Group members:
Prof. Andrzej Galeski (http://www.cbmm.lodz.pl/polfizyk.htm, andgal@bilbo.cbmm.lodz.pl)
Dr. Eva Piorkowska (epiorkow@bilbo.cbmm.lodz.pl)
Dr. Andrzej Pawlak (apawlak@bilbo.cbmm.lodz.pl)
Mail: Centre of Molecular and Macromolecular Studies
Polish Academy of Sciences
90-363 Lodz, ul. Sienkiewicza 112, Poland
Tel.: (0-42) 6818952
Fax: (0-42) 6847126
Our activity is aimed at the studies of a negative pressure buildup during polymers crystallization. The negative pressure arises in pockets of melt occluded by growing polycrystalline aggregates-spherulites because of density change during crystallization. In pockets the density change is not compensated by influx of melt. We have shown that the negative pressure results in the local lowering of equilibrium melting temperature which is reflected in the depression of spherulite growth rate and in the increase of lamellae thickness. The negative pressure in occluded pockets of melt increases until cavitation occurs which is accompanied by an emission of ultrasound. Both, the localized stress buildup and associated cavitation influence mechanical properties of crystalline polymers. The cavitation process depends on the crystallization temperature.
Related papers:
1.A.Galeski, E.Piorkowska; Localized Volume Deficiencies as the Effect of Spherulite Growth. I. The Two-Dimensional Case. J. Polym. Sci., Polym. Phys. Ed. 21, 1299 (1983).
2.A.Galeski, E.Piorkowska; Localized Volume Deficiencies as the Effect of Spherulite Growth. II. The Three Dimensional Case. J. Polym. Sci., Polym. Phys. Ed. 21, 1313 (1983).
3.A.Galeski, L.Koenczoel, E.Piorkowska, E.Baer; Acoustic Emission During Crystallization of Polymers. Nature 325, 40 (1987).
4.A.Galeski, E.Piorkowska, L.Koenczoel, E.Baer; Acoustic Emission During Crystallization of Polymers. J. Polym. Sci., Part B: Polym. Phys. 28, 1171 (1990).
5.A.Pawlak, A.Galeski; Stability of Spherulite Growth Rate. J.Polym.Sci., Part B:Polym.Phys. 28, 1813 (1990).
6.E.Piorkowska, A.Galeski; Crystallization of Isotactic Polypropylene and High Density Polyethylene under Negative Pressure Resulting from Uncompensated Volume Change. J.Polym.Sci.,Part B: Polym.Phys., 31, 1285 (1993)
7.A.Pawlak, E.Piorkowska; Effect of Negative Pressure om Melting Behaviour of Spherulites in Thin Films of several Crystalline Polymers. J.Appl.Polym.Sci., 74, 1380 (1999).
8. R.Nowacki, J.Kolasinska, E.Piorkowska; Cavitation during Isothermal Crystallization of Isotactic Polypropylene. In preparation.
Question, comments: pressure@sunserv.kfki.hu
Last modification: Febr. 10, 2000