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:
Cast amorphous one mil films of poly(ethylene terephthalate)were allowed to crystallize isothermally in silicone oil over the temperature range 25-240°C. The crystallization paths were followed by recording the percent of transmission of 4000 A. light through the films as a function of time at specific temperatures. At temperatures between 70 and 90°C. the transmission increased to a value higher than the initial transmission and did not decrease with time. From about 95 to 125°C. the curves showed a similar increase, followed by a decrease to a minimum and then an increase to a new maximum before leveling off. The shapes of these curves were interpreted in terms of the sizes of the growing spherulites. The first detectable signs of crystallization were observed at 96.5°C., as evidenced by density and densitometer measurements. It is shown that the polymer passed through a temperature range beginning at the glass transition point (66°C.) and extending to about 95°C., where molecular and chain rearrangements occurred without crystallization. Half lives and rate constants were found to increase exponentially over the range 96.5-119.5°C. Above approximately 125°C., the crystallization process took place at such a rapid rate that accurate data were impossible to obtain. Activation energies were calculated from the rate constants and from an estimation of induction times from the light transmission-time curves. These values were found to be 37 and 30 kcal./mole, respectively. The density-time data were also fitted to the Avrami relationship. Evaluation of the constants indicated that the initial crystallization growth was lineal.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1965.070091110
