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  • Polymer and Materials Science  (6)
  • HPLC
  • 1975-1979  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 69 (1978), S. 189-210 
    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: The solution instability (also called ageing or degradation) of high purity polyacrylamides(PAAm) was examined for a number of different molecular weights. This instability set in by a decrease of the solution viscosity and of [η] depending on time with simultaneous loss of flocculation activity.The instability appears only at molecular weights M̄ 〉 1,5 mill. in aqueous solutions; in formamide and ethyleneglycole PAAm-solutions however are stable. The viscosity loss was observed at a concentration range c = 0,001 to 5%. The standardization of several pH-values at a range from 1 to 12 by means of buffer substances as well as the addition of hydrochinone, chinone, NaNO2 and Na2SO3 do not lead to a stable solution. Only at pH = 5 a stable solution was obtained but by changing the buffer substance at the same pH the solution became instable again. Addition of isopropanol leads to stable aqueous PAAm-solutions from technical products as well as high purity polyacrylamides.The mechanism of the solution instability is not a decrease of the molecular weight due to chain scission but a change of conformation of the solution structure from single molecules based on hydrogen bonds.
    Notes: Die Lösungsinstabilität(auch Alterung oder Viskositätsabbau genannt) von hochreinen Polyacrylamiden (PAAm) verschiedener Molekulargewichte wurde untersucht. Diese Instabilität äßert sich durch eine Abnahme der Lösungsviskosität und des [η] in Abhängigkeit von der Zeit bei gleichzeitigem Flockungsverlust.Die Lösungsinstabilität tritt nur bei Molekulargewichten M̄ 〉 1,5 Mill. in wäßriger Lösung auf. PAAm.-Lösungen in Formamid und äthylenglykol sind stabil. Die Viskositätsabnahme erfolgt in einem Konzentrationsbereich von c = 0,001 bis 5%. Die Einstellung verschiedener pH-Werte im Bereich von pH = 1 bis 12 mittels Puffersubstanzen sowie die Zusätze von Hydrochinon, Chinon, NaNO2 und Na2SO3 führen nicht zu einer Lösungsstabilität. Nur pH = 5 zeigte sich eine Stabilisierung der Lösung, die jedoch beim Wechsel der Puffersubstanz bei gleichem pH wiederum in eine Instabilität überging. Zusätze von Isopropanol führen sowohl bei technischen Handelsprodukten als auch bei hochreinen Laborprodukten zu einer Stabilisierung wäßriger PAAm-Lösungen.Der Mechanismus der Lösungsinstabilität besteht nicht in einem Molekulargewichtsabbau durch Kettenbruch, sondern offenbar in einer änderung der Lösungsstruktur der Einzelmoleküle unter Beteiligung von Wasserstoff-Brücken.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is proposed that the mobility of sufficiently long molecules undergoing translational diffusion through solid polyethylene is significantly reduced by tie molecules and fixed entanglements within the interlamellar regions of the matrix. The effect on the diffusion coefficient both of diffusant molecular length and of the host matrix morphology is considered, and a semiquantitative relation between them obtained. This indicates that the mobility of long diffusants is higher in polyethylene which has been cooled slowly from the melt than it is in quenched polyethylene, in marked contrast to the behavior of gaseous and other small diffusants.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion coefficient for two diffusants of the type n-(CH2)NX is measured, where N ≃ 25, 45 and X is a suitable label; the matrix is linear polyethylene cooled at two widely differing rates from the melt. The measuring technique used is a recently developed one based on infrared microdensitometry. The results indicate that these diffusants diffuse faster in the slowly cooled matrix, in marked contrast to the behavior of gaseous diffusants. They are in agreement with the predictions of the model developed in a previous paper (part I), in which the constraints imposed by interlamellar tie molecules on long diffusants were shown to be important.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 69 (1978), S. 169-188 
    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: The present manuscript describes a solution polymerization representing uniform, unbranched, ultrahigh molecular weight polyacrylamides (PAAm) which are free of additives and rest initiator. In addition to the determination by time-conversion-curves, molecular weight and molecular weight distribution of the polymers were characterized definitely by infrared spectroscopy, elemental analyses and thermogravimetry. Among other things it was established that PAAm binds about 2-9% water in spite of intensiv drying. This amount of water is extensively independent of the morphologie of the samples. Orientating measurements of the unknown [η]-M-relationships in formamide and ethylene glycol were made, showing an exponent in ethylene glycol of a 〈0,5. The [η]-M-relationships of H2O, formamide and ethylene glycol cut each other in a molecular weight range from 3·105 to 4·105 (g/mol). The determined ηsp/c-c-functions from ultrahigh molecular weight PAAm in water are not straight lines. By plotting after the Schulz-Blaschke-equation one gets straight lines, the constant KSB = 0,24 being independent from the solvent.
    Notes: In der vorliegenden Arbeit wird eine Lösungspolymerisation zur Darstellung von einheitlichen, linearen, ultrahochmolekularen Polyacrylamiden (PAAm) beschrieben, welche frei von Zusätzen sowie frei von Restinitiator sind. Neben der Bestimmung von Zeitumsatzkurven, Molekulargewicht sowie Molekulargewichtsverteilung wurden die erhaltenen Polymeren mittels IR-Spektroskopie, Elementaranalyse sowie thermogravimetrischen Untersuchungen eindeutig charakterisiert. Unter anderem wurde dabei festgestellt, daß PAAm trotz intensiver Trocknung (Gefriertrocknung etc.) ca. 2 bis 9% Wasser bindet. Dieser Wassergehalt ist weitgehend unabhängig von der Morphologie der Proben. Zu den bisher unbekannten [η]-M-Beziehungen in Formamid und äthylenglykol wurden orientierende Messungen durchgeführt, wobei sich in äthylenglykol ein Aufweitungsparameter a 〈0,5 ergab. Die [η]-M-Beziehungen in Wasser, Formamid und Äthylenglykol schneiden sich danach in einem Molekulargewichtsbereich von 3 · 105 bis 4 · 105 (g/mol). Die in Wasser ermittelten ηsp/c-c-Funktionen von ultrahochmolekularem PAAm stellen keine Geraden dar. Bei der Auftragung nach der Schulz-Blaschke-Gleichung ergeben sich wieder Geraden, wobei die Konstante KSB = 0,24 lösungsmittelunabhängig ist.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    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: Das Anwachsen von Zugspannung und Scherung zu Beginn einer konstanten Scherung wurde an Lösungen linearer Makromoleküle untersucht, um Aussagen über nichtlineare Viskoelastizität zu machen. Die Polyacrylamide (PAAm)…wurden in Wasser, Formamid und Ethylenglycol gelöst. Die Polymeren wurden in diesem Labor hergestellt. Sie waren unverzweight und initiatorfrei. Die Polystyrolproben (PS) von der Pressure Chemical Company wurden in Dekalinlösung untersucht. PAAm zeigt mit steigendem Molekulargewicht und steigender Konzetration zunehmend typischen Gelcharaketer in allen drei Lösungsmitteln. für homogene Systeme wurde Gelbruch und ein „undershoot“ beob-achtet. Zum ersten Ma1 konnten „overshoot“ aufgrund von verhakten Ketten und auf-grund von energetisch assoziierten Ketten voneinander unterschieden werden. Dies Ver-halten zeigt einen grol3en Gegensatz gegenuber dem PS/Dekalin-System und zeigt die Starke der Nebenvalenzbindungen in den PAAm-Systemen.
    Notes: The growth of stress (shear stress and normal stress) at the onset of steady shear flow was investigated for linear chain macromolecular fluids to determine nonlinear viscoelasticity. The polyacrylamides (PAAm) were dissolved in H2O, formamide and ethyleneglycol. The polymers were prepared in this laboratory. They were unbranched and free of initiator. The polystyrene (PS) samples from Pressure Chemical Company were studied in decalin solutions. PAAm shows increasingly typical gel character - in all 3 solvents - with increasing molecular weight and polymer concentration. For homogeneous systems gel fracture and undershoot were observed. Further for the first time overshoot due to entangled molecules and overshoot due to energetically associated chains have been distinguished. This behaviour is a strong contrast to the PS/decalin system and demonstrates the strength of the second valence bondings in the PAAm-systems.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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