Abstract
In this paper, the quiescent crystallization of polycaprolactone (PCL) melts is studied by rheological measurements coupled to calorimetry and optical microscopy. Based on a comparison between the different techniques, we find that the increase in viscoelastic properties during crystallization starts only when a relatively high degree of crystallinity is reached, which corresponds to a much developed crystalline microstructure. Like other semicrystalline thermoplastic polymers, the crystallization of PCL can be seen as a gelation process. In this case, however, we find a peculiar critical gel behavior, as the liquid-to-solid transition takes place at a very high (~20%) relative crystallinity, and this value is independent of temperature. These facts, and the comparison with optical microscopy observations, suggest that the microstructure at the gel point is controlled by the interactions between the growing crystallites. The gel time (from rheometry) and the half-crystallization time [from differential scanning calorimetry (DSC)] both show an Arrhenius-like behavior and have the same pseudoactivation energy. A practical implication of this parallel behavior of t gel and t 0.5 is that the rheological measurements can be used to extend to higher temperatures the study of crystallization kinetics where DSC is not sufficiently sensitive.
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References
Acierno S, Grizzuti N (2003) Measurements of the rheological behaviour of a crystallizing polymer by an “inverse quenching” technique. J Rheol 47(2):563–576
Acierno S, Grizzuti N, Winter HH (2002) Effects of molecular weight on the isothermal crystallization of poly(1-butene). Macromolecules 35(13):5043–5048
Boutahar K, Carrot C, Guillet J (1998) Crystallization of polyolefins from rheological measurements relation between the transformed fraction and the dynamic moduli. Macromolecules 31:1921–1929
Chambon F, Winter HH (1987) Linear viscoelasticity at the gel point of a crosslinking PDMS with imbalanced stoichiometry. J Rheol 31(8):683–697
Gelfer M, Horst RH, Winter HH, Heintz AM, Hsu SL (2003) Physical gelation of crystallizing metallocene and Ziegler–Natta ethylene–hexene copolymers. Polymer 44:2363–2371
Horst RH, Winter HH (2000) Stable critical gels of a crystallizing copolymer of ethene and 1-butene. Macromolecules 33(1):130–136
Khanna YP (1989) Estimation of polymer crystallinity by dynamic mechanical techniques. J Appl Polym Sci 37:2719–2726
Khanna YP (1993) Rheological mechanism and overview of nucleated crystallization. Macromolecules 26(14):3343–3639
Krishnamoorti R, Giannelis EP (1997) Rheology of end-tethered polymer layered silicate nanocomposites. Macromolecules 30:4097–4102
Madbouly SA, Ougizawa T (2003) Rheological investigation of shear-induced crystallization of poly(ε-caprolactone). J Macromol Sci Part B B42(2):269–281
Pogodina NV, Winter HH (1998) Polypropylene crystallization as a physical gelation process. Macromolecules 31(23):8164–8172
Schwittay C, Mours M, Winter HH (1993) Rheological expression of physical gelation in polymers. Faraday Discuss 101:93–104
Van Krevelen DW (1972) Properties of polymers correlation with chemical structure. Elsevier, Amsterdam
Winter HH, Chambon F (1986) Analysis of linear viscoelasticity of a crosslinking polymer at the gel point. J Rheol 30(2):367–382
Winter HH, Mours M (1997) Rheology of polymers near liquid–solid transitions. Adv Polym Sci 134:165–234
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This paper was presented at the second Annual European Rheology Conference (AERC) held in Grenoble, France, 21–23 April 2005.
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Acierno, S., Di Maio, E., Iannace, S. et al. Structure development during crystallization of polycaprolactone. Rheol Acta 45, 387–392 (2006). https://doi.org/10.1007/s00397-005-0054-2
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DOI: https://doi.org/10.1007/s00397-005-0054-2