Search results for "Materials compostos"
showing 10 items of 14 documents
The Role of Covalent Functionalization in the Thermal Stability and Decomposition of Hybrid Layered Hydroxides
2020
The room temperature synthesis of two Co-based hybrid layered hydroxides containing the same organic ligand (suberate [Sub]), one connected through purely electrostatic interactions (CoAl layered double hydroxide [LDH]), and the other covalently functionalized (α-CoII simonkolleite phase) has been carried out. The magnetic properties exhibit an acute difference in the magnetization temperatures (from ≈10 K for the CoAl-LDH to ≈55 K for the α-CoII). Moreover, the role of the covalent functionalization in the thermal stability and the decomposition has been investigated by a forefront characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spect…
Thermal analysis applied to the characterization of degradation in soil of polylactide: I. Calorimetric and viscoelastic analyses
2010
[EN] An accelerated soil burial test has been performed on a commercial polylactide (PLA) for simulating non-controlled disposal. Degradation in soil promotes physical and chemical changes in polylactide properties, which can be characterized by Thermal Analysis techniques. Physical changes occurred in polylactide due to the degradation in soil were evaluated by correlating their calorimetric and visco-elastic properties. It is highly remarkable that each calorimetric scan offers specific and enlightening information. Degradation in soil affects the polylactide chains reorganization. A multimodal melting behavior is observed for buried PLA, degradation in soil also promotes the enlarging th…
Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites
2017
[EN] The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from - 130 degrees C to 130 degrees C) and frequency ranges (from 10(-2)-10(7) Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulc…
Degradation of Plasticised Poly(lactide) Composites with Nanofibrillated Cellulose in Different Hydrothermal Environments
2022
AbstractIn this study, bionanocomposite films based on poly(lactide) (PLA) plasticised with poly(ethylene glycol) (PEG) (7.5 wt%) and reinforced with various contents of nanofibrillated cellulose (NFC) (1, 3, 5 wt%) were prepared. The hydrothermal degradation was investigated through immersion in several aqueous environments at temperatures of 8, 23, 58, and 70 °C as a function of time (7, 15, 30, 60, 90 days). The effect of water immersion on the physicochemical properties of the materials was assessed by monitoring the changes in the morphology, thermo-oxidative stability, thermal properties, and molar mass through field emission scanning electron microscopy (FE-SEM), thermogravimetric an…
One-pot synthesis of a new generation of hybrid bisphosphonate polyoxometalate gold nanoparticles as antibiofilm agents
2019
International audience; A reduced polyoxovanadate functionalized with bisphosphonate molecules was synthesized and used to prepare in one step hybrid organic-inorganic polyoxometalate decorated gold nanoparticles. These new composites were shown to strongly inhibit P. aeruginosa and S. epidermidis biofilms growth, the three components constituting the nanoparticles (Au 0 core, vanadium and alendronate) acting synergistically.
Thermal kinetics for the energy valorisation of polylactide/sisal biocomposites
2018
[EN] The thermal stability and decomposition kinetics of PLA/sisal biocomposites was discussed to evaluate the suitability of their use in energy recovery processes such as pyrolysis and combustion. The influence of the addition of sisal up to 30%wt, the presence of coupling agent, and the atmosphere of operation, i.e. inert or oxidative was discussed by means of multi-rate linear non-isothermal thermogravimetric experiments. All biocomposites showed a mean high heating value of 15 MJ/kg indicating their suitability for energy recovery processes. The thermal requirements of PLA/sisal decomposition were assessed in terms of onset decomposition temperature and apparent activation energy. A mi…
Prussian blue@MoS2 layer composites as highly efficient cathodes for sodium- and potassium-ion batteries
2018
Prussian blue (PB) represents a simple, economical, and eco‐friendly system as cathode material for sodium‐ion batteries (SIBs). However, structural problems usually worsen its experimental performance thus motivating the search for alternative synthetic strategies and the formation of composites that compensate these deficiencies. Herein, a straightforward approach for the preparation of PB/MoS2‐based nanocomposites is presented. MoS2 provides a 2D active support for the homogeneous nucleation of porous PB nanocrystals, which feature superior surface areas than those obtained by other methodologies, giving rise to a compact PB shell covering the full flake. The nanocomposite exhibits an ex…
Relevant factors for the eco-design of polylactide/sisal biocomposites to control biodegradation in soil in an end-of-life scenario
2017
[EN] The eco-design considers the factors to prepare biocomposites under an end-of-life scenario. PLA/sisal biocomposites were obtained from amorphous polylactide and sisal loadings of 10, 20 and 30 wt% with and without coupling agent, and subjected to biodegradation in soil according to standard IS0846. Mass loss, differential scanning calorimetry and size-exclusion chromatography were used for monitoring biodegradation. A statistical factorial analysis based on the molar mass M-n, and crystallinity degree X-c pointed out the relevance and interaction of amount of fibre and use of coupling agent with the time of burial in soil., During the preparation of biocomposites, chain scission provo…
Protection of high-density polyethylene-silicon composites from ultraviolet-visible photodegradation
2017
[EN] The extent of the ultraviolet¿visible (UV¿vis) photoirradiation effect on high-density polyethylene (HDPE) and HDPE¿sili-con (Si) composites is reported in terms of the addition of Si microparticles at contents of 0.1, 1, and 5 wt %. A standard acceleratedUV-vis exposure was applied over 2750 h, corresponding to 22 months in Florida. Thermogravimetry, differential scanning calorimetry,and Fourier transform infrared spectroscopy were used as reliable techniques for monitoring the quality of the HDPE-Si composites. Theincreasing addition of Si microparticles delayed the photodegradation of the HDPE¿Si composites. Because of their strong light-scattering effects, Si microparticles blocked…
Water absorption and hydrothermal performance of PHBV/sisal biocomposites
2014
[EN] The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (TH ¿ 26, 36 and 46 C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water d…