ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The dissolution temperature of the crystalline platelets of polyacrylonitrile in propylene carbonate bears a linear relationship with the crystallization temperature Tc. The step heights ζ of the crystalline platelets measured by electron microscopy increase with increase in crystallization temperature, in accordance with the current theory of high polymer crystallization in dilute solution. The step heights were found to be 100, 130, and 150 A. for Tc of 95, 116, and 125°C., respectively. By extrapolating the experimental values of Ts to the value at ζ = ∞, a characteristic constant (Tm)∞ is obtained. The (Tm)∞ was 175°C. for the sample studied in propylene carbonate. The interfacial free energy, σe, calculated from the melting point and the step height is of the order of 1950 cal./mole of emerging chain repeat unit, or 45 ergs/cm.2 as compared to 1900 cal./mole or 70 ergs/cm.2 for polyethylene. It appears that the surface free energies of various organic polymers are remarkably similar. Although the degree of crystalline perfection of polyacrylonitrile is inferior to that of organic crystals with three-dimensional order, polyacrylonitrile displays a crystallization behavior similar to other semicrystalline polymers; this conclusion is supported by the linear relationship between Ts and Tc, the variation of the step height with the crystallization temperature, and the sigmoid relationship of the fractional change in specific volume as a function of time during crystallization.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1965.100030207
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