Kinetisch kontrollierte Formation von Nanokristallen in statistischen Polypropylencopolymeren
Structure formation in statistical propylene-1-alkene copolymers
Isotactic polypropylene is a semi-crystalline polymer, in which the crystalline phase can adopt different structures. These include mesomorphic and monoclinic phases which form on rapid and slow melt-crystallization, respectively. Additionally, the size and shape of crystals depend largely on the condition of crystallization.
Addition of low amount of comonomers like ethylene, 1-butene, 1-hexene, or 1-octene, has major impact on equilibrium transition temperatures and on the kinetics of crystallization. Furthermore, there is observed partial replacement of monoclinic structure by triclinic structure, and distinct reduction of the crystallinity.
In the present research, we analyze quantitatively the effect of addition of different 1-alkene comonomers on the structure formation of isotactic polypropylene, with special emphasis on application of high rates of cooling on solidification. It is a primary goal of this study, to provide information about controlled generation of semi-crystalline structures with crystals of well-defined internal/crystal structure, shape, size, and thermodynamic stability. To achieve this goal, we modify (i) type and concentration of co-units, which act as constitutional defects, and (ii) the pathway of crystallization, with the main parameters (a) cooling-rate on melt-crystallization, and (b) temperature and time of annealing.
This research can be considered as continuation of earlier investigation on ethylene-1-octene copolymers, in which we explored in particular the effect of addition of 1-octene on kinetically-controlled formation of pseudo-hexagonal polyethylene, and on general thermal and mechanical properties.
Selected publications
R. Androsch, J. Blackwell, S.N. Chvalun, B. Wunderlich
Wide- and Small-Angle X-ray Analysis of Poly(ethylene-co-octene)
Macromolecules 32, 3735-3740 (1999).
R. Androsch, B. Wunderlich
A Study of Annealing of Poly(ethylene-co-octene) by Temperature-Modulated and Standard Differential Scanning Calorimetry
Macromolecules 32, 7238-7247 (1999).
R. Androsch, B. Wunderlich
Analysis of the Degree of Reversibility of Crystallization and Melting in Poly(ethylene-co-1-octene)
Macromolecules 33, 9076-9089 (2000).
I.S. Kolesov, R. Androsch, H.-J. Radusch
Effect of Crystal Morphology and Crystallinity on the Mechanical alpha- and beta-Relaxation Processes of Short-Chain Branched Polyethylene
Macromolecules 38, 445-453 (2005).
