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
A. Ribes-Greus. Influence of chitin nanocrystals on the dielectric behaviour and conductivity of chitosan-based bionanocomposites. Composites Science and Technology 2018; 167:323-330
A comparative study of the dynamic mechanical relaxation spectra of high-and low-density polyethylenes irradiated with ␥-radiation from a Co 60 source was performed. The irradiation doses ranged from 0 to 100 Mrad. All the samples were previously characterized by determination of the molecular weight distribution, the number of functional groups, and the crystalline fraction. All the relaxation zones between Ϫ145°C and the melt were studied in the frequency range from 0.3 to 30 Hz. The changes observed in the mechanical relaxation spectra were related to modifications in the chemical structure and morphological parameters attributed to the exposure of the samples to the ␥-radiation.
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