion‐exchange method between sodium ions in clay layers and stearyltrimethyl ammonium chloride in the various solvents, including deionized water, ethanol, acetone, and toluene. The montmorillonite has the largest d001 spacing, as determined by X‐ray diffraction in toluene, than the other solvents considered. Ethanol can completely wash out the overexchanged stearyltrimethyl ammonium chloride among layers of montmorillonite. However, deionized water is the preferred ion‐exchange solvent. The thermal stability of organophilic montmorillonite was investigated by high‐resolution thermogravimetric analysis (TGA). Polystyrene–montmorillonite nanocomposites were obtained by suspension free radical polymerization of styrene in the dispersed organophilic montmorillonite. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that montmorillonite had been exfoliated. 5.0 wt % of clay in the synthesized nanocomposite was found to be the optimum content that improved both thermal and mechanical properties over those of pure polystyrene under the experimental conditions applied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 101–109, 2004
Synthesis and characterization of new arylamine chitosan derivatives
Authors: Taboada Edelio , Cabrera Gustavo , Cardenas Galo 
Published: November 2003

AbstractThe synthesis of new chitosan derivatives and their complete characterization by elemental analysis, Fourier transform infrared, thermogravimetric analysis, and cross‐polarity/magic‐angle‐spinning 13C NMR is described. A chitosan that was 96.5% deacetylated and had a viscosimetric molecular weight of 131,000 g/mol was prepared. N‐(3,5‐Diethylaminobenzoyl) chitosan with a degree of substitution of 29% and N‐(4‐ethylaminobenzoyl) chitosan with a degree of substitution of 60% were obtained. Such derivatives could be used as metal‐chelating polymers, as flocculants, and in biomedical applications because of the aryl amine moieties in their structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 807–812, 2004
Predictive modeling of microcracking in carbon‐fiber/epoxy composites at cryogenic temperatures
Authors: Timmerman John F. , Seferis James C. 
Published: November 2003

AbstractThe temperature at which microcracking occurred in symmetrical cross‐ply carbon‐fiber/epoxy composite materials was predicted with a yield‐stress‐based failure model. A fracture mechanics analysis of thein situstrength of the ply groups in a composite material was combined with a compound beam determination of thermal stress development to create the predictive model. This approach, unlike many other models, incorporated the change in the material properties with temperature with the room‐temperature properties of the laminate to predict the low‐temperature behavior of the ply groups. Dynamic mechanical analysis was used to assess microcracking at cryogenic temperatures through the observation of discontinuities in the material properties during failure. Four different material systems were studied, and the model accurately predicted the onset temperature for microcracking in three of the four cases. It was shown that the room‐temperature properties of a fiber‐reinforced polymeric composite laminate, appropriately modified to account for property variations at low temperatures, could be used to predict transverse microcracking as a response to thermal stresses at cryogenic temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1104–1110, 2004
Poly(sulfobetaine)s and corresponding cationic polymers. X. Viscous properties of zwitterionic poly(sulfobetaine) derived from styrene–(N,N‐dimethylaminopropyl maleamidic acid) copolymer in aqueous salt solutions
Authors: Lee Wen‐Fu , Chen Yan‐Ming 
Published: November 2003

AbstractA styrene–[N,N‐dimethyl (maleamidic acid) propyl ammonium propane sulfonate] (SDMMAAPS) copolymer was synthesized through an amidoacidation reaction of styrene–maleic anhydride (SMA) alternating copolymer with N,N‐dimethylaminopropylamine (ring‐opening reaction), which was then reacted with propane sultone. The effect of various salt solutions on the intrinsic viscosity of this ampholytic ADMMAAPS copolymer was investigated. The results showed that the effect of counter ions on the intrinsic viscosity of SDMMAAPS was not entirely similar to that of other zwitterionic poly(sulfobetaine)s. The greatest difference from other poly(sulfobetaine)s is the carboxylic group on the polymer chain unit of SDMMAAPS. The Huggins constants for SDMMAAPS in aqueous salt solutions, however, were also quite different from those of other sulfobetaine copolymers, such as styrene–N,N‐dimethyl (maleimido propyl) ammonium propane sulfonate] (SDMMAPS) copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 726–734, 2004
Compatibilization of high‐impact polystyrene/high‐density polyethylene blends by styrene/ethylene–butylene/styrene block copolymer
Authors: Chirawithayaboon Asira , Kiatkamjornwong Suda 
Published: November 2003

AbstractCompatibilization of polymer blends of high‐impact polystyrene (HIPS) and high‐density polyethylene (HDPE) blend by styrene/ethylene–butylene/styrene (SEBS) was elucidated. Polymer blends containing many ratios of HIPS and HDPE with various concentrations of SEBS were prepared. The Izod impact strength and elongation at break of the blends increased with increases in SEBS content. They increased markedly when the HDPE content was higher than 50 wt %. Tensile strength of blends increased when the SEBS concentration was not higher than 5 pphr. Whenever the SEBS loading was higher than 5 pphr, the tensile strength decreased and a greater decrease was found in blends in which the HDPE concentration was more than 50 wt %. The log additivity rule model was applied to these blends, which showed that the blends containing the HIPS‐rich phase gave higher compatibility at the higher shear rates. Surprisingly, the blends containing the HDPE‐rich phase yielded greater compatibility at the lower shear rates. Morphology observations of the blends indicated better compatibility of the blends with increasing SEBS concentration. The relaxation time (T2) values from the pulsed NMR measurements revealed that both polymer blends became more compatible when the SEBS concentration was increased. When integrating all the investigations of compatibility compared with the mechanical properties, it is possible to conclude that SEBS promotes a certain level of compatibilization for several ratios of HIPS/HDPE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 742–755, 2004
Processability and mechanical performance of hybrid composites based on poly(ether sulfone) modified with a glass fiber–reinforced liquid crystalline polymer
Authors: García M. , Eguiazábal J. I. , Nazábal J. 
Published: November 2003

AbstractHybrid composites, based on poly(ether sulfone) (PES) and glass fiber–reinforced copolyester liquid crystalline polymer (gLCP) up to 40% gLCP, were obtained by injection molding: these polymers were immiscible. Despite its higher viscosity, the gLCP acted as a processing aid for PES. The Young's modulus of the composites increased linearly with gLCP content, attributed to the opposing effects of increasing skin thickness and decreasing orientation of the fibrillated LCP in the skin. The break properties decreased with increasing gLCP content, mainly because of the lack of adhesion between the phases. The notched impact strength increased substantially on addition of 10% gLCP, suggesting that the dispersed rigid particles changed the fracture behavior of PES. The composite with 10% gLCP appeared to be the most attractive because it showed an increase in stiffness of 18%, 6.5‐fold impact strength, and a tensile strength similar to that of PES. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 854–860, 2004
Swelling and diffusion studies of poly(N‐isopropylacrylamide/itaconic acid) copolymeric hydrogels in water and aqueous solutions of drugs
Authors: Taşdelen Betül , Kayaman‐Apohan Nilhan , Güven Olgun , Baysal Bahattin M. 
Published: November 2003

AbstractN‐Isopropylacrylamide/itaconic acid hydrogels (NIPAAm/IA) containing different amounts of itaconic acid prepared by irradiating with γ‐radiation were used in experiments on swelling and diffusion of the model drugs methylene blue, lidocaine, and sildenafil citrate (VIAGRA). The NIPAAm/IA hydrogels containing 0–3 mol % itaconic acid irradiated at 48 kGy has been used for swelling and diffusion studies in water and aqueous solutions containing the above‐mentioned model drugs. For these hydrogels, swelling studies indicated that swelling increased with the following order: water > lidocaine > methylene blue > VIAGRA. Diffusions of water and the drugs within hydrogels were found to be non‐Fickian in character. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 911–915, 2004
Free‐radical copolymerization and kinetic treatment of methyl methacrylate with N‐P‐tolylmaleimide
Authors: Yang Liting , Liu Yanhong , Li Yanfang , Gao Jungang , Zhang Liucheng , Jin Riguang 
Published: November 2003

AbstractThe free‐radical copolymerization of methyl methacrylate (MMA) with N‐P‐tolylmalemide (NPTMI) at 77°C in cyclohexanone solution initiated by AIBN was studied. The copolymer composition was calculated from the nitrogen content estimated by the Mico–Kijedldahl's method and by elemental analysis. The reactivity ratios have been calculated by Fineman and Ross method. The monomer reactivity ratios were rNPTMI = 1.24, rMMA = 2.1. The glass transition temperature (Tg) of the copolymers were determined by torsion braid analysis (TBA). The thermal stability was determined by thermogravimetric analysis (TGA). T50, temperature at which the weight loss reaches 50%, was abstained. The results showed that the Mn and Mw increased, whereas the NPTMI feed content increased. The Tg and T50 increased dramatically. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 867–870, 2004
Preparation of a porous conducting polymer film by electrochemical synthesis–solvent extraction method
Authors: Li Liang , Yan Feng , Xue Gi 
Published: November 2003

AbstractPorous conducting polypyrrole (PPy) films have been obtained by electrochemical synthesis–solvent extraction method. The results of scanning electron microscopy (SEM) show that the size and the distribution of pores can be controlled during the electrochemical synthesis. The porous PPy films have sufficiently good mechanical properties, and electrochemical voltammetric studies imply that the porous films also have high electrical conductivity and good electrochemical reversibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 303–307, 2004
Influence of molecular weight of poly(ortho‐ethoxyaniline) on the corrosion inhibition efficiency of mild steel in acidic media
Authors: Daouadji M. Mekki , Chelali N. 
Published: November 2003

AbstractThe present work revealed that the chemical polymerization of ortho‐ethoxyaniline yields two types of polymers not only with different spectroscopic properties but also with different molecular weights: (1) a green form, which corresponds to the high molecular weight fraction of the polymer with a molecular weight of 800,000 g mol−1 based on the polystyrene calibration. It is mainly composed of quinoid and benzoid structures, which is an indication of a half‐oxidized polymer (emeraldine). This form of the polymer is insoluble in water‐miscible solvents like ethanol and methanol and thus cannot be tested in terms of corrosion inhibition efficiency; (2) a red form, which corresponds to the low molecular weight fraction of the polymer with a molecular weight of 44,000 g mol−1. It is composed mostly of quinoid structures and exhibits an oxidation state similar to that of the completely oxidized polymer (pernigraniline). In our case, the polymer fraction, which is soluble in alcohol, was first tested as a corrosion inhibitor for mild steel in acidic media, not only at conventional molecular weight (44,000 g mol−1) but also at different molecular weights. These different molecular weights of the polymer were obtained by adding varying amounts of neutral salt to the synthesis environment. Next, the effect of the molecular weight of the red form of the polymer on the corrosion inhibition efficiency of mild steel in hydrochloric acid solutions was investigated. The obtained results showed that the adsorption of the polymer alcoholic form obeys a Temkin adsorption isotherm with no significant change as function of inhibition efficiencies for a series of molecular weights ranging from13,000 to 124,000 g mol−1. The effect of temperature on the corrosion behavior of mild steel in 1M HCl with addition of 100 ppm of the alcoholic form of poly(ortho‐ethoxyaniline) was studied in the temperature range 25–60°C. The associated activation corrosion energy was determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1275–1284, 2004
Swelling behavior and determination of diffusion characteristics of acrylamide–acrylic acid hydrogels
Authors: Işık Belma 
Published: November 2003

AbstractIn this study, a random copolymer of acylamide and acrylic acid [poly(AAm‐co‐AA)] was prepared by a redox copolymerization method of their aqueous solutions. The effects of initial AAm/AA mole ratio, PEG 4000 content, and N,N′‐methylenebisacrylamide concentration on swelling behavior were investigated in water. Average molecular weights between crosslinks, percentage swelling, swelling equilibrium values, and diffusion/swelling characteristics (i.e., the structure of network constant, the type of diffusion, the initial swelling rate, swelling rate constant) were evaluated for every hydrogel systems. The hydrogels showed mass swelling capabilities in the range 789–1040% (for AAm/AA hydrogels), 769–930% (for AAm/AA hydrogels in the presence of PEG 4000), and 716–1040% (for AAm/AA hydrogels containing different concentrations of the crosslinker). The swelling capabilities of the hydrogels decreased with the increasing AA, PEG 4000, and crosslinker concentrations. The diffusion of water into AAm/AA hydrogels was found to be a non‐Fickian type. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1289–1293, 2004
Effect of water potential on sol–gel transition and intermolecular interaction of gelatin near the transition temperature
Authors: Miyawaki Osato , Norimatsu Yuko , Kumagai Hitoshi , Irimoto Yoshinobu , Kumagai Hitomi , Sakurai Hidetoshi 
Published: November 2003

AbstractThe sol–gel transition of gelatin, measured by thermal analysis and viscosity measurement, was analyzed in terms of the change in hydration state of polymer molecules. A new thermodynamic model was proposed in which the effect of water potential is explicitly taken into account for the evaluation of the free energy change in the sol–gel transition process. Because of the large number of water molecules involved and the small free energy change in the transition process, the contribution of water activity, aW, was proved to be not negligible in the sol–gel transition process in solutions containing such low‐molecular cosolutes as sugars, glycerol, urea, and formamide. The gel‐stabilization effect of sugars and glycerol was linear with aW, which seemed consistent with the contribution of water potential in the proposed model. The different stabilization effect among sugars and glycerol was explained by the difference in solvent ordering, which affects hydrophobic interaction among protein molecules. The gel‐destabilization effect of urea and formamide could be explained only by the direct binding of them to protein molecules through hydrogen bonding. On the contrary, the polymer–polymer interaction, measured by the viscosity analysis, in polyethyleneglycol and dextran solutions was not sensitive to the change in aW, suggesting that no substantial change in hydration state with aW occurred in these polymer solutions. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 482–491, 2003
Topological effects on the electrophoretic mobility of rigid rodlike DNA in polyacrylamide gels
Authors: Heuer Daniel M. , Saha Sourav , Archer Lynden A. 
Published: November 2003

AbstractThe electrophoretic migration of rigid rodlike DNA structures with well defined topologies has been investigated in polyacrylamide (PA) hydrogels prepared by copolymerization of acrylamide and N, N′‐methylenebisacrylamide. Previous studies have reported structural and dynamic characteristics of linear and branched DNA during electrophoresis in PA gels using a variety of experimental parameters. However, a thorough investigation aimed at establishing specific relationships between topological features of rigid rodlike DNA structures and their electrophoretic behavior is still needed. In order to study these topological effects on mobility, an intensive examination of the electrophoretic mobility of small linear and starlike DNA was performed. A series of model DNA structures with well‐defined branched topologies were synthesized with varying molecular parameters, such as number of arms surrounding the branch point and arm length. The electrophoretic mobility of these structures was then contrasted with a series of data obtained using linear DNA of comparable molecular size. When large DNA stars (M ≥ 60 bp) were compared with linear DNA of identical molecular weight, the Ferguson plots were quite different. However, small DNA stars (24–32 bp) and linear analogues had identical Ferguson plots. This indicates that a different motional mode or greater interaction with the gel exists for the larger DNA stars. When the total molecular weight of the DNA stars was held constant and the number of arms varied, the Ferguson plots for all the stars were identical. Additionally, a critical pore size was reached when the ratio of linear DNA mobility to star DNA mobility increased dramatically. Thus, while the incorporation of a single branch point can produce a large reduction in mobility, above a critical molecular size, the incorporation of additional branch points does not appear to provide further reduction in mobility. This finding is consistent with the transport properties of large synthetic star polymers, where a large reduction in their diffusion coefficient is observed when a single branch is added. When additional arms are incorporated, large synthetic stars do not display an appreciable further reduction in diffusion coefficient. The effect of arm length on mobility for rigid rod DNA stars was also studied. For four‐arm DNA stars, the mobility was found to scale as an exponential function of the arm length. Finally, a recently proposed phenomenological model was used to successfully fit the mobility data for linear rigid rod DNA at various concentrations of PA. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 471–481, 2003
Increasing age and APACHE II scores are the main determinants of outcome from pancreatic necrosectomy
Authors: Connor S , Ghaneh P , Raraty M , Rosso E , Hartley M N , Garvey C , Hughes M , McWilliams R , Evans J , Rowlands P , Sutton R , Neoptolemos J P 
Published: November 2003

Abstract

Background
The aim of this study was to identify factors associated with death after surgery in patients with extensive pancreatic necrosis.

Methods
Sixty-four patients who underwent pancreatic necrosectomy between 1996 and 2002 were studied.

Results
The median age was 60·5 (95 per cent confidence interval (c.i.) 57 to 64) years and 40 patients (62·5 per cent) were tertiary referrals. The initial median Acute Physiology And Chronic Health Evaluation (APACHE) II score was 9 (95 per cent c.i. 7·9 to 10·1) and there were 21 deaths (32·8 per cent). Twenty-eight patients (43·8 per cent) underwent minimally invasive retroperitoneal pancreatic necrosectomy (MIRP) and the remainder had open pancreatic necrosectomy (OPN); 44 (72·1 per cent) of 61 patients had infected pancreatic necrosis at the time of the first procedure. Seven patients who underwent MIRP died compared with 14 after OPN (P = 0·240). Patients who died were older than those who survived, with higher APACHE II scores at presentation, and before and after surgery (P = 0·001). Survivors had significantly longer times to surgery than those who died (P = 0·038). All 21 patients who died required intensive care compared with 26 of 43 survivors (P &lt; 0·001). Thirty of 36 patients who had the OPN procedure required intensive care compared with only 17 of 28 patients who had MIRP (P = 0·042). Logistic regression analysis showed that only postoperative APACHE II score was an independent predictor of increased mortality (P = 0·031).

Conclusion
Advanced age and increasing APACHE II score, and a need for postoperative intensive care, were the most important predictors of outcome after pancreatic necrosectomy.
Risk factors predicting the development of complications after foreign body ingestion
Authors: Lai A T Y , Chow T L , Lee D T Y , Kwok S P Y 
Published: November 2003

Abstract

Background
The aim of this study was to determine the predictive risk factors for complications resulting from foreign body ingestion.

Methods
A consecutive series of 1338 patients with suspected foreign body ingestion presenting from 1996 to 2000 were studied retrospectively. The potential risk factors for complications after foreign body ingestion were analysed by multivariate logistic regression and included concurrent medical illness, age, duration and types of symptoms, types of foreign body ingested, positive cervical radiographic findings and the level of foreign body impaction.

Results
Fish bone (62·7 per cent) was the commonest type of foreign body ingested. Most of the objects were impacted at or above the cricopharyngeus, the commonest site being the valleculae (31·4 per cent). Multivariate analysis showed that presentation delayed for more than 2 days (P &lt; 0·001), positive cervical radiographic findings (P &lt; 0·001) and foreign body impacted at the cricopharyngeus (P = 0·009) or upper oesophagus (P = 0·005) were significant independent risk factors associated with the development of complications after foreign body ingestion.

Conclusion
In patients with a foreign body seen on plain cervical radiography, presentation delayed for more than 2 days after ingestion, and foreign body impacted at the level of the cricopharyngeus or oesophagus there is a high degree of correlation with the occurrence of complications. Awareness should be raised when these risk factors are present.