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  • 1970-1974  (5)
  • 1
    Electronic Resource
    Electronic Resource
    X-ray diffraction study of bulk poly N-substituted maleimides (1972)
    Springer
    Colloid & polymer science 250 (1972), S. 474-481 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Eine Serie von 7 aliphatischen und 6 aromatischen Poly-N-substituierten Maleimiden (PNMI) wurden mit radikalischer Polymerisation synthetisiert. Die Proben wurden mit Hilfe von Messungen der intrinsic-Viskosität, des Molekulargewichts-Zahlenmittels und der Glas-Temperatur charakterisiert. Röntgendiagramme der Proben zeigen zwei ziemlich breite Maxima, entsprechend der nichtkristallinen Struktur. Die Lage des inneren Piks hängt streng von der Länge der substituierten Gruppen ab und kann mit diesbezüglichen zwischenmolekularen Abständen verknüpft werden: Das beobachtete lineare Anwachsen des mit dem inneren Maximum verknüpften Abstandes entspricht nämlich der Anzahl der Methylengruppen in der substituierten aliphatischen Kette und weist darauf hin, daß sich die laterale Konformation vergrößert. Der äußere Pik entspricht mittleren intramolekularen Abständen längs der Kette und hängt nur wenig von den substituierten Gruppen ab. Die Distanz paßt zur Annahme einer 4/1-Helix-Konformation. In der Arylserie erscheint ein 3. Maximum, das auf das Auftreten von 3/1 Helices hinweist. Die berechneten Dimensionen von Kettenbündeln aus der Verbreiterung des inneren Maximums sind von der Größenordnung des doppelten inter-molekularen Abstands und zeigen somit an, daß keine wohldefinierte Nahordnung besteht. Ein Modell für die Packung der PNMI-Moleküle mit substituierten Seitengruppen wird vorgeschlagen.
    Notes: Summary A series of 7 aliphatic and 6 aromatic poly N-substituted maleimides (PNMI) was synthetized by free radical polymerization. The series was characterized by means of intrinsic viscosity, number average molecular weight and glass transition temperature measurements. The X-ray diffractograms of all samples show two rather broad maxima indicative of non-crystalline structures. The location of the innermost peak strongly depends on the length of the substituted groups and can be associated to intermolecular vectors. The observed linear increase of the spacing associated to the inner maximum with the number of methylene groups of the substituted aliphatic chain favours the idea of predominantly extended lateral conformations. The outer peak due is to intramolecular average distances along the backbone chain and slightly depends on the shape of the substituted groups. This repeat distance fits well with the assumption of a 4/1 helix for the chain conformation. In the aryl series a third maximum appearing as a shoulder on the outer peak suggests the presence of chain sequences coiled in 3/1 helices. The “chain bundle” dimensions calculated from the broadening of the innermost maximum are of the order of two intermolecular vectors suggesting, hence, the absence of a well defined short range order. A model for the packing of PNMI molecules with lengthy substituted groups is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01507515
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  • 2
    Electronic Resource
    Electronic Resource
    Diffraction studies of plastically deformed polyethylene (1970)
    Springer
    Colloid & polymer science 242 (1970), S. 1093-1102 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Verzweigte Polyäthylene (Lupolen) mit 0.5, 7, 16 und 34 seitständigen CH3-Gruppen je 103 CH2 wurden im Temperaturbereich zwischen 0° und 100°C verstreckt und die Umwandlungen in der Einschnürung mit Klein-und Weitwinkel-Röntgenstreuung untersucht. Mit steigendem Verzweigungsgrad wird der maximal erreichbare Verstreckungsgrad verringert und das Erscheinen der Langperiode der neuen Faserstruktur zu niedrigeren Verstreckungsgraden verschoben. Ferner tritt bei den letzten zwei Proben beim Verstrecken bei den höchsten Temperaturen keine Einschnürung mehr ein. Die beobachteten Effekte sind teilweise eine Folge der Verzweigungen. Doch scheint es sehr wahrscheinlich, daß sie noch viel mehr durch das sehr hohe Molekulargewicht der stärker verzweigten Proben bedingt sind. Die LangperiodeL T der neuen Faserstruktur kann bis zur UnterkühlungT m −T d =100°C sehr gut als Funktion der VerstreckungstemperaturT d und des Verzweigungsgrades in der FormL T =L T =0°C [0.85+15/(T m −T d )] dargestellt werden. Wird die Unterkühlung größer als 100°C, so bleibt die Langperiode unverändert. Die KonstanteL T =0°C ist die Langperiode beiT d =0°C d. h. bei einer Unterkühlung von 100°C oder mehr. Der SchmelzpunktT m entspricht der bei 20°C zu einem Verstreckungsgrad 6 gezogenen Probe. Der Verzweigungsgrad beeinflußtL T =0°C undT m , doch nicht die Koeffizienten 0.85 und 15.
    Notes: Summary Branched polyethylenes (Lupolen) with 0.5, 7, 16 and 34 nonterminal CH3 groups per 103 CH2 were drawn between 0° and 100°C and the transformation in the neck investigated by small-angle and wide-angle X-ray scattering. The maximum draw ratio obtainable decreases and the long period of the new fiber structure appears at lower draw ratio with increasing degree of branching. Moreover, no necking is observed at higher temperature with the last two samples. These effects are partly caused by branching but may be also the consequence of the rather high molecular weight of the highly branched samples. The long periodL T of the new fiber structure as function of temperature of drawing(T d ) and branching ratio can be well represented byL T =L T =0°C [0.85+15/(T m −T d )] up to a supercoolingT m −T d =100°C. At higher supercooling the long period is identical with that at 100°C supercooling. The constantL T =0°C is the long period obtained with drawing at 0°C, i. e., at a supercooling of 100°C or more andT m is the melting point of the sample drawn atT d =20°C to a draw ratio ratio 6. The branching influencesL T =0°C andT m but not the coefficients 0.85 and 15.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02084715
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  • 3
    Electronic Resource
    Electronic Resource
    Plastic deformation of polypropylene VII. Long period as function of temperature and rate of drawing (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1749-1756 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polypropylene fibers prepared by quenching in ice-water were drawn at 25, 80, 120, and 140°C to a draw ratio between 6 and 8 at draw rates 0.05, 0.5, 5, and 50 cm/min. The long period increases almost linearly with the draw rate for drawing at 25°C and decreases for drawing at higher temperatures. The effect in the latter cases is an annealing effect. As a consequence of the shorter exposure of the drawn fibers to the high temperature at higher draw rate, the long-period growth proceeds for a shorter time and hence results in a smaller increase of long period. At 25°C, however, the long-period growth is negligible. The increase of long period with draw rate is the consequence of higher adiabatic heating as calculated from the energy input during the plastic deformation which transforms the spherulitic into the fibrous structure. One concludes that the long period established during this transformation depends on the maximum temperature reached in the micronecking zone and not on the macroscopically observed temperature of the sample in the neck.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.160100911
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  • 4
    Electronic Resource
    Electronic Resource
    Detection of “memory” effects in polyethylene by magnetic susceptibility (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 2273-2282 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relevance of diamagnetic susceptibility as a tool for the structure analysis of solid high polymers is stressed in the light of some new examples. The present results complement previous data and offer new aspects on the diamagnetic investigations of longchain hydrocarbons, especially polyethylene (PE). The molecular susceptibility is proportional to the average number of repeat units in the chain. The proportionality factor defines an intermolecular constant μk which characterizes different physical states. This was found to be 2.5 × 10-6 for the liquid and 3.5 × 10-6 cgs for the crystalline state of paraffins and polyethylene (solution-crystallized). For melt-crystallized material, μk, approaches the typical value of the liquid paraffin in agreement with previous results. Such a low μk is probably related to the increased disorder of the paracrystalline lattice domains, in contrast to the more ordered microparacrystallites in the so-called “single crystals,” where μk = 3.5 × 10-6. In single crystals of branched PE, μk approaches 2.5 × 10-6 with increasing branching ratio. Like paraffins in the gaseous state, molten PE, with chains longer than 1000 Å, has μk = 0. If the solution-crystallized material is molten for 10 min and thereafter cooled, μk retains the original value 3.5 × 10-6 cgs characteristic of the crystalline state. Hence, solution-crystallized polyethylene apparently possesses a kind of “memory.” Such a “memory” can, nevertheless, be partly destroyed when molten PE is stirred for 10 min and then quenched. Aggregates of solution-precipitated crystals with 3% branching concentration give μk = 2.9 ± 0.2 × 10-6 in good agreement with x-ray diffraction data. Finally, experimental details on the magnetic measurements are critically discussed, and various aspects of improvements for further investigations are also described.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180111116
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  • 5
    Electronic Resource
    Electronic Resource
    Plastic deformation of polypropylene. V. Annealing of drawn polypropylene (1971)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 141 (1971), S. 91-116 
    Details
    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: Proben aus isotaktischem Polypropylen bei 20 und 100°C zu einem Dehnungsverhältnis von 6 oder 10 verstreckt, wurden mit freien und festgehaltenen Enden zwischen 40 und 155°C für verschieden lange Zeiten zwischen 1 und 103 Minuten getempert. Alle Tempereffekte sind ausgeprägter für Proben, die frei schrumpfen können, als für Proben mit festgehaltenen Enden. Die Desorientierung des Kristallgitters und das Schrumpfen schreiten extrem rasch fort und erreichen in kurzer Zeit Sättigungswerte, die charakteristisch für die Tempertemperatur sind. Bei höheren Tempertemperaturen kann man nur noch die Sättigungswerte beobachten, da der ganze Vorgang in weniger als einer Minute beendet ist. Das Langperiodenwachstum, der Dichteanstieg und die Erhöhung der Intensität der Kleinwinkelstreuung sind dem Logarithmus der Temperzeit proportional. Deshalb dauern diese Effekte mit zwar stetig abfallender Steigung noch lange an, nachdem die Desorientierung und das Schrumpfen schon längst zu einem Stillstand gekommen sind. An Hand des Zweistufenmodells der plastischen Deformation von kristallinen Hochpolymeren, das die Bildung von zugfesten, gut orientierten und durch zwischenfibrillare Verbindungsmoleküle verknüpften Mikrofibrillen annimmt, können die Beobachtungen befriedigend gedeutet werden.
    Notes: Isotactic polypropylene samples drawn at 20 and 100°C to a draw ratio 6 and 10 were annealed with free and fixed ends between 40 and 155°C for periods of time between 1 and 103 min. All the annealing effects proceeded farther with unclamped samples free to shrink than with clamped samples. The disorientation of crystal lattice and the shrinkage are extremely fast reaching saturation values characteristic for the temperature of annealing. At higher annealing temperature, one could observe merely the saturation values with the whole transition being completed in less than 1 min. The long period growth, the increase in density, and the intensity of small-angle X-ray scattering are linear functions of the logarithm of annealing time and hence persist with gradually decreasing rate long after the completion of disorientation and shrinkage. The observed effects can be well explained on the basis of the two-stage model of plastic deformation of crystalline polymers which assumes the formation of strong well-aligned microfibrils connected by interfibrillar tie molecules.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1971.021410108
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