Search results for "Aquinas"
showing 10 items of 86 documents
Thermal analysis applied to the characterization of degradation in soil of polylactide: II. On the thermal stability and thermal decompositon kinetics
2010
[EN] The disposal stage of polylactide (PLA) was assessed by burying it in active soil following an international standard. Degradation in soil promotes physical and chemical changes in the polylactide properties. The characterization of the extent of degradation underwent by PLA was carried out by using Thermal Analysis techniques. In this paper, studies on the thermal stability and the thermal decomposition kinetics were performed in order to assess the degradation process of a commercial PLA submitted to an accelerated soil burial test by means of multi-linear-non-isothermal thermogravimetric analyses. Results have been correlated to changes in molecular weight, showing the same evolutio…
Reprocessed polylactide: Studies of thermo-oxidative decomposition
2012
The combustion process of virgin and reprocessed polylactide (PLA) was simulated by multi-rate linear non-isothermal thermogravimetric experiments under O2. A complete methodology that accounted on the thermal stability and emission of gases was thoroughly developed. A new model, Thermal Decomposition Behavior, and novel parameters, the Zero-Decomposition Temperatures, were used to test the thermal stability of the materials under any linear heating rate. The release of gases was monitored by Evolved Gas Analysis with in-line FT-IR analysis. In addition, a kinetic analysis methodology that accounted for variable activation parameters showed that the decomposition process could be driven by …
Thermal and thermo-oxidative stability of reprocessed poly(ethylene terephthalate)
2013
An exhaustive assessment of the behaviour of virgin and mechanically reprocessed poly(ethylene terephthalate) (PET) facing thermal and thermo-oxidative decomposition processes is presented in this work, as an approach for the energetic valorisation of post-consumer PET goods. Multi-rate linear-non-isothermal thermogravimetric (TGA) experiments under inert (Ar) and reactive (O2) conditions were performed to virgin PET and its recyclates in order to simulate the thermal behaviour of the materials facing pyrolysis and combustion processes. The release of gases was monitored by evolved gas analysis of the fumes of the TGA experiment, by in-line Fourier-transform infrared (IR) analysis, with the…
Proton Conducting Electrospun Sulfonated Polyether Ether Ketone-Graphene Oxide Composite Membranes
2017
[EN] A series of novel composite membranes, based on sulfonated poly(ether ketone) (SPEEK) with a graphene oxide (GO) layer, were prepared. One contained a GO layer sandwiched between the SPEEK-polyvinyl alcohol (PVA) matrix (SPEEK/PVA@GO), and another deposited thin layers of GO on the nanofibers of SPEEK-polyvinyl butyral (PVB), with both sandwiched in the phase matrix of SPEEK-PVA (SPEEK/PVA@GO-NF). Various nanofiber thicknesses were studied by varying the electrospinning time. The prepared composite membranes with different nanofiber thicknesses were characterized by scanning electron microscopy, water uptake, ionic exchange capacity, thermogravimetric analysis, mechanical properties an…
Bene vivere politice
2022
Abstract This chapter approaches the question of biopolitics in ancient political thought looking not at specific political techniques but at notions of the final aim of the political community. It argues that the “happiness” (eudaimonia, beatitudo) that constitutes the greatest human good in the tradition from Aristotle to Thomas Aquinas is not a “biopolitical” ideal, but rather a metabiopolitical one, consisting in a contemplative activity situated above and beyond the biological and the political. It is only with Thomas Hobbes that civic happiness becomes “biopolitically” identified with simple survival; for modernity, as Hannah Arendt puts it, mere being alive becomes the greatest human…
Effect of graphene nanoplatelets on the dielectric permittivity and segmental motions of electrospun poly(ethylene-co-vinyl alcohol) nanofibers
2021
The influence of the addition of graphene nanoplatelets (GNPs) on the intra/inter – molecular segmental motions of poly(ethylene-co-vinyl alcohol) (EVOH) was assessed by means of dielectric thermal analysis (DETA). The relaxation spectra were studied in terms of the dielectric permittivity (ε′) and the dielectric loss tangent (tan δ) at wide ranges of frequency (from 10−2 to 107 Hz) and temperature (from -150 to 140 °C). Two relaxation zones were disthinguished. Below the glass transition temperature (Tg), two β-relaxations were observed, which are characteristic local modes of mobility of the EVOH side groups, and related to the influence of the different surroundings of ethylene or vinyl …
Electrospun Poly(ethylene-co-vinyl alcohol)/Graphene Nanoplatelets Composites of Interest in Intelligent Food Packaging Applications
2018
Graphene nanoplatelets (GNPs) were synthetized from graphite powder and, thereafter, embedded in poly(ethylene-co-vinyl alcohol) (EVOH) fibers by electrospinning in the 0.1&ndash
Crosslinked chitosan/poly(vinyl alcohol)-based polyelectrolytes for proton exchange membranes
2019
[EN] The preparation polyelectrolytes based on crosslinked poly(vinyl alcohol) (PVA) and chitosan (CS) was considered as a feasible alternative to develop highly functionalised, cost-effective and eco-friendly membranes for proton exchange fuel cell technologies. CS/PVA-based membranes were combined with sulfosuccinic acid (SSA) as crosslinking and sulfonating agent, and glycerol (GL) to promote flexibility and favour their manageability. The chemical structure, the thermo-oxidative behaviour, the ethanol uptake, the electric, the proton conductivity, and the performance in direct ethanol fuel cell (DEFC) were assessed. In general, all the CS/PVA-based polyelectrolytes showed a synergetic i…
Functionalised poly (vinyl alcohol)/graphene oxide as polymer composite electrolyte membranes
2019
[EN] Crosslinked poly(vinyl alcohol) (PVA) based composite films were prepared as polyelectrolyte membranes for low temperature direct ethanol fuel cells (DEFC). The membranes were functionalised by means of the addition of graphene oxide (GO) and sulfonated graphene oxide (SGO) and crosslinked with sulfosuccinic acid (SSA). The chemical structure was corroborated and suitable thermal properties were found. Although the addition of GO and SGO slightly decreased the proton conductivity of the membranes, a significant reduction of the ethanol solution swelling and crossover was encountered, more relevant for those functionalised with SGO. In general, the composite membranes were stable under …
A kinetic study of the formation of smectic phases in novel liquid crystal ionogens
2013
[EN] A multi-rate non-isothermal kinetic analysis of the isotropic-melt to liquid crystalline phase transition of novel liquid crystalline ionogenic copolymers, LCIs, the 10-(4-methoxyazobenzene-4'-oxy)decyl methacrylate]-co-2-(acrylamido-2-methyl-1-propanesulfonic acid)s, 10-MeOAzB/AMPS, copolymers, has been performed by means of calorimetric experiments. An analytical methodology which includes the study of the phase transition rate parameter, the determination of the activation energies by using Kissinger and Flynn-Wall-Ozawa models, and the study of the phase transition kinetics by the use of the Avrami theory, has been applied. The formation of the mesophases from the isotropic state o…