Changes of the Molecular Mobility of Poly(ε-caprolactone) upon Drawing, Studied by Dielectric Relaxation Spectroscopy
- 29 Downloads
Dielectric relaxation spectroscopy (DRS) of poly(ε-caprolactone) with different draw ratios showed that the mobility of polymer chains in the amorphous part decreases as the draw ratio increases. The activation energy of the α process, which corresponds to the dynamic glass transition, increases upon drawing. The enlarged gap between the activation energies of the α process and the β process results in a change of continuity at the crossover between the high temperature a process and the α and β processes. At low drawing ratios the a process connects with the β process, while at the highest drawing ratio in our measurements, the a process is continuous with the α process. This is consistent with X-ray diffraction results that indicate that upon drawing the polymer chains in the amorphous part align and densify upon drawing. As the draw ratio increases, the α relaxation broadens and decreases its intensity, indicating an increasing heterogeneity. We observed slope changes in the α traces, when the temperature decreases below that at which τ α ≈ 1 s. This may indicate the glass transition from the ‘rubbery’ state to the non-equilibrium glassy state.
KeywordsSemicrystalline polymer Dielectric relaxation spectroscopy Molecular mobility
Unable to display preview. Download preview PDF.
This research forms part of the research programme of the Dutch Polymer Institute (DPI), project#623.
- 1.Omid, Y.; Hamid, G. Development of a simple model to characterize the complex constrained polymer chains in polymer nanocomposites at the interphase of amorphous/semicrystalline ethylene vinyl acetate and nanosheets. J. Compos. Mater. 2016, 51(2), 179–186.Google Scholar
- 17.Pieruccini, M.; Ezquerra, T. A.; Lanza, M. Phenomenological model for the confined dynamics in semicrystalline polymers: the multiple α relaxation in cold-crystallized poly(ethylene terephthalate). J. Chem. Phys. 2007, 127(10), DOI: 10.1063/1.2771166Google Scholar
- 21.Frűbing, P.; Kremmer, A.; Gerhard-Multhaupt, R.; Spanoudaki, A.; Pissis, P. Relaxation processes at the glass transition in polyamide 11: from rigidity to viscoelasticity. J. Chem. Phys. 2006, 125(21), DOI: 10.1063/1.2360266Google Scholar
- 25.Alcock, B.; Cabrera, N. O.; Barkoula, N. M.; Raynolds, C. T.; Govaert, L. E.; Peijs, T. The effect of temperature and strain rate on the mechanical properties of highly oriented polypropylene tapes and all-polypropylene composites. Compos. Sci. Technol. 2007, 67(10), 2061–2070.CrossRefGoogle Scholar
- 33.Schröter, K.; Unger, R.; Reissig, S.; Garwe, F.; Kahle, S.; Beiner, M.; Donth, E. Dielectric spectroscopy in the αβ splitting region of glass transition in poly(ethyl methacrylate) and poly(n-butyl methacrylate): different evaluation methods and experimental conditions. Macromolecules 1998, 31(25), 8966–8972.CrossRefGoogle Scholar
- 36.Götze, W. in “Liquid, Freezing and the Glass Transition”, ed. by Hansen, J. P.; Levesque, D.; Zinn-Justin, J., North-Hollond, Amsterdam, 1991, p. 287.Google Scholar