Abstract:The effects of multiple mechanical recycling on amorphous polylactide (PLA) were simulated by means of five successive injection-grinding cycles. The influence of the induced thermo-mechanical degradation on the dielectric properties of PLA was analysed. The relaxation spectra were studied in terms of the complex dielectric permittivity (ε' and ε'') and the dielectric loss tangent, tg(δ) in the frequency range from 10 -2 to 10 7 Hz over the temperature interval from 0ºC to 140ºC. It was possible to distinguish two relaxations zones, one at low temperatures and high frequencies (β relaxation) and another at higher temperatures and lower frequencies (α relaxation). The individual relaxations were characterised using the Havriliak-Negami model and the effect of conductivity at high temperatures was subtracted. The thermal activation of the β relaxations were explained on an Arrhenius model basis while the α relaxation was modelled using Vogel-Fulcher-Tammann-Hesse (VFTH) equations. The study of the segmental dynamics showed a decrease in the fragility parameters, connected with the decrease of molar mass, along with an increase in the free volume, the higher the number of reprocessing cycles were applied, particularly up to the second reprocessing step.J.D. Badia, L. Monreal, V. Sáenz de Juano-Arbona, A. Ribes-Greus, Dielectric spectroscopy of recycled polylactide, Polymer Degradation and Stability, Volume 107, September 2014, Pages 21-27, ISSN 0141-3910, http://dx

In vitro validation of biomedical polyester-based scaffolds: Poly(lactide-coglycolide) as model-case.

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Fractal superlattices consist of a series of thin layers of two semiconductor materials alternately deposited on each other with widths corresponding to the rules of construction of a fractal set. The scattering of electrons in superlattices is obtained using the transfer matrix method for generalized Cantor fractal potentials that are characterized by a lacunarity parameter. The numerical results show the self-similarity of the reflection coefficient and the appearance of lacunarity-independent energies with perfectly transparent tunneling due to the bound states of the particle in each of the individual potential wells.

No abstract