Triple crystallization behavior of fractionated ethylene/α-olefin copolymers of different catalyst type
Non-isothermal crystallization processes in fractions of Ziegler-Natta (ZN) and single site (SS) based ethylene/1-butene and ethylene/1-hexene copolymers have been studied by differential scanning calorimetry (DSC). Fractionation of used copolymers was done according to molar mass (MM) and composition (comonomer content). It was observed in DSC scans that for fractions with high MM (larger than 10 kg/mol) in addition to the main high-temperature crystallization peak (HTCP), a very-low temperature crystallization peak (VLTCP) is present at temperatures in between 60–75 °C. Such peak is absent for the first fractions having very-low MM. The partial crystallinity and peak temperatures, obtained from VLTCP, increase with MM and level off at MM around 60–100 kg/mol. It was found that the crystallinity as related to the area of the VLTCP is catalyst type dependent, and is higher for the SS catalyst compared to the ZN. Peak temperature of VLTCP linearly decreases with increasing comonomer content at fixed MM while the partial crystallinity practically does not change with comonomer content.
KeywordsLinear low-density polyethylene Ethylene/α-olefins Fractions Very-low temperature crystallization peak Differential scanning calorimetry
The Estonian Science Foundation is acknowledged for support under grant no. 6553 and Borealis Polymers OY (Finland) for structural characterization of the studied materials. We also acknowledge the Targeted Financing of Estonian Ministry of Education and Research for the grant no. SF0142687s05.
- 1.Mathot VBF, Pijpers JFJ (1988) Integration of fundamental polymer science and technology. Proceedings of International Discussion Meeting, Rolduc Abbey, Netherlands, 26–30 April, 1987. Elsevier Applied Science, London, p 381Google Scholar
- 2.Mathot VBF, Scherrenberg RL, Pijpers MFJ, Engelen YMT (1996) New trends in polyolefin science and technology. Hosoda S. Ed.; Research Signpost, Trivandum, IndiaGoogle Scholar
- 8.Mathot VBF (1994) Calorimetry and thermal analysis of polymers. Hanser, Munich-Germany-Vienna-New YorkGoogle Scholar
- 17.Tashiro K, Imanishi K, Izumi Y, Kobayashi M, Kobayashi K, Satoh M, Stein RS (1995) Cocrystallization and phase segregation of polyethylene blends between the D and H species. 7. Time-resolved synchrotron-source small-angle X-ray scattering measurements for studying the isothermal crystallization kinetics: comparison with the FTIR Data. Macromolecules 28:8477–8483CrossRefGoogle Scholar
- 23.Pino P, Oschwald A, Ciardelli F, Carlini C, Chiellin E (1975) In: Chien JCW (ed) Coordination polymerization of a-Olefins. Elsevier, New YorkGoogle Scholar
- 47.Wilfong DL (1989) LLDPE TREF fractions, crystallization behavior and morphology. Polym Mater Sci Eng 61:743–747Google Scholar