Search results for "Ageing"
showing 10 items of 609 documents
Hydrothermal ageing of radiation cured epoxy resin-polyether sulfone blends as matrices for structural composites
2010
Abstract The hydrothermal ageing of epoxy–thermoplastic blends, used as matrices for carbon fibre composites, cured by electron beam, has been studied. Two different thermoplastic percentages have been adopted. A suitable choice of both curing process and formulation parameters allows to carry out irradiation at mild temperature with several advantages, coming from a “non thermal” process, for both the final properties of the materials and the environment. Nevertheless the occurring of vitrification phenomena needs the use of a short thermal treatment after irradiation on the already solid materials, in order to complete the cure reactions. Radiation cured epoxy based matrices have been sub…
Study by FT-IR spectroscopy of ageing of adhesives used in restoration of archaeological glass objects
1999
Abstract A study by FT-IR spectroscopy which aims to compare the stability of five polymers, Araldit XW396/XW 397, Vitralit 7256, Loctite 350, Desmodur N 75/Viacryl SM 564/65 and Krafft silicone commonly used in the restoration of archaeological glass objects when subjected to thermal ageing, UV light ageing and cyclic ageing in SO 2 pollutant chamber has been carried out. Two series of test specimens were prepared in order to reproduce the two methods of application of polymers commonly used in restoration treatments as adhesive and consolidant or coating of glass fragments. Modifications in the chain or side chain structure of polymers, alterations of carbonyl groups in Araldit and isocya…
Gamma-radiation ageing of a low density polyethylene. Effects of irradiation temperature and dose rate
1993
Abstract Ageing due to gamma radiation of a low density polyethylene at various dose rates and temperatures is studied; the effect of thermal treatment only is also considered. The modifications induced in the molecular and crystallinity behaviour of the polymer are investigated by means of gel extraction, measurements of intrinsic viscosity and thermal analysis. Results indicate the occurrence of both crosslinking and oxidative degradation; the extent of the latter increases on decreasing the irradiation dose rate and on increasing the irradiation temperature. Some exceptions are found because of the increase in the mobility of free radicals at high temperature. These effects modify also t…
Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends. Thermal, mechanical and morphological behaviour
2011
Abstract A model epoxy resin/anhydride system, modified with a polyethersulfone (PES) engineering thermoplastic toughening agent, has been studied under hydrothermal ageing in order to investigate the modification of the thermal, morphological and mechanical behaviour through dynamical mechanical thermal analysis, SEM microscopy and fracture toughness test respectively. Two different concentrations of the toughening agent were used in the blends and two ageing conditions have been considered, consisting of the immersion of the samples in distilled water at constant temperature of 70 °C for 1 week and for 1 month. Dynamical mechanical thermal analysis results on hydrothermally aged materials…
A new equipment to measure the combined effect of humidity, temperature, mechanical stress and UV exposure on the creep behaviour of polymers
2008
To be able to study and predict the physical properties of a polymeric material under different environmental conditions is very important. Moisture, UV irradiation, thermal and mechanical stresses can dramatically change the characteristics of the material and hinder some specific applications. In this work, a new equipment able to perform creep tests under different environmental conditions (temperature, humidity, stress) is presented. Some preliminary results are also presented using a sample of polyamide 6. As this polymer is sensitive to all these variables, it is appropriate to verify the effectiveness of the new instrument.
Lipid and fatty acid profile of the retina, RPE/choroid and lacrimal gland, and associations with dietary fatty acids in human subjects
2008
Purpose The contribution of dietary lipids to the accumulation of lipids in the retina during ageing and in the course of age related maculopathies remains under debate. Our objective was to establish associations between fatty acid profiles of ocular structures, and adipose tissue as a surrogate for the past dietary intake of the subjects. Methods Lipids and fatty acids were analyzed by tandem thin-layer chromatography-flame ionization detection and gas chromatography-flame ionization detection from the neural retina, RPE/choroid, lacrimal gland and adipose tissue, collected from 19 women and 8 men, aged 59–95 years. Results DHA concentrations in the neural retina were positively associate…
Troubles du goût et de l'odorat chez les seniors
2022
Association between osteocalcin and cognitive performance in healthy older adults.
2016
INTRODUCTION: cognitive deterioration and reductions of bone health coincide with increasing age. We examine the relationship between bone composition and plasma markers of bone remodelling with measures of cognitive performance in healthy adults.METHODS: this cross-sectional study included 225 old (52% women, mean age: 74.4 ± 3.3 years) and 134 young (52% women, mean age: 23.4 ± 2.7 years) adult participants from the MyoAge project. Whole body bone mineral density was measured by dual-energy X-ray absorptiometry. Blood analyses included a panel of bone-related peptides (dickkopf-1, osteoprotegerin, osteocalcin (OC), osteopontin, sclerostin, parathyroid hormone and fibroblast growth factor …
Advanced Composites and Applications: Book of abstracts
2023
The section ‘Advanced Composites and Applications’ was organized by the Institute for Mechanics of Materials of the University of Latvia (LU MMI) on 16.02.2023 as a part of the annual 81th scientific conference of the University of Latvia. It was organized remotely in Zoom. The official language of the section was English. The duration of the presentation was 10 minutes. The section was devoted to the discussion of the recent results within following topics: structure and properties of polymers and polymer-based composites, long-term properties, creep, and environmental ageing, composites for advanced applications, mechanical aspects of technology, and multifunctional properties.
Impact of oak tannin selection and barrel toasting on the oxidative stability of dry white wine
2018
International audience; The article focuses on the impact of selecting barrel toasting and oak tennin on the dry white wine's oxidative stability. It reports that the management of the barrel ageing is the most important step for the production of premium quality wines and its role in the micro-oxygenation and enrichment of odorant compounds. The oak wood contains the antioxidant capacity. The barrel ageing on the oxidative stability of white wine includes experimental setup, analysis and chemical profiles.