bluuebunny/crossref_metadata_2025 huggingface dataset:
Macromolecular stabilizers for polymers
Authors: Pospíšil Jan
Published: April 2003

Inherent chemical activity, physical persistence and good compatibility are factors determining the efficiency of a stabilizer observed during the degradation of amorphous and crystalline synthetic polymers. Synthesis of macromolecular stabilizers is one of the ways used to solve the problem of physical persistency of stabilizers under severe aggressive environmental attacks on polymers. General types of macromolecular stabilizers, routes to their synthesis and characteristic examples of macromolecular antioxidants, UV absorbers, hindered amine light stabilizers, flame retarders and biostabilizers, as well as of polyfunctional systems are given. Problems connected with the use of macromolecular stabilizers are mentioned.
A contribution to the UV degradation of polyurethanes
Authors: Rek Vesna , Braver Mladen , Jocić Tanjuša , Govorćin Emi
Published: April 2003

The effects of the nature of the polyols used in polyurethane (PUR) synthesis on the structural transformations after ageing by UV irradiation has been studied. The investigations were performed on PUR prepared from polyester and polyether diol oligomers.

The characterization of the samples before and after ageing in view of the structural changes, which influence the course of the photooxidative degradation and photocrosslinking as well as in view of changes of mechanical properties has been done. Comparative investigations were performed by spectroscopic and viscometric measurements.

The results show pronounced heterogeneity of the degradative reactions, including the existence of crosslinking processes and producing thus very inhomogeneous polymeric material. The course and the intensity of photooxidative degradation of PUR differ together with changes of mechanical properties depending whether polyester or polyether polyol have been used. The processes of photooxidative degradation is less expressed in polyesterurethane then in polyurethane based on polyether, under the same conditions of experiments. Different structures of polyester diols caused the various ageing behaviour of PUR too.
Degradation of adhesive composites
Authors: Kovačević Vera , Hace Drago , Bravar Mladen , Cerovečki Zeljko , Mudri Irinej
Published: April 2003

Composite materials consisting of natural leather and polyurethane elastomers, and bonded together by polyurethan adhesives, were submitted to accelerated ageing at various testing conditions.

The extent of the degradation of these composites was evaluated through the determination of mechanical strength reduction and through the insight into the structural and chemical transformations of the adhesive polymeric materials.

Founded data correlations indicate to the mechanism and to the relevant factors that influence of ageing processes.
Beurteilung von hals‐verbindungen
Authors: Nyitrai Zsuzsanna , Lovas Ilona , Ocskay György , Wein Tibor
Published: April 2003

QUALIFICATION OF HALS COMPOUNDS

A complex method of examination has been developed suitable for the qualification of light stabilizers; by this method, according to experience, the efficacy of HALS compounds can be extensively and expediently characterized.

Several light stabilizers of the HALS‐type were examined and qualified, used alone or together with a UV‐absorber.

It has been found that, when selecting the appropriate structure for a given polymer, the weatherability of polyolefine foils is effectively increase to six‐eightfold; the increase is even tenfold when the stabilizer is combined with a benzophenone‐type compound.

As a utilization of these experiences, a contract with the industry, led to the production of an LDPE based agricultural foil with a life‐time of several years.
Specimen temperature as a constant marginal condition and as a variable test parameter during accelerated weathering
Authors: Kockott Dieter
Published: April 2003

The influence of the specimen temperature on many ageing processes is well known. Two aspects is dealt with:

Measurements of the specimen temperature on several positions of a specimen in commercial weathering devices at different exposure conditions. Technical measures to achieve to uniform ageing at all positions of a planar and homogeneous specimen. Examples from practical use.

Changing specimen temperatures (+60°C to −20°C) during the course of accelerated weathering, i.e. a combination of conventional accelerated weathering with a temperature cycle test.
Influence of production parameters on ageing processes of thermoplastics
Authors: Sasse H. Rainer , Boué Andreas
Published: April 2003

Specimens of unmodified polypropylene have been manufactured using extreme adjustings of injection moulding machines and extruders. After artificial weathering, distinct relations of ageing processes to thermal and mechanical production parameters were found, which are not influenced by different melting temperatures. It can be started in particular, that during injection moulding a larger shear stress (resulting in more distinct orientation) results in

a greater change in residual stresses

an earlier gloss reduction

a shorter initial period before cracking.

During extrusion a lower cooling rate (resulting in a coarser structure) leads to

a greater change in residual stresses

an earlier and more distinct gloss reduction

an earlier loss of ultimate strain.

It remains unknown, whether

these relationships will be similar with other thermoplastic materials than PP

these relationships appear to the same relative extend with stabilized systems

it may be advantageous, to use the observed effects by adjusting the injection moulding and extrusion machines in a special way.

It seems to be significant to do more research work in this field.
Ageing of polyethylene filled with a mineral filler
Authors: Peeva Lili , Evtimova Sonya , Fileva Blagovesta , Taveteva Vichra
Published: April 2003

The thermo‐oxidation resistance and weatherability of LDPE and HDPE compositions, containing up to 45 wt.% calcium carbonate, are investigated. The thermo‐oxidation resistance is investigated by dynamic DTA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behaviours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing.
Structure and aging in the welded bonds of PP‐ homopolymer with PP‐ copolymer (PP‐R)
Authors: Muschik H. , Dragaun H.
Published: April 2003

The present study deals with changes of welded material of pipes and fittings (isotactic polypropylene homo and copolymer PP‐R grey pigmented) during the standardized internal pressure tests, which are commonly used for these products.

Technical welding of polyolefines causes characteristic structures, which depend on the natural of the welded material and the welding conditions.

In this investigation both the transition of material in the welding seam and the changes of internal stresses during internal pressure tests at 95°C until 18.100h test time were examined. The methods we used were Differential calorimetry of think layers, Polarization‐ and Electron microscopy, Fluorescence spectroscopy with extreme high local resolution.

The effects of decomposition of the macromolecules in the welded samples during the internal pressure tests will be described in a separate paper (1).

The internal pressure tests at 95O C cause a recrystallization and an increase of the particle size in the structure of the welding seam and in the structure of the welded parts themselves. Under the above described testing conditions the orientations and internal stresses initiated by the welding procedure will relaxe influenced by heat. However the creep effects that occur in the material when exposed to pressure introduce new internal stresses. It could be shown that in perfectly welded parts a continuous transition from PP to PPCO occurs, which did not change after long time application of internal pressure tests.
Solvolytic degradation of aliphatic polyesteroligomers: Poly(tetramethylene adipate) diol
Authors: Mormann Werner , Wagner Josef
Published: April 2003

Poly(tetramethylene adipate)diol having a molar mass of 2000 was stored at temperatures of 60 and 80°C in the presence of water or 1,4‐butanediol and a common PUR‐catalyst like 1,4‐diazabicyclo [2.2.2]octane (DABCO) or dibutyltindilaurate (DBTL) and the solvolysis was investigated. The rate of solvolysis is low at 60°C except for DBTL and shows a drastic increase at 80°C. In the alcoholysis reaction DBTL is a much more active catalyst than DABCO. The rate of hydrolysis is slower probably because the catalysts are deactivated by the acidic products formed in this process. The mechanical properties of polyurethanes made from the degraded polyols are in good correlation with the decrease in molar mass.
Viscoelastic properties of short fiber filled SBR composites
Authors: Rueda Luis Ibarra , Antón Celia Chamorro , Rodríguez M. Carmen Tabernero
Published: April 2003

This paper examines the effects of deformation amplitude, temperature and frequency on the dynamic properties of SBR‐short fiber composites. The presence of the fiber increases the storage modulus at any deformation amplitude. Depending on the nature of the fiber, the linear response zone of the modulus versus deformation either diminishes or disappears. The loss factor tan δ is higher in fiber composites. Although the peaks do not vary in magnitude, they occur at different deformation amplitudes.

Temperature increase causes the moduli to decrease, the gradient, however, being less pronounced for fiber composites. The relaxation spectra show a damping peak which correlates to the principal relaxation process in the elastomeric matrix. The temperature at which this peak appears is displaced towards higher values with increasing excitation frequency. This allows the determination of the apparent relaxation activation energy, which is higher in fiber plus adhesive composites (225 – 275 kJ/mol), as compared to the fiber‐free composite (194 kJ/mol), as a consequence of stronger fiber‐matrix interaction.
Preparation and properties of UV‐curable polydimethylsiloxane urethane acrylate
Authors: Chiang Wen‐Yen , Shu Wey‐Jye
Published: April 2003

A new type of a UV‐curable polyurethane acrylate resin based on hydroxyterminated polydimethylsiloxane (PDMS) soft segments with molecular weight 1800 and 2,4‐toluene diisocyanate (TDI)/2‐hydroxyethyl methacrylate (HEMA) hard segments were synthesized. The reactivity of 2,4‐TDI with the hydroxy groups of silanol and HEMA was discussed by means of IR measurements. The characteristic absorption peaks of the —NCO groups of 2,4‐TDI in the para‐ and ortho‐position should decline with increasing the reaction time. The measurements of fundamental physical properties of this type of UV‐curable materials had been widely studied in addition to the effects of using various reactive diluents and some pigments. This kind of resin with good optical, electrical insulating, and adhesive properties on various matrices, could be improved in chemical properties and reduced in viscosity while promoting the coating processability by mixing with various reactive diluents. The excellent adhesive properties on glass plates can be attributed to the similar structure between the PDMS soft segments and glass which makes the application in the coating industry possible.
Coordination polymers, 1. Magnetic, spectral, and thermal properties of coordination polymers derived from terephthalaldehyde bis(S‐benzyldithiocarbazate)
Authors: Paliwal L. J. , Kharat R. B.
Published: April 2003

New Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) coordination polymers of Schiff base ligand derived from terephthalaldehyde and S‐benzyldithiocarbazate have been synthesized in DMF media. The coordination polymers have been characterized by their elemental analysis, magnetic susceptibility, and by electronic and infrared spectral measurements.

The thermal stability of each polymer was found out by thermogravimetric analysis. The thermal stability of coordination polymers obtained from thermograms has the following order:
\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Zn} \simeq {\rm Fe} > {\rm Co} > {\rm Ni} > {\rm Min} \simeq {\rm Cu}$\end{document}
Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers are of a six‐coordinated octahedral structure while Cu(II) and Zn(II) coordination polymers are found to be four‐coordinated square planar and tetrahedral structure, respectively. The ligand‐field and nephelauxetic parameters have been determined from the spectra, using ligand‐field theory of spin‐allowed transitions which are found consistent with six‐coordinate structure for Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers. Elemental analyses indicates a ligand: metal ratio of 1 : 1 in all the coordination polymers and the association of water molecules with central metal atom in case of Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers.
Molecular weight distribution of living polymers in a semi‐batch reactor
Authors: Tappe R. , Bandermann F.
Published: April 2003

For anionic polymerization with slow initiation and rapid propagation step analytical expressions are presented to calculate average molecular weights and molecular weight distributions for a semi‐batch process, in which a monomer solution contaminated by impurities is fed to an initiator solution in the reactor. The validity of the model was checked for the case of the polymerization of isoprene by n‐butyllithium in n‐heptane. The differences observed between theoretical and experimental values are explained by the changes in the rate constants of the initiation and the propagation step caused by the change in the polarity of the reaction solution by the continuously fed impurities. Furthermore it is shown that polymers with bimodal molecular weight distributions are formed if the semi‐batch procedure is followed by a batch one to increase the monomer conversion.
Einfluß der polymerisationsbedingungen auf die morphologie von schwefel‐styrol‐polymerisaten
Authors: Haase R. , Bongardt J. , Schick Ch.
Published: April 2003

Für ein Polymersystem Schwefel‐Styrol mit 10% Styrol wird die Abhängigkeit der Morphologie von der Polymerisationstemperatur und ‐zeit beschrieben. Neben der charakteristischen orthorhombischen Phase wurden röntgenographisch eine monokline und eine pseudoorthorhombische Phase nachgewiesen. Außerdem liegt, abhängig von den Polymerisationsparametern, ein amorpher Anteil vor.
Synthesis and characterization of resins from 4‐ethylphenol and cinnamaldehyde
Authors: Opresnik Marko , Šebenik Anton , Žigon Majda , Osredkar Uči
Published: April 2003

The mechanisms of the reaction between 4‐ethylphenol and cinnamaldehyde were studied by means of HET 2DJ 13C‐NMR spectroscopy, 1H‐NMR spectroscopy and GPC. In the first step of the reaction the addition of 4‐ethylphenol to carbonyl group and to double bond of cinnamaldehyde takes place. In the second step of the reaction the CH(OH)‐group reacts with 4‐ethylphenol to form branched products of red coloured resins with an average molecular weight of 600. The reaction takes place at temperatures above 100°C in strong acid medium.
Nucleophilic addition to phenylisocyanates: A theoretical study
Authors: Wilhelm D. , Huber J. , Piecha G. , Wilhelm R.
Published: April 2003

The enthalpies for the addition of hydroxide anion to substituted phenylisocyanates have been calculated with MNDO. The results obtained correlate well with the rates of addition of 2‐ethylhexanol to phenylisocyanates. This allows us to estimate the rates for nucleophilic addition within reasonable limits without the need for experiments.
Radical high pressure polymerization of ethylene with stable initiators
Authors: Luft Gerhard , Fischer Norbert , Dorn Max
Published: April 2003

In order to assess the suitability of stable initiators for the high pressure polymerization of ethylene, polymerization tests were carried out in a stirred autoclave in continuous operation. The pressure used was 1700 bar, the average residence time 30 seconds and the temperature was adjusted to between 200 and 360°C. The initiator concentration in the ethylene feed varied between 4 and 40 mol ppm. Di‐tert‐butyl peroxide, di‐tert‐amyl peroxide, tert‐butyl hydroperoxide, and 3,4‐di‐methyl‐3,4‐di‐phenyl hexane, a CC labile compound, were chosen for use as stable initiators. The level of conversion and the specific initiator consumption were determined. The polymers obtained were characterized by measuring their density, average molecular weight, and melt flow index. The stable initiators used were all characterized by a very low level of consumption. In the case of dialkyl peroxides and alkyl hydroperoxide, the optimum application temperature is substantially above 200°C and above 300°C in the case of the CC labile initiator. Under these conditions, polymers with a low density, a low molecular weight, a narrow molecular weight distribution and a high melt flow index were obtained.
Photooxidative behaviour of polypropylene fire retarded with instumescent additive
Authors: Camino G. , Arnaud R. , Costa L. , Lemaire J.
Published: April 2003

A typical intumescent fire retardant additive for polypropylene, which is a mixture of ammonium polyphosphate and pentaerythritol, does not sensibly modify the photooxidative behaviour of unstabilized polypropylene whereas it modifies that of polypropylene stabilized with a substituted o‐hydroxybenzophenone and a sterically hindered amine. The photostabilizing effectiveness of the amine is probably decreased owing to protonation by polyphosphoric acid. On the contrary, the photo‐protection effectiveness of the o‐hydroxybenzophenone is increased in the presence of the intumescent fire retardant. This might be due to a photoinhibition effect of pentaerythritol.
Radiation induced graft copolymerization V. Graft copolymerization of methyl acrylate onto nylon‐6 fiber
Authors: Nayak Padma L. , Lenka Subasini , Basak Anindita
Published: April 2003

The radiation induced graft copolymerization of methylacrylate onto nylon‐6 fiber at room temperature and in nitrogen medium was investigated. The effects of monomer, dose rate, inhibitor etc. on the graft yield have been investigated. The effect of solvents on the rate of grafting was studied from which the chain‐transfer constant (Cs) of the solvent has been evaluated. Addition of certain inorganic salts was found to act as scavengers. The value of Gb, the number of branches per 100 eV of energy absorbed in the substrate polymer, was calculated. The density, moisture regain, alkali solubility, dyeability and thermal properties of the grafted nylon‐6 fiber have been evaluated.
Polyethyleneterephthalate with increased viscosity by chemical crosslinking
Authors: Fakirov Stoyko , Evstatiev Michail
Published: April 2003

An attempt is made to improve the processing and operation properties of polyethyleneterephthalate (PETP) containing chemically bound pentaerythrol as modifier by increasing its viscosity through slight chemical crosslinking in the solid state.

It is established that thermal treatment in vacuum for 8 h at 240°C of PETP containing 0.3 mol‐% pentaerythrol leads to an increase in its molecular weight from 20000 to 40000 mainly as a result of additional solid state polycondensation. Further more, annealing in vacuum for 6 h at 250°C of the polymer containing 0.4 mol‐% pentaerythrol leads to the formation of a loose three dimensional network resulting from chemical crosslinking in the solid state.

It is shown that this crosslinking material has improved processing behaviour during injection moulding due to the increased viscosity of the melt.
Bestimmung der elektrokinetischen fasereigenschaften mit hilfe der elektroendosmotischen methode
Authors: Pfeifer Stanisław , Włochowicz Andrzej
Published: April 2003

Es wurde die Bestimmung der elektrokinetischen Eigenschaften von Polyacrylnitrilfasern (PAN) mit Hilfe der elektroosmotischen Methode beschrieben und auf ihre Vor‐und Nachteile hingewiesen. Es zeigte sich, daß die Werte der elektrokinetischen Parameter wie elektroosmotische Stromstärke (Qc) und elektrokinetisches Potential (ζ) von der Masse und der Struktur der untersuchten Proben abhängen. Die Untersuchung dieser Abhängigkeit am Beispiel von Polyamid‐, Polyester‐ und Polyacrylnitrilfasern was das Ziel dieser Arbeit. Es zeigte sich, (a) daß es nicht möglich ist, anhand der elektroosmotischen Methode die echten ζ‐Werte zu bestimmen, und (b) daß es nicht notwendig ist, bei einem relativen Vergleich des Zeta‐Potentials verschiedener Fasern die Beziehung ζ = f(m) zu bestimmen.
On the chemical reactivity of cotton cellulose in xanthogenation
Authors: Amine Abou‐State M. , Ali Abdel Fattah H. , Mostafa Naglaa Y. S.
Published: April 2003

Hydrochloric acid prehydrolysis of cotton cellulose resulted in a less accessible fine strucuture, higher crystallinity and lower reactivity in xanthogenation than sulphuric acid prehydrolysis. The reactivity was improved only when the duration of the hydrochloric acid treatment was reduced to 1 h. Hydrochloric acid prehydrolysis‐soda‐anthraquinone pulping raised the yield of α‐cellulose and improved greatly the affinities towards water and alkali, and resulted in much better reactivity in xanthogenation. The optimum quinone concentration was 0.2%. A comparison between the most reactive pulps obtained by sulphuric acid prehydrolysis‐soda‐anthraquinone pulping and hydrochloric acid prehydrolysis‐soda‐anthraquinone pulping indicated that hydrochloric acid allowed a great reduction in the duration of both prehydrolysis and pulping. Both acids resulted in the same α‐cellulose and the same degree of polymerization, but hydrochloric acid led to higher yield, higher crystallinity, more open and accessible fine structure, and much better reactivity in xanthogenation. However, in absence of anthraquinone, hydrochloric acid prehydrolysis resulted in a less accessible fine structure and lower reactivity in xanthogenation.
Effect of gamma radiation on low density polyethylene
Authors: Mukherjee A. K. , Tyagi P. K. , Gupta B. D.
Published: April 2003

Low density monofilaments of polyethylene with varying draw ratios were subjected to high energy radiation using Co60 gamma radiation source. It was found that the tensile strength is sharply improved with the increasing dose up to 20 Mrd beyond which a sharp decrease in tenacity and initial modulus was observed. The swelling behaviour also decreased with the increased in dose of irradiation. However, density showed an increasing trend. The shrinkage behaviour of all the filaments was found to increase with increasing dose and draw ratios. The results have been explained in terms of continuous increase in crosslink density with the increasing dose of irradiation along with loss of crystallinity, which appears to be more severe in the latter stages of exposure. The samples exhibited memory effect after redrawing at 100°C and cooling under tension followed by further heating at 110°C under relaxed condition. The shrinkage was still much higher but independent of draw ratio.
Acrylic copolymers with controlled properties
Authors: Sândescu F. , Simionescu C. I.
Published: April 2003

A method of the control of copolymer endgroups in a solution‐suspension copolymerization process was elaborated. The method is based on the utilisation of an initiating system containing three components: S2O2‐8 /HSO‐3 /Fe2+, their ratio and the ratio S2O2‐8 /comonomer mixture being optimized. In this way it is possible to control the content of endgroups of the copolymer, the saturation value, the M̄n values and polydispersity, without using comonomers with polar groups –SO3H or –OSO3H. Due to their conformational peculiarities and their packing manner in concentrated solutions, the macromolecular chains with a high endgroup content behave much better during the solving and spinning processes.

Thus, an increase of the content of copolymer endgroups favours not only the tinctorial properties, but also the spinnability of the spinning dopes obtained from the respective copolymers.

The proposed method for the copolymer endgroup control is more economical than the utilization of the comonomers with polar groups.
Preparation and characterization of some polyesterurethanes and polyesterurethane‐ureas based on 1,3‐bis(carboxymethoxy)benzene
Authors: Shaaban Abd‐El‐Fattah Fadel , El‐Safty Maher Abd‐El‐Rahman , Moustafa Hamed Yosef , Messiha Nagi Naguib
Published: April 2003

Hydroxy terminated polyesters were prepared by a melt condensation technique using 1,3‐bis(carboxymethoxy)benzene and various diols. They were characterized by hydroxy number, acid number, and intrinsic viscosity measurements. The polyesters were reacted with excess toluene‐2,4‐diisocyanate to yield isocyanate terminated prepolymers which were subsequently reacted with diols or benzidine. These polymers were characterized by IR and 1H‐NMR spectra, viscosity measurements, and thermogravimetric analysis.
Chlorocarboxylation of polyethylene, IV. Radical scavenging action of maleic anhydride
Authors: Joshi Shashikant G. , Kulkarni Bhaskar D.
Published: April 2003

Radical scavenging action of maleic anhydride (MA) is observed during chlorocarboxylation of polyethylene (PE) (CCPE). Reduction in the rate of chlorination is observed in the presence of MA in the CCPE process as compared to the rate of chlorination of PE (CPE) alone. Reduction in the rate of chlorination is due to the competitive nature of CCPE process and the radical scavenging action of MA. Radical scavenging action arises as a result of the formation of MA excimers of very short half life and their interactions with solvent. Other reactions responsible for scavenging action may also exist and are discussed.

The kinetics of the scavenging process is studied by considering number of sites (N̄0Cl), (N̄Cl + N̄MA) occupied during CPE and CCPE processes, respectively. The temperature dependence of the apparent rate constant kSCV is investigated and reveals that activation energy and pre‐exponential factor are of the order of 10.3 kcal/mol and 9.1 s‐1, respectively.
Particle size distribution of polypropylene produced in continuous polymerisation
Authors: Carson Ian G.
Published: April 2003

A theoretical relationship has been developed between the particle size of polyolefin powders and that of the Ziegler‐Natta catalyst from which they are derived. This has been extended to examine how the yield on catalyst and the residence time distribution in a continuous stirred tank reactor affect the particle size distribution. Experimental confirmation of these relationships has been obtained using TiCl3 catalyst of near‐spherical morphology prepared by low‐temperature reduction of titanium tetrachloride with triethyl aluminium in solution.
Automatic polymerization reactor with on‐line data measurement and reactor control
Authors: Budde Uwe , Reichert Karl‐Heinz
Published: April 2003

An automatic polymerization reactor has been developed for on‐line measurement of conversion, viscosity, and molecular weight distribution of homogeneous free radical polymerization.

For on‐line measurements during polymerization a fraction of the reaction mixture is pumped as bypass through a densimeter and a viscometer. In time intervals of 15 min samples are taken, diluted semi‐automatically, and then injected into a high performance gel permeation chromatography for determination of the molecular weight distribution of the polymers. A microcomputer collects these data, calculates the conversion of reaction and the output data for different control units.

Methyl methacrylate is polymerized batch‐wise in solution with ethyl acetate as solvent and dicyclohexyl peroxydicarbonate as initiator. Semi‐batch polymerizations with constant reaction rate are performed by feeding initiator which is controlled by open‐loop and closed‐loop control.
Die elektrochemische Polymerisation. Ein interessantes Prinzip zur Synthese von elektrisch leitfähigen Polymeren
Authors: Naarmann Herbert
Published: April 2003

In einem kontinuierlichen Prozeß werden organische Polymerfilme — mit intrinsischer elektrischer Leitfähigkeit — durch anodische Oxidation direkt aus den Monomeren hergestellt.

Die Arbeit beschreibt die Synthese, die Variationsbreite des Verfahrens sowie wesentliche Eigenschaften der neuen Polymeren.

Im Gegensatz zu den klassischen Kunststoffen, die nach radikalischen oder ionischen Polymerisationen oder auch durch Polyadditions‐ oder ‐kondensationsverfahren gewonnen werden, stellt die elektrochemische Oxidation, z.B. von Pyrrol zu „Polypyrrol”︁, ein neues Polymerisationsprinzip dar. Aber nicht nur das Syntheseprinzip, auch die Eigenschaften des neuen Polymeren sind ungewöhnlich.
Polymerization of diallyl dimethyl ammonium chloride in inverse emulsion. I. Kinetics and mechanism
Authors: Huang P. C. , Reichert K.‐H.
Published: April 2003

An aqueous solution of diallyl dimethyl ammonium chloride was dispersed in an isoparaffinic liquid. A mixture of sodium di‐2‐ethyl‐hexyl sulfosuccinate and sorbitan monooleate was used as emulsifier. The polymerization was initiated by an oil soluble azo initiator and conducted in a stirred tank reactor at constant temperature. The initial rate of polymerization can be expressed as following in the region studied:

A kinetic model is presented by which the rate of polymerization can be calculated up to high conversions by considering gel effect and initiator decomposition. Based on experimental results the loci of polymerization are assumed to be the micelles and latex particles. The polymerization mechanism is conform to the Smith‐Ewart mechanism. The influences of ion strength and partition equilibria on the rate of polymerization were studied and are considered to be the causes of the 3rd order with respect to the monomer concentration.
Bruchmechanische Zähigkeitscharakterisierung polymerer Werkstoffe vom elastischen bis zum plastischen Deformationsbereich
Authors: Könnecke Klaus
Published: April 2003

Die vergleichende Zähigkeitsbeurteilung von Materialien, die einen sehr weiten Zähigkeitsbereich überspannen, erfordert eine Meßmethode, die vom spröden, überwiegend elastischen bis hin zum duktilen, vollplastischen Deformationsverhalten ohne Bruch der Probekörper brauchbare Ergebnisse liefert. In dieser Arbeit wird bestätigt, daß mit der Bestimmung des bruchmechanisch definierten Parameters „J‐Integral”︁ ein hierfür geeignetes Verfahren zur Verfügung steht.

Insbesondere wird deutlich gemacht, daß über die bereits mehrfach für langsame Deformationen beschriebene Anwendung hinaus diese Methode auch für hohe Verformungsgeschwindigkeiten eingesetzt werden kann. Damit eröffnet sich eine neue Möglichkeit zur vollständigen bruchmechanischen Charakterisierung des Deformationsverhaltens von Polymeren unter Schlagbeanspruchung.

Anhand einer Reihe von Werkstoffen auf PP‐Basis mit sehr unterschiedlichen Zähigkeitseigenschaften wird die in der Praxis erreichbare Aussagefähigkeit der Methode gezeigt.
Die wichtigsten polymerphysikalischen Aspekte des Polycarbonats
Authors: Morbitzer L. , Grigo U.
Published: April 2003

Die sich ausweitenden Einsatzbereiche des Polycarbonats

Polycarbonat auf Basis von Bisphenol A (im Text als BPA‐PC oder einfach als PC bezeichnet)

. (PC) machen es notwendig, das Verständnis für die physikalischen Grundlagen auch in die mehr anwendungsorientierten Bereiche hineinzutragen. Der vorliegende Artikel macht den Versuch, die wichtigsten polymerphysikalischen Aspekte, auf denen eine Vielzahl von technologischen Eigenschaften beruht, in Form einer Übersicht darzustellen. Behandelt werden: Deformationsmechanismen, dynamisch‐mechanisches Relaxationsverhalten, Spannungs‐Dehnungsverhalten, Zäh/Spröd‐Übergang, Einfluß der Probendicke, physikalische Alterung, Orientierungsverhalten, Spannungsrißbildung in Medien.
Einfluß der chemischen Struktur auf die mechanischen Eigenschaften von modifizierten Polycarbonaten
Authors: Weymans G. , Berg K. , Morbitzer L. , Grigo U.
Published: April 2003

Ausgehend von den bisher erarbeiteten Vorstellungen über die Festkörperstruktur des Bisphenol‐A‐Polycarbonats wird die Auswirkung einer chemischen Substitution des Bisphenols auf die thermischen, mechanischen und mechanisch‐dynamischen Eigenschaften diskutiert. Innerhalb der Substanzklasse der Polycarbonate zeigt sich dabei hinsichtlich der beobachteten mechanischen Phänomene ein erheblicher Einfluß der chemischen Struktur. Vor allen Polycarbonaten ist das Bisphenol‐A‐Polycarbonat besonders hinsichtlich seiner Tieftemperatur‐Eigenschaften ausgezeichnet. Der Spröd/Zäh‐Übergang als Funktion der Temperatur korreliert mit der Hochtemperaturflanke des mechanischen Nebenrelaxationsgebietes. Eine die experimentell beobachteten Phänomene vollständig charakterisierende Theorie muß als wesentlichen Parameter die konformative Beweglichkeit der Polycarbonat‐Ketten berücksichtigen.
Effect of vulcanization temperature on the cure characteristics and vulcanizate properties of natural rubber and styrene‐butadiene rubber
Authors: Kurian T. , George K. E. , Francis D. J.
Published: April 2003

Gum compounds of natural rubber (NR) and styrene‐butadiene rubber (SBR) are vulcanized at different temperatures and the cure characteristics and vulcanizate properties are compared. The optimum cure time at a particular vulcanization temperature could be expressed empirically in terms of that temperature using an exponential relation. The crosslink density of the vulcanizates is found to decrease with an increase in the vulcanization temperature. For a given compound there is a particular vulcanization temperature which gives the best compromise of properties for specific applications.
Graft copolymerization of methyl methacrylate on poly(vinyl chloride)
Authors: Ghosh Premamoy , Bhattacharyya Arabinda Shekhar , Maitra Somnath
Published: April 2003

Chemical modification of poly(vinyl chloride), PVC, by an amine renders the polymer more reactive towards graft copolymerization with a vinyl monomer. The graft copolymerization of methyl methacrylate (MMA) on PVC modified by treatment with n‐butylamine (n‐BA) was started thermally at 30° using benzoyl peroxide (Bz2O2) as initiator and under photoactivation at 40° using benzophenone (BP) as photo sensitizer. The gross polymer products from selected experiments were fractionally separated into the constituent polymeric entities viz., poly(methyl methacrylate), PMMA (homopolymer), PVC‐g‐PMMA (graft copolymer), and unreacted (aminated) PVC following a method of fractional precipitation. The separated fractions were characterized by IR spectroscopy and thermogravimetry. The mechanisms of graft copolymerization for the two different systems have been discussed. In each case, grafting efficiencies of the order of 30–70% and graft copolymers having compositions given as PMMA/PVC (w/w) equal to 2–3 were readily obtained.
GPC estimation of molecular mass distribution of addition polymers from bisphenol‐a‐diglycidyl ether and amines
Authors: Szesztay Márta , László‐Hedvig Zsuzsanna , Tüdős Ferenc , Hörhold Hans Heinrich , Klee Joachim
Published: April 2003

Thermally polymerized samples of linear addition polymers of bisphenol‐A‐diglycidyl ether (DGEBA) and the following three different amines (A): benzylamine (BA), p‐chloroaniline (PCA), and cyclohexylamine (CHA) were chromatographed by gelpermeation chromatography (GPC) using THF as eluent. The solvation effect of hydroxyl groups by THF has been taken into consideration when calibrating the system and interpreting the chromatograms. The comparison of the chromatograms suggests that the polymer with CHA is cyclized already in the range of small molecular masses (including dimers) and in an early stage of reaction. The comparison of average molecular masses of the samples as measured with independent methods—vapour pressure osmometry (VPO) and GPC—shows that the cyclization of the polymers with BA and PCA takes place to a lower extent, the latter polymer being less capable of cyclization.
Synthèse de Copolymères Greffés Poly(ethylène‐g‐Méthacrylate de méthyle) et leur Influence sur les Propriétés Mécaniques des Alliages de Polyéthylène avec le Polychlorure de Vinyle
Authors: Boutevin Bernard , Piétrasanta Yves , Sarraf Tarek
Published: April 2003

Les copolymères greffés P(E‐g‐MMA) sont préparés par réaction du méthacrylate de méthyle (MMA) en masse sur le polyéthylène basse densité ozonisé. La masse moyenne des greffons de PMMA variable suivant la température et le temps de réaction est de 7700 et 21400. Ces copolymères sont testés comme émulsifiants de mélanges de PE et de PVC dont les propriétés mécaniques, la contrainte à la rupture σR, l'allongement à la rupture εR% et le module d'élasticité E sont mesurées avant et après l'addition de 5% en poids de copolymère. Pour le mélange PE‐PVC 50‐50 σR passe de 0,60 à 1,10 kg/mm2, la variation de εR est plus complexe. La visualisation, au microscope électronique à balayage, des fractographies de ces divers mélanges, montre une diminution d'au moins un facteur 10 de la taille des phases après addition de copolymère et confirme bien le rôle d'émulsifiant d'émulsifiant de ceux‐ci permettant d'obtenir ainsi de nouveaux alliages PE‐PVC dont les propriétés sont comparées avec celles d'alliages préparés par d'autres auteurs avec d'autres émulsifiants.
Surface sulphonated highly crosslinked styrene‐divinylbenzene copolymers
Authors: Kolarz Boz̊ena N. , Trochimczuk Andrzej , Wojaczyńska Maria
Published: April 2003

A series of surface sulphonated macroporous styrene‐divinylbenzene (S‐DVB) copolymers containing various amounts of —SO3H groups was obtained. Porous structure, surface hydrophilicity and polarity, and sorption properties of these copolymers as well as those of starting S‐DVB resin towards some substances which are present in blood were determined. The sorption degree becomes the smaller the higher is the surface polarity. The partially sulphonated copolymers may find an application in hemoperfusion.
Thermal chlorination of atactic polypropylene
Authors: Mukherjee A. K. , Patri M.
Published: April 2003

Chlorination of atactic polypropylene (APP) was thermally initiated and carried out in carbon tetrachloride (CCl4) solution. It was found that with the increase in dilution, there is an increase in the extent of chlorination, as measured in terms of % weight‐gain. The reason for this behaviour has been ascribed to a greater degree of opening up and mobility of APP chains thus increasing the accessibility of the replaceable sites to chlorine. The order of the reaction with respect to APP concentration was found to be 0.84, the overall activation energy (Er) being 5.29 kcal/mol. Increase in flow rate leads to an increase in the extent of chlorination and was found to be increasing linearly with a flow rate up to 1 l/h beyond which it levels off. IR spectroscopy and 13C‐NMR studies indicate the chlorination occurring in all the three types of replaceable H‐atoms in APP. The mechanism appears to be initial substitution of tertiary H‐atom by free chlorine radical followed subsequently by replacement of secondary and primary H‐atoms via either progressive substitution or elimination‐addition mechanism.
Effect of blending techniques on the curing of elastomer blends
Authors: Joseph R. , George K. E. , Samad E. A. A. , Francis D. J.
Published: April 2003

Compounding of styrene‐butadiene copolymer/polybutadiene, natural rubber/ethylene‐propylene‐diene terpolymer and natural rubber/butadiene‐acrylonitrile copolymer blends was done in three different ways and their curing behaviour and the tensile properties of the vulcanizates are compared.
Adsorption of phenols on carbonaceous adsorbents produced from phenol‐formaldehyde‐resin mixed with olive stones
Authors: Simitzis Johannis , Sfyrakis Johannis
Published: April 2003

Mixtures of phenol‐formaldehyde‐resin and pressed olive stones in a weight ratio of 20/80 were cured as small cylinders and then pyrolyzed. Some samples were also activated by steam. For these specimens and for two commercial activated carbons of laboratory or industrial uses the specific surface area, the structure, the adsorption properties, and the adsorption capacity were determined. The results indicate that the carbonaceous material produced by activation has greater values for the examined properties in comparison to the only pyrolyzed and the two commercial activated carbons, respectively. It was found that the Freundlich‐equation is valid for the adsorption of 4‐nitrophenol on all carbonaceous materials examined. The produced carbonaceous materials have different kinds of pores than the commercial activated carbons. The experimental results are explained with regard to the molecular dimensions of the adsorptive substances and the polarization effect of the substituents of the benzene ring.
Modification of starch by graft copolymerisation with methyl methacrylate
Authors: Egboh S. H. O. , Jinadu B.
Published: April 2003

Methyl methacrylate (MMA) was grafted onto starch using ceric ammonium nitrate as initiator. The graft copolymers were isolated by selective solvent extraction in a Soxhlet apparatus. The effects of reaction time, initiator concentration, temperature, monomer, and acid concentrations on the graft yields were investigated. A preliminary kinetic study of the graft copolymerisation reactions shows that they follow the conventional kinetic behaviour of free radical polymerisation.
Thermoplastic blends of physically crosslinked multiblock copolymers and copolymers with uniform grafts
Authors: Xie Hongquan Q. , Li Shirong R.
Published: April 2003

Two multiblock copolymers of styrene and propylene oxide and four acrylate copolymers with uniform polystyrene grafts were prepared and blended. The blends are melt processable and their properties varied from thermoplastic elastomers to toughened plastics. The relationship between mechanical properties and composition of the thermoplastic blends indicated that all the blends exhibited a synergism, which is probably due to the increase of miscibility between the components caused by the same physical crosslinks — the glassy domains aggregated from both the polystyrene grafts and polystyrene blocks. The synergistic effect seemed more evident when two different graft copolymers were blended together than when one multiblock copolymer was blended with one graft copolymer. In all cases a maximum tensile strength appeared at the blend with 90 wt.‐% of the component, possessing higher tensile strength and ultimate elongation.
Differential technique in thermally stimulated depolarization current measurements
Authors: Topić Mladen
Published: April 2003

Two modes of differential technique in thermally stimulated depolarization current (TSDC) measurements were applied on novolac phenol‐formaldehyde (NPF) resin in the temperature range which covered the dipolar α peak and the detrapping ρ peak. The first mode, already described in literature, was carried out with one polarized and one unpolarized sample connected serially. The comparison between the usual and differential run allowed one to discuss the mechanism of the charge release and the interference of the local electric fields with the depolarization processes. The other mode, proposed for the first time in the present work, was performed with two parallelly connected samples polarized oppositely. The dipolar peaks were cancelled while the detrapping peaks appeared as a difference. By performing the polarization with partial opposition it was possible to modulate the magnitude of the peaks. The proposed technique can be used as a method for distinguishing between dipolar and space charge peaks and for increasing the resolution in TSDC curves. The problem of extraction of the background currents of different origins by various differential methods is discussed.
Sorption von Silber an chlormethyliertem Polystyrol
Authors: Lieser K. H. , Hofmann B. , Stingl U.
Published: April 2003

Silberionen werden aus wäßrigen Lösungen an chlormethyliertem Polystyrol mit einem Verteilungskoeffizienten von etwa 100 ml/g gebunden, dagegen nicht an Polystyrol selbst. Dies spricht für eine direkte Wechselwirkung zwischen Ag+‐Ionen und den Chloratomen des chlormethylierten Polystyrols im Sinne der Bildung eines 1 : 1‐Komplexes. In Anwesenheit von 0,1 mol/1 Ammoniumionen werden im Bereich von pH 4 bis pH 6 etwas niedrigere Verteilungskoeffizienten gefunden, in Anwesenheit von 10−3 mol/l Na2S2O3 betragen sie nur etwa 6 ml/g. Aus Lösungen, die 1 mol/l NaCl oder 0,1 mol/l Na2S2O3 oder 10−3 mol/l NaCN enthalten, wird Silber nicht in meßbaren Mengen sorbiert, weil die Komplexbildung in Lösung überwiegt. Die experimentellen Ergebnisse und ihre Bedeutung für die Praxis werden diskutiert. In Trennsáulenversuchen wird die Abtrennung von Silberionen aus verdünnten Lösungen demonstriert.
Gemeinsame kondensation von bisphenol A, melamin und formaldehyd
Authors: Braun Dietrich , Vargha Viktoria
Published: April 2003

Die gemeinsame Kondensation von Bisphenol A, Melamin und Formaldehyd wurde mit Hilfe der Gelpermeationschromatographie, der 13C‐NMR‐Spektroskopie, IR‐Spektroskopie und Elementaranalyse untersucht. Wegen der hohen Kondensationsgeschwindigkeit verläuft die Reaktion in Gegenwart der drei Komponenten nur im Bereich von pH 6−10 kontrollierbar. Bei pH 6 und 7 überwigt die Kondensation zwischen Melamin und Formaldehyd. Mit steigendem pH‐Wert tritt die Reaktion von Bisphenol A mit Formaldehyd in den Vordergrund und führt bei pH 10 zu hochmolekularen Kondensationsprodukten.

Auf direkte Cokondensation hinweisende Methylenverknüpfungen zwischen der phenolischen Komponente und Melamin konnten nicht nachgewiesen werden. Die Kondensationsprodukte des Melamins bzw. des Bisphenol A mit Formaldehyd lassen sich aber nicht mehr vollständig aus den Reaktionsgemischen der Vorkondensation abtrennen, was dafür spricht, daß die Komponenten über Methylenetherbrücken und/oder intermolekularen Wasserstoffbrücken miteinander verknüpft sind.
Improved method for the preparation of ethylene adsorbent from copper(I) chloride and polystyrene resin having amino groups
Authors: Komiyama Makoto
Published: April 2003

Selective adsorbent for ethylene was prepared by stirring 101 mmol of copper(I) chloride and 10 g of a macroreticular type polystyrene resin having amino groups in 1:1 acetonitrile‐water mixture (80 cm3) for 2 h at 20°C, followed by the evaporation of the liquid at 20°C under 3 mmHg. The adsorbent exhibits much larger adsorption rate than the one prepared by the evaporation of the liquid at 80°C. In addition, desorption of the adsorbed ethylene for the present adsorbent is more efficient than the one obtained at 80°C. The adsorbing capacity for ethylene of the present adsorbent is 7.6 times as large as that for ethane, and the adsorbing capacity for nitrogen and hydrogen is none at 20°C under 1 atm. The significant effect of the preparation temperature on the adsorbing and desorbing abilities of the adsorbents is ascribed to difference in the porosities of the resins in the adsorbents. The present adsorbent has a large potential for the application to separation of ethylene from gas mixtures in industry.
Preparation of cyclodextrin membrane‐modified electrodes as sensor materials
Authors: Komiyama Makoto
Published: April 2003

Cyclodextrin membrane‐modified electrodes as sensor materials have been prepared by dipping platinum electrodes in the water suspensions of an oriented cyclodextrin polymer, followed by drying the polymer layers on the electrodes. The polymer is obtained by the solid‐liquid reaction between the crystal of cyclodextrin inclusion complex and hexamethylene diisocyanate in anisole. The thickness (2 − 80 μm) of the cyclodextrin membrane is satisfactorily controlled by changing the concentration of the water suspension of the polymer. The cyclodextrin membranemodified electrodes show a significant response to p‐nitrophenolate in water which is highly in contrast with no measurable response to o‐ and m‐nitrophenolates.