Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Melt crystallization of polypropylene: Structure formation (1984)
    Springer
    Polymer bulletin 11 (1984), S. 41-47 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The steps of order formation during the polypropylene cooling from superheated to supercooled melt were determined by wideangle X-ray scattering. The symmetrical Gaussian halo at the temperatures higher than 280°C is the manifestation of intermolecular short-range order. Below 280°C the additional halo corresponding to the intramolecular short-range order connected with the helix fragments formation appeared. In the supercooled melt just before the beginning of the crystal formation process the diffractogram profile was similar to that of the paracrystalline form consisting of the long distance one-dimensional order domains. The existence of this metastable form with mesomorphous structure was confirmed by NMR and IR data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401713
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Topomorphic states and phase transitions connected with the crystallization of polymersPresented at the 5th Discussion Conference on Phases and Interphases in Polymers, Prague (1976) (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 206-211 
    Details
    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: The crystallization of flexible-chain molecules of different degrees of coiling is considered. The nature of the phase transition during crystallization is discussed. The revision of established notions on phase transitions in polymers leads to the concept of crystalline topomorphism, i.e., the existence of two crystalline types with different modes of packing of macromolecules in the macroscopic crystal though they belong to the same lattice class: folded-chain crystal (FCC) and extended-chain crystal (ECC). Phase diagrams in coordinates of degree of coiling vs temperature are plotted. The values of molecular orientation and temperatures at which each of both mechanisms of crystallization takes place are evaluated. The mechanisms of ECC growth under equilibrium conditions and under conditions of molecular orientation are discussed. It is shown that the melting of ECC obtained by the process of orientational crystallization is a second order phase transition, being analogous to a crystal-nematic phase transition. At the same time the melting of FCC provides all the features of a first order transition.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200307
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    X-ray studies of smectic-crystal and crystal-smectic transition in oriented polypropylene (1982)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 483-485 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Kristallisation von Polypropylen im orientierten parakristallinen Zustand und der Übergang in den smektischen Zustand beim isometrischen Schmelzen der kristallisierten Proben wurden untersucht. Die Ergebnisse werden unter der Annahme struktureller Umwandlungen der makromolekularen Helices interpretiert, was ein lokales Schmelzen der Helices voraussetzt.
    Notes: The results of the study of polypropylene crystallization from the oriented paracrystalline state and the transition to the smectic state observed during isometric melting of the samples crystallized in this manner are interpreted from the viewpoint of structural transition in helical polypropylene macromolecules inevitably involving the local melting of helices.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1982.010330808
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Thermokinetic analysis of polymorphous transformations in the crystallization and orientation of flexible-chain polymers (1990)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 41 (1990), S. 147-152 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Kristallisation von flexibelkettigen Polymeren, die unterschiedliche polymorphe Modifikationen bilden können, wurde unter thermodynamischen Aspekten und unter Berücksichtigung kinetischer Faktoren betrachtet. An den Beispielen Poly(caproamid) und Poly(vinylidenfluorid) wurden die Äderungen der freien Energie bei der Bildung unterschiedlicher kristalliner Modifikationen berechnet, und Phasendiagramme in den Koordinaten Knäuelungsgrad der Makromoleküle und Temperatur wurden dargestellt. Auf diese Weise war es möglich, die thermokinetischen Bedingungen für die Bildung der Gleichgewichts- und der metastabilen Modifikationen sowie für die Übergänge zwischen ihnen anzugeben.
    Notes: The crystallization of flexible-chain polymers capable of forming different polymorphous modifications was considered by using the thermodynamic approach and taking into account kinetic factors. Taking as examples poly(caproamide) and poly(vinylidene fluoride), the changes in free energies in the generation of different crystalline forms were calculated and phase diagrams were plotted in the coordinates degree of coiling of macromolecules and temperature. it was thus possible to establish the thermokinetic conditions for the formation of equilibrium and metastable modifications and the transitions between them.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1990.010410302
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Main features of polypropylene crystallization from the quenched state (1985)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 36 (1985), S. 301-305 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Röntgenweitwinkelstreuung wurde die Strukturbildung des isotaktischen Polypropylens beim Übergang vom abgeschreckten in den kristallinen Zustand untersucht. Anhand der Temperaturabhängigkeit der Gestalt der amorphen Streukurve wurde die Zusammensetzung von Proben mit unterschiedlichem Kristallinitätsgrad und unterschiedlichem parakristallinen Anteil quantitativ bestimmt. Mit Hilfe der IR-Spektroskopie wurde gezeigt, daß die Verstreckung des abgeschreckten Polypropylens das Einfrieren der Konformationsordnung der Makromoleküle bewirkt. Dieses Einfrieren behindert den Übergang in den kristallinen Zustand beim Erwärmen.
    Notes: The structure formation during transition from the quenched into the crystalline state has been studied for isotactic polypropylene by wide-angle X-ray scattering. Based on the temperature dependence of the shape of the curve of amorphous scattering the composition of samples with different degrees of crystallinity and different content of paracrystalline form was determined quantitatively. By means of IR spectroscopy it was shown that stretching of quenched polypropylene leads to the freezing of the conformational array in macromolecules. This freezing hinders the transition into the crystalline state upon heating.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1985.010360602
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A possibility of observing the structure forming process in polypropylene crystallization (1982)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 427-428 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Existenz einer spezifischen metastabilen Phase erlaubt es, mehrstufige elektronenmikroskopische Untersuchungen der Bildung der übermolekularen Struktur bei der Kristallisation von Polypropylen im orientierten Zustand durch zuführen. Der Vergleich mit Elektronenbeugungsaufnahmen liefert einen direkten Beweis dafür, daß die Bildung von Struktureinheiten der übermolekularen Ordnung im kristallinen Polypropylen, d. h. der Fibrillen und Lamellen, während der Orientierung erfolgt und die Kristallisation diese Strukturen nur fixiert.
    Notes: The existence of the specific metastable phase made it possible to carry out multistage electron microscopic investigation of the supermolecular structure formation in the crystallization of polypropylene in the oriented state. Comparison with the data of electron diffraction yielded a direct evidence of the fact that the formation of structural units of the supermolecular organization of crystalline PP, i.e. fibrils and lamellae, occurs in the stage of orientation, and crystallization itself only fixes these structures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1982.010330705
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Pre-transition phenomena in the crystallization and melting of flexible-chain polymers (1986)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 37 (1986), S. 329-332 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Im isotaktischen Polypropylen wird sowohl bei der Kristallisation als auch beim Schmelzen stets ein Übergangszustand mit gleicher Struktur durchlaufen, der durch die Anwesenheit von mehr oder weniger großen Bereichen mit flüssigkristalliner Ordnung gekennzeichnet ist. Das Auftreten dieser metastabilen Strukturen ist eine Folge der Kettenstruktur der Makromoleküle und sollte bei den Übergängen in allen isotaktischen Polymeren zu erwarten sein.
    Notes: In isotactic polypropylene both crystallization and melting are always accompanied by a transition through the states characterized by the same structure with the presence of more or less large regions having the order of the liquid crystalline type. The appearance of these metastable structures is a consequence of the chain structure initially inherent in the macromolecules and should be expected in transitions of all isotactic polymers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1986.010370601
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...