ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Crystallization kinetics of Hercules polypropylenes were studied between 133 and 155°C. using dilatometers. The crystallization rates of these samples became too rapid below 133°C. for accurate dilatometric measurements. One sample (A) was a commercial sample containing stabilizer and 9% extractable polymer (with boiling n-heptane). B was an experimental extracted sample containing no stabilizer. A portion of B was thermally degraded under vacuum at 350°C. for 7 hr. (C). The DPn′s of A, B, and C were 2300, 7300, and 1200, respectively. Their melting points were determined dilatometrically, under conditions approaching equilibrium, and were 175, 176, and 173°C., respectively. 95% of the crystallization can be described by an Avramitype equation with an n value of 3, indicating a three-dimensional growth with residual nucleation or a two-dimensional growth with spontaneous nucleation. The heterogeneities may result from catalyst residues. The crystallization rate of A was lower than that of B or C at a given temperature, possibly due to the presence of atactic polymer. At a given temperature C crystallized faster than B, which may be an effect of the difference in molecular weight. Plotting the rate as a function of the degree of undercooling (ΔT) increases the difference between B and C.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1959.1203813310
