Search results for "Absorption"
showing 10 items of 2701 documents
Absorption kinetics and swelling stresses in hydrothermally aged epoxies investigated by photoelastic image analysis
2015
Abstract The present work proposes an experimental optical methodology able to measure the transient swelling stresses induced by the water uptake ageing of polymers. In particular, the work describes the implementation of a Photoelastic technique to quantify internal stresses arising during the hydrothermal ageing of cast epoxy samples. The material investigated is a model DGEBA/DDS epoxy system. Curing and post-curing cycles have been optimised in order to obtain a fully cured, high T g , and completely stress free initial condition. Rectangular beam samples were then left in a hydrothermal bath at 90 °C, and regularly monitored by gravimetric and photoelastic analyses. The quantitative e…
Basalt Fibre Composite with Carbon Nanomodified Epoxy Matrix under Hydrothermal Ageing
2021
This work aimed to investigate the effect of hybrid carbon nanofillers (e.g., carbon nanotubes/carbon nanofibers in the ratio 1:1 by mass) over the electrical and flexural properties for an epoxy matrix and corresponding basalt fibre reinforcing composite (BFRC) subjected to full-year seasonal water absorption. Hydrothermal ageing was performed by full immersion of the tested materials into distilled water according to the following model conditions (seasons). The mechanical properties were measured in three-point bending mode before environmental ageing and after each season. Upon environmental ageing, the relative change of flexural strength and elastic modulus of the epoxy and NC was wit…
Water absorption and hydrothermal ageing of epoxy adhesives reinforced with amino-functionalized graphene oxide nanoparticles
2021
Abstract The study is focused on quantitative characterization of water absorption and hydrothermal ageing effects in a room-temperature amine cured epoxy adhesive widely used in automotive, aerospace, construction, and marine industries. Amino-functionalized graphene oxide (mGO) nanoparticles were incorporated into the epoxy (up to 1.72 wt.%) enabled cross-linking reactions and providing high interfacial adhesion, superior reinforcement efficiency and enhanced resistance to hydrothermal ageing of nanocomposites. Anomalous water absorption accompanied by progressive weight loss of samples (down to 7%) is fitted by two-stage models considering additive and coupled contribution from water dif…
Hydrothermal Aging of an Epoxy Resin Filled with Carbon Nanofillers
2020
The effects of temperature and moisture on flexural and thermomechanical properties of neat and filled epoxy with both multiwall carbon nanotubes (CNT), carbon nanofibers (CNF), and their hybrid components were investigated. Two regimes of environmental aging were applied: Water absorption at 70 °
Hybrid layers of etch-and-rinse versus self-etching adhesive systems.
2010
Objective: To evaluate the effectiveness in the formation of resin tags, adhesive lateral branches and hybrid layers of five adhesive systems, when bonding to dentine. Material and Methods: Flat dentin surfaces from 25 molars were bonded with several adhesive systems according to the manufacturers? instructions. Composite build-ups were constructed incrementally with Tetric Ceram. The Specimens were sectioned parallel to the long axis. One section was treated with phosphoric acid and sodium hypochlorite in order to reveal the hybrid layer formation. The other section was stored in 30% hydrochloric acid to detect resin tags and adhesive lateral branch formation. Results: The two etch-and-rin…
Durability of Biodegradable Polymer Nanocomposites
2021
Biodegradable polymers (BP) are often regarded as the materials of the future, which address the rising environmental concerns. The advancement of biorefineries and sustainable technologies has yielded various BP with excellent properties comparable to commodity plastics. Water resistance, high dimensional stability, processability and excellent physicochemical properties limit the reviewed materials to biodegradable polyesters and modified compositions of starch and cellulose, both known for their abundance and relatively low price. The addition of different nanofillers and preparation of polymer nanocomposites can effectively improve BP with controlled functional properties and change the…
Landfill gas upgrading with pilot-scale water scrubber: Performance assessment with absorption water recycling
2012
Abstract A pilot-scale counter current absorption process for upgrading municipal solid waste (MSW) landfill gas to produce vehicle fuel was studied using absorption, desorption and drying units and water as an absorbent. Continuous water recycling was used without adding new water to the system. The process parameters were defined by a previous study made with this pilot system. The effect of pressure (20–25 bar), temperature (10–25 °C) and water flow speed (5.5–11 l/min) on the upgrading performance, trace compounds (siloxanes, halogenated compounds) and water quality were investigated. Raw landfill gas flow was kept constant at 7.41 Nm3/h. Methane (CH4) and carbon dioxide (CO2) contents …
Upgrading landfill gas using a high pressure water absorption process
2014
Abstract The upgrading of landfill gas (methane 54.2 ± 2.0%, carbon dioxide 42.1 ± 2.4% and nitrogen 3.7 ± 1.2%) was studied with a pilot-scale high pressure water absorption system consisting of absorption, desorption and gas drying units. The gas was upgraded in two phases and with two absorption columns operating in sequence in pressures up to 180 bar, and with initial pressures of 8 and 10 bar. This type of high pressure process, where water is used for increasing the gas pressure, does not need a separate compression unit to produce the gas pressure required by gas vehicles. Product gas with a methane contents ranging from 83.0% to 92.1% was achieved with differing process parameters, …
The vibrational levels of methane obtained from analyses of high-resolution spectra
2006
International audience; Methane and its tetrahedral isotopologues are spherical-top molecules whose high-resolution rovibrational spectra can only be analyzed in detail, thanks to sophisticated symmetry-adapted tensorial models. However, the effective Hamiltonian parameters of such models do not give direct access to the positions of the vibrational sublevels. In this paper, we present a calculation of the vibrational level positions for 12CH4, 13CH4, 12CD4 and 13CD4 performed using the effective Hamiltonian parameters obtained through recent analyses. We also include the results of a re-analysis of the octad system of 12CH4 performed with a higher order of the development which slightly im…
A five-coordinate manganese(iii) complex of a salen type ligand with a positive axial anisotropy parameter D.
2017
A new high-spin d4 roughly trigonal–bipyramidal (TBP) manganese(III) complex with a salen type ligand (H2L), namely MnL(NCS)·0.4H2O, has been synthesised and characterised by elemental analysis, ESI mass spectrometry, IR and UV-vis spectroscopy, and spectroelectrochemistry. X-ray diffraction analysis revealed an axial compression of the approximate TBP. Temperature dependent magnetic susceptibility and variable-temperature variable-field (VTVH) magnetisation measurements, as well as high-frequency and -field EPR (HFEPR) spectroscopy, were used to accurately describe the magnetic properties of this complex and, in particular, determine the spin Hamiltonian parameters: g-values and the zero-f…