bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compression creep of molten polystyrene
Authors: Aleman J. V. 
Published: April 2003

AbstractViscoelastic parameters of polystyrene (PS) melt in compression creep have been measured in an lnstron capillary‐rheometer.Bulk compression creep compliance B(t) shows plateau regions in the molten state (B1) and the glassy state (Bg), both decreasing with increasing stress. Shifting of B(t) curves provides master curves suitable to analysing the total (superposed elastic and viscous deformations) bulk compression behaviour. The steady‐state creep compliance (Bs) allows to describe the recoverable elastic energy (Be) and seems to be related to the extrusion die swell (B/B). Volume viscosity (ηk) decreases with decreasing stress (P), increasing compression rates (k) and decreasing temperature (T).
Variation in molecular weight and molecular weight distribution of aged iPP filaments as revealed by HTGPC
Authors: Sadiku Emmanuel Rotimi , Peacock Norman 
Published: April 2003

AbstractExperiments on the molecular weight variations of physically, room temperature aged isotactic polypropylene (iPP) filaments were done using the High Temperature Gel Permeation Chromatography (HTGPC). Evidence emanating from the studies indicates a very marginal change in molecular weight of the materials during aging.The granules of the materials were chosen as the reference standard. Based on the polydispersity D = Mw/Mn of the granules, filaments of commercial grades GYE 47 and PXC 31399 were characterized between an aging period ranging from 2 weeks to 8 months. The filaments of the GYE 47 grade have their distributions D lowered on the average by about 12%. On the other hand, those of the PXC 31399 grade have a less definite trend in change, but on the average, D is lowered by about 20%. The distributions of this latter grade are highly scattered over the period of aging. The GYE 47 grade shows a reduction in the distribution of a near asymptotic nature. It is believed that the disparity in the trend of change of D between the two samples could be attributed to their relative thermodynamic stability with the PXC 31399 grade being less stable.
Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier
Authors: Patel Rasmika H. , Patel Ranjan G. 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di‐ and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol−1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA‐diluent systems.
Study of multicomponent complexes between polycarboxylic acid, transition metal ions and non‐ionic polymers
Authors: Chatterjee S. K. , Khan A. M. , Ghosh Sudipta , Yadav D. 
Published: April 2003

AbstractMulticompoent complexes of a typical polyelectrolyte like poly(acrylic acid) (PAA) have been prepared by incorporating transition metal ions (e. g. Cu(ll) and Ni(ll)) and non‐ionic polymers (e. g. PVP, PEO) in the polyelectrolyte chain in a definite sequence. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectroscopy. A scheme is suggested to explain the mode of formation of such complexes.
Propriétés électriques et adhésion aux interfaces polypropylène greffé‐aluminium
Authors: Lavielle Lisette , Prévot Jean‐Louis , Schultz Jacques 
Published: April 2003

AbstractL'étude des caractéristiques intensité‐potentiel en courant continu pour des assemblages films de polypropylènes greffés‐aluminium permet de proposer un modèle électrique de I'interface polymère‐métal, associant une barrière de Schottky constante à une charge d'espace modulée selon le niveau d'adhésion. Cette charge d'espace est liée à l'afflux des groupements carboxyliques greffés sur le polypropylène vers la surface de l'aluminium. La présence d'une interphase dans l'adhésion entre polyoléfine et métal est ainsi prise en compte dans les mesures électriques.
Termination reaction in the chain oxidation of caprolactam
Authors: Lánská Božena , Makarov Genadii G. , Šbenda Jan 
Published: April 2003

AbstractThe oxidation of caprolactam initiated with 0.008‐0.82 mol/kg 1,1′‐azo‐di(cyclohexane carbonitrile) was studied in the temperature range 80–98°C. At the conversion lower than 3%, caprolactam hydroperoxide, adipimide, and hydrogen peroxide were determined in the oxidation products. Depending on the initiator concentration, the kinetic chain length of oxidation ranged between 3 and 30. The formation rate of hydrogen peroxide was equal to one half of the rate of initiation reaction, i. e. to one half of the rate of bimolecular termination in the steady state. It may be assumed that hydrogen peroxide is formed by the bimolecular termination reaction. This is in agreement with the fact that hydrogen peroxide was not found in the thermally initiated oxidation of caprolactam which proceeded with the kinetic chain length more than 300. Another product of the bimolecular termination reaction of caprolactam peroxy radicals is adipimide, which is also formed by their monomolecular decomposition.
Water‐soluble polyamides as potential drug carriers, II. Amine‐functionalized poly (α,β‐d,l‐aspartamide) derivatives
Authors: Neuse Eberhard W. , Perlwitz Axel , Schmitt Siegfried 
Published: April 2003

AbstractSeveral derivatives of poly(α,β‐D,L‐aspartic acid) (2) comprising amine functions as side chain components are synthesized for use as macromolecular drug carriers. The structures of the target polymers are designed so as to provide complete solubility in water, a prerequisite for smooth intravenous administration, and the strategy of derivatization reflects the requirement for the performance of all reaction steps in a partially or entirely aqueous phase. The poly(aspartic acid) (2) — a known synthetic polyamide obtained from poly(succinimide) (1) and composed of both α‐ and β‐ peptide units in the chain — is coupled with ethylenediamine, diethylenetriamine, N‐(2‐hydroxyethyl)ethylenediamine, and hydrazine, respectively, in the presence of water‐soluble carbodiimides. This gives the poly(aspartamides) 3 to 6 possessing primary amino side groups. More efficaciously, circumventing the intermediacy of the polyacid 2, polymers 3 to 6 are obtained through nucleophilic opening of the imide rings in 1 by the same amine reactants. The analytically and spectroscopically characterized, water‐soluble target polymers 3 to 6 have inherent viscosities ranging from 5 to 20 ml g−1 and possess the structural prerequisites for side‐chain drug anchoring involving the spacer‐bound amino groups. The susceptibility of these functional groups to substitution as a measure of their drug binding capabilities is demonstrated by conversion of 5 and 6 to the N‐acryloylated derivatives 7 and 8 — with 7 further derivatized to give 9 — and by condensation of 5‐formylsalicylic acid with the bidentate — ethylenediamine side group in 4 to give the conjugate 10 containing the bioactive salicylyl group as a side‐chain component.
Introduction of hydroxyethyl and glycidyl ester groups into methyl methacrylate copolymers by polymer analogous reactions
Authors: Sandner Barbara , Ziegler Hans‐Jörg , Bischof Claus 
Published: April 2003

AbstractThe reactions of 2‐chloroethanol and epichlorohydrin (ECH), respectively, with alkali salts of partially hydrolyzed methyl methacrylate (MMA) polymers as well as with MMA copolymers containing free carboxy groups were studied. Quaternary ammonium halogenides R4NX are effective catalysts of these reactions. Up to 80% of alkali carboxylate groups were converted into hydroxyethyl ester groups to yield completely soluble copolymers. By reaction of ECH with alkali salts of the copolymers, crosslinked products were obtained. The gel fraction may be reduced from 87% to 5% if the reaction is carried out in the presence of R4NX. MMA‐copolymers containing free carboxy groups react with an excess of ECH in the presence of R4NX via the chlorohydrin ester and dehydrochlorination (transepoxidation) to produce completely soluble glycidyl ester copolymers of low chlorine content (≤0.4%). Yields of epoxy groups up to 95% have been attained.
Bifunctional initiators, II. Bulk polymerization of styrene initiated by 4,4′‐azobis(4‐cyanopentanoyl)‐bis (α‐methylolbenzoin methyl ether)
Authors: Önen Aysen , Yağci Yusuf 
Published: April 2003

AbstractAzo‐benzoin initiators are useful for the synthesis of polymers with photoactive end groups. The kinetics of the bulk polymerization of styrene initiated by 4,4′‐azobis(4‐cyanopentanoyl)bis(α‐methylolbenzoin methyl ether) (ABME) was investigated. On the basis of kinetic parameters, it was found that azo‐benzoin initiators exhibit initiator properties similar to that of common azo initiators. A relatively high chain transfer constant of the initiator (C1) may be attributed to the presence of α‐methylolbenzoin methyl ether groups in the structure.
Kinetic studies on bitumen air‐blowing polymerization in presence of sodium sulphide
Authors: Antony T. P. , Francis D. Joseph 
Published: April 2003

AbstractSodium sulphide is found to accelerate the rate of bitumen air‐blowing polymerization. The kinetic analysis of the process showed that it behaves as a first order reaction below 280°C. The rate constants obtained were used to determine the Arrhenius activation parameters.
Syntheses and properties of UV‐autocurable prepolymers. Semicrystalline urethane‐multiacrylates
Authors: Chiang Wen‐Yen , Chan Shao‐Ching 
Published: April 2003

AbstractA series of UV‐autocurable urethane‐multiacrylate prepolymers, which were semicrystalline and showed melting points in the region of 40–50°C, was synthesized. Also, the effects of curing temperature and acrylic functionality on the structure and properties of the cured films were investigated.These prepolymers are solids and opaque at room temperature. In general, UV curing reactions of solid prepolymers are less efficient when compared with those of liquid prepolymers. UV curing reactions at curing temperatures below the melting point (Tm) of the prepolymers produced semicrystalline urethane‐multiacrylate cured films. On the contrary, UV curing reactions above Tm destroyed the crystalline phase of the prepolymers and improved the transparency of the cured films. The films cured below Tm of the prepolymers had higher both breaking strength and Young's modulus, and a higher glass transition temperature (Tg), but a lower elongation at break than those cured above Tm. Such curing temperature effects were attributed to the retention or disappearance of the crystalline structure of the prepolymers during UV curing reaction. At curing temperatures below Tm, an increase in acrylic functionality of the prepolymer resulted in a fast curing rate and a higher crosslinking density of the cured films. Therefore, an increase in acrylic functionality of the prepolymers gave cured films with higher breaking strength and Young's modulus, but a lower elongation at break.
Synthese und charakterisierung von stationären phasen auf der basis von mit epoxidiertem polybutadien (PBDE) modifizierten polykieselsäuren. I. Untersuchungen zur oberflächenmodifizierung von polykieselsäuren mit epoxidierten polybutadienen
Authors: Heublein G. , Erler U. , Ulbricht A. , Winkelmann H. 
Published: April 2003

AbstractDie vollständige Modifizierung der Oberfläche polykieselsäurehaltiger Adsorbentien mit epoxidierten Polybutadienen gelingt bei optimaler Syntheseführung unter Kombination von Eigenschaften des Polymeren (Funktionalität, pH‐Stabilität) und des anorganischen Trägers (Druckstabilität, Textur). Dabei werden bei Verwendung von Polybutadienen mit hohem Anteil 1,4‐verknüpfter Struktureinheiten die besten Ergebnisse erzielt. Mit zunehmender Oberflächenpolymerkonzentration verändern sich die Eigenschaften der erhaltenen Reaktionskomposite wie beispielsweise das Adsorptionsverhalten gegenüber Farbstoffen, die spezifische Oberfläche, das Brutto‐σ‐Akzeptor‐verhalten und die Oberflächenpolarität in charakteristischer Weise. Die Übertragbarkeit einer optimierten Syntheservariante der Reaktionskomposite auf typische Trägermaterialien für verschiedene Einsatzgebiete wie beispielsweise HPLC, Affinitätschromatograpie oder Wirkstoffimmobilisierung wird bewiesen.
Synthese und charakterisierung von stationären phasen auf der basis von mit epoxidiertem polybutadien (PBDE) modifizierten polykieselsäuren. III. Untersuchungen zur synthese aminofunktionalisierter trenn‐und trägermaterialien
Authors: Erler U. , Heublein G. 
Published: April 2003

AbstractDurch heterogene polymeranaloge Reaktionen epoxidierter Polybutadiene mit Oberflächen von polykieselsäurehaltigen Adsorbentien können bei der Umsetzung von Epoxygruppen des Polymeren mit reaktiven Diaminen aminofunktionalisierte Trenn‐ und Trägermaterialien erhalten werden. Der Vergleich der Eigenschaften von Reaktionscompositen, welche unter Variation der Synthesebedingungen nach verschiedenen Verfahren hergestellt wurden, eröffnet die Möglichkeit, im Sinne einer gezielten Reaktionssteuerung sowohl Polymer‐ und Amingehalt als äuch den Anteil primärer und sekundärer Aminogruppen der resultierenden Materialien speziellen Anwendungszwecken anzupassen.
Dynamic vulcanization of PVC‐epoxidized natural rubber miscible blend: The effects of dimaleimide crosslinking
Authors: Varughese K. T. , De P. P. , Sanyal S. K. 
Published: April 2003

AbstractPoly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) miscible blends were vulcanized “dynamically” by N,N′‐m‐phenylene dimaleimide during the melt blending process. ENR component in the blend was partially crosslinked in this process. Miscibility of the blend components was not impaired. On the other hand the microheterogeneity between ENR and PVC was reduced due to the improved interfacial adhesion. Dynamically vulcanized PVC/ENR blends improved the elastic deformation. Thermal stability was greatly improved in blends due to the dimaleimide vulcanization process.
Polymerisation von n‐substituierten maleimiden in epoxidverbindungen, 1
Authors: Lüders Günter , Merker Eberhard , Raubach Heinz 
Published: April 2003

AbstractN‐substituierte Maleimide Polymerisieren in Glycidethern mit einer Reaktion erster Ordnung, ausgelöst durch eine Startreaktion zweiter (pseudo‐erster) Ordnung. Die Aktivierungsenergie der Startreaktion liegt mit fast 70 kJ/mol oberhalb, die der Polymerisation mit 48 kJ/mol weit unterhalb der Werte der rein thermischen Maleimidpolymerisation von etwa 60 kJ/mol. Die Werte werden durch DSC‐Untersuchungen von Bismaleimiden in Diepoxiden bestätigt. Die Startreaktion verläuft ab 100°C mit deutlichef Exothermie unter Epoxidverbrauch, Rotfärbung und Bildung von Radikalen mit g = 2.0034.Die Polymerisation wird durch Säuren und nicht durch Radikalfänger abgebrochen. Es werden Maleimid‐Oligomere mit Pn = 5 – 7 erhalten, die glycidether‐spezifische Gruppen tragen und katalytisch wirken. Eine anionische Initiierung wird diskutiert.
Polymerisation von N‐substituierten maleimiden in epoxidverbindungen, 2
Authors: Lüders Günter , Schulz Günter , Goering Harald , Raubach Heinz 
Published: April 2003

AbstractDie Polymerisation von N‐substituierten Maleimiden in Epoxiden wird durch eine Startreaktion zweiter (pseudo‐erster) Ordnung anionisch initiiert. Die Gesamtreaktion wurde mit Hilfe der Ausschlußchromatographie (SEC) bis zu hohem Umsatz verfolgt. Unter 180°C werden Oligomere des Phenylmaleimids mit einem Polymerisationsgrad bis 10 und enger Molmassenverteilung gebildet. Die Geschwindigkeitskonstante der Polymerisation ist k1(120°C) = 2,18·10‐5 (SEC) bzw. 5,24·10‐5 s‐1 (Dilatometrie). Uber 200°C werden Copolymere mit Alternierungstendenz erhalten. Mit Hilfe der Ergebnisse wird das dynamisch‐mechanische Verhalten von Modellformstoffen aus Bismaleimiden und Bisphenol A‐Epoxidharzen interpretiert.
Neue polymer‐additive, 2. Pigmente und flammhemmer auf basis von modifizierten siliciumdioxiden
Authors: Bräuer Leopold , Gruber Heinrich , Greber Gerd 
Published: April 2003

AbstractStyrol‐modifiziertes Siliciumdioxid (SD) wurde mit aromatische Amino‐Gruppen enthaltenden Vinylmonomeren copolymerisiert. Durch Diazotierung des so erhaltenen Amino‐SD und Kupplung mit Phenolen wurden neue Pigmente auf SD‐Basis hergestellt. Pigmente und Flammhemmer wurden auch durch Kondensation der Amino‐SD mit Carboxyl‐Gruppen enthaltenden Farbstoff‐ bzw. Flammhemmer‐Komponenten erhalten. Durch den Einsatz der gepfropften SD sind Additive mit hohem Wirkstoffgehalt zuganglich. Diese neuen Additiv‐Typen auf SD‐Basis, in denen organische Wirkkomponenten durch stabile kovalente Bindungen mit dem anorganischen Additiv SD verknüpft sind, zeichnen sich durch gute Verträglichkeit, hohe Temperaturbeständigkeit und Migrationsechtheit aus.
Oberflächenstrukturierung polymerer fasern durch uv‐ laserbestrahlung. 10. UV‐laserinduzierte pfropfcopolymerisation von acrylsäure auf polypropylen
Authors: Kesting Wolfgang , Knittel Dierk , Schollmeyer Eckhard 
Published: April 2003

AbstractOberflächen von Polypropylen (PP)‐Folien werden durch UV‐laserinduzierte Pfropfcopolymerisationsreaktionen von Acrylsäure anionisch modifiziert. Die Bestrahlung der hydrophoben PP‐Folien erzeugt hierbei eine Hydrophilie. Die Ausbeute von aufgepfropften Polyacrylsäure‐Seitenketten wird in Abhängigkeit der experimentellen Parameter bestimmt. Im Gegensatz zu Pfropfcopolymerisationsreaktionen mit herkömmlichen UV‐Strahlungsquellen (Hg‐Hochdruckdampflampen) kann schon mit sehr kurzen UV‐Laserbestrahlungszeiten eine chemische Modifizierung der PP‐Oberfläche erzielt werden. Darüber hinaus ist die Verwendung von Photoinitiatoren und Photosensibilisatoren nicht notwendig.
Durability of radiation sterilized polymers, XIV. The effect of nucleating agent on the melt behaviour of irradiated polypropylene
Authors: Aziz Sharifah H. , Kadir Zahrah Abdul , Yoshii F. , Makuuchi K. , Ishigaki I. 
Published: April 2003

AbstractBy the addition of nucleating agent (NA), the molecular weight of gamma‐irradiated polypropylene (PP) decreases more than that of PP without NA. In the first run of differential scanning calorimetric (DSC) measurement, the melting point (T m) of PP with NA was lower than the one without NA because of larger molecular scission which occurred during irradiation. On the contrary, in the second run, Tm of PP with NA, was found to be higher than that of PP without NA. Due to the presence of NA, the molecular chains become shorter during irradiation and therefore rearrangement of the chains is easier during crystallization after the first run, this contributes to an increase in Tm.
Polyurethane‐crosslinked epoxy resins. I. Mechanical behavior
Authors: Han J. L. , Tseng S. M. , Mai J. H. , Hsieh K. H. 
Published: April 2003

AbstractPolyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU‐crosslinked DGEBA.The tensile strength of both the PU(PBA)‐crosslinked DGEBA and PU(PTMO)‐crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content.Izod impact property of these PU‐crosslinked DGEBA indicated that the PU(PBA)‐crosslinked DGEBA had much more significant improvement than the PU(PTMO)‐crosslinked DGEBA. On the contrary, the fracture energy (G1 C value) of the resultant PU‐crosslinked DGEBA showed that the PU(PTMO)‐crosslinked DGEBA had much higher G1 C values than the PU(PBA)‐crosslinked DGEBA.
Oriented polymer networks obtained by photopolymerization of liquid‐crystalline monomers
Authors: Broer D. J. , Gossink R. G. , Hikmet R. A. M. 
Published: April 2003

AbstractIn this paper a new class of oriented polymers is introduced: highly crosslinked polymer networks obtained by photopolymerization of oriented liquid crystalline (LC) monomers. Orientation of these monomers can be induced in the same manner as usual for conventional LCs applied in LCDs: with the aid of an electric or a magnetic field, or using surface orientation. Photopolymerization offers the advantage that a temperature can be chosen right within the LC temperature region.The resulting polymer networks show a high degree of ordering which is somewhat dependent on the polymerization temperature, as demonstrated by the amount of birefringence. This ordering is maintained over a wide temperature region, contrary to that in LC side‐chain polymers. Apart from their optical properties, uniaxially ordered polymer networks show anisotropy also in other physical properties, such as the thermal expansion coefficient and modulus.
Wirkungsweise von stabilisatoren in polymeren unter berücksichtigung der 2‐hydroxyphenylbenzotriazole
Authors: Kramer Horst E. A. 
Published: April 2003

AbstractIn the first part a survey is given on UV screeners, UV absorbers, quenchers of excited states, antioxidants and peroxide decomposers.In the second part UV absorbers, e. g. Tinuvin P (2‐(2'‐hydroxy‐5'‐methylphenyl) benzotriazole, Scheme 8) are described in detail where intramolecular proton transfer occurs in the excited state (TIN(intra) ). This proton transfer may be accompanied and/or followed by very fast and effective temperature dependent radiationless deactivation processes which are promoted by internal vibrations and librations of the molecule. ‐ In polar solvents or in polymers with polar groups some of the molecules convert their intramolecular hydrogen bond into an intermolecular one (TIN (inter) ). TIN (inter) cannot be considered any longer as UV stabilizer. Due to its high triplet quantum yield it may even initiate photodegradation processes of itself and of the polymer. From this follows that the TIN molecule can only act as stabilizer if the intramolecular hydrogen bond is intact. This can be answered from the UV absorption spectrum.
Photoconductive polymers: Structure, mechanisms and properties
Authors: Haarer Dietrich 
Published: April 2003

AbstractCharge carrier transport properties of organic polymers can vary over a wide range. The paper shows that the electron‐ and hole mobilities of polymers with pendant photoconductive groups (i. e. carbazole) are on the order of 10‐6 cm2/Vs. In these materials the flow of electronic charge is maintained by the overlap of the π‐orbitals of the pendant molecular groups. The large variation of this short‐range interaction, depending on the local configurations encountered in polymer glasses, leads to a large variation of hopping probabilities and, hence, to wide rate‐distributions. These distributions are reflected in the slow algebraic decay characteristics of the observed photocurrents. The typical time exponents α (α < 1) are shown to carry a great deal of physical information, if the dynamical range of the experiments is sufficiently large. The paper also refers to quasi‐conjugated polymers (polysilanes) whose dynamic transport parameters are about 103 times better (faster) as compared to polymers with pendant groups. These new materials open interesting aspects for the development of new polymeric materials with better transport parameters and, hence, shorter 'switching times'.