Kinetics of competitive crystallization of β- and α-modifications in β-nucleated iPP studied by isothermal stepwise crystallization technique
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Crystallization kinetics of β-nucleated isotactic polypropylene (β-iPP) under isothermal conditions were investigated by differential scanning calorimetry. iPP was nucleated by a trisamide derivative, namely tris-2,3-dimethyl-hexylamide of trimesic acid (TATA). In the presence of TATA possessing dual nucleating ability, the formation of the α- and β-form occurs simultaneously. An isothermal stepwise crystallization method is suggested in this study, which can separate the crystallization process of β- and α-iPP and consequently their crystallization kinetics can be evaluated separately. The results indicated that the mechanism of crystallization changes in temperature especially in the vicinity of the upper critical temperature of the formation of the β-phase. In addition, it was found that the ratio of the growth rates of β- and α-modification determines the characteristics of crystallization and influences the apparent rate constant of crystallization of both polymorphs.
KeywordsCrystallization kinetics Avrami method Mixed polymorphic composition α- and β-iPP Isothermal stepwise crystallization (ISC) technique
One of the authors (Alfréd Menyhárd) would like to express his indebtedness to the János Bolyai Research Scholarship of the Hungarian Academy of Sciences for the financial support.
- 2.Varga J. β-Modification of isotactic polypropylene: preparation, structure, processing, properties, and application. J Macromol Sci Phys. 2002;B41:1121–71.Google Scholar
- 5.Juhász P, Belina K. Crystallization and morphology of propylene/pentene random copolymers. J Reinf Plast Compos. 2001;20:2–11.Google Scholar
- 11.Keda N, Kobayashi T, Killough L. Novel β-nucleator for polypropylene. Polypropylene ‘96. World Congress. 1996.Google Scholar
- 19.Dou Q, Lu Q. Effect of calcium malonate on the formation of β crystalline form in isotactic poly(propylene). Polym Adv Technol. 2008;19:1522–7.Google Scholar
- 23.Wunderlich B. Macromolecular physics. London: Academic Press; 1979.Google Scholar
- 26.Kolmogoroff AN. On the statistics of crystallization process in metals. Isvest Akad Nauk SSSR Ser Math. 1937;3:335.Google Scholar
- 34.Varga J, Garzó G. Isothermal crystallization of the β-modification of polypropylene. Acta Chim Acad Sci Hung. 1991;128:303–17.Google Scholar
- 35.Varga J, Fujiwara Y, Ille A. βα-Bifurcation of growths during the spherulitic crystallization of polypropylene. Period Polytech Chem Eng. 1990;34:255–71.Google Scholar