Crystallization kinetics of iPP: Influence of operating conditions and molecular parameters

• Published in: Journal of applied polymer science Vol. 104; no. 2; pp. 1358 - 1367
• Main Authors: La Carrubba, V., Piccarolo, S., Brucato, V.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.04.2007; Wiley
• Subjects: Applied sciences; Crystallization; density; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; polyolefins; processing; Properties and characterization; WAXS; Tacticity; density; Cooling rate; Propylene polymer; Crystallinity; Experimental study; Modeling; WAXS; Molecular weight property relation; Kinetic model; Melt crystallization; polyolefins; Isotactic polymer; crystallization; Olefin polymer; processing; Property structure relationship; Kinetics; Nucleating agent
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.25871

An analysis of the crystallization kinetics of different grades of isotactic polypropylene (iPP) is here presented. To describe the crystallization kinetics as a function of molecular and operating parameters, the methodological path followed was the preparation of quenched samples of known cooling histories, calorimetric crystallization isotherms tests, differential scanning calorimetry cooling ramps, wide angle X‐ray diffraction (WAXD) measurements, and density determination. The WAXD analysis performed on the quenched iPP samples confirmed that during the fast cooling at least a crystalline structure and a mesomorphic one form. The diffractograms were analyzed by a deconvolution procedure, to identify the relationship between the cooling history and the distribution of the crystalline phases. The whole body of results (including calorimetric ones) provides a wide basis for the identification of a crystallization model suitable to describe solidification in polymer‐processing operations, based on the Kolmogoroff–Avrami–Evans nonisothermal approach. The kinetic parameters, determined for all the materials, are discussed, highlighting the effect of molecular parameters on the crystallization kinetics: molecular mass and distribution, tacticity, nucleating agents, and ethylene units content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1358–1367, 2007