bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactive polymers, 51. The temperature behaviour of macroporous methacrylate sorbents
Authors: Hradil J. , Švec F. 
Published: April 2003

AbstractThe behaviour of macroporous methacrylate copolymers was investigated in the temperature range between 20 and 270°C. On the basis of retention of methyl alcohol and n‐decane a discontinuity at 40°C was recorded in all cases, interpreted by the increasing mobility of chains of surface layers of the polymer globules. This temperature agrees with the reported Tg value of poly(glycidyl methacrylate) and is independent of further substitution of the polymer chain with ionogenic groups. At 210–250°C depolymerization takes place; in the case of methacrylic acid copolymers cyclic anhydrides are formed, while in the case of esters alkyls are eliminated. Modified copolymers of 2,3‐dihydroxypropyl methacrylate with ionogenic groups are more stable thermally — the depolymerization proceeds under the same conditions to a smaller degree. Heating is connected with changes in the morphology of particles and pores, and also in the polarity of the polymers noticeable by the ratio of retentions of alcohols and paraffins and by the heat of dissolution.
Use of a design for the optimization of rheological properties of mixtures of lauryl acrylate‐stearyl methacrylate copolymers and a resinic ester
Authors: Perillon J. L. , Lanteri P. , Longeray R. , Dreux J. , Mathieu D. , Feneuille D. , Luu R. Phan Tan 
Published: April 2003

AbstractThe use of modern methods of building optimal experimental matrices is especially suitable for optimization of properties of polymeric compound mixtures. We show how, with a limited number of well defined experiments, we optimized rheological properties of a mixture of a lauryl acrylate‐stearyl methacrylate based copolymer and a resinic ester. The methodology is founded upon the determination of coefficients of a mathematical model postulated a priori, describing the property studied in function of variables of composition. This model is then used for forecasting purposes to determine simultaneously the copolymer composition and the ratio of different ingredients to obtain a mixture possessing the expected rheological properties. These mixtures were studied to elaborate a truly polyvalent cross‐country ski‐wax.
Photo‐induced polymerization of diethyleneglycol diacrylate in the presence of poly(methyl methacrylate). 3. Structure of the resulting polymer network
Authors: Braun D. , Gehrisch R. 
Published: April 2003

AbstractIn view of the manufacture of printing plates, films consisting of diethyleneglycol diacrylate and poly(methyl methacrylate) acting as a binding agent were cured by UV‐radiation. 9‐Phenyl acridine was used as the photoinitiator.During polymerization of the diacrylate a highly crosslinked polymer network is formed, having strong inhomogeneities concerning crosslink density. Because of incompatibility between poly(diethyleneglycol diacrylate) and poly(methyl methacrylate) phase separation occurs. However, entanglements of the PMMA chains with the polymer network cause the formation of a semi‐interpenetrating polymer network, thus preventing a two‐phase morphology with a typical domain structure.
Chemical heterogeneity of a partially modified dextran with ethyl carbonate groups
Authors: Arranz F. , Sánchez‐Chaves M. 
Published: April 2003

AbstractA sample of a partially modified dextran with ethyl carbonate groups was fractionated by cross‐fractionation. Two systems THF/hexane and DMF/0.5% aqueous NaCl were selected on the basis of cloud‐point determinations. The chemical composition distribution (CCD) and molecular weight distribution (MWD) curves were constructed from fractionation data. The chemical heterogeneity observed may be correlated with the pattern of reaction of dextran with ethyl chloroformate. The cumulative data were fitted by the two‐parameter MWD functions of Tung and of Wesslau.
Celluloseaktivierung: Geeignete behandlungen und strukturveränderungen
Authors: Focher B. , Sarto V. , Prati G. 
Published: April 2003

AbstractDie Passivität der Zellstoffe wird verschiedenen Faktoren zugeschrieben: Der Regularität der primären Struktur der Celluloseketten, deren steifer Beschaffenheit sowie deren Fähigkeit, während der Biosynthese die Gestalt von langen Bändern anzunehmen, welche in hohem Maße zur Bildung eines Wasserstoffbrückennetzes neigen. Das Ergebnis ist ein hochgeordnetes und dicht gepacktes Polymeres.Es wird über die Aktivierung von Zellstoffausschuß berichtet, der infolge Derivatisierungsreaktionen und biologischer Konversion als Rohstoff für die Herstellung von Erzeugnissen mit hohem Mehrwert verwendet werden kann.Die Auflösung der Abfallstoffe in nichtwäßrigen Lösungsmitteln wird als mögliche Alternative gegenüber den üblichen Verfahren zur Herstellung von Kunstfasern besprochen.Zwecks Aktivierung der Zellstoffe wurden physikalische (γ‐ und UV‐Bestrahlung), physikalisch‐chemische (Quellung, Entkristallisation und Auflösung) sowie chemische Verfahren (Copolymerisation) angewendet. Die Aktivierung der Zellstoffe wurde mittels Untersuchung ihrer Struktur (Röntgenstrukturanalyse, Festkörper‐NMR‐Spektroskopie, Doppelbrechung) ermittelt. Außerdem wurde die Geschwindigkeit der enzymatischen Hydrolyse bestimmt.
Anionic polymerization of isoprene with n‐butyllithium in n‐heptane in a continuous stirred tank reactor
Authors: Bandermann Friedhelm , Tappe Ralf 
Published: April 2003

AbstractThe living anionic polymerization of isoprene with n‐butyllithium in n‐heptane in a continuous stirred tank reactor was investigated. It is shown that there exist no multiple steady states for monomer and initiator conversions and for molecular weights at monomer and initiator feed concentrations >4 mol/1 and >0,02 mol/1, respectively, as postulated by Porter et al.6, but that the results may well be described by the known model of Sinn1.
Solvolyse‐ und umesterungsreaktionen bei der vernetzung von alkyd‐ und acrylatharzen mit melaminvernetzern
Authors: Pohl Horand Uwe , Traenckner Hans‐Joachim 
Published: April 2003

AbstractEin Acrylat‐ und unterschiedlich aufgebaute Alkydharze werden mit Melaminharz vernetzt. In Abhängigkeit von der Zeit werden bei einer Einbrenntemperatur von 130°C anwendungstechnische Eigenschaften, Quellgrade, relative IR‐Extinktionen und flüchtige Komponenten im Abgas quantitativ bestimmt und daraus der iso‐Butanolumsatz für die Fremd‐ und Selbstvernetzung berechnet. Zusätzlich zu den Vernetzungsreaktionen tritt beim Alkydharz eine Solvolyse‐ und beim Acrylatharz eine Umesterungsreaktion durch Reaktion der Estergruppen mit dem aus dem Melaminharz abgespaltenen iso‐Butanol auf. Die Solvolyse wird durch Untersuchung von spezifischen Spaltprodukten mittels IR, GPC und GC/MS abgesichert. Ein Reaktionsweg zum Ablauf der Solvolyse wird vorgeschlagen.
Morphologie und technologische eigenschaften von polycarbonat/ABS‐mischungen
Authors: Weber Gunter , Schoeps Jochen 
Published: April 2003

AbstractPC/ABS‐Mischungen stellen ein ternäres Mehrkomponentensystem aus Bisphenol A‐PC, SAN und einem SAN gepfropften Polybutadienkautschuk dar. Die Morphologie der PC/ABS‐Mischungen wurde in Abhängigkeit vom PC:SAN‐Mengenverhältnis und von der Schmelzentemperatur bei der Verarbeitung mit Hilfe der Elektronenmikroskopie untersucht. Der Verteilungszustand der Elastomerkomponente und die partielle Mischbarkeit der Thermoplastkomponenten beeinflussen die technologischen Eigenschaften der PC/ABS‐Mischungen. Die Wärmeformbeständigkeit hängt von der Zusammensetzung der Mischungen ab und nimmt mit steigendem PC‐Anteil zu. Für ein hohes Kerbschlagzähigkeitsniveau sind eine mit PC angereicherte SAN‐Mischphase sowie eine gleichmäßige Dispergierung der Pfropfkautschukpartikel notwendig. Die Mischphasenbildung hängt von der Zusammensetzung und der Verarbeitungstemperatur der Mischungen ab. Steigende Verarbeitungstemperaturen führen zu einer PC/SAN‐Entmischung. Der Einfluß der Verarbeitungstemperatur auf die Zähigkeit ist bei denjenigen PC/ABS‐Mischungen gering, in denen die PC‐Komponente eindeutig die Matrix darstellt.
Simulated lightning tests on baymetex C protected graphite‐epoxy laminates
Authors: Ebneth Harold 
Published: April 2003

AbstractHighly nickel‐coated graphite fabrics will provide adequate composite structure protection from zone 1 A and 2 A lightning strikes, as simulated lightning tests showed. The coating level used will depend on the damage tolerance and structural make‐up of the part to be protected. Mechanical tests show that the nickel‐coated graphite fabric has a positive effect in compression of the panels. The compressive strength is about 25% better than the panel with a non‐metallized fabric ply.
Effect of copolymers modifying PVC on its physical and mechanical properties and its UV‐radiation resistance. v. photooxidation of PVC in films containing mma/ma, vc/vac, mbs or abs
Authors: Kamińska A. , Kaczmarek H. 
Published: April 2003

AbstractPhotooxidation of PVC caused by 253.7 nm wavelength UV‐radiation in pure and modified PVC films has been investigated. The IR spectra analysis pointed out that the presence of modifying copolymers ABS, MBS, MMA/MA or VC/VAC in PVC films causes the increase of the efficiency of photooxidative processes which lead to the formation of hydroxy groups. ABS and MBS cause also the increase of the efficiency of these reactions which lead to the formation of carbonyl groups, while MMA/MA hampers these processes. VC/VAC has no definite influence on their course. With the increase of the copolymer content (1 – 10%) in PVC films, an increase of their influence on photooxidation was observed.
Einfluß von imidhydantoinpolymeren auf den reststrom modifizierter metalloxid‐halbleitertransistoren
Authors: Yokoyama Takashi , Kinjo Noriyuki , Wakashima Yoshiaki 
Published: April 2003

AbstractCopolymere, die Hydantoin‐ und Imidgruppen enthielten, wurden hergestellt und auf die Oberfläche von MOSFET (Metalloxid‐Halbleitereffekt‐Transistor) aufgetragen, um den Einfluß des Copolymeren auf Halbleiteranlagen darzustellen. Der Einfluß der Polymeren auf den Reststrom der Anordnung wurde hinsichtlich des Gehalts an Verunreinigungen, der Erweichungstemperatur, der Zusammensetzung etc. untersucht. Es wurde beobachtet, daß der Reststrom bei Polymeren, die nur Imidgruppen enthielten, mit steigender Erweichungstemperatur sowie bei den Copolymeren mit steigendem Hydantoingruppengehalt ansteigt.
Temperature dependence of surface tension of poly(vinyl chloride)
Authors: Pigłowski Jacek 
Published: April 2003

AbstractThe thermal dependence of the surface tension of poly(vinyl chloride) (PVC) containing typical additives was determined below the glass transition temperature. From the results, the surface tension of PVC melts was evaluated and possible differences between the real value and estimate are discussed. It is suggested that the surface tension does not affect the wall‐slipping properties of PVC melts.
Processibility of starch‐graft‐polyacrylonitrile copolymers
Authors: Patel A. R. , Patel M. R. , Patel K. C. , Patel R. D. 
Published: April 2003

AbstractStarch‐graft‐polyacrylonitrile (S‐g‐PAN) has been prepared from granular starch of common millet (Penicum miliaceum, L) and its processibility has been examined using the Brabender Plasticorder. Glycerine, a known plasticizer for starch does not work as plasticizer for S‐g‐PAN. A mixture of 1 : 1 starch : S‐g‐PAN and 25% glycerine can be processed and a film can be extruded. The strength of the film was less than that of pure starch. The film prepared from the mixed graft copolymer of S‐g‐PAN and S‐g‐PMA had high tensile strength. The data on flow activation energy obtained from the torque‐rheometer are also reported.
Zur variierung des diethylenglykolgehalts von PETP bei dessen synthese aus dimethylterephthalat und ethylenglykol
Authors: Mössner Wolfgang , Vollmert Bruno 
Published: April 2003

AbstractDie Kontrolle über den Diethylenglykol (DEG)‐Gehalt ist sowohl bei der großtechnischen als auch bei der Labor‐Synthese von Polyethylenterephthalat (PETP) von Bedeutung. Im Rahmen der Reaktionsführung wurde die Synthese in drei Abschnitte unterteilt und die Abhängigkeit des DEG‐Gehalts von deren Dauer untersucht. Es wurden Präparate mit DEG‐Gehalten zwischen 2,6 und 10,4 mol‐% dargestellt. Die Ergebnisse werden in Zusammenhang mit den für die DEG‐Bildung in der Literatur vorgeschlagenen Reaktionen diskutiert.
Reactive polymers, 53. separation of platinum metals on the copolymer of glycidyl methacrylate—ethylene dimethacrylate modified with ethylenediamine
Authors: Švec F. , Kálalová E. , Kálal J. 
Published: April 2003

AbstractA macroporous copolymer of glycidyl methacrylate — ethylene dimethacrylate, modified with ethylenediamine, is able to bind only ionic particles (PdCl4)2− from strongly acid solutions containing palladium‐ and copper salts. After washing the sorbent, the metal can be quantitatively desorbed with a concentrated hydrochloric acid solution. The procedure can be utilized for the regeneration of inactive palladium catalysts in industry. Moreover, using the same sorbent and the same principles, it is possible to separate a mixture of platinum metals in acid solutions as (RhCl6)3−, (PtCl6)2−, and (PdCl4)2− by eluting them with a solution of hydrochloric or nitric acid with increasing concentration, the efficiency being 100%.
The effectiveness of radiation as a function of angle of incidence on the surface of specimen
Authors: Trubiroha Peter 
Published: April 2003

AbstractThe effectiveness of radiation as a function of angle of incidence on polymer films has been calculated and examined by exposure tests. Theoretical considerations for different coefficients of transmission and different indices of refraction show that the radiation with normal incidence is the most effective. However, it is concluded that a photoreceptor which is cosine corrected for a solid angle of 2π sr does undervalue radiation with oblique incidence. The exposure tests confirm these theoretical results but also show an additional unexplained peak of effectiveness for radiation with angles of incidence of about 20°.
Formation and role of ester groups in the thermal stabilization of PVC
Authors: Lévai Gy. , Ocskay Gy. , Nyitrai Zs. 
Published: April 2003

AbstractThe stabilizing action of calcium‐zinc stearate and pentaerythritol systems in PVC cannot only be ascribed to the ability of binding hydrogen chloride, but also to the replacement of labile chlorine atoms of the PVC chain by stearate groups. In this way the growth of the polyene sequences is inhibited. On the other hand sufficient amounts of pentaerythritol and calcium stearate effectively inhibit the detrimental catalytic action of zinc chloride formed.A mathematical equation was deduced based on this mechanism, which satisfactorily describes the correlations among the induction period, the stabilizer concentration and the ester groups formed during thermal ageing.
Variations in some of the properties of PVC sheets during natural and artificial ageing
Authors: Gantcheva T. , Marinova A. , Genova P. 
Published: April 2003

AbstractWe have investigated variations in mechanical properties such as tensile strength and specific elongation as well as the variations in electrical properties such as the dielectric loss angle, permitivity and surface resistivity of PVC sheets of various thicknesses exposed during 24 months in weathering and up to 400 h in a Xenotest‐1200. Using the test data, an evaluation of the influence of the scale coefficient during ageing was achieved. The test data showed that lower variations in the investigated properties were seen in the case of the thicker sheets.After various ageing periods a correlation between the surface roughness, mechanical and electrical properties could be seen. More important variations could be seen during the ageing period ranging from 50 h to 6 months.Speculations were made about the reasons causing the variations observed in the properties of PVC sheets during ageing.
Diffusion und alterung
Authors: Wurster T. , Franck A. , Eyerer P. 
Published: April 2003

AbstractDie Rückdiffusion eines Testmediums (hier: Methan) nach unvollständiger Sorption erfordert ‐ im Vergleich zur Messung der Permeation ‐ eine wesentlich kürzere Priifzeit. Sie kann Veranderungen vorzugsweise in den oberflächennahen Bereichen anzeigen. Bei Polyethylen (PE) verringerte sich die Rückdiffusion nach Bewitterung. Dieser Effekt wird auf erhöhte Kristallinität zurückgeführt; denn bei der Alterung erhöht sich die dafür signifikante Dichte. Auch wenn dieser Kunststoff mit energiereichen Strahlen behandelt wird, vermindert sich die Rückdiffusion. Hier überlagern sich Wirkungen der Alterung (s.o.) und der Vernetzung. Bei allen Untersuchungen wurde die Trägergasmethode mit der Pneumatik und dem Detektor (FID) eines Gaschromatographen angewendet. Daraus ergeben sich empfindliche, spezifische Messungen bei einfachem apparativem Aufbau und die Möglichkeit zur zerstörungsfreien Kunststoffprüfung. Die Details der Meßzelle werden erläutert.
UV‐stabilization of ABS with sterically hindered amines. Results of an ESR‐study
Authors: Loelinger Hans , Gilg Bernard 
Published: April 2003

AbstractABS polymers have been limited in outdoor applications due to their poor weathering characteristics. On exposure to light the polybutadiene phase on the exposed side of the sample is photooxidized resulting in loss of impact strength and discoloration. We have found that the combination of a hindered amine light stabilizer (HALS) and a benzotriazole UV absorber dramatically outperforms either component alone. This L‐S blend provides a level of impact strength retention many times that of unstabilized ABS and also protects the polymer from discoloration. The present study describes the results of an E.S.R. investigation intented to explain the synergistic effect between HALS and benzotriazole UV absorber. Since the photostabilizing effect of HALS is associated with the reaction of the nitroxide radicals formed upon irradiation, the concentration of these radicals, as a function of light exposure time, was determined. Two types of . radicals were found. First, a broad . signal with an anisotropic hyperfine nitrogen interaction, was detected. This signal is characteristic of the . radicals localized in the SAN matrix. Second, a narrow . signal with an isotropic hyperfine nitrogen interaction, corresponding to nitroxide radicals localized in the polybutadiene phase, was also found. The . concentration in the SAN matrix and in the polybutadiene phase could, therefore, be determined separetely, as a function of light exposure time.In both phases, a maximum of . is observed after approximately 50 hours exposures. However, the maximum . concentration is ten times higher in the polybutadiene phase of ABS stabilized with a blend 0,5% HALS/0,5% UV Absorber than in the BR phase of an ABS containing only 0,5% HALS. On the other hand, there is only a slight increase of . radicals in the SAN phase when 0,5% UV absorber is added on top of 0,5% HALS. A comparable effect is observed in the polybutadiene phase when 8% titanium dioxide is added to an ABS stabilized with 0,5% HALS.Since the polybutadiene phase is the most sensitive toward photooxidative degradation, these results rationalize the observed synergistic effect of the combinations of HALS/Benzotriazole UV absorber.
Aspects of the stabilization mechanisms of phenolic antioxidants in polyolefins
Authors: Gugumus Francois 
Published: April 2003

AbstractKinetic factors as well as physical parameters such as volatility are often considered in explaining the different antioxidant efficiencies of monophenols and polyphenols. The objective of this work is to examine these factors in comparing the behavior of different sterically hindered phenols in processing stabilization and long term heat aging. For this purpose, mainly data relative to phenols of the 3,5‐di‐tert.butyl‐4‐hydroxyphenyl propionate type in polypropylene are examined. It is found that the stabilizing efficiency of phenolic antioxidants of the propionate type in processing of polypropylene is a function of the concentration of phenolic groups, regardless of the number of phenolic groups attached to a single molecule.To explain the superiority of the polyphenols over the monophenol in long term heat aging, a reaction model involving chemical as well as physical aspects is proposed.The kinetics of stabilization are applied to the interpretation of oven aging data. For this purpose, two concepts are considered, the well‐known critical antioxidant concentration and another one, the critical oxidation level. It is found that the results are best accounted for by the latter.
Study of photooxidative processes during the induction period
Authors: Tüdós Ferenc , Kelen Tibor , Bálint Gabriella 
Published: April 2003

AbstractVarious processes taking place during the induction period of the change of a property accepted as a measure of the photostability, were investigated in polypropylene, PVC and EPDM rubber.In polypropylene containing stabilizer, changes in stabilizer concentration and in molecular mass could be detected before the end of the induction period of the carbonyl formation. Kinetics and other characteristics of these changes depend on the type and amount of the stabilizers applied.Hydrogen chloride evolution in UV‐irradiated PVC is accompanied also by carbonyl formation. In the presence of a metal soap stabilizer, carbonyl formation can be detected even during the induction period of hydrogen chloride evolution.In case of EPOM rubber compounds, the study of thermal stability gives information about the changes in the first period of photodegradation when mechanical stability still remains unchanged.
Wirksamkeit sterisch gehinderter amine bei anspruchsvollen applikationen von polypropylen
Authors: Pavol Čaučik , Marta Považancová , Júalius Durmis , Milan Karvaš 
Published: April 2003

AbstractThe influence of some types of antioxidants on the efficiency of low molecular hindered amine light stabilizers (HALS) has been investigated in a comparison with the behaving of high molecular HALS. Most of the antioxidants used exhibit favourable influence. Convenience of both low and high molecular HALS in compounds depends on the character of the stabilised product and the technological conditions for its production.
Artificial ageing of low density polyethylene film containing chemically bound UV ‐ stabilizer
Authors: Misǎk M. Mlinac , Ranogajec F. , Fleš D. , Jovanović D. 
Published: April 2003

AbstractThis paper deals with photostabilization of low density polyethylene films (LDPE) grafted with the UV‐stabilizer 2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxy‐propoxy) benzophenone (HMB). The influence of grafting yield and the other grafting conditions upon photostabilization efficiency of LDPE films were then studied. The chemically bound monomer (HMB) was localized mainly near the surface of an LDPE film.The grafted LDPE film was exposed to an ultraviolet radiation source, and the degree of oxidation and other photooxidative changes were determined by transmission IR and ATR IR spectroscopy. Experimental results show that radiation grafting of a UV‐stabilizer upon LDPE films is an efficient photostabilization method.
On the mechanical ageing of polymers
Authors: Vassileva S. , Natov M. 
Published: April 2003

AbstractThe breaking of the polymers under operational conditions is a result of the simultaneous action of oxygen, humidity, and mechanical stresses. The mechanical ageing of a longtime life of the model polymer materials was investigated in function of the applied static stress. It was established that the time required for the breaking of the model polymers varies regularly as a function of the magnitude of the applied force. Expressed graphically, this dependence is S‐shaped. The action of the mechanical stress alters the tension of the valence bonds, hence also the vibration frequency, and consequently the energy term in the Arrhenius equation. The assumption that mechanical stress alters only the activation energy of the breaking processes does not lead to a dependence between longtime life and stress which corresponds to actual observations.