bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beiträe zur künstlichen bewitterung von PVC
Authors: Imhof Jörg , Haberleitner Robert 
Published: April 2003

AbstractDie künstliche Bewitterung von PVC‐Proben liefert nicht unter allen Bedingungen gleichartige Ergebnisse, wie im Freien. Gut bewährt haben sich die Xenotest‐Prüfungen bei weißen Fensterprofilmustern, sowie bei grau eingestellten Dachfolien. Die Bewitterung im QUV‐Gerät, unabhsngig von der Bestückunq, gibt eine wesentlich schnellere Veränderung als im Freien, wobei manche Effekte die im Freien auf‐treten, im QUV durch den Zeitraffereffekt nicht erkennbar werden.
Measurement of thermooxidative stability of polyolefins by isothermal differential thermal analysis
Authors: Kramer E. , Koppelmann J. , Dobrowsky J. 
Published: April 2003

AbstractIsothermal differential thermal analysis (DTA) is a well known method of testing thermooxidative stabilities of polyolefins. Oxidation induction times, measured up to 7000 hours and over a temperature range from 260°C to 130°C has been used to study the stability of polybutene‐1 in the melt state.The Arrhenius plots of DTA results show that straight line extrapolation from high to low temperatures is not possible. Thermoanalytically measured oxidation induction times and mechanical failure in oven ageing experiments agree well for polybutene‐1. Measurements of molecular weight and of mechanical properties of polybutene‐1 during the induction period of oven ageing experiments revealed that molecular weight and tensile properties are not sensitive indicators for the beginning of ageing. The state of deterioration can be estimated easier by measurement of residual lifetime in the isothermal DTA experiment. At high ageing temperatures the residual lifetime decreased linearly during the induction period, at ageing temperatures below 160°C the decrease of residual lifetime was found degressive.Finally the extraction of stabilizer by not water could be measured by isothermal DTA.
Transformation products of antioxidants: The role in stabilization mechanisms
Authors: Pospíšil Jan 
Published: April 2003

AbstractAntioxidants acting in polymers by chain‐breaking and hydroperoxide decomposing mechanisms are chemically transformed during the stabilization process as a consequence of trapping radicals R•, RO• or RO and/or reactivity with hydroperoxides. New chemical compounds with typical structures characteristic of the starting stabilizer are formed stepwise in the polymer mass. Most of these transformation products participate actively in consecutive steps of polymer degradation. Finally observed phenomena depend on the concentration of individual transformation products. Generally, autocooperative effects with starting stabilizers take place. Important data regarding properties of transformation products have been summarized.
Macromolecular stabilizers for polymers
Authors: Pospíšil Jan 
Published: April 2003

AbstractInherent 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

AbstractThe 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

AbstractComposite 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

AbstractQUALIFICATION OF HALS COMPOUNDSA 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

AbstractThe 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

AbstractSpecimens 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

AbstractThe 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

AbstractThe 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

AbstractPoly(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

AbstractThis 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

AbstractA 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

AbstractNew 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

AbstractFor 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

AbstractFür 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

AbstractThe 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

AbstractThe 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

AbstractIn 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

AbstractA 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

AbstractThe 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

AbstractAn 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

AbstractEs 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.