bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oberflächenstrukturierung polymerer Fasern durch UV‐Laserbestrahlung. 14. Neue Modellvorstellungen und Simulation durch zelluläre Automaten
Authors: Kesting Wolfgang , Bahners Thomas , Knittel Dierk , Schollmeyer Eckhard 
Published: April 2003

AbstractBei der Bestrahlung von Polymeren mit gepulstem UV‐Excimer‐Laserlicht werden unter geeigneten Bedingungen regelmäßig orientierte Berg‐ und Talstrukturierungen auf der Polymeroberfläche ausgeprägt. Im Rahmen dieser Arbeit werden in geeigneten Modellvorstellungen mögliche Mechanismen einer UV‐laserinduzierten Strukturbildung vorgestellt und beschrieben. Es wird davon ausgegangen, daß der Lichtenergieeintrag in die Polymeroberfläche in hohen Aufheizraten zur Erwärmung und Aufschmelzung führt. Unter dem Einfluß eingefrorener Eigenspannungen setzen in einer dünnen, aufgeschmolzenen Schicht der Polymeroberfläche lokal begrenzte Schrumpfbzw. Fließvorgänge ein, indem sich einzelne Teilsysteme (Schmelzvolumenelemente, Makromoleküle) in einem geordneten Verhalten umlagern. Dieses irreversible Phänomen einer Selbstorganisation verläuft hierbei unter ständigem Verbrauch von Energie, welche durch den Lichtenergieeintrag und durch die im Material gespeicherte elastische Energie zur Verfügung gestellt wird. Mit einem Computermodell eines zellulären Automaten werden die wesentlichen Merkmale dieser thermomechanisch induzierten Strukturbildung veranschaulicht.
Magnetic bead cellulose
Authors: Lenfeld Jiří 
Published: April 2003

AbstractMangetic bead cellulose was prepared from viscose and ferrite powder by employing the suspension procedure using the thermal sol‐gel transition. The particles thus obtained can be stirred if acted upon by an external rotary magnetic field of a common permanent magnet. Isolation of the particles from reaction suspensions should proceed in a thin layer using a strong magnetic field. Magnetic bead cellulose prepared from supermagnetic powder of the SmCoFe alloy shows a better behaviour in the magnetic field than ferrite materials.
High pressure polymerization of ethylene with a homogeneous metallocene catalyst
Authors: Luft Gerhard , Batarseh Brigitte , Cropp Richard 
Published: April 2003

AbstractSoluble metallocene catalysts can be easily metered into high pressure polymerization reactors. The performance of a homogeneous zirconocene catalyst for the polymerization of ethylene under high pressures was tested at 1500 bar and temperatures between 80 and 260°C in the presence of methyl aluminoxane as cocatalyst. Besides the productivity of the catalyst and the overall rate of polymerization, the most important properties of the prepared polymers were determined. The results were compared with those found earlier with a heterogeneous titanium catalyst supported on magnesium dichloride.
Ionic strength dependence of the stability of polyelectrolyte complexes. Its importance for the isolation of multiply charged polymers
Authors: Trinh Cam Khon , Schnabel Wolfram 
Published: April 2003

AbstractComplexes of polyanions and polycations that precipitate at low ionic strength, [I], from aqueous solutions become soluble when [I] is increased. The critical ionic strength for resolubilization [I]crit has been determined for various combinations of polyanions and polycations. [I]crit depends on the chemical nature of the polyelectrolytes. Provided the difference in [I]crit is sufficiently large, different polyelectrolytes of the same charge state can be separated via selective precipitation with the aid of an appropriate polyelectrolyte of opposite charge state. The method has been exemplified by separating albumin from polyphosphate via precipitation as polyelectrolyte complex with poly(N‐ethyl‐4‐vinylpyridinium bromide). The process was performed at pH 8, where albumin acts as polyanion.
Lichtinduzierte polymerisation, 3. Polymerisation von methylmethacrylat mit 2,3‐dimethyl‐4,6‐diphenylchinolin/bis(2‐ethoxyethyl)ether
Authors: Braun Dietrich , Hettig‐Rupaner Claudia 
Published: April 2003

Abstract2,3‐Dimethyl‐4,6‐diphenylchinolin ist ein initiierendes Chinolinderivat, dessen Lichtabsorption weiter oberhalb 300 nm liegt als die von 2,3‐Dimethyl‐4‐phenylchinolin. Daher werden mit diesem Initiator bei der lichtinduzierten Polymerisation von Methylmethycrylat in Gegenwart des Wasserstoffdonators Bis(2‐ethoxyethy1)ether (Diethylenglycoldiethylether, DEGDEE) bei sonst gleicher Polymerisationskinetik höhere Bruttopolymerisationsgeschwindigkeiten erreicht.
Analysis of epoxy resins by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Pasch Harald , Unvericht Reinhard , Resch Martin 
Published: April 2003

AbstractBisphenol A‐based epoxy resins were analysed by matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS). The samples were separated into their oligomers according to the degree of polymerization and the type of functional groups. Nine different functional species were found to be present in bisphenol A‐epichlorohydrin resins. In the case of resol epoxy resins, in addition to the oligomer distribution, the distribution of the methylol groups was determined. The quantitative treatment of the spectra and the determination of the average functionality and the molar mass of the samples is discussed.
Copolyimides: Thermal and mechanical properties
Authors: Gupta Ashok K. , Choudhary Manjeet S. , Varma Indra K. 
Published: April 2003

AbstractPolyamic acids with different proportions of benzidine (Bz) and 4,4′‐diamino‐diphenylmethane (DADPM) were prepared by polycondensating different molar ratios of Bz and DADPM with pyromellitic dianhydride (PMDA) in dimethyl formamide. Chemical cyclodehydration of copolyamic acids by acetic anhydride/pyridine resulted in corresponding copolyimides. Polymers were characterized by determination of intrinsic viscosity and nitrogen content. Thermal stability was investigated by thermogravimetric analysis. Some of the copolyamic acids were wet spun into fibres and subsequently converted to polyimides. Copolyimide fibres containing benzidine moiety had better mechanical properties than those containing DADPM.
Studies on miscibility of blends of thermoplastic polyurethane and poly(ethylene‐co‐methyl acrylate)
Authors: Santra Robin N. , Chaki Tapan K. , Roy Sanjay , Nando Golok B. 
Published: April 2003

AbstractBlends of polyether‐based thermoplastic polyurethane (TPU) and poly(ethylene‐co‐methyl acrylate) (EMA, 21 wt.‐% MA) were prepared by melt mixing and subsequent compression moulding. Infrared spectroscopy studies and dynamic mechanical analysis reveal that the polymers are miscible in the entire composition range.
Synthesis and characterization of functionalized phenyl acrylate polymer supports
Authors: Narasimhaswamy T. , Murthy N. T. , Sumathi S. C. , Reddy B. S. R. 
Published: April 2003

AbstractVarious substituted phenyl acrylates (4‐nitro (NPA), 4‐benzoyl (BPA), 2‐carbomethoxy (CPA), 2‐formyl (FPA) and 2,4,6‐trichloro (TCPA) phenyl acrylate) were copolymerized with 4 mol‐% DVB in aqueous suspension at 80°C. The resulting copolymers were characterized by means of FT‐IR and high resolution solid state 13C NMR spectroscopy. The particle size distribution and average particle size of the typical systems were determined. Scanning electron microscopy provided information about size, shape and morphological features of the resins. The thermal stabilities of the resins were determined by thermogravimetric analysis.
Graft polymerization of acrylamide onto maize starch using potassium persulfate as initiator
Authors: Khalil M. I. , Mostafa Kh. M. , Hebeish A. 
Published: April 2003

AbstractGraft polymerization of acrylamide (Aam) onto maize starch using potassium persulfate as initiator was investigated under different conditions including concentration of initiator and monomer, polymerization time and temperature and liquor ratio. Based on the results obtained, appropriate conditions for grafting acrylamide onto starch were established. These conditions were also used for grafting other monomers onto maize starch. Results obtained indicate that acrylamide acquires the highest graft ability while acrylic acid acquires the least, while acrylonitrile and methacrylic acid in between. The water solubility of both nitrogen‐ and carboxy‐containing copolymers increases by increasing the monomer content up to a certain value, then it decreases.
The copolymerization of styrene with the cyclic carbonate of glycidyl methacrylate
Authors: Wendler K. , Fedtke M. , Pabst S. 
Published: April 2003

AbstractThe free‐radical copolymerization of styrene with (2‐oxo‐1,3‐dioxolan‐4‐yl)methyl methacrylate (cyclic carbonate of glycidyl methacrylat; GMACC) was carried out in N,N‐dimethylformamide and toluene solution under batch conditions. In toluene, a precipitate was formed during polymerization. The composition of the copolymers was determined by 1H‐NMR, IR spectroscopy and elemental analysis. The monomer reactivity ratios were calculated by different methods from the copolymer composition data. The values obtained for the different techniques were compared and showed a good agreement.
Sulfobetaine polyurethane ionomers. 3. Dielectric and mechanical properties of polyester polyurethane ionomer films and related compounds with Pb2+ and Co2+
Authors: Diaconu I. , Coman P. , Buruianǎ T. , Buruianǎ E. C. 
Published: April 2003

AbstractTensile and dielectric relaxation properties of sulfobetaine polyurethane ionomers based on polyesters were studied comparatively to the non‐ionic polyurethane and derived compounds with Pb2+ and Co2+, using stress‐strain and thermally stimulated depolarization currents (TSDC) methods. Introduction of ionic centers into polyurethane chain improves the tensile properties and modifies the TSDC spectra. These effects are assigned to an enhancement of the microphase segregation. Complexation with Pb2+ and Co2+ diminishes the tensile properties, suggesting that an increase of phase mixing occurs determined by a partial neutralization of ionic centers. Treatment with H2S slightly increases tensile properties and changes TSDC spectra owing to the presence of the semiconducting microphases formed by clustering of the metal sulfides PbS and CoS, respectively.
Preparation of block copolymers with macro‐azonitriles as the initiator
Authors: Yürük H. , Ulupìnar S. 
Published: April 2003

AbstractBlock copolymers containing poly(ethylene oxide) or poly(propylene oxide) prepolymer segments and methyl methacrylate were prepared. A stepwise procedure was first employed to prepare macro‐azocarbamates by capping hydroxy‐terminated poly(ethylene oxide) or poly(propylene oxide) with 3‐isocyanatomethyl‐3,5,5‐trimethylcyclohexyl isocyanate and subsequently reacting this intermediate with 4,4′‐azobis(4‐cyano‐n‐pentanol)Systematic name: 2, 2′‐azobis(5‐hydroxy‐2‐methylpentanenitrile).
. The resulting polymeric azocarbamates were used as free‐radical initiators for the polymerization of methyl methacrylate. Various modes of preparation and the properties of the copolymers are described. Formation of block copolymers is illustrated by several analyses and measurements of elastic modulus versus temperature.
Photo‐oxidative degradation of PPO/PET blends
Authors: Chandra R. , Mishra S. , Kumar P. , Rajabi L. 
Published: April 2003

AbstractPhoto‐oxidative degradation of blends of poly(ethylene terephthalate) (PET) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was studied considering the mutual influence of both components. The photo‐oxidation of these systems was investigated in the temperature range 30–100°C to study the effects of segmental motion of polymer chains. For short time of UV‐illumination at 365 nm the process is diffusion controlled and can be explained with the help of Waite's theory. The segmental interactions of polymer segments in the blends also affect the diffusion coefficients and the activation energy values. Higher values of the activation energy of PET in the blends cause a decrease of chain breaking.
Poly(benzoxazinone‐imide)s and poly(benzoxazinone‐phenylquinoxaline‐imide‐amide)s containing hexafluoroisopropylidene units
Authors: Hamciuc C. , Bruma M. , Mercer F. , Belomoina N. M. , Popescu F. 
Published: April 2003

AbstractFluorine‐containing poly(benzoxazinone‐imide)s and poly(benzoxazinone‐phenyl‐quinoxaline‐imide‐amide)s have been synthesized by solution polycondensation of di‐acid dichlorides containing imide and hexafluoroisopropylidene groups with 4,4′‐di‐aminodiphenylmethane‐3,3′‐dicarboxylic acid or with mixtures of the latter with a di‐amino phenylquinoxaline. These polymers show high thermal stability, the decomposition temperatures being in the range of 450–470°C.Transparent flexible films were cast from the solutions of the corresponding polyamidic acid intermediates that after thermal cyclization showed low dielectric constant which recommends them for future applications in microelectronics.
Ceric‐induced grafting of ethyl‐acrylate onto sodium alginate
Authors: Shah Samir B. , Patel Chandrakant P. , Trivedi Harikrishna C. 
Published: April 2003

AbstractSodium alginate was graft‐copolymerized with ethyl acrylate using ceric ammonium nitrate as an initiator. In order to optimize the conditions for grafting, the concentrations of nitric acid, initiator and monomer together with temperature, time and amount of substrate were varied. The kinetic scheme of free radical graft copolymerization has been proposed and the equations relating the values of rate of polymerization, rate of graft copolymerization and rate of homopolymerization are also suggested. The experimental results agree very well with the proposed kinetic scheme.
Water‐soluble polyamides as potential drug carriers, VII. Synthesis of polymers containing intrachain‐ or extrachain‐type amine ligands by interfacial polymerization
Authors: Chiba Urvashi , Neuse Eberhard W. , Swarts Jannie C. , Lamprecht Gert J. 
Published: April 2003

AbstractAliphatic polyamides comprising poly(ethylene oxide) chain segments of various lengths, designed for use as drug carriers, are synthesized by interfacial polymerization of succinyl chloride with the two Jeffamine types ED‐900 and ED‐2001, formally described by the supplier as O,O'‐bis(2‐aminopropyl)poly(ethylene glycol) 800 and O,O'‐bis(2‐aminopropyl)poly(ethylene glycol) 1900. Copolyamides comprising both short‐chain diamine and Jeffamine segments are similarly prepared, as are polyamides made up of cystine and diamine segments. The polymerizations are performed in a two‐phase methylene chloride‐water system at temperatures near or below 0°C. The product polymers, crudely fractionated by staged aqueous‐phase dialysis at an ultimate molecular‐mass cut‐off of 25000, are collected after freeze‐drying as water‐soluble resins or solids and are characterized microanalytically and by 1H NMR spectroscopy. Inherent viscosities are in the range of 10–20 ml g−1. The drug‐binding potential of a representative target polymer is probed by the covalent anchoring of a ferrocene compound used as a drug model, giving a water‐soluble polymer‐ferrocene conjugate.
Study on poly(2,6‐dimethyl‐1,4‐phenylene oxide)/SBS triblock copolymer blends
Authors: Chiu Hsien‐Tang , Hwung Dao‐Shinn 
Published: April 2003

AbstractThe relationship between the miscibility and the physical properties of polymer blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and polystyrene (PS), high‐impact polystyrene (IPS) and poly(styrene‐block‐butadiene‐block‐styrene) (SBS), which are blended in different compositions by a twin‐screw extruder is discussed. The three types of SBS that were used are SBS1, SBS2 and SBS3 having different styrene/butadiene ratios. Dynamic mechanical analysis and differential scanning calorimetry were used to study the miscibility. The morphology was examined by SEM. The miscibility of the blends decreases with decreasing PS content. The notch sensitivity is improved by blending. Finally, the micelle model was used to explain the testing phenomena.
Die kristallisation von polybutylenterephthalat (PBT) und polycarbonat (PC) im polymerblend PBT/PC
Authors: Radusch H.‐J. , Androsch R. 
Published: April 2003

AbstractDas Kristallisationsverhalten sowohl von PBT als auch von PC ist im definiert verarbeiteten Blend infolge intermolekularer Wechselwirkungen zwischen den unterschiedlichen Molekülen in der Schmelze verändert.Die über die Glasübergangstemperaturen gemessene teilweise Mischbarkeit der amorphen Phasen führt bei PBT zu einer Erniedrigung des Kristallinitätsgrades, wenn die kinetischen Bedingungen des Kristallisationsprozesses keine kristallisationsbedingte Entmischung zulassen. Der auf den PBT‐Anteil normierte Kristallinitätsgrad ist bei kleinen Abkühlgeschwindigkeiten vom PC‐Anteil unabhängüg.In der Mischung PBT/PC 40/60 Gew.‐% kommt es bei hohen Kühlraten zu einer fraktionierten Kristallisation. Die Kristallisationstemperatur bei anisothermer Kristallisation ist bei geringen PC‐Gehalten durch Änderung des Keimbildungsmechanismus erhöht. Bei isothermer Kristallisation steigt mit zunehmendem PC‐Anteil die Kristallisationshalbwertszeit des PBT an.Das normalerweise amorphe PC kann in Gegenwart von PBT in den PC‐reichen Mischungen besonders schnell kristallisieren, wobei der Kristallisations‐ bzw. Ordnungsprozeß des PC in situ mittels der Röntgenbeugung gemessen wurde. Kalorimetrische Untersuchungen bestätigen dieses Ergebnis und erlauben eine quantitative Abschätzung des PC‐Kristallinitätsgrades zu ca. 20% im Blend PBT/PC 5/95 Gew.‐%.
Studies on vinyl ester resin and its urethane derivative as coating materials
Authors: Pachha R. R. , Thakkar J. R. , Patel R. D. , Patel R. G. , Patel V. S. 
Published: April 2003

AbstractThe present paper is concerned with the coating applications of a vinyl ester resin derived from diglycidyl ether of bisphenol‐A and its urethane derivative. The mild steel panels coated with the synthesized resins were evaluated for their gloss on the surface, scratch hardness and chemical resistance. The incorporation of styrene in the resin systems improves the properties of coatings remarkably.
Studies on antioxidants, 1. Phenolic antioxidants as stabilizers for polypropylene
Authors: Raja A. , Pendyala V. N. S. , Xavier S. F. , Shah A. C. , Nair K. B. 
Published: April 2003

AbstractA group of phenolic antioxidants was synthesized, characterized and the performance of these antioxidants in polymer processing was tested in the polymer melt by multiple extrusions. The change in melt flow was observed and compared with the change in melt flow by use of commercially available antioxidants. All the antioxidants examined had the same phenolic stabilization moiety but varied in the size of the substituents in the para‐position of the aromatic ring. Increasing length of the side chain considerably influences the behaviour of the antioxidants in the polymer and thus their effectiveness.
Crystallization behavior of polypropylene filled with calcium carbonate of various shape
Authors: Mitsuishi Kazuta , Ueno Satoru , Kameyama Kenro 
Published: April 2003

AbstractCalcium carbonate of various particle shape (spheric, cubic, needle‐shaped type) and polypropylene (PP) were mixed on a two roll mill and the mixture was pressed into plates. The effect of particle shape on the crystallization behavior of PP/CaCO3 composites, such as crystallization peak temperature (TMAX), crystallized pattern, etc., was investigated with differential scanning calorimetry measurements. The value of TMAX is explained by the total surface area of added CaCO3 particles; TMAX of needle‐shaped series is larger than that of cubic or spheric ones. TMAX of various shaped CaCO3‐filled PP totally depends on the cooling rate and maximum temperature in the non‐isothermal crystallization, respectively.
The utilisation of latex reclaim rubber in natural rubber
Authors: George Reena Susan , Joseph Rani 
Published: April 2003

AbstractScrap latex products contain rubber hydrocarbon of very high quality, that is only slightly crosslinked. A novel economic technique for converting such latex waste into a processible material is developed. This paper reports the effect of adding this latex reclaim to natural rubber. It is shown that latex reclaim can replace raw natural rubber up to about 50 wt.‐% without affecting mechanical properties.
Concentration effects of methylalumoxane, zirconocene dichloride and trimethylaluminum in ethylene polymerization
Authors: Rieger Bernhard , Janiak Christoph 
Published: April 2003

AbstractA quantitative study was carried out on the homogeneous zirconocene dichloride/methylalumoxane/trimethylaluminum (Cp2ZrCl2/MAO/TMA) catalyst system in ethylene polymerization. The effects of variation of the AlMAO/Zr ratio, absolute Zr concentration, and addition of TMA on ethylene polymerization activity and polymer properties were investigated. The polymerization profiles for small AlMAO/Zr ratios and the changes with the Zr concentration are explained with a complexation equilibrium for the active homogeneous complex and with the change to a heterogeneous catalyst upon polymer precipitation. Good polymer productivities can be achieved at AlMAO/Zr < 1000 when working at Zr concentrations between 10−4 and 10−5 mol/l with addition of TMA (AlMAO/AlTMA≈ 1.4).
Cationic polyelectrolytes, XII. PEG‐precursor for water‐soluble cationic polymers with tertiary n‐atoms in the main chain
Authors: Drǎgan Stela , Ghimici Luminiţa 
Published: April 2003

AbstractWater‐soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M̄n of PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N‐dimethyl‐1,3‐diaminopropane and N,N‐diethyl‐1,3‐diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M̄n = 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG chain presence.
Laser‐induced crosslinking of siloxanes: A semi‐empirical molecular orbital study
Authors: Roth Wolfgang , Lorenz Michael , Clark Timothy 
Published: April 2003

AbstractThe semi‐empirical molecular orbital method AM1 has been used as a tool for the prediction of radical intermediates and crosslink structures that may be of importance in the direct laser excitation of siloxanes. Special emphasis was put on configuration interaction (Cl) in order to calculate energies and geometries of excited triplet states as well as potential curves of triplet reactions. Heats of formation of intermediates and reaction enthalpies of monomolecular fragmentation reactions of T1 excited states of 2‐phenyl‐1,1,1,2,3,3,3‐heptamethyltrisiloxane and octamethyltrisiloxane were calculated. In the former case bimolecular reactions were also considered. Dissociation of a methyl group was found to be the most probable monomolecular fragmentation. Consecutive reactions of the silyl radical formed lead to crosslink structures like SiCH2Si and SiC6H4Si. Biphenyl‐ and phenylcyclohexadienyls are the most probable crosslink structures of bimolecular reactions with phenyl exciplexes as intermediates. Experimental evidence is given for these crosslink structures.
Untersuchungen zur reaktion von o‐kresol mit formaldehyd unter verwendung tertiärer amine
Authors: Roatsch Birgit , Reinisch Gerhard , Hinzmann Karin , Samland Birgit , Schirmer Matthias 
Published: April 2003

AbstractThe reaction between o‐cresol and formaldehyde was investigated using various tertiary amines as catalysts. The influence of the reaction parameters basicity, temperature, reaction time and concentration of formaldehyde was discussed. To yield preferentially 2,4‐bis(hydroxymethyl)‐6‐methylphenol the conditions of synthesis were optimized. The formation of bi‐ and polynuclear products cannot be avoided.