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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 209-218 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An industrial semibatch nylon 6 reactor has been optimized using a one-variable (at a time) search technique. The vapor release rate from the reactor and the final monomer conversion have been constrained to lie very close to the values currently present. The degree of polymerization of the product is , similarly, constrained to lie at a value of 152. The optimal pressure histories for two values of the jacket fluid temperature, Tj, have been evaluated using two objective functions, I1 and I3, namely, the total reaction time (I1 = tf) and the concentration of the cyclic dimer (I3 = [C2]f) in the product. It is observed that as Tj is increased from 270 to 280°C, I1 improves while I3 worsens simultaneously. This suggests that these two optimal points lie on the Pareto set for the two-objective function problem. © 1995 John Wiley & Sons, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1184-1189 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Application of shear is found to increase the rate of solution polymerization of acrylonitrile in N,N-dimethyl formamide (DMF) initiated by benzoyl peroxide by as much as 400 percent of the value in absence of shear. The solvent DMF acts as an inert and maintains a homogeneous reaction mass during the entire course of polymerization. To study the effect of shear systematically, a special dilatometer has been constructed such that a constant shear rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^. $\end{document} could be applied to the reaction mass. The rule of solution polymerization has been measured under the variation of \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \gamma \limits^. $\end{document} and monomer concentration in the system. The measurements of induction time on the addition of a strong inhibitor, hydroquinone, reveal that the increase in the rate of polymerization with shear rate can be largely attributed to the change in the initiator efficiency. As a further confirmation of the above hypothesis, the decomposition of benzoyl peroxide in nitrobenzene at 80°C was measured and was found to increase significantly on application of shear. This confirms the importance of mass-transfer resistance in removal of CO2, and the increase in the rate of polymerization of acrylonitrile occurs because the decomposition of benzoyloxy radicals is favored in the forward direction. Since the polymerization of acrylonitrile is preferentially initiated by phenyl radicals, the rate of polymerization is found to increase.
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  • 3
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Temperaturabhängigkeit des dielektrischen Verhaltens von drei vernetzten Polyesterharzen, basierend auf der Kondensation von Chlormethylacetat mit Bisphenol-A (I), 2,2-Di-(4-hydroxy-3,5-dichlorphenyl)-propan (II) und 2,2-Di-(4-hydroxy-3,5-dibromphenyl)-propan (III), wurde im Mikrowellenbereich bei einer Wellenlänge von 3,21 cm untersucht. Die Dielektrizitätskonstanten dieser Polyester sind 2,93 (I), 2,914 (II) und 2,77 (III); sie ändern sich im Temperaturbereich von 30 bis 85°C nicht. Die Erniedrigung der Dielektrizitätskonstante durch Einbau von 2,2-Di-(4-hydroxy-3,5-dichlorphenyl)-propan und 2,2-Di-(4-hydroxy-3,5-dibromphenyl)-propan in die Polyesterkette wird auf die Abnahme an Ester-und Äthergruppen pro Gewichtsanteil an gehärtetem Polyester zurückgeführt. Der Verlustfaktor des Polyesterharzes aus Biphenol-A ist bei 55 °C am größten ; die Relaxationszeit dieses Polyesters beträgt 1 bis 7 · 10-11 sec bei 55°C. Dieses Ergebnis kann der freien Drehbarkeit der Ätherbindung zugeschrieben werden, die durch Abwesenheit von Halogen in den 3,5-Positionen des Bisphenols-A mög-lich ist. Es kann ferner auf der Abwesenheit von sekundären Kräften zwischen den Ketten wegen der voluminösen p-Phenylengruppen in der Polyesterkette und der Vernetzung durch voluminöse Moleküle wie Styrol beruhen. Im Falle der chlorierten und bromierten Polyester sind Bewegungen um die Äther- und Esterbindungen schwierig. Der Verlustfaktor des chlorierten Bisphenol-A-Polyesters variiert weniger mit der Temperatur als der des bromierten Polyesters. Das kann an im Brompolyester vorkommendem Homopolystyrol oder an großen Vernetzungsbrük-ken aus Polystyrol liegen.Diese Ergebnisse werden auch durch Hydrolyseuntersuchungen der Grundharze und durch den “heat distortion point” der vernetzten Polyester gestützt.
    Notes: The variation of dielectric behaviour with temperature of three crosslinked polyester resins based on the condensates of chloro-methyl acetate and bisphenol-A, 2,2-di-(4-hydroxy 3,5-dichloro phenyl) propane and 2,2-di-(4-hydroxy 3,5-dibromo phenyl) propane were studied in the microwave frequency region at wave length 3.21 cm. The dielectric constants of these polyesters are 2.93, 2.91 and 2.77 respectively and do not change with temperature in the 30-85°C region. The decrease in dielectric constant after incorporating 2,2-di-(4-hydroxy 3,5-dichloro phenyl) propane and 2,2-di-(4-hydroxy 3,5-dibromo phenyl) propane in the polyester chain is attributed to the decrease in the number of ester and ether groups in the polyester chain per unit weight of the cured polyesters. It is found that the loss factor for bisphenol-A based polyester resin is maximum at 55°C and the relaxation time of this polyester is 1-7 · 10-11 sec at 55°C. It can be assigned to the free motion of ether linkages due to the absence of halide groups at 3,5 position of bisphenol-A incorporated in the polyester chain. This can also be attributed to the absence of secondary forces between the chains due to the presence of bulky p-phenylene groups in the polyester chain and crosslinking by bulky molecules like styrene. In case of chlorinated and brominated polyesters, the motion about ether and ester linkages is difficult. The chlorinated bisphenol-A polyester has less variation in loss factor as compared to that of bromo polyester. It may be due to the homo polystyrene or large polystyrene segments present in bromo polyester.These results are also supported by the studies on hydrolytic stability of their base resins and by the heat distortion point of the crosslinked polyesters.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 44 (1975), S. 47-65 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Sieben Polyester mit verschiedenem Halogengehalt wurden hinsichtlich der Kinetik ihres Abbaus sowie ihrer flammhemmenden Wirkung untersucht. Davon hatten die Polyester Nr. 1,2,3 und 4 ein Molverhältnis von Chlorendischer Säure (Diels-Alder-Addukt aus perchloriertem Cyclopentadien und Maleinsäureanhydrid) zu Isophthalsäure von 0.25, 0.67, 1.5 und 4.0. Die Polyester 5, 6 und 7 basierten auf Dimethyl-di-(p-oxyacetoxymethylphenyl)-methan, Dimethyl-di-(3,5-dichlor-4-oxyacetoxymethylphenyl)-methan und Dimethyl-di-(3,5-dibrom-4-oxyacetoxymethylphenyl)-methan.Die Untersuchungen wurden mittels thermogravimetrischer Analyse (TGA), Differentialthermoanalyse (DTA), IR-Spektroskopie und Glühstab-Analyse ausgeführt. Die thermische Stabilität dieser Polyester nahm in der folgenden Reihenfolge ab: 5 〉 6 〉 7 〉 1 〉 2 〉 3 〉 4, wenn man die Schwellentemperatur als Maß für die thermische Stabilität betrachtet. Die aus TGA-Kurven ermittelte Temperatur bei 50-proz. Gewichtsverlust stützt dies zu einem gewissen Ausmaß. Die Untersuchungen ergaben ferner einen zweistufigen Abbau. Die erste Stufe erstreckte sich von 250-450°C, die zweite von 450-600°C. Bei der ersten Stufe verengt sich der Temperaturbereich für den Abbau mit ansteigendem Halogengehalt. Bromierung ist wirkungsvoller als Chlorierung. Die Aktivierungsenergie für den Abbau dieser Polyester zeigte den selben Trend wie die thermische Stabilität. Aber die Flammhemmung ist etwa umgekehrt zur thermischen Stabilität. Diese Untersuchungen bestätigen auch einen cyclischen Mechanismus für die Flammhemmung.
    Notes: Seven polyesters having different amounts of halogen were studied for kientics of degradation and fire retardant efficiency. Out of them, the polyesters number 1, 2, 3, and 4 had the molar ratios of chlorendic acid to isophthalic acid of 0.25, 0.67, 1.5, and 4.0 respectively. The polyesters number 5, 6, and 7 were based on dimethyl-di-(p-oxyacetoxymethylphenyl)-methane, dimethyl-di-(3,5-dichloro-4-oxyacetoxymethylphenyl) methane and dimethyl-di-(3,5-dibromo-4-oxyacetoxymethylphenyl)-methane respectively. These studies were done with the help of thermogravimetric analysis (TGA), differential thermal analysis (DTA), infra-red spectroscopy and glow rod apparatus. The thermal stability of these polyesters decreased in the following order: 5 〉 6 〉 7 〉 1 〉 2 〉 3 〉 4, taking the threshold temperature as a measure of the thermal stability. The 50% weight loss temperature determined from TGA curves supported this to some extent. These studies further revealed that these polyesters degrade in two stages. The first stage of degradation ranged from 250-450°C. The second stage of degradation is in the range of 450-600°C. In the first stage, the range of temperature for degradation is constricted by increasing the halogen content. Bromination is more effective than chlorination. The activation energy for degradation of these polyesters showed the same trend as the thermal stability. But the flame resistance is somewhat in the reverse order of thermal stability. These studies also confirm a cyclic mechanism for flame retardancy.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 507-520 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A theoretical model is developed for the effect of segmental diffusion on reversible step growth polymerization. This model is an adaptation of the molecular model of Chiu et al. for characterizing the Trommsdorff effect in free-radical polymerization. The model is applied to the specific case of solid-state polymerization of spherical pellets of nylon 6. The results of the simulation are found to show qualitative trends as found by Gaymans et al. experimentally. The parameters of the model are curve fitted to their data using an optimal parameter estimation computer code. It is found that the optimal values of the parameters, which can be independently measured, are quite close to the values reported in the literature. The effect of varying the individual parameters on the progress of polymerization is also studied.
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  • 6
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Hydroxyl terminated natural rubber (HTNR) was prepared by the depolymerization of masticated natural rubber in the presence of H2O2 in toluene. Probable mechanisms leading to the formation of side reaction products are proposed based on the analytical data. A comparative study of some formulation variables was made for their effect in improving the flow characteristics and mechanical properties of an aluminized polyurethane (PU) propellant system based on HTNR. This PU system has also been compared for its theoretical performance characteristics with some other state-of-the-art systems.
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The relationship between the microstructure and corresponding mechanical properties developed during injection molding of blends containing a liquid crystalline polymer (LCP) as the minor component and an engineering polymer system has been studied. A wholly aromatic copolyester LCP (Vectra A950) was melt blended at different compositions with a thermoplastic matrix consisting of a commercial compatibilized blend of polyamide-6 and ABS (Triax 1180). These blends were prepared under two different sets of injection molding conditions. In the first case, a higher melt temperature, higher barrel temperature, lower injection pressure, lower mold temperature, and shorter residence time in the mold were used during injection molding, as compared with the second case. The mechanical properties of the blends were superior to those of the base polymer. In the second case, the resulting injection-molded specimens had a distinct skin-core morphology where elongated fibrils of LCP constituted the skin layer. The mechanical properties of the blends processed under the second set of processing conditions were superior to those of the first, though the trends in both cases were the same. To study the effects of process variables the 15% LCP blend and the second set of processing conditions were taken as the base. Samples were injection-molded by varying one parameter at a time. It was seen that the properties of the blend were increased by maintaining a lower barrel temperature, greater injection pressure, lower injection speed, higher mold temperature, and a greater residence time in the heated mold. Thus it was found that the processing conditions played a vital role in determining the mechanical properties and morphology of the polyblends. © 1996 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 64 (1977), S. 169-177 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ungesättigte Polyester aus Bisphenol-A bzw. dimethyl-di-3,5-dichlor-4-hydroxyphenyl-methan und Dimethyl-di-3,5-dibrom-4-hydroxyphenyl-methan wurden einer 18 Mrad Dosis aus einer Co60-Quelle ausgesetze. Untersuchungen des Halogengehalts, der Säurezahl, der Grenzviskosität und des Isomerengehalts vor und nach der Bestrahlung deuten auf eine verhältnismäßig hohe Strahlungsbeständigkeit hin.
    Notes: Unsaturated polyesters made by using bisphenol-A, dimethyl-di-(3,5-dichloro-4-hydroxyphenyl) methane, and dimethyl-di-(3,5-dibromo-4-hydroxyphenyl) methane, respectively, were exposed to a does of 18 Mrad from a Co60 source. On irradiation, there is very little change in the halogen content in the polyesters, determined by Parr Bomb method. This indicates their stability to γ-irradiation. Study of acid value, intrinsic viscosity and isomerisation of these polyesters before and after irradiation corroborates to some extent that incorporation of aromatic rings in the polyester chain stabilises it against radiation. Minor changes in acid values and intrinsic viscosities are discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 139 (1970), S. 103-113 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Maleinsäure/Fumarsäure-Isomerisierung in ungesättigten Polyestern konnte mittels IR-Spektren untersucht werden, ohne daß Modellverbindungen notwendig waren. Hierzu diente die Lösung folgender Gleichung für zwei verschiedene Polyester oder für einen Polyester bei zwei Konzentrationen, um die molaren dekadischen Extinktionskoeffizienten für den Maleinsäurebaustein bei 675 cm-1 und für den Fumarsäurebaustein bei 980 cm-1 zu ermitteln Die Prozentgehalte an Malein- und Fumarsäurebausteinen sind durch folgende Gleichungen gegeben: Wegen sterischer Hinderung erscheint die CH-Schwingung (out of plane) für Maleinsaure bei der etwas niedrigeren Frequenz 675 cm-1. Steigendes Verhältnis Maleinsäure zu gesättigter Säure im Polyester vermehrte die Inversion von Maleinsäure zu Fumarsäure wegen der vergrößerten Knäuelung und Erhöhung der Knäueldichte. Das gleiche zeigte sich bei Polyestern aus Phthälsaureanhydrid wegen der o-ständigen Carboxylgruppe und im Vergleich mit Adipinsäure und Isophthalsäure, denn die Isomerisierung von Maleinzu Fumarsäure war in Polyestern aus Phthalsäureanhydrid größer als bei jenen aus Isophthalsäure und Adipinsäure. Enthielten die Polyester auch Bisphenol-A-bausteine, so war die Isomerisierung gering, weil die Phenylbausteine eine geringere Knäuelung verursachen. Dagegen stieg der Isomerisierungsgrad bei Polyestern mit 2.2-Di-(4-hydroxy-3.5-dibromphenyl)-propan und 2.2-Di-(4-hydroxy-3.5-dichlorphenyl)-propan wegen der gro̊eren sterischen Hinderung. Jedoch ist es auch möglich, daß geringe, wahrend der Polykondensation frei gewordene Halogenmengen die Isomerisierung katalysierten. Das gleiche wurde mit Polyestern, die auch Chlorendicsäure (1.4.5.6.7.7-Hexachlor-5-norbornen-2.3-dicarbonsäure) enthielten, beobachtet ; der Grad der Isomerisierung stieg mit wachsendem Säureanteil. Die stärkere Katalyse wird auf die kleinere Bindungsenergie nicht aromatisch gebundenen Halogens zurückgeführt.
    Notes: For study of maleate/fumarate isomerisation in unsaturated polyesters infrared technique was used without using model compounds. This was done by solving the following equation for two different polyesters or one polyester with two concentrations for the molar extinction coefficients at 675 cm-1 for maleate and 980 cm-1 for fumarate. Percentages of maleate and fumarate are given by following equations: The out of plane vibration of CH for maleate appeared at slightly lower frequency, i.e. at 675 cm-1 due to steric hindrance. It was noted that the increase of the ratio of maleate to saturated acid in the polyester enhances the conversion from maleate to fumarate due to coiling tendency of the chain and causing steric compression. This tendency was also shown by phthalic anhydride based polyesters due to ortho carboxylic group compared with adipic acid and isophthalic acid. It is evident from more conversion from maleate to fumarate in case of phthalic anhydride based polyesters than that of isophthalic acid and adipic acid based polyesters.In case of bisphenol-A based polyesters, low conversion from maleate to fumarate took place, because of less coiling of between the two segments of the chain which are phenyl groups associated through carboxyl group of maleate. Conversion was more pronounced in polyesters based on 2.2-di-(4-hydroxy-3.5-dibromophenyl) propane and 2.2-di-(4-hydroxy-3.5-dichlorophenyl)-propane due to steric hindrance. An alternative explanation for more conversion from maleate to fumarate in case of halogenated bisphenol based polyesters may be due to catalysing effect of the small amount of halogen evolved during polycondensation. Similarly in chlorendic acid (1.4.5.6.7.7-hexachloro-5-norbornene-2.3-dicarboxylic acid) based polyesters, the isomerisation from maleate to fumarate increases as the chlorendic acid content in the polyester increases. In this case catalysing effect of chlorine evolved during polycondensation may be more effective because dissociation of halogen from non-aromatic system is easier than from aromatic system.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 423 (1976), S. 91-96 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über einige Zirkonium (IV)-oxid-VerbindungenEinige neue Zirlconium(IV)-oxid-Komplexe, ZrO(An)2, ZrO(Gly)2, ZrO(HSal)2, ZrO(HPth)2, ZrO(Pic)2(HPic)2 und ZrO(Quin)2(HQuin)2 wurden dargestellt durch Reaktion von ZrO(CH3C00)2CH3COOH mit Anthranilsäure (HAn), Glycin (HGly), Salicylsäure (H2Sal), Phthalsäure (H2Pth), Picolinsänre (HPic) und 8-Oxychinolin (HQuin). Ihre wichtigsten IR-Banden und, soweit möglich, molaren Leitfähigkeiten und Molekulargewichte werden mitgeteilt.
    Notes: Some new oxozirconium(IV) complexes: ZrO(An)2, ZrO(Gly)2, ZrO(HSal)2, ZrO(HPth)2, ZrO(Pic)2(HPic)2, and ZrO(Quin)2(H Quin)2 have been isolated from the reactions of ZrO(CH3COO)2CH3COOH with anthranilic acid (HAn), glycine (HGly), salicylic acid (H2Sal), phthalic acid (H2Pth), picolinic acid (HPic), and 8-quinolinol (HQuin) respectively. Their important infrared bands and wherever possible molar conductance and molecular weight have been reported.
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