bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model investigation of the co‐condensation of melamine and phenol components in MPF thermoset moulding materials
Authors: Braun Dietrich , Unvericht Reinhard 
Published: April 2003

AbstractPossible co‐condensation reactions during processing of melamine‐phenol moulding materials (MPF) were investigated by reacting suitable model compounds for both components at elevated temperatures in the melt. The investigation of the reaction products using MALDI mass spectrometry and 13C‐NMR‐spectroscopy gives evidence to the formation of co‐condensation products from the two resins even in the absence of acidic curing agents. During crosslinking of those mixtures, the phenolic resin is thus integrated into the melamine network by covalent bonds, and not as a separate interpenetrating network.
Synthesis, characterization, kinetic study and glass fibre‐reinforced composites of solid diglycidylether of bisphenol‐S
Authors: Parekh Jayesh K. , Patel Ranjan G. 
Published: April 2003

AbstractA solid diglycidylether of bisphenol‐S was prepared. The curing reactions of this resin were studied kinetically by differential scanning calorimetry (DSC) using 4,4′‐diaminodiphenylmethane (DDM), 4,4′‐diaminodiphenyl sulfone (DDS) or dicyanodiamide (DICY) as curing agents. The activation energies of the curing reactions range within 60.3–87.6 kJ mol−1. The thermal stability of the cured products was studied by thermogravimetric analysis (TGA). Using the above compounds, different glass fibre‐reinforced epoxy composites were fabricated. The composites have good thermal stability, good mechanical strength and electrical insulation properties and chemical resistance.
Evaluation of the compatibility of polystyrene/poly‐(vinyl acetate) blends through viscosity measurements. Effect of solvent
Authors: Raval Heta , Devi Surekha 
Published: April 2003

AbstractThe compatibility of polystyrene/poly(vinyl acetate) (PS/PVAC) blends was studied by means of viscosity measurements in three different solvents, i. e. methyl ethyl ketone, toluene and 1,4‐dioxane. The viscosity values of the blends dissolved in these solvents show positive deviations from the ideal values. Hence it is concluded that the PS and PVAC in the solvents under study show some compatibility. The relative deviation from the ideal values varies from solvent to solvent and is interpreted in terms of differences in the strength of polymer‐solvent interaction.
Molecular structure of liquid‐crystalline copolyesters of vanillic acid, 4‐hydroxybenzoic acid and poly(ethylene terephthalate)
Authors: Li Xin‐Gui , Huang Mei‐Rong , Guan Gui‐He , Sun Tong 
Published: April 2003

AbstractThermotropic liquid‐crystalline copolyesters made from vanillic acid (V), 4‐hydroxybenzoic acid (B) and poly(ethylene terephthalate) (E) were examined by 1H‐NMR and GPC investigations. Nine possible diads could be identified and assigned. The sequence distribution of V/B/E copolyesters tends to change from random to block with an increase of B content in the copolyesters. The sequence distribution also varies slightly with catalyst concentration and polycondensation time. GPC results suggest that the V/B/E copolyesters have narrower molecular weight distribution (MWD) than B/E copolyesters. The MWD of the copolyesters narrows gradually with increasing V content from zero to 5 mol‐%. The GPC chromatograms of the most V/B/E copolyesters show double peaks, which is different from the single peak of the GPC chromatograms of the B/E copolyesters.
Effect of pre‐irradiation on radiation stability of co‐polypropylene
Authors: Manaf I. , Yoshii F. , Makuuchi K. 
Published: April 2003

AbstractThe radiation stability of the pre‐irradiated copolymer of polypropylene containing 2.5 wt.‐% ethylene units is compared with a copolymer of polypropylene with a nucleating agent with regard to radiation sterilization of medical devices. It is found that transparency property of the propylene‐ethylene copolymer is improved through pre‐irradiation processes. This finding was compared with the co‐polypropylene with nucleating agent which also gives a better transparency property. In comparison, it is found that pre‐irradiated copolymer exhibits better radiation stability during irradiation and during storage after irradiation. The radiation stability of the pre‐irradiated copolymer is due to its lower crystallinity caused by the formation of branches during the pre‐irradiation process.
α‐olefin oligomers and polymers with metallocene catalysts
Authors: Hungenberg Klaus‐Dieter , Kerth Jürgen , Langhauser Franz , Müller Hans‐Joachim , Müller Patrick 
Published: April 2003

AbstractMetallocenes offer new synthetic routes to olefin oligomers and polymers covering a wide range of molecular weights and melting points. This paper deals with some important features of the preparation of oligomers, wax‐like polymers as well as highmolecular‐weight polymers via metallocene catalysis. Taking the oligomerization of hexene as an example, a simple kinetic scheme is established, which is suitable to describe the course of the reaction and the resulting oligomer distribution with metallocenes as catalysts. For low and high‐molecular‐weight polymers, the metallocene route to polypropylene is compared to existent processes in terms of reaction conditions and product properties. An attempt is made to separate the effect of different chain defects like chain ends, regioirregularities and comonomers on the melting point.
Determination of phenolic antioxidants in polyethylene with dissolution by n‐heptane in an autoclave
Authors: Macko Tibor , Siegl Robert , Lederer Klaus 
Published: April 2003

AbstractA new procedure for quantitative analysis of phenolic antioxidants in polyolefins was tested. Thereby polyethylene samples were dissolved in pure n‐heptane or in n‐heptane/isopropanol mixture (1 000/5, v/v) in an autoclave at 160–170°C under elevated pressure. After precipitation of the polymer by cooling to room temperature, the obtained solution was either directly analysed by means of HPLC equipped with an UV‐detector, or the supernatant solvent used for the extraction was evaporated in vacuum at room temperature and the residue redissolved in acetonitrile. The concentration of antioxidants in the solution was determined by isocratic HPLC. The advantage of this procedure is the short time of about 2 h needed for analysis and the good reproducibility of results (σ = 3–5%).
Modification of wastes of PAN‐fibers for adsorption applications
Authors: Simitzis J. 
Published: April 2003

AbstractWastes of acrylic fibers were chemically modified in order to obtain adsorbents. The fibers were thermally treated with aqueous solutions of H2SO4 or NaOH at various concentrations. The adsorption ability of the modified acrylic fibers and commercial adsorbents for comparison reasons was evaluated on the basis of dye‐adsorption of methylene blue (having electron donor groups) and alizarin yellow (having mainly electron acceptor groups). The chemical structure of the modified acrylic fibers was determined by IR spectroscopy.The experimental results of the dye adsorption were theoretically treated by using a diffusion‐limited adsorption method, which was applied for short reaction times. Adsorption kinetics parameters and the diffusion coefficients were calculated. The electron donor‐acceptor (EDA) interactions between the functional groups of the polymers and those of the dyes influence strongly the adsorption process. The modified acrylic fibers adsorb both dyes better than the commercial adsorbents.
Triglycidyl isocyanurate isomers
Authors: Vargha Viktória , Gács‐Baitz Eszter 
Published: April 2003

AbstractTriglycidyl isocyanurate (TGIC) was separated from the resinous reaction product of cyanuric acid and epichlorohydrin by crystallization from methanol. The crystallization fractions were separately characterized by means of functional group analysis, IR‐spectroscopy, high‐resolution 1H‐NMR and 13C‐NMR spectroscopy, simultaneous thermal analysis and DSC. The structure of the two diastereomer racemates of TGIC (β‐TGIC and α‐TGIC) was studied by using high‐resolution NMR spectroscopy and the 1H‐NMR spectra were calculated for both. It was found that the high‐melting fraction (m. p. 156°C) which precipitated from the methanol‐solution relates to the β‐diastereomeric racemate of TGIC. All other methanol‐soluble or slightly soluble fractions crystallized from the methanol solution (melting range 100–103°C) represent the α‐diastereomer racemate of TGIC, with the β‐diastereomer racemate always being present. Recrystallization from methanol always resulted in the presence of both diastereomers. This may indicate the presence of mixed crystals.
Homopolyesters of modified N‐(hydroxyphenyl) trimellitic acid imides
Authors: Gedan‐Smolka Michaela , Jehnichen Dieter , Fischer Dieter , Häußler Liane , Böhme Frank , Rätzsch Manfred 
Published: April 2003

AbstractPolycondensation reactions of N‐(3‐acetoxyphenyl) trimellitic acid imide and N‐(2‐methyl‐4‐acetoxyphenyl) trimellitic acid imide were carried out in bulk or in the inert reaction medium Marlotherm‐S® under various reaction conditions. All synthesized homopoly(ester imide)s are insoluble in common organic solvents, not meltable and highly crystalline. The thermostability of the synthesized polyesters is very high and comparable with that of the polyester on the basis of N‐(4‐acetoxyphenyl) trimellitic acid imide. But also the modified monomer units do not lower the melting temperature range, in which the polyester could be processed from the melt.The average degree of polycondensation depends mainly on reaction temperature and reaction time. Shifts of \documentclass{article}\pagestyle{empty}\begin{document}$$\nu _{c &#x02010; c_{ar} }$$\end{document} in the FTIR spectra allow to identify various substituted monomer units also in copolyesters.
Modification reactions on thermotropic liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s with bi‐ and trivalent 2‐oxazoline couplers
Authors: Baier Angela , Böhme Frank , Vogel Roland , Martin Heino , Leistner Dirk 
Published: April 2003

AbstractCarboxy‐terminated liquid‐crystalline poly(ethylene terephthalate‐co‐oxybenzoate)s with 60 and 75 mol‐% oxybenzoate units were modified with phenyl‐1,4‐bis(2‐oxazoline) and phenyl‐1,3,5‐tris(2‐oxazoline) in plasticorder and extruder. The modification gave rise to significant increase in molecular weights and also slight crosslinking and branching. The course of the reaction was followed by means of torque‐vs.‐time curves measured during the plasticorder modification. In spite of strong increase in melt viscosities the processability of the modified copolyesters was not worsened. Samples were injection‐moulded and tested. Modifications improved the mechanical properties, distinctly. Especially, samples which were slightly crosslinked with phenyl‐1,3,5‐tris(2‐oxazoline) demonstrated outstanding tensile and impact strengths. Significant differences in fracture behaviour could be evidenced by recording impact bending tests.
Copolymerisation von 1,3‐butadien mit isobutylvinylether im vergleich dreier ziegler‐natta‐katalysatorsysteme
Authors: Kaulbach Ralph , Gebauer Ulrich , Lechner Manfred D. , Gehrke Klaus 
Published: April 2003

AbstractIsobutylvinylether (IBVE) läßt sich mit den Ziegler‐Natta‐Katalysatorsystemen Nd(oct)3/Al2Et3Cl3/Al(i‐but)3, Ni(oct)2/BF3OEt2/Al(Et)3 und Al(i‐but)3/Iod/TiCl4, die für eine cis‐1,4‐Polybutadienherstellung (BD) geeignet sind, polymerisieren. Die Umsätze bei der Copolymerisation mit dem Neodymsystem sind nur gering, mit den verwendeten Nickel‐ und Titankatalysatoren dagegen über 50%. Die Copolymerisationsparameter beider Monomerer sind für alle drei Katalysatorsysteme > 1, wobei jeweils rIBVE > rBD ist. Bei geringen Isobutylvinyletheranteilen werden hohe cis‐1,4‐Gehalte der Butadiensequenzen im Copolymeren erhalten. Alle Molmassenverteilungen der Homo‐ und Copolymeren sind unimodal.
Der einfluß von faseroberflächen auf die matrixhärtung bei faserverbundwerkstoffen
Authors: Peter Karin , Gerhard‐Abozari Eva , Höcker Hartwig 
Published: April 2003

AbstractDer Einfluß der Extraktion von Verstärkungsfasern auf ihre Oberflächenbeschaffenheit und ihr Benetzungsverhalten mit einer Epoxidharzmatrix sowie der Härtungsverlauf im Verbund wurden untersucht. Eine Zunahme der Polarität der Faseroberfläche infolge Extraktion führt zu einer verbesserten Benetzbarkeit durch die Epoxidharzmatrix, und die Härtung der Matrix verläuft schneller mit höheren Umsätzen und Vernetzungsgraden. Im Gegensatz dazu verschlechtert sich die Benetzbarkeit und verringern sich Härtungsgeschwindigkeit, Umsatz und Vernetzungsgrad, wenn durch die Extraktion die Polarität der Faseroberfläche sinkt.
Continuous fractionation of poly(acrylic acid)
Authors: Haberer Markus , Wolf B. A. 
Published: April 2003

Abstract45 g of poly(acrylic acid) (PAA 500) with a trimodal molar mass distribution (M̄w = 500 kg/mol, (M̄w/M̄n) −1 = 2.33) were fractionated by means of CPF (continuous polymer fractionation) in two steps using 1,4‐dioxane as solvent. The counter‐current extraction was performed in a glass column (length: 190 cm, diameter: 1.5 cm) filled with a network of wires, introducing the feed 75 cm from its upper end. The distribution of the highest molar mass fraction (M̄w = 760 kg/mol) is unimodal and comparatively narrow ((M̄w/M̄n) −1 = 0.66). Indications exits that fractionation is not only taking place with respect to molar mass but also with respect to tacticity.
Synthesis and hydrolytic stability of model poly(ester urethane ureas)
Authors: Fambri Luca , Penati Amabile , Kolarik Jan 
Published: April 2003

AbstractHydrolysis of poly(ester urethane ureas) (PURUs) is a complex phenomenon which impedes the analysis of the relationships between their composition and hydrolytic stability. Hydrolytic stability of PURUs decreases due to rising (i) polyol acidity, (ii) content of ester groups, (iii) flexibility and (iv) hydrophilicity of the backbones; molar mass of polyols does not seem to have any appreciable effect on it. Negative influence of ether groups (which have better hydrolytic stability than ester groups) is probably linked to the increase in the backbone flexibility and, consequently, to easier access of water molecules to ester groups. Positive effect of aromatic rings in polyols can be ascribed to enhanced rigidity of the backbones as well as to increased hydrolytic stability of adjacent ester groups due to the resonance effect. It can be presumed that the mentioned effects will superpose and simultaneously predestine the resulting hydrolytic resistance. Considering the observed tendencies, it is possible to qualitatively predict the trends how the hydrolytic stability will respond to changes in PURUs composition.
Curing of unsaturated polyester resins with low exotherm peak
Authors: Penczek Piotr , Rudnik Ewa , Arczewska Bogumiła , Ostrysz Ryszard 
Published: April 2003

AbstractThe curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α‐methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.
Obtention de composites fibres de verre‐polyesters par voie photochimique
Authors: Medenouvo F. , Fouassier J. P. 
Published: April 2003

AbstractL'élaboration des fibres de verre renforcées par des matériaux composites à base de polyester/styrène par l'utilisation d'un procédé photochimique est présentée ainsi que le choix d'un système photoamorceur efficace capable d'initier la réaction de polymérisation. Les propriétés mécaniques des laminates ainsi traités sont similaires à ceux obtenus par l'utilisation d'un processus conventionnel. L'efficacité du mélange de photosensibilisateurs, photoamorceurs et additifs est discutée.
Photooxidation of poly(vinyl chloride) at 254 nm in the absence and presence of phthalate plasticizers
Authors: Denizligil S. , Schnabel W. 
Published: April 2003

AbstractIrradiation of neat PVC at λinc = 254 nm under air induces the formation of conjugated double bonds, (CHCH)n (quantum yield ϕ ≈︁ 1.6 · 10−4 for n = 3). Simultaneously, CCl bonds are split (ϕ ≈︁ 8 · 10−2). With the aid of FTIR spectroscopy the following oxidation products were detected: OH, CHCHC(O), CHClCH2C(O)OH, CHClCH2C(O)H, CHClC(O)CHCl, CHClC(O)Cl. Irradiation of PVC plasticized with about 42 wt.‐% phthalate results in similar chemical changes. However, to some extent the chemical alterations are due to an indirect radiation effect. PVC, isolated from plasticizer after irradiation, was found to contain phthalate fragments attached to the polymer. Moreover, in plasticized PVC the formation of carbonyl groups is enhanced as was evidenced regarding the generation of CHCIC(O)CHCl groups. On the other hand, cleavage of CCl bonds and intermolecular crosslinking is retarded by phthalates. The exposure gel doses for unplasticized and plasticized PVC are 3 · 10−5 and 2 · 10−4 Einstein cm−2, respectively.
Elastomeric properties of ethylene/propylene copolymers prepared by zirconocene/methylaluminoxane catalysts
Authors: Banzi Viviano , Angiolini Luigi , Caretti Daniele , Carlini Carlo 
Published: April 2003

AbstractEthylene/propylene copolymers (EPM) have been prepared by a liquid propylene suspension process, using homogeneous catalysts based on nonbridged zirconocenes and methylaluminoxane (MAO). When bis(η5‐cyclopentadienyl)zirconium dichloride (Cp2ZrCl2), bis(η5‐cyclopentadienyl) dimethyl zirconium (Cp2ZrMe2) and bis(η5‐cyclopentadienyl), dibenzyl zirconium (Cp2ZrBz2) were used as catalyst components, EPM having low average molecular weight (MW) were in general obtained in low yield. On the contrary, a very large improvement of productivity and MW was observed when bis(η5‐indenyl)zirconium dichloride (Ind2ZrCl2) and bis(η5‐indenyl) dimethyl zirconium (Ind2ZrMe2) as well as bis(η5‐tetrahydroindenyl)zirconium dichloride [(IndH4)2ZrCI2] were employed in combination with MAO. In particular, this last catalytic system allowed one to obtain EPM with a narrower distribution of MW in addition to the above characteristics. Better performances, in terms of rheological and elastomeric properties, were also found for the crude and vulcanized samples prepared by (IndH4)2ZrCl2/MAO catalyst.
Inner surface and void system of regenerated cellulose fibers
Authors: Schurz Josef , Lenz Jürgen , Wrentschur Erich 
Published: April 2003

AbstractBoth the inner surface and the void system of different cellulose regenerate fibers are investigated with X‐ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10−4–10−3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
Reaction calorimetric investigation of the ring‐opening polymerization of ε‐caprolactone
Authors: Rafler Gerald , Bonatz Eckhard 
Published: April 2003

AbstractThe ring‐opening polymerization of ε‐caprolactone was investigated by means of the Mettler RC1 reaction calorimeter. In the range of small and medium monomer conversions this method can successfully be used for the determination of the course of the bulk polymerizations. The experimental results obtained by calorimetric and gravimetric method, respectively, are compared and the course of the polymerization is discussed in dependence on the reaction parameters (initiator, temperature).
Comparative studies of chemical kinetics of an epoxy‐amine system
Authors: Eloundou Jean Pascal , Feve Michel , Harran Daniel , Pascault Jean Pierre 
Published: April 2003

AbstractChemical reaction kinetics of an aliphatic diepoxy‐diamine system (DGEBD/4D) has been studied between 50°C and 95°C by two different calorimetric techniques; DSC in isothermal conditions on the one hand, conservation in thermostated tubes with successive extractions of samples studied by DSC in the dynamic temperature mode on the other hand.Experiments show that the kinetics determined by isothermal DSC are systematically faster than those obtained with the other technique, this advance starting during the initial phase of the reaction. We show that this gap comes from the mass difference between the samples used in the two techniques, and can be explained by two different reasons. On the one hand, there appears a delay in the attainment of the thermal equilibrium at the beginning of the kinetics in the thermostated tubes, the samples having a greater mass. On the other hand, experiments have shown that there is a catalytic effect caused by the contact of reactive system with air (probably due to the action of atmospheric water). The area/volume ratio of samples being greater for samples studied by isothermal DSC, the catalytic effect is favoured to a greater extent in the case of this technique, which induces a faster rate of reaction at the beginning of the kinetics.So, as the kinetic curves x = f(t) have different forms, they are described by different kinetic models. The Spacek‐model adequately describes the kinetic curves determined by isothermal DSC, with exponent values p = 1.20 and q = 0.45. The curves obtained by the technique of conservation in thermostated tubes are well described by the second order autocatalytic model, the ratio of the reactivities of primary and secondary amines having the value n = 1.1.Furthermore the Tg variation curve with the extent of reaction in the thermostated tubes agrees very well with the equation proposed by Pascault and Williams.
Kinetic study on depolymerization by glycolysis of poly(ethylene terephthalate) with bisphenol A
Authors: Wang Ding‐Chang , Chen Liu‐Wang , Chiu Wen‐Yen 
Published: April 2003

AbstractGlycolysis of poly(ethylene terephthalate) with bisphenol A at high temperature (190°C–230°C) was carried out in an autoclave reactor. Kinetic study on depolymerization of glycolysis was conducted. The reaction temperature and the ratio of bisphenol A to poly(ethylene terephthalate) played the key roles on the reaction rate and the extent of glycolysis. For describing the kinetic behavior properly, a mechanism consisting of six principle equilibrium reactions was proposed. Based on this mechanism, the kinetic parameters were obtained through the Runge‐Kutta numerical integration. Excellent agreements between the calculated values and the experimental data were achieved, thus verified the appropriateness of the proposed mechanism.
Surface modification of a polypropylene film by microwave plasma and the adhesion of a vacuum‐deposited aluminium layer
Authors: Garby L. , Chabert B. , Sage D. , Soulier J. P. 
Published: April 2003

AbstractIn order to improve the adhesion properties of polypropylene on a thin aluminium layer deposited under vacuum, a superficial modification of the polymer has been carried out by exposing the polymer surface to a microwave plasma from gas of different nature and composition.The concentration of the present species in the sample proximity (downstream) has been measured by emission spectroscopy.Superficial polymer modifications have been analysed by ESCA and by measuring contact angles with polar and apolar liquids. The adhesion measurements have been performed by pull‐off tests.The wettability increase has been attributed to the creation of a very thin superficial layer which is partially soluble in methanol and includes carboxylic and ethylenic functions being observed by ESCA.Wettability and adhesion depend on the composition of the gas mixture used. They increase with the atomic oxygen quantities which are created in the discharge and carried away in post‐discharge by the gas flow. A relationship has been established between the tensile stress values obtained by the pull‐off test and the polar interaction values measured during dewetting.