bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of mixer rotor speed on interfacial crosslinking of epoxidized natural rubber and poly(acrylic acid)
Authors: Mallick A. , De S. K. , Pfeiffer D. G.
Published: April 2003

It is evident from Monsanto rheometric studies, dynamic mechanical analysis (DMA), physical property measurements and scanning electron microscopy (SEM) that the mixer rotor speed has an effect on the crosslinking of poly(acrylic acid) (PAA)/epoxidized natural rubber (ENR) blends. These studies reveal that mixing at high rotor speed deteriorates the crosslinking process between PAA and ENR. Infrared (IR) spectroscopic studies suggest that during mixing at high rotor speed ENR elastomer chains suffer breakdown through mechanochemical reactions.
Microemulsion polymerization of butyl acrylate. 1. Effect of initiator type and concentration
Authors: Potisk Pavol , Capek Ignác
Published: April 2003

The oil‐in‐water‐type (o/w) microemulsion polymerizations of butyl acrylate initiated by a water‐ (ammonium peroxodisulfate, AP)—and oil‐soluble (dibenzoyl peroxide, DBP, and 2,2′‐azoisobutyronitrile, AIBN) radical initiators were investigated. Polymerizations with AP were faster than those with DBP or AIBN. The rate of polymerization shows initiation and termination intervals, but no constant interval. The rate of polymerization is found to be proportional to the 0.46th, 0.53rd and 0.24th power of the AP, AIBN and DBP concentration. The rate per particle is found to be proportional to the 0.29th, 0.32nd and 0.37th power of the AP, AIBN and DBP concentration. The number of radicals per particle was found to increase with increasing the initiator concentration. The most pronounced increase in the number of particles with increasing the initiator concentration was observed with AP, much less with AIBN and the slight decrease with DBP. The molecular weights of polymers were found to vary only slightly with increasing the initiator concentration. The formation of radicals proceeds in the aqueous phase (AP and a water‐soluble fraction of AIBN or DBP) and the monomer‐swollen micelles (AIBN or DBP) as well. The polymer particles grow by recruiting monomer and emulsifier from the free monomer‐swollen emulsifier micelles.
A biomaterial‐based carbon fiber
Authors: Zhang Mingqiu , Zhu Shiping , Zeng Hanmin , Lu Yun
Published: April 2003

An attempt to convert natural sisal fiber into low cost carbon fibrous materials was made. The pretreatment, pyrolysis and carbonization processes of raw sisal fiber as well as structure and properties of the resultant product were investigated. It was found that the sisal‐based carbon fiber with moderate mechanical performance can be manufactured under the conditions applied. In addition, the application of the obtained sisal‐based carbon fiber serving as functional material is presented.
Zerstörungsfreie Prüfung von Polymeren mittels photothermischer Meßmethoden. 3. Einfluß von mikroskopischen und makroskopischen Oberflächenrauheiten auf das photoakustische Signal,
Authors: Schloßer Uwe , Bahners Thomas , Schollmeyer Eckhard
Published: April 2003

Für die textile Analytik stellt sich die photoakustische Spektroskopie durch ihre Eigenschaften als vorteilhaftes Verfahren zur Farbstoff‐ und Farbstoffkonzentrationsbestimmung dar. Eingeschränkt wird dieses Verfahren besonders durch die Oberflächengestalt der Proben. In dieser Arbeit wird der Einfluß von mikroskopischen und makroskopischen Oberflächenstrukturen auf das photoakustische Signal untersucht. Der Beitrag einzelner unterschiedlicher Probenschichten zum photoakustischen Signal wird über die Modulationsfrequenz der einfallenden Strahlung reguliert. Dabei wird festgestellt, daß nur die mikroskopische Rauheit einen signifikanten qualitativen Einfluß auf das photoakustische Signal zeigt. Die makroskopische Oberflächenstruktur bestimmt die Intensität des Signals durch eine „effektive Oberfläche”︁, zeigt aber keinen Einfluß auf die Frequenzabhängigkeit des photoakustischen Signals.
Alkane als initiatoren zur radikalischen polymerization
Authors: Braun Dietrich
Published: April 2003

Alkanes with highly substituted carbon‐carbon bonds can be cleaved in free radicals by homolytic dissociation under the influence of thermal energy. The energy of dissociation is mainly determined by the type and size of the respective substituents. For tetraarylbutane dinitriles the temperatures of decomposition are in the range of other technically used initiators. But nevertheless, these compounds are up to now rather seldom used to initiate free radical polymerizations. This is connected with the special mechanism of initiation: the formed highly substituted alkyl radicals are relatively stable and show only a rather low reactivity against the usually used monomers. Therefore, in the beginning of the polymerization the radical concentration is rather high which leads not only to addition to monomers but also to a pronounced primary radical termination. In some cases this termination process is reversible which results in an unusual polymerization kinetics. Depending on the type of monomer and the degree of reversibility of the primary radical termination, either a period of “dead‐end” polymerization follows or the cleavage of the oligomers at the chain end results in a re‐initiation process with a “normal” polymerization with increased rate. The reaction mechanism, kinetics and some possible applications of such initiating alkanes are reported.
Copolymers with periodic comonomer sequences
Authors: Eisenbach Claus D. , Lieberth Wolfgang , Sperlich Bernd
Published: April 2003

The free radical copolymerization and multipolymerization of olefins with acrylic monomers in the presence of acids has been studied. It was found that Brönsted acids are as suitable complexing agents for the acrylic comonomer as the up to now exclusively used Lewis acids. The effectiveness of the Brönsted acids, e.g. carboxylic acids, for obtaining alternating copolymers increased with the pKs value, and trifluoroacetic acid turned out to be the acid of choice. The variation of the Lewis acid‐type complexation agents was extended by the zinc chloride diethylether complex which is advantageous over ZnCl2 or other Lewis acids because of its good solubility and recycling practicability, which is also a feature of the Brönsted acids. The versatility of the new complexing agent systems was demonstrated in a series of co‐ and multipolymerizations, and ethyl cyanoacrylate was employed for the first time as electron acceptor comonomer. The properties of the copolymers with periodic comonomer sequences varied systematically with their composition, e.g. the glass transition temperature and the degree of crystallinity.
Propylene polymerization with metallocene catalysts in industrial processes
Authors: Langhauser F. , Kerth J. , Kersting M. , Kölle P. , Lilge D. , Müller P.
Published: April 2003

Product demands for polypropylene polymers cover a wide range of properties. Metallocene catalysts open up the way to influence the molecular properties of polypropylene by altering the ligand system of the metallocene complexes. This leads to new products with application properties which are not available with conventional catalysts. Concepts are presented to adapt metallocenes to modern, industrial polymerization processes. Some examples illustrate the particular advantages of this new generation of catalysts.
Funktionalisierte Kammpolymere: Synthesen, modifizierung und anwendungen
Authors: Ritter Helmut
Published: April 2003

The present paper deals with the synthesis and modification of functionalized polymers characterized by a special molecular architecture. The reactivity of a functionalized polymer with comb‐like structure can be controlled in a significant manner by the crystalline order of the side chains. In contrast, photocrosslinking of comblike polymers containing cinnamic components in the side chains influences the crystallization process. The air drying process of a modified polybutadiene system with comb‐like structure was shown to depend sensitively on the side chain order. Enzymatic synthesis of new monomers and polymers is briefly reviewed. The complexing capability of cyclodextrines were used to synthesize polyrotaxanes. Finally, the synthesis of a chiral polymerizable dendrimer containing eight estergroups in the monomer unit is presented.
Hochmolekulare lösliche polymere mit coronandenstruktur‐synthese und eigenschaften
Authors: Klemm Elisabeth , Kottner Nils , Alhakimi Gamil
Published: April 2003

New polymers with an alternating sequence of aliphatic chains and coronands were synthesized via Diels‐Alder addition polymerization of bis(2‐pyrones) with bismaleimides. The chemical structures of these polymers 6 are supported by NMR spectra, model reactions and crystal X‐ray structure analysis. The tetrafunctional maleimide 5 was synthesized and the cyclization of 5 to the bicycle 9 with 2 mol monopyrone 8 was carried out.
Polyoxazoline auf fettchemischer Basis
Authors: Beck M. , Birnbrich P. , Eicken U. , Fischer H. , Fristad W. E. , Hase B. , Krause H.‐J.
Published: April 2003

A new, economic technique was developed for the production of 2‐alkyl‐2‐oxazolines with saturated, unsaturated or OH‐functionalized alkylrests. In the process the fatty acids are changed into polymerizable monomers.

The cationic polymerization of fattyalkyl‐2‐oxazolines was investigated in unpolar solvents and in bulk. It reacts in a living mechanism. The polymerization is remarkable inert against impurities like water or ethanolamide. A reaction enthalpy of ΔH = 85,9 kJ/mol was found for the bulk polymerization of 2‐pentadecyl‐2‐oxazoline.
Optimization of mechanical strength of reinforced composites. 1. Study on the effect of reactive bismaleimide on the mechanical performance of CaCo3‐filled polypropylene
Authors: Khunova V. , Sain M. M.
Published: April 2003

The effect of 3‐phenylene bismaleimide on the mechanical performance of an inorganic filler‐based polypropylene composite was studied. The selection of processing temperature played a significant role in the preparation of such composites. A positive effect of the bismaleimide compound was obtained for a processing temperature above the decomposition temperature of bismaleimide. The chemical composition of the modified composite was correlated to its mechanical strength by experimentation involving a rotatable design. An interaction between polymer and CaCO3 has been proposed based on ESCA analysis.
Study on blending of millable polyurethane derived from castor oil with natural rubber
Authors: Suresh K. I. , Thachil E. T.
Published: April 2003

A millable polyurethane prepared from castor oil was blended with natural rubber in a two‐roll mill and sulfur‐cured. It was observed that blending of more than 50/50 (by weight) of the polyurethane with natural rubber was not feasible. Blends were found to have improved tensile modulus and abrasion resistance compared to pure natural rubber. Curing studies on the blends revealed that blending with urethanes enhanced the reversion resistance of natural rubber. The gel contents, measured by Soxhlet extraction using tetrahydrofuran, were above 90%.
Faser‐matrix‐haftung in kunststoffverbunden aus thermoplastischer matrix und flachs. 1. Die ausrüstung mit silanen
Authors: Mieck K.‐P. , Nechwatal A. , Knobelsdorf C.
Published: April 2003

Flachsfasern können auf Grund ihres Eigenschaftsprofils als Verstärkungsmaterial in Verbundwerkstoffen genutzt werden. Als wichtiger Anwendungsfall bietet sich die Substitution von Glasfasern in Compounds aus Glasfasern und dem Standardkunststoff Polypropylen an. Problematisch für diesen Einsatz sind die hohe Wasseraufnahme der Naturfaser und deren geringe Haftung zum hydrophoben Polymeren.

Es wurde daher versucht, die Adhäsion zur Polypropylenmatrix durch Applikation von bifunktionellen Silanen zu erhöhen. Während alkylgruppenfunktionalisierte Silane nur eine unbedeutende Verbesserung der Faser‐Matrix‐Haftung bewirken, konnte jedoch eine deutliche Steigerung mit solchen Silanen erzielt werden, deren funktionelle Gruppe unter Verarbeitungsbedingungen des Verbundwerkstoffes radikalisch reagiert. Für vinyl‐ und methacrylgruppenfunktionalisierte Silane wurde die Abhängigkeit zwischen dem Hydrolysekatalysator, der die Radikal‐Reaktion initiierenden Verbindung, der Silanauflage und dem Adhäsionsniveau untersucht und unter optimalen Konzentrationsverhältnissen die Silanauflage variiert.
Oberflächenchemisches verhalten von modifizierten CaCo3‐füllstoffen
Authors: Lühr Jens , Janowski Frank
Published: April 2003

Die Adsorption von Stearinsäre an CaCO3‐Füllstoffen ist vom Multilayer‐Typ, wobei die Monoschichtmenge proportional der Füllstoffoberfläche ist und fest gebunden wird. Aufgrund der Kopf‐Schwanz‐Anordnung des Modifikators nimmt die Hydrophilie bei Modifikatorkonzentrationen oberhalb der für die Bildung einer Monoschicht benötigten zu.

Die Adsorption von Isopropyltriisostearoyltitanat an CaCO3‐Füllstoffen ist vom Monolayertyp, dabei ist eine Proportionalität mit der Füllstoffoberfläche festzustellen. Mit steigender Modifikatorkonzentration nimmt die Hydrophobie zu.
Polymers with acyloxime ester groups in the main chain. 2. Photochemical synthesis of block copolymers
Authors: İmamoǧlu Tülin , Önen Ayşen , Yaǧci Yusuf
Published: April 2003

Block copolymers of styrene and methyl methacrylate (MMA) were prepared in a two‐stage free‐radical polymerization by means of an azo‐acyloxime ester (AOE) initiator. In the first stage, photosensitive styrene prepolymers were synthesized by using AOE initiator. These polymers were photolysed in the presence of MMA in the second stage to form block copolymers. The block copolymer structure was elucidated by means of extraction by appropriate solvents, GPC analysis and IR and NMR spectral measurements.
Synthese und charakterisierung von flüssigkristallinen hauptkettenpolyestern zur verwendung in mischungen mit thermoplasten
Authors: Braun Dietrich , Lienert Matthias , Wilhelm Volker
Published: April 2003

Bei flüssigkristallinen Hauptkettenpolyestern aus Hydrochinon‐ und Terephthalsäurederivaten lassen sich die Schmelztemperaturen durch “Anheften” von flexiblen Seitenketten und raumfüllenden Gruppen stark absenken. Poly(2′‐phenyl‐1′,4′‐phenylen‐2,5‐dihexyloxyterephthalat) liegt im festen Zustand sogar amorph vor; die Glasübergangstemperatur beträgt 47°C, der Phasenübergang zur isotropen Schmelze erfolgt bei 184°C. Neben tiefen Phasenübergangstemperaturen zeichnet sich dieser Polyester durch eine gute Löslichkeit in Toluol und THF aus. Bis zu 40 mol‐% der 2,5‐Dihexyloxyterephthalsäre lassen sich durch unsubstituierte Terephthalsäure ersetzen, ohne die Phasenübergangstemperaturen und die Löslichkeit des Polyesters wesentlich zu beeinflussen. Der Copolyester mit 40 mol‐% Terephthalsäure zeigt im Zugversuch nach DIN 53455 einen E‐Modul von 7700 MPa.
Optimization of mechanical strength of reinforced composites. 2. Reactive bismaleimide‐modified polypropylene composites filled with talc and zeolite
Authors: Khunova V. , Sain M. M.
Published: April 2003

The effect of 3‐phenylene bismaleimide as a modifier for talc and zeolite‐filled polypropylene composites has been studied. The usefulness of the experimental design to assure best product properties has also been illustrated. Polypropylene shows a variable degree of filling capacity depending on the type of filler. A high‐strength composite can be prepared with suitably modified zeolite‐filled polypropylene even if filler is the dominant phase in the composite matrix. An improved interfacial interaction between polypropylene and filler is proposed to be the reason for this improvement of strength.
Effect of ageing on the dielectric behaviour of silicone‐EPDM blends
Authors: Kole S. , Khastgir D. , Tripathy D. K. , Bhowmick A. K.
Published: April 2003

Dielectric measurements in the frequency (1–105 Hz) and temperature (25–200°C) domains have been carried out for silicone, EPDM, and their 50/50 (by weight) blend before and after ageing in water, steam and air. Low values of permittivity and loss tangent for EPDM reflect its non‐polar and loss‐free nature. Thermal depolarisation is also observed with EPDM and the air‐aged specimen shows little rising trend due to dipole orientation. Silicone is found to be polarised in two steps. Changes in dielectric properties and DC resistivity on hydrothermal weathering and air ageing confirms that charge carriers contribute in the low‐temperature step and polar silanol groups contribute in the high‐temperature region. The properties of the 50:50 blend are very much sensitive to the medium of ageing. Hydrothermal ageing improves the quality of the dielectric of silicone due to removal of charge carriers and the suppression of silicone hydrolysis by EPDM. Ageing of the blend in air increases the polarisation to a very high level owing to the charge carriers, the additional interface and the dipoles formed during ageing. Activation energies suggest that the low temperature polarisation step is associated with charge carrier mobility and orientation of pendent groups.
Faser‐Matrix‐Haftung in Kunststoffverbunden aus thermoplastischer Matrix und Flachs, 2. Die anwendung von funktionalisiertem polypropylen
Authors: Mieck K.‐P. , Nechwatal A. , Knobelsdorf C.
Published: April 2003

Die Haftung von Flachsfasern in einer Polypropylenmatrix in Flachs/PP‐Verbunden konnte durch Anwendung von mit Maleinsäureanhydrid (MAH) gepfropften Polypropylenen als Haftvermittler verbessert werden. Dabei wurde der Haftvermittler zunächst vor der Verbundherstellung auf die Flachsfasern aufgebracht. Die damit erreichbaren Steigerungen der Scher‐ und Zugfestigkeit der Verbunde um ca. 100% bzw. ca. 25% hängen von der Pfropfrate und der mittleren Molmasse der Pfropfcopolymeren ab. Ähnliche Ergebnisse lassen sich erzielen, wenn mit MAH modifiziertes PP als Matrixmaterial ohne Vorbehandlung der Flachsfasern verwendet wird.
Oligomerization of 1‐decene with Ziegler‐Natta catalysts
Authors: Tembe G. L. , Bandyopadhyay A. R. , Pillai S. M. , Satish S. , Ravindranathan M.
Published: April 2003

The catalytic oligomerization of 1‐decene has been carried out employing several transition metal complexes of Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V) in combination with alkyl aluminum halides as cocatalysts. The chromium(III)‐Et3Al2Cl3 system exhibits good oligomerizing activity yielding dimers (C20), trimers (C30) and tetramers (C40) of 1‐decene. The kinematic viscosities and pour points of hydrogenated oligomers have been determined and compared with those of commercial samples. The probable mechanism of oligomerization of 1‐decene on this catalyst is described.
Temperature effect on impact fracture toughness and fracture mechanism of phenolphthalein poly(ether ketone)
Authors: Han Yanchun , Li Binyao , Yang Yuming , Feng Zhiliu , Wang Xuhui
Published: April 2003

Phenolphthalein poly(ether ketone) (PEK‐C) was tested using an instrumented impact tester to determine the temperature effect on the fracture toughness Kc and critical strain energy release rate Gc. Two different mechanisms, namely the relaxation processes and thermal blunting of the crack tip were used to explain the temperature effect on the fracture toughness. Examination of the fracture surfaces revealed the presence of crack growth bands. It is suggested that these bands are the consequence of variations in crack growth along crazes that are formed in the crack tip stress field. As the crack propagates, the stress is relaxed locally, decreasing the growth rate allowing a new bundle of crazes to nucleate along which the crack advances.
Rheologische Eigenschaften von mit Holzmehl gefülltem Polypropylen
Authors: Natov Miltscho , Wassilewa Stefanka , Kowatschewa‐Welewa Stanislawa
Published: April 2003

Die rheologischen Eigenschaften von mit unterschiedlichen Mengen Holzmehl gefülltem Polypropylen, von mit 1,4‐cis‐Polyisopren

Systematischer Name: Poly(1‐methyl‐cis‐1‐butenylen).

elastifiziertem Polypropylen und von ternären Blends aus Polypropylen, Polyisopren und Holzmehl wurden untersucht. Die Fließkurven der Schmelzen wurden mit einem Kapillarviskosimeter erhalten, und daraus wurden der Fließindex, der Konsistenzkoeffizient und die Strömungsgeschwindigkeit durch die Kapillare bestimmt. Die Schmelzen zeigen einen pseudoplastischen Strömungscharakter, wobei am leichtesten die Blends mit 7 bis 15 Gew.‐% Elastomeranteil strömen. Aus der Scherviskosität wurde mit der Gleichung von Frenkel‐Eyring die Aktivierungsenergie der viskosen Strömung berechnet. Das elastifizierte Polypropylen zeigt eine erhöhte Schlagfestigkeit, ein holzartiges Aussehen und eine größere Wetterbeständigkeit als das mit Holzmehl gefüllte Polypropylen ohne Elastomeranteil.
Characterization of low‐molecular‐weight oligomers in recycled poly(ethylene terephthalate)
Authors: Dulio Valeria , Po Riccardo , Borrelli Raffaella , Guarini Alessandro , Santini Claudio
Published: April 2003

Low‐molecular‐weight compounds extracted from recycled poly(ethylene terephthalate) (PET) from post‐consumer soft‐drink bottles, treated at 150–220°C in vacuo or extruded at several temperatures and two different mass flow rates, were characterized by high performance liquid chromatography (HPLC), size exclusion chromatography (SEC) and desorption chemical ionization/mass spectrometry (DCI/MS). Among these products, cyclic and linear oligomers (polymerization degree 2–6) were identified, and their distribution was determined.

As a consequence of vacuum treatment of PET, the overall oligomer content decreases with increasing temperatures. Conversely, the extrusion at crescent temperatures causes an increase of the oligomer concentration; the same effect was observed by increasing the residence time. A further effect was represented by the enlargement of molecular weight distributions, i.e. larger rings and longer chains were formed in greater amounts at higher temperatures and residence times; a significant fraction of medium‐molecular‐weight oligomers (M̄n = 1400–1900) was also formed.
Dextran functionalized by 4‐nitrophenyl carbonate groups. Aminolysis reactions
Authors: Ramirez J. C. , Sánchez‐Chaves M. , Arranz F.
Published: April 2003

The modification reaction of dextran with 4‐nitrophenyl chloroformate using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. Under the used experimental conditions only acyclic carbonate groups have been detected. Preliminary experiments have shown that the reaction of 4‐nitrophenyl carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino‐type drugs (phenethylamine and tyramine) were satisfactorily bound to activated dextran with 4‐nitrophenyl carbonate groups. The heterogeneous hydrolysis of dextran‐phenethylamine or dextran‐tyramine adducts showed that no significant hydrolysis takes place under the applied conditions (pH 1 and pH 9, 37°C).
Zur kinetik und teilchenbildung der fällungspolymerisation von acrylsäure in gegenwart von polystyrol‐block‐polyethylenoxid‐copolymeren
Authors: Fengler Stephan , Reichert Karl‐Heinz
Published: April 2003

Für die radikalische Fällungspolymerisation von Acrylsäure in Toluol wurde ein Tensidsystem (Polystyrol‐block‐Polyethylenoxid‐Copolymer/Wasser) verwendet, welches es gestattet, feinteilige (Ø = 50–300 nm), über Monate stabile Polyacrylsäuredispersionen mit einem Feststoffgehalt bis zu 40 Gew.‐% herzustellen.

Die in einem Reaktionskalorimeter on‐line bestimmte Polymerisationsgeschwindigkeit zeigt einen stark autokatalytischen Verlauf, wobei die zeitliche Lage und die Höhe des Maximums der Polymerisationsgeschwindigkeit sehr stark vom Wassergehalt abhängig sind. Es wurde der Einfluß der Zusammensetzung (Blocklängen) des Tensides sowie der Tensid‐, Initiator‐ und Monomerkonzentration auf Polymerisationsgeschwindigkeit und Teilchengröße untersucht. Es hat sich gezeigt, daß vor allem durch Variation der Blocklängen des Copolymeren gezielt auf die Teilchenzahl und damit auf den Teilchendurchmesser Einfluß genommen werden kann.

Zur Beschreibung des Einflusses der einzelnen Prozeßparameter auf den Verlauf des Polymerisationsprozesses und auf die Produkteigenschaften wird ein Modell vorgeschlagen, welches auf der Theorie der homogenen Nukleierung und dem Einfluß des Wassers auf das Quellungsgleichgewicht der Polyacrylsäureteilchen beruht.
Thermal stability of blends of poly(vinyl chloride) with polyester elastomer
Authors: Park In‐Hwan , Jang Ja‐Soon , Chujo Yoshiki
Published: April 2003

The thermal stability of poly(vinyl chloride) (PVC) under air atmosphere was improved by blending with PETE (polyester elastomer). Its enhanced stability could be explained by a reaction between the ester component of PETE and HCl from dehydrochlorination of PVC, which was identified by IR‐ and 1H‐NMR spectroscopy. The best result of thermal stability was shown at a composition of 100 parts of PVC with 4 parts of PETE. By surveys of glass transition temperatures, it was found that all PVC/PETE blends were ununiformly distributed. During processing, the fusion time and torque at fusion decreased as the quantity of PETE increased. The mechanical properties of the blends were also changed; as the quantity of PETE increased, tensile strength of the blends decreased, while impact strength increased.
Oligomeric benzophenones as antioxidants for cellulose triacetate
Authors: Patel D. K. , Menon S. R. , Patel M. M. , Parmar J. S.
Published: April 2003

Cellulose triacetate films stabilized with oligomeric 2‐hydroxybenzophenone derivatives were subjected to oven ageing. The antioxidant efficiency of the oligomeric stabilizers was determined by carrying out measurements of percentage weight loss, change in carbonyl index and hydroxy index, and change in tensile strength and elongation at break. In general, the oligomeric benzophenones show better performance than their monomeric precursors in stabilizing cellulose triacetate.
The effect of ultrasound in ethyl methacrylate polymerization and depolymerization reactions
Authors: Erolan Nezih , Arisan Füsun , Çatalgil‐Giz Huceste
Published: April 2003

The effect of ultrasound in ethyl methacrylate polymerization and depolymerization and the chain termination mechanism for ethyl methacrylate have been studied. Polymerization conversion at 60°C did not depend on energy (80 W) and frequency (35 kHz) of ultrasound applied. In ultrasound depolymerization studies at 20°C the governing termination mechanism was found to be disproportionation and the lower limiting molecular weight was Mn = 500 000.
Simple models for stress relaxation and yield phenomenon of phenolphthalein poly(ether ketone)
Authors: Han Yanchun , Yang Yuming , Li Binyao
Published: April 2003

According to stress relaxation curves of phenolphthalein poly(ether ketone) (PEK‐C) at different temperatures and the principle of time‐temperature equivalence, the master curves of PEK‐C at arbitrary reference temperatures are obtained. A coupling model (Kohlrausch‐Williams‐Watts) is applied to explain quantitatively the different temperature dependence of stress relaxation behavior and the relationship between stress relaxation and yield phenomenon is established through the coupling model.
Reaktive membrancopolymere auf acrylbasis
Authors: Abel Christiane , Malsch Günter , Lehmann Ingeburg , Ziegler Hans‐Jörg , Scharnagl Nico , Becker Margot , Hicke Hans‐Georg
Published: April 2003

Die Copolymerisation des Acrylnitrils mit Maleinsäureanhydrid (MSA) wurde mit dem Ziel untersucht, acylfunktionalisierte Reaktivpolymere mit Filmbildungseigenschaften herzustellen, um diese in der Anwendung als Membran für kovalente Enzymfixierungen zu nutzen. Die radikalinitiierte Synthese der Copolymeren wurde in Lösung (Dimethylformamid (DMF), Dimethylacetamid (DMAC), γ‐Butyrolacton, Ethylencarbonat), durch Fällungscopolymerisation (Dioxan) sowie in Substanz durchgeführt.

Die Polymercharakterisierung erfolgte durch IR‐Spektroskopie, Elementaranalyse, Kernresonanzspektroskopie, Gelpermeationschromatographie, Viskosimetrie, Osmometrie und Potentiometrie.

Die Kinetik wurde durch dilatometrische Untersuchungen bis zu hohen Umsätzen verfolgt. Danach weist der Anhydridgehalt im Monomergemisch einen signifikanten Einfluß auf die Bruttopolymerisationsgeschwindigkeit und die Molmasse der Polymeren auf. Mit steigendem Anhydridanteil wird die Bruttopolymerisationsgeschwindigkeit herabgesetzt und eine Verringerung der Molmasse herbeigeführt. Die Copolymerisation von Acrylnitril und Maleinsäureanhydrid führt mit Ausnahme der Lösungspolymerisation in DMF bzw. DMAC zu Polymeren mit Molmassen oberhalb 30 000 g/mol, was ihre Anwendung als Membran ermöglicht. Die Einbaurate an Maleinsäureanhydrid in den Membranpolymeren ist bis einschließlich einer äquimolaren Zusammensetzung des Monomergemischs nicht größer als 5 mol‐%. Derartig niedrige MSA‐Reaktivgruppenanteile erweisen sich jedoch als ausreichend, um an einer aus einem Lösungspolymerisat (γ‐Butyrolacton, M̄η = 49 000 g/mol, c = 0,3 mol‐%) formierten Membran eine Enzymimmobilisierung mit Amyloglucosidase nachzuweisen.
Die swell of liquid crystal‐forming solutions of hydroxypropyl cellulose through a long capillary die
Authors: Suto Shinichi , Yoshida Shingo
Published: April 2003

The die swell and shear viscosity of lyotropic liquid crystal‐forming hydroxypropyl cellulose solutions in N,N‐dimethylacetamide were determined over a relatively wide range of shear stress or polymer concentration at 30°C by using a long capillary die with an aspect ratio of 114. The dependence of die swell on the concentration was similar to that of shear viscosity: a maximum at a critical concentration Ca and a minimum at another critical concentration Cb (Ca < Cb). The dependence of the swell on shear stress is greatly affected by the solution phase: in an isotropic range (below Ca), the die swell increased monotonously with shear; in the vicinity of Ca, the die swell exhibited a maximum; in a biphasic range (between Ca and Cb), the die swell decreased monotonously; in a single‐phase anisotropic range (above Cb), the die swell exhibited a minimum. Above Cb, extrudate distortion was observed and disappeared around the shear where the die swell exhibited a minimum.
Copolymerisation von butadien mit 1‐octen und 1‐dodecen mit einem neodymkatalysatorsystem
Authors: Kaulbach Ralph , Gebauer Ulrich , Gehrke Klaus , Lechner M. D. , Hummel Klaus
Published: April 2003

Für die Copolymerisationen des Butadiens mit 1‐Octen und 1‐Dodecen wurde das Katalysatorsystem Neodymoctoat/Ethylaluminiumsesquichlorid/Aluminiumtriisobutyl bei dem für die Polymerisation von Butadien optimalen Verhältnis der Katalysatorkomponenten eingesetzt. Der Einfluß der Monomermischungszusammensetzung auf die Copolymerzusammensetzung, den Umsatz, die Mikrostruktur, die zahlenmittleren Molmassen sowie die Molmassenverteilungen wurde untersucht. Die Copolymerisate besitzen einen deutlich höheren Verzweigungsgrad als das Polybutadien. Die Copolymerisationsparameter wurden nach Kelen‐Tüdßos bestimmt und ergaben für beide Copolymerisationen unterschiedlich große Parameter (rButadien ≫ rOlefin). Neben der 1H‐NMR Spektroskopie erfolgte der Copolymernachweis durch die Olefinmetathese.
Conductive resins used for tantalum capacitors — mechanical study of bonded joints
Authors: Ulrich M. , Dauphin J.‐Y. , Sarraf L. , Loucheux C.
Published: April 2003

Silver‐filled polymer coatings and adhesives are used to ensure the cathodic junction of tantalum capacitors. The aim of the present work was to choose new polymerizable materials agreeing with an industrial thermal test: Rapid Test Solder Heating (RTSH). In a first step, the physical chemistry of the main commercial coatings used at the present time was studied. Four commercial silver coatings (epoxy, polyester, polyimide and polyacrylate binders) and one conductive epoxy adhesive were tested. The tensile strengths of the different joints were evaluated both at room temperature and 150°C. The examination of the metallographic cross sections and of the surface fractures were conducted using a scanning electronic microscope (SEM). The failure strength of the joints is discussed in relation with the nature of the binders, the temperature, the cure cycles and the presence of silver fillers blended with the polymer resins.
PP/LDPE blends filled with short polyamide fibers
Authors: Arroyo Miguel R. , Lopez‐Manchado Miguel Angel
Published: April 2003

The effect of short polyamide 66 (PA) fibers on the tensile, flexural, and impact behaviour of low density polyethylene (LDPE), polypropylene (PP), and their blends has been investigated. The moduli of the composites increase as fiber and PP contents increase, and this effect is more noticeable at LDPE/PP ratios above 1. However, the effect of the fibers on the tensile and flexural strength of these materials depends on matrix composition. So, the polyamide fibers act as a reinforcing agent for polymer matrices with LDPE/PP ratios above 1, but with PP as the continuous phase a decrease in the tensile strength is observed. In all cases, at the same fiber content, the strength of the composites increases as PP percentage increases. On the other hand, the addition of PA fibers gives rise to an increase of the tenacity of the composites with PP percentages above 50% in the matrix composition. From the observed results a higher reinforcing effect and a better affinity between the polyamide fibers and the LDPE are suggested.
Synthesis and characterization of photopolymers with azo units. Interfacial polyaddition, photolysis, photodegradation
Authors: Nuyken Oskar , Stebani Jürgen , Lang Armin
Published: April 2003

The synthesis of an aryl alkyl azo diisocyanate and a model azo urea is described. From the azo diisocyanate new azo polyureas were created by interfacial polyaddition. Molecular weights Mn in the range of 6000 to 9000 were determined by gel permeation chromatography (GPC). Photolysis and thermolysis of both, model compounds and polymers, were studied by UV‐spectroscopy and differential scanning calorimetry (DSC), respectively, and the results were compared with those of similar azo amides. Photochemical polymer degradation was followed by GPC.
Model investigation of the co‐condensation of melamine and phenol components in MPF thermoset moulding materials
Authors: Braun Dietrich , Unvericht Reinhard
Published: April 2003

Possible 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

A 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

The 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

Thermotropic 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

The 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

Metallocenes 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

A 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

Wastes 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

Triglycidyl 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

Polycondensation 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}$$\nu _{c ‐ c_{ar} }$$\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

Carboxy‐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

Isobutylvinylether (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

Der 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

45 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.