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 sample of commercial atactic polypropylene was extracted with ether and the residue extracted with boiling n-heptane. Six fractions of the heptane-soluble material, which is very similar to that obtained by heptane extraction of isotactic polypropylene, were obtained by stepwise addition of acetone to a solution in cyclohexane. Densities, melting points, and x-ray photographs of the fractions and the unfractionated material were obtained and infrared absorption spectra used to estimate tacticity. Molecular weights, determined by means of a vapor pressure osmometer, ranged from about 3000 to about 25,000. That of the fraction of highest molecular weight was in good agreement with a separate determination by means of osmotic pressure measurements. Separation in fractionation occurred in order of decreasing molecular weight and increasing crystallinity as estimated from densities and x-ray photographs. Tacticity also seems to increase with decreasing molecular weight. Melting points of the fractions were not entirely in the order expected from their molecular weights and estimated crystallinities, and it is possible that low DP isotactic material may be preferentially concentrated in the highest molecular weight fraction. It is emphasized that the unfractionated material may contain polymers possessing a range of order intermediate between those of purely atactic and purely isotactic polymer and that refractionation may be required in order to characterize the material completely.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1965.070090603
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