bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Effective and Green Catalytic Approach Toward α,ω‐Dihydroxy‐Telechelic Poly(trimethylenecarbonate)
Authors: Helou Marion , Miserque Olivier , Brusson Jean‐Michel , Carpentier Jean‐François , Guillaume Sophie M. 
Published: September 2009

Abstractα,ω‐Dihydroxy‐telechelic poly(trimethylenecarbonate), HO‐PTMC‐OH, is synthesized from the controlled “immortal” ring‐opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt2 or, more efficiently, [(BDI)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3‐2,6‐iPr2)2) as catalyst precursor, in the presence of a diol HO‐R‐OH (R = (CH2)2 or CH2C6H4CH2; 0.5–10 equiv. vs Zn) acting both as co‐initiator and chain transfer agent. Alternatively, HO‐PTMC‐OH is prepared upon hydrogenolysis of HO‐PTMC‐OCH2Ph, initially prepared from the ROP of TMC using the [(BDI)Zn(N(SiMe3)2)]/PhCH2OH system, under smooth operating conditions using Pd/charcoal. Well‐defined dihydroxy‐functionalized PTMCs of molar mass ranging from $\overline M _{\rm n}$ = 2 000 to 109 500 g · mol−1 were thus quantitatively obtained and fully characterized by NMR, MALDI‐TOF‐MS and SEC analyses. The versatility of this “immortal” ROP allows the preparation of alike α,ω‐functional polyester such as linear HO‐poly(lactide)‐OH, as well as star polymers such as the glycerol‐based PTM‐OH3.magnified image
Molecular Weight and Branching Distribution of a High Performance Metallocene Ethylene 1‐Hexene Copolymer Film‐Grade Resin
Authors: Vadlamudi M. , Subramanian G. , Shanbhag S. , Alamo R. G. , Varma‐Nair M. , Fiscus D. M. , Brown G. M. , Lu C. , Ruff C. J. 
Published: September 2009

AbstractSummary: The bivariate, or cross branching distribution of a gas‐phase produced, film‐grade ethylene 1‐hexene copolymer with enhanced Elmendorf tear in machine direction, MD, and in transverse direction, TD, (> 400 g/mil) and high dart impact has been characterized through the analysis of fractions obtained by molecular weight and 1‐hexene composition. The molecular weight fractions, obtained by a solvent‐non‐solvent fractionation technique, are each mixtures of molecules with at least two different 1‐hexene compositions, one component with a constant relatively high density (∼1 mol% hexene) and a second of a lower density broadly distributed along the molecular weight fractions. The content of the low density component increases with increasing molecular weight of the fraction while the level of 1‐hexene decreases. The mixed compositional character of these fractions is easily inferred by their high crystallization rates and both high melting and crystallization temperatures compared to the values of model random ethylene copolymers. The set of compositional fractions obtained by TREF display an increasing 1‐hexene concentration with increasing molecular weight, and except for the highest molecular weight components (Mw > 150,000 g/mol) their melting and crystallization behavior followed the random pattern. Higher than expected melting temperatures and a constancy of the high melting temperature peak with increasing crystallization temperature, suggests that the intra‐chain 1‐hexene distribution of the highly branched, high molecular weight fraction deviates strongly from the random behavior. These structural features and the bimodal character of the composition distribution of this resin, that contains high molecular weight chains with both low and high 1‐hexene contents, are correlated with the enhanced key film properties.
Advances in Crystallization Elution Fractionation
Authors: Monrabal B. , Romero L. , Mayo N. , Sancho‐Tello J. 
Published: September 2009

AbstractSummary: Crystallization Elution Fractionation has been optimized to improve resolution power and reduce co‐crystallization. Most important step to be optimized is the first separation cycle of Dynamic Crystallization which can be investigated with the help of Crystallization Analysis Fractionation experiments. A new approach to reduce co‐crystallization and improve resolution is presented by applying successive cooling and heating cycles in a long column. The new process known as Multiple Crystallization Elution Fractionation adds extended separation at each cooling and heating cycles.
Solution Crystallization Analysis by Laser Light Scattering (SCALLS)
Authors: van Reenen Albert , Brand Margaretha , Rohwer Erich , Walters Piet 
Published: September 2009

AbstractSummary: Solution crystallization analysis by laser light scattering offers a direct way of studying the solution crystallization of polyolefins. The technique yields similar results to Crystaf, but in a shorter time and with apparently greater sensitivity in some cases. The use of SCALLS is demonstrated for the study of selected propylene/higher α‐olefin copolymers. Some conclusions are also drawn regarding the effect of molecular weight on the solution crystallization of polyolefins.
Fractionation and Crystallization of Isotactic Poly(propylenes) Prepared with a Heterogeneous Transition Metal Catalysts
Authors: Amer Ismael , van Reenen Albert 
Published: September 2009

AbstractSummary: A series of poly(propylenes) (PPs) were prepared by slurry polymerization using a MgCl2‐supported transition metal catalyst. Two different external donors (EDs) were used: diphenyl dimethoxysilane (DPDMS) and methylphenyl dimethoxysilane (MPDMS). The molecular weight (MW) of the PPs was controlled using molecular hydrogen that was used as a transfer agent. To obtain materials with differing molecular weight and similar tacticities, polymers were fractionated with prep‐TREF. DSC analyses of blends of TREF fractions showed that the crystallization behaviour of the polymer blends are strongly affected by the configuration (tacticity) and MW of the PP.
Comparison of Fractionation Methods for the Characterisation of Short Chain Branching as a Function of Molecular Weight in Ethylene 1‐Olefin Copolymers
Authors: Piel Christian , Jannesson Eira , Qvist Åsa 
Published: September 2009

AbstractSummary: Rapid and automated analysis of polyolefins is becoming essential for product development in industry. Quantifying short chain branching in ethylene 1‐olefin copolymers is common practice. Several different methods are available to perform this type of analysis. Preparative fractionation followed by subsequent analysis of the fraction by SEC and NMR, SEC‐FTIR and SEC‐IR were studied towards their applicability in polyolefin research and product development environment. The method of choice is defined by prerequisites such as accuracy, labour and time demands but also in versatility and practicability. The most accurate method is limited in terms of sample throughput and the most practical method is limited towards resolution of very low branching. SEC‐FTIR is capable to measure even heterogeneous low branched samples like bimodal high density polyethylene in rapid and satisfactory matter.
Application of a Multiple Linear Regression Model to Fixed Bands IR Detector Data in GPC‐IR Analysis of Polyolefins
Authors: Ortín A. , Monrabal B. , Montesinos J. , del Hierro P. 
Published: September 2009

AbstractSummary: An infrared detector based on a set of narrow band optical filters was coupled to a high temperature Gel Permeation Chromatograph (GPC) producing continuous chromatograms of absorbance after the molar mass fractionation. A multiple linear regression (MLR) model was established to relate the measured absorbance to the average octene weight percent in industrial ethylene‐octene copolymer samples. This method is compared to univariate and multivariate band ratio models. The application of these models to produce molar mass compositional distributions is also outlined.
NMR Characterization of Ethylene/Propylene Copolymers and Propylene Impact Copolymers from MgCl2/TiCl4/ID+AlR3/ED Catalytic Systems
Authors: Camurati Isabella , Gioia Giuseppe , Piemontesi Fabrizio , Tartarini Stefano , Bonazza Alessandra , Farotti Annamaria , Colonnesi Marcello 
Published: September 2009

AbstractSummary: The aim of this work was to study the comonomer distribution and the chemical composition distribution generated by different Ziegler‐Natta (ZN) systems (different internal donors, ID, dicyclopentadienyl‐dimethoxy silane, D donor, as the external donor) and to define the potentialities of different IDs to produce improved heterophasic copolymers (HECO). A methodology to quantify the amount of ethylene‐propylene copolymer (EP) portion in ZN‐HECO and ethylene content of the EP portion by 13C‐NMR was established. By using this method, it was possible to analyze the composition of ZN‐HECO obtaining results comparable to those obtained with a more complex fractionation technique.
Use of FT‐IR Spectrometry for On‐Line Detection in Temperature Rising Elution Fractionation
Authors: Zhang Zengrong 
Published: September 2009

AbstractSummary: Temperature rising elution fractionation (TREF) has become a popular analytical technique that is able to determine the chemical composition distribution (CCD) of an ethylene/α‐olefin copolymer. An infrared (IR) detector is commonly used in TREF detection to measure the concentration of the polymer solution exiting the column as a function of elution temperature. The chemical composition of the eluting polymer at a given elution temperature can be predicted from the relationship between comonomer content and TREF elution temperature pre‐established through 13C nuclear magnetic resonance (NMR) analysis of TREF fractions. In this article, a Fourier transform infrared (FT‐IR) spectrometer has been coupled with a TREF instrument to provide a more powerful tool for characterizing complex olefin copolymers. The Partial Least Squares (PLS) technique is used when analyzing the FT‐IR spectra of the eluting polymer solutions. The power of on‐line FT‐IR detection in TREF is demonstrated using a few complex copolymer systems, such as ethylene‐octene copolymer, polystyrene grafted ethylene‐vinyl acetate copolymer and ethylene‐methyl acrylate copolymer.
Study of Multi‐Site Nature of Supported Ziegler‐Natta Catalysts in Ethylene‐Hexene‐1 Copolymerization
Authors: Matsko Mikhail A. , Echevskaya Ludmila G. , Zakharov Vladimir A. , Nikolaeva Marina I. , Mikenas Tatyana B. , Vanina Marina P. 
Published: September 2009

AbstractSummary: Heterogeneity of active centers (AC) of titanium‐magnesium catalysts (TMC) and vanadium‐magnesium catalyst (VMC) in ethylene‐hexene‐1 copolymerization has been studied on the base of data of polymer molecular weight distribution (MWD) deconvolution technique and copolymer fractionation onto narrow fractions. It was found that 3 and 4 Flory components (groups of active centers) are required to describe experimental MWD curves of copolymers produced over TMC with different Ti content. In the case of VMC MWD of homopolymer and copolymer are characterized by set of 5 Flory components (5 groups of AC).Different character of inter‐relationship between MW and short chain branching (SCB) was found for ethylene‐hexene‐1 copolymers produced over different catalysts: heterogeneous type in the case of TMC and more uniform for copolymer prepared over VMC. The content of Ti affects on the slope of that profile in copolymers produced over TMC.The results indicated that TMC and VMC are different greatly on the heterogeneity of active centers to the formation of polymers with different molecular weights and to formation of copolymers with different inter‐relationship between MW and short chain branching. TMC produces polymers with more narrow MWD but it contains highly heterogeneous centers regarding comonomer reactivity ratios. VMC produces polymers with broad and bimodal MWD but it contains more homogeneous centers regarding comonomer reactivity ratios.
Simultaneous Deconvolution of Molecular Weight Distribution and Chemical Composition Distribution of Ethylene/1‐Olefin Copolymers Synthesized with Multiple‐Site‐Type Catalytic Systems
Authors: Anantawaraskul Siripon , Bongsontia Warawut , Soares João B.P. 
Published: September 2009

AbstractSummary: Ethylene/1‐olefin copolymers synthesized with multiple‐site‐type catalytic systems typically exhibit broad molecular weight distribution (MWD) and chemical composition distribution (CCD). These microstrucral characteristics can be described by the presence of several active site types, each of which produces chains with distinct chain microstructures. In this work, a new approach to identify the number of active site types and chain microstructures produced on each active site type was developed based on simultaneous deconvolution of the bivariate MWD/CCD information. Chain microstructures produced on each active site type are assumed to follow Stockmayer's bivariate distribution. The proposed approach was validated with simulated data of model ethylene/1‐butene and ethylene/1‐octene copolymers.
Study of Very Low Temperature Crystallization Process in Ethylene/α‐Olefin Copolymers
Authors: Tarasova E. , Poltimäe T. , Krumme A. , Lehtinen A. , Viikna A. 
Published: September 2009

AbstractSummary: The crystallization behavior of Ziegler‐Natta (ZN) and single site (SS) based ethylene/1‐butene and ethylene/1‐hexene copolymers and SS copolymer fractionated by composition and molar mass (MM) has been studied by differential scanning calorimetry. It was observed that in addition to the high temperature crystallization peak (HTCP), and for ZN copolymers in addition also to low temperature crystallization peak (LTCP), a very‐low temperature crystallization peak (VLTCP) is present at temperatures in between 60–75 °C. Peak temperature of VLTCP, TVLTCP, decreases with increasing comonomer content (Ccomon) at fixed MM. If Ccomon is kept approximately constant, TVLTCP increases with increasing MM. It turns out that TVLTCP does not depend on the type of catalyst used. The degree of crystallinity calculated from the VLTCP is independent of the chemical nature of the comonomers present, but slightly changes with Ccomon. It also steeply increases with MM and levels off at MM around 50 kg/mol. It was found that the crystallinity as related to the area of the VLTCP is catalyst type dependent, and is higher for the SS catalyst used compared to the ZN catalyst.
The Application of Silane as a Processing Aid (PA) in High Speed Extrusion
Authors: Amin Al‐Robaidi 
Published: September 2009

AbstractSummary: Silane grafting is one of the most recently used technologies in manufacturing crosslinked products due to its enormous advantages. In highspeed extrusion Polymer Processing Aid materials (PPA) additives are usually a copolymer of vinylidene fluoride and hexafluoropropylene. They are added during extrusion process to improve the process‐ability and to eliminate surface meltfracture that's occurred during processing of various polyolefin's resins.In this paper an attempt was made to investigate the application of VTEOS (Vinyltriethoxysilanes) and VTMOS (Vinyl trimethoxysilane) as a replacement of PPA and to determine its improvement in high speed extrusion of Polyethylene cable. It has been found that silane did contribute to eliminate meltfracture and improvement has been made. Nevertheless interaction phenomenon with carbon black and other additives did influencing significantly the performance of the silane and minimized its efficiency. Rheological measurements confirm this behaviour.Factors such as chemical reaction, physical adsorption and abrasiveness are involved in many of these situations. The presence of other storage stabilizer in the polyethylene contributes in negative way as well for formulation deficiency. Special attention in selecting the ingredient to minimize adverse effect is also very important in assuring optimum effectiveness.
Metal Nanoparticle/Polymer Hybrid Particles: The Catalytic Activity of Metal Nanoparticles Formed on the Surface of Polymer Particles by UV‐Irradiation
Authors: Tamai Toshiyuki , Watanabe Mitsuru , Teramura Tomohiro , Nishioka Noboru , Matsukawa Kimihiro 
Published: September 2009

AbstractSummary: Polymer particles decorated with metal nanoparticles were prepared by UV‐irradiation of polystyrene particles incorporating polymethylphenylsilane (PS/PMPS) and P[S‐co‐NIPAM]/PMPS particles (NIPAM: N‐isopropyl acrylamide) in the presence of metal salts. The metal nanoparticle/polymer hybrid particles were used as a catalyst for the reduction of 4‐nitrophenol with NaBH4. The Pd‐ and Ag‐P(S‐co‐NIPAM)/PMPS hybrid particles had larger metal nanoparticles and the lower catalytic activity than those of Pd‐ and Ag‐PS/PMPS, respectively. The surface functional group of the polymer particles affected the formation of the metal nanoparticles and their catalytic activity.
Simulation of Crystallization Analysis Fractionation (Crystaf) of Linear Olefin Block Copolymers
Authors: Anantawaraskul Siripon , Somnukguande Punnawit , Soares João B. P. 
Published: September 2009

AbstractSummary: Linear olefin block copolymers (OBCs) have microstructures that are unique among polyolefins and exhibit properties that are different from those of other polyolefin elastomers. Characterizing their chain microstructures is a challenging task, as conventional characterization techniques cannot probe directly block length distribution or composition. In this work, we used a Monte Carlo model to predict the microstructure details of OBCs and a modified version of the Crystaf model previously developed in our groups to describe theoretical Crystaf profiles for model OBCs. This model can be used as a tool to interpret Crystaf results of these interesting new polyolefins and to relate them to OBC microstructures. Effects of polymerization parameters on OBC microstructure and Crystaf profiles were also discussed.
Urodynamic assessment of anterior vaginal wall surgery: A randomized comparison between colporraphy and transvaginal mesh
Authors: Ek Marion , Tegerstedt Gunilla , Falconer Christian , Kjaeldgaard Anders , Rezapour Masoumeh , Rudnicki Martin , Altman Daniel 
Published: September 2009

AbstractAimsTo investigate the urodynamic effects of anterior vaginal wall prolapse surgery using either trocar guided transvaginal mesh or colporraphy.MethodsA prospective, randomized multicenter trial enrolling 50 patients: 27 underwent anterior colporrhaphy and 23 anterior trocar guided transvaginal mesh. Urodynamic assessment was performed pre‐ and two months postoperatively.ResultsDe novo stress urinary incontinence was significantly more common after trocar guided transvaginal mesh surgery compared to colporraphy. In comparison to baseline urodynamics, transvaginal mesh surgery resulted in a significant decrease in maximal urethral closing pressures (MUCP) whereas conventional anterior colporraphy had no significant effect on urodynamic parameters.ConclusionTrocar guided transvaginal mesh of anterior vaginal wall prolapse results in a lowering of MUCPs and increases the risk for de novo stress urinary incontinence compared to colporraphy. Neurourol. Urodynam. 29:527–531, 2010. © 2009 Wiley‐Liss, Inc.
Transurethral incision of the bladder neck to treat bladder neck dysfunction and voiding dysfunction in patients with high‐level spinal cord injuries
Authors: Ke Qian‐Sheng , Kuo Hann‐Chorng 
Published: September 2009

AbstractPurposeDetrusor–sphincter dyssynergia (DSD) and bladder neck dysfunction (BND) may cause voiding dysfunction in patients with spinal cord injury (SCI). We report the surgical outcomes in patients with high‐level SCI who underwent transurethral incision of the bladder neck (TUI‐BN).Patients and MethodsTwenty‐two patients with SCI at or above the mid‐thoracic level who presented with voiding dysfunction due to BND with different types of DSD received TUI‐BN. Surgical outcome was determined by comparing preoperative with postoperative urodynamic parameters and clinical presentations. Satisfactory outcome was defined as having improvement of AUA/IPSS quality‐of‐life (QoL) index by ≥2.ResultsAmong the patients, 19 (86.4%) were men and 3 (13.6%) were women. Thirteen patients had cervical and nine had thoracic SCI. Postoperatively, spontaneous voiding by abdominal triggering with an open urethral sphincter was noted in 19 patients (86%) and AD had resolved in 15 patients (88.2%). Detrusor pressure decreased significantly in 9 patients who had a high voiding pressure at baseline, and increased significantly in 13 patients who showed impaired detrusor contractility preoperatively. Eighteen patients (82%) reported satisfactory outcome, increased maximum flow rate (Qmax), decrease in postvoid residual (PVR) postoperatively. In addition, 82% of the patients were catheter free or reported a decrease in the frequency of clean intermittent catheterization after TUI‐BN.ConclusionsTUI‐BN is effective in restoring spontaneous voiding, increasing Qmax, and decreasing PVR in high‐level SCI patients. TUI‐BN also leads to improvement in reducing bladder outlet resistance, reduction in occurrence of AD episodes, and improvement in QoL. Neurourol. Urodynam. 29:748–752, 2010. © 2010 Wiley‐Liss, Inc.
Comparison of ambulatory versus conventional urodynamics in females with urinary incontinence
Authors: Dokmeci Fulya , Seval Murat , Gok Haydar 
Published: September 2009

AbstractAimsWe planned to compare the diagnostic accuracy of conventional urodynamics (UD) and ambulatory UD for the detection of detrusor over activity (DOA) and/or urodynamic stress incontinence (USI) in women presenting with urinary incontinence.MethodsWe prospectively enrolled 44 women with urinary incontinence and performed both urodynamic (UD) studies after they completed the UDI‐6 questionnaire. During ambulatory UD one micturition cycle was recorded. According to responses for individual items on the UDI‐6, patients were divided into three groups to define incontinence type irrespective of scoring.ResultsMean age was 52.2 and mean duration of the symptoms was 4.94 years. The ambulatory UD detected an underlying pathophysiology of urinary incontinence (77.3%) in significantly more women than the conventional UD (6.8%) (P = 0.001). Among women with stress incontinence, 56% had USI on the ambulatory UD and none had abnormalities on the conventional UD (P = 0.002). Seventy‐two percent of women with mixed symptoms had abnormal findings (USI and/or DOA) on the ambulatory UD and 9% had abnormal findings on the conventional UD (P = 0.001).ConclusionsOur findings suggest that ambulatory UD done in a clinical setting during one micturition cycle with unstandardized provocative activities detects an underlying pathophysiology (urge incontinence, stress incontinence, mixed incontinence) more often than conventional UD in supine position Conventional UD has a higher false‐negative rate in diagnosis of DOA and/or USI compared to ambulatory UD. Neurourol. Urodynam. 29:518–521, 2010. © 2009 Wiley‐Liss, Inc.