Polymer crystallization kinetics by use of light depolarization technique which is sensitive to the changes of depolarised light intensity during fast crystallization has been studied theoretically [1-3]. A statistical stack of parallel birefringent plates with a distribution of dimensions and orientations has been considered. Closed-form expressions for the intensity of transmitted light have been derived as dependent on structural characteristics [2,3]. It has been shown that intensity of light depolarized cannot be treated as a direct measure of crystallinity degree because it is a non-linear function of the product of the crystallinity degree and the average crystal thickness [3]. Conditions for the linear approximation range are discussed. The work provided basis for construction of optical device [4] used for measurements of crystallization kinetics of various polymers [5]. The advantage of the optical method relies on high sampling rate allowing on-line measurements with lack of inertia effects present in other methods, like calorimetry.

Distribution of plates in the sample viewed along the light beam. The circle represents the cross-section of the light beam [2].

Scheme of light depolarization set-up. P-polarizer, S-sample, A-analyser, D-detector [2].

[1]. Ziabicki A, Misztal-Faraj B., Interpretation of light depolarization data in terms of polymer crystallinity, MATERIALS SCIENCE-POLAND, 24, 493-505, 2006.

[2]. Ziabicki A., Transmission of light through a statistical system of birefringent plates, JOURNAL OF OPTICS A - PURE AND APPLIED OPTICS, 7, 774-782, 2005.

[3]. Ziabicki A., Misztal-Faraj B., Applicability of light depolarization technique to crystallization studies, POLYMER, 46, 2395-2403, 2005.

[4]. Misztal-Faraj B., Sajkiewicz P., Savytskyy H., Bonchyk O., Gradys A., Ziabicki A., Following phase transitions by depolarization by depolarizing light intensity. The experimental setup, POLYMER TESTING, 28, 36-41, 2009.

[5]. Sajkiewicz P., Gradys A., Misztal-Faraj B., Quantitative analysis of crystallization kinetics by light depolarization technique. Possibilities and limitations, EUROPEAN POLYMER JOURNAL, 46, 2051-2062, 2010.