Search results for " DEGRADATION"
showing 10 items of 510 documents
Thermo-oxidative stabilization of poly(lactic acid) with antioxidant intercalated layered double hydroxides
2016
Two antioxidant modified layered double hydroxides (AO-LDHs) were successfully prepared by the intercalation of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (IrganoxCOOH) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) in the layered structure of LDH. It was found that by anchoring the phenolic moieties to the LDH layers the antioxidant power is retained in the case of Trolox, and even amplified in the case of IrganoxCOOH. A small amount of the two AO-LDHs was incorporated into poly(lactic acid), PLA, by solution mixing and melt extrusion. The thermo-oxidative stability of the composites was compared with that of the neat PLA and PLA containing free AOs. SEC analy…
Effects of aging in salt spray conditions on flax and flax/basalt reinforced composites: Wettability and dynamic mechanical properties
2016
Abstract In the last years, the industrial policies are more attentive to issues concerning sustainability, recycling and environmental care. Therefore, the use of natural fibres in composite materials has spread more and more. This paper deals with flax and basalt fibres within an epoxy matrix by investigating the wettability and the dynamic mechanical properties of the resulting composites, subjected to long-term aging tests in critical environmental conditions. The first laminate was constituted by stacking ten layers of bidirectional flax fabrics. The second one was produced by replacing two external flax layers with two layers of basalt mat, for each side of the laminate. Both laminate…
A comparative study of photocatalytically active nanocrystalline tetragonal T zyrcon- type and monoclinic scheelite-type bismuth vanadate
2018
The authors from Vinča Institute of Nuclear Sciences acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project no: 172056 ). The work of K. Smits was supported by Latvian National Research Program IMIS2 (Grant no. 302/2012 ).
Hydrothermal ageing of polylactide/sisal biocomposites. Studies of water absorption behaviour and Physico-Chemical performance
2014
An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a fast…
Effectiveness of some protective and self-cleaning treatments: a challenge for the conservation of temple G stone in Selinunte
2021
Abstract The Temple G of the Archaeological Park of Selinunte (Italy), the largest in Europe, is one of the most impressive temples in the Magna Grecia. Today, it is completely destroyed due to a strong earthquake occurred in the Middle Ages. The used stone is a calcarenite coming from the ancient and renowned quarries of Cusa near the acropolis. This work comes from the today’s proposal of Temple G anastylosis. The goal of the work is to provide the results relating the protective effectiveness of three polymer formulations, appropriately selected, on stone samples taken from the “Capitello” quarry, part of “Cusa quarries”. The formulations functionality was deployed by adding TiO2 nanopar…
Photoelectrochemical removal of chlorfenvinphos by using WO3 nanorods: Influence of annealing temperature and operation pH
2019
[EN] A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400¿°C and 600¿°C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenv…
Nano-hybrids based on quercetin and carbon nanotubes with excellent anti-oxidant activity
2016
Abstract Multi-functional nano-hybrids based on Quercetin (Q), a natural antioxidant, and functionalized Carbon Nanotubes (CNTs) have been formulated and used to prepare Ultra High Molecular Weight PolyEthylene (UHMWPE)-based nanocomposites. The study of the nanocomposites rheological behaviour shows that the immobilization of Q molecules onto CNTs outer surface leads to a beneficial effect on the state of the interface between polymer and nanoparticles. Additionally, the investigation of the thermo- and photo-oxidation processes reveals that the hybrids nanoparticles are able to exert a remarkable stabilizing action, due to strong physical interaction between Q and CNTs. In particular, the…
Halloysite nanotubes/pluronic nanocomposites for waterlogged archeological wood: thermal stability and X-ray microtomography
2020
Filling a polymer with halloysite nanotubes is considered a promising strategy to generate nanocomposites with tailored physicochemical properties. We have focused our attention on pluronic block copolymer/halloysite nanocomposites prepared by melt blending. The effect of composition on thermal stability and polymer crystallinity was investigated by thermogravimetry and differential scanning calorimetry. Electron microscopy was used to monitor the nanoparticle distribution in the polymeric matrix. The pluronic thermal stability is reduced by the clay nanoparticles. Concerning the polymer crystallinity, it is slightly decreased even if the melting temperature is lowered by halloysite. Furthe…
Enhanced Solar Light Photocatalytic Activity of Ag Doped TiO2–Ag3PO4 Composites
2020
Composites comprised of Ag3PO4 and bare TiO2 (TiO2@Ag3PO4) or silver doped TiO2 (Ag@TiO2&ndash
A grain-scale model for high-cycle fatigue degradation in polycrystalline materials
2018
Abstract A grain-scale three-dimensional model for the analysis of fatigue intergranular degradation in polycrystalline materials is presented. The material microstructure is explicitly represented through Voronoi tessellations, of either convex or non-convex domains, and the mechanics of individual grains is modelled using a boundary integral formulation. The intergranular interfaces degrade under the action of cyclic loads and their behaviour is represented employing a cohesive zone model embodying a local irreversible damage parameter that evolves according to high-cycle continuum damage laws. The model is based on the use of a damage decomposition into static and cyclic contributions, a…