Formulation of new materials based on geopolymer binders and different road aggregates

International audienc

Effect of Nanoclay Hydration on Barrier Properties of PLA/Montmorillonite Based Nanocomposites

International audienceIncorporating Cloisite 30B (C30B) in poly(lactic acid) (PLA) matrix was investigated as functions of the content and of the hydration state of nanoclays. Two series of PLA based nanocomposites were prepared by melt compounding using nanoclays in hydrated state (undried C30B) or preliminary dried (dried C30B). Their structure was characterized by transmission electron microscopy (TEM) observations and X-ray diffraction (XRD) measurements which highlighted the coexistence of exfoliated, intercalated, and aggregated structures. Rheological measurements put forward better degrees of dispersion and of exfoliation for nanocomposites containing undried C30B. From differential scanning calorimetry (DSC) measurements, a slight change in crystallinity was measured owing to the nucleating effect induced by the nanoclays. The transport properties were analyzed from permeation and sorption kinetics. A significant improvement of the water and oxygen barrier properties was obtained, especially for nanocomposites with undried C30B, while a reduction in diffusion was evidenced. This peculiar behavior was correlated to the presence of water molecules included in C30B contributing to a better dispersion and orientation of the nanoplatelets into the PLA matrix

Impact of hydrophobic plasma treatments on the barrier properties of poly(lactic acid) films

International audienceDifferent hydrophobic plasma treatments (CF4, CF4/H2, CF4/C2H2, tetramethyl silane (TMS)) were applied to the poly(lactic acid) (PLA) film in order to improve its water and oxygen barrier properties. The plasma parameters, such as power, gas flow and treatment time, were optimized according to the water contact angle measurements. X-ray photoelectron spectroscopy measurements revealed the presence of either fluorine (CF, CF2, CF3) or silicon (SiOxCy) functional groups on the film surface after the fluorinated or TMS plasma treatments, respectively. The thermal properties of the treated PLA films were studied by means of the differential scanning calorimetry (DSC) measurements and were found not to be influenced by the plasma treatment. The water permeability measurements showed an improvement of the PLA barrier properties as a result of all plasma treatments used and, particularly, after CF4/C2H2 plasma. The water vapour sorption measurements confirmed well the improvement of the water barrier properties by the reduction of the water solubility. No impact of the plasma treatment on the oxygen barrier properties of the PLA film was observed, even at high relative humidity (up to 90%)

Improvement of Water Barrier Properties of Poly(ethylene- co -vinyl alcohol) Films by Hydrophobic Plasma Surface Treatments

International audienc

Improvement of Water Barrier Properties of Poly(ethylene- co -vinyl alcohol) Films by Hydrophobic Plasma Surface Treatments

International audienc

A Single-Component Molecular Metal Based on a Thiazole Dithiolate Gold Complex

International audienceA single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 S·cm−1) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S·cm−1 at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system

Second asymptomatic carotid surgery trial (ACST-2) : a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86-1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91-1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable