Time filter

Source Type

Brest, France

Jouault N.,CEA Saclay Nuclear Research Center | Dalmas F.,CNRS East Paris Institute of Chemistry and Materials Science | Said S.,LIMATB | Di Cola E.,European Synchrotron Radiation Facility | And 3 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

In this paper we present a direct measurement of stretched chain conformation in polymer nanocomposites in a large range of deformation using a specific contrast-matched small angle neutron scatttering (SANS) method. Whatever are the filler structure and the chain length the results show a clear identity of chain deformation in pure and reinforced polymer and offer more insight on the polymer chain contribution in the mechanical reinforcement. It suggests that glassy layer or glassy paths, recently proposed, should involve only a small fraction of chains. As a result, the remaining filler contribution appears strikingly constant with deformation as explained by continuous locking-unlocking rearrangement process of the particles. © 2010 The American Physical Society. Source

Tissier F.,EA 4324 ORPHY | Mallem Y.,University of Nantes | Goanvec C.,EA 4324 ORPHY | Didier R.,EA 4324 ORPHY | And 11 more authors.

Background and aims: Statins are prescribed for their preventative effects within atherosclerosis development. To our knowledge, no study focusing on very low-dose (non-hypolipidemic effect) and long-term atorvastatin treatment in vivo was available. Our aim was to assess the effect of such atorvastatin treatment on the mechanical and functional characteristics of arteries in the context of primary prevention. Methods: An atorvastatin treatment (2.5 mg/kg/day) was tested against controls on 34 male 3 to 12 month-old WHHL rabbits. No effect on total cholesterol, triglycerides, HDL or LDL was observed. The arterial stiffness was evaluated on vigil animals by pulse wave velocity (PWV) measurement. Then, in vitro measurements were made to evaluate (1) the endothelial and vascular smooth muscle function, (2) the elasticity of the arterial wall and (3) the composition in collagen and elastin in the aorta. Results: The PWV increasing observed with age in control group was canceled by treatment, creating a significance difference between groups at 12 months (5.17 ± 0.50 vs 2.14 ± 0.34 m s-1 in control and treated groups respectively). Vasoreactivity modifications can't explain this result but maintain of elasticity with treatment in large arteries was confirm by a static tensile test. A first possible explanation is the change of wall composition with treatment, validated by the percentage of elastin at 12 months, 4.4% lower in the control group compared to the treated group (p < 0.05). Conclusions: This study shows that a non-hypocholesterolemic statin treatment could improve vessel elasticity in the atherosclerotic WHHL model. The great novelty of this work is the vessel wall composition changing associated. This first approach in animal opens the reflection on the use of these low doses in humans. This could be interesting in the context of arterial stiffening with aging, non-hyperlipidemic atherosclerosis or with cholesterol reduce by another therapy or lifestyle modification. © 2016 Elsevier Ireland Ltd. Source

Hassan H.,University of Tours | Hocine N.A.,INSA Val de Loire | Mederic P.,LIMATB | Deffarges M.-P.,University of Tours | Poirot N.,GREMAN
Journal of Applied Polymer Science

This work focuses on the effect of nanoclay mass fraction on the properties of polyamide 12 matrix. Relationships between mechanical, thermal, and structural properties of polyamide 12/Cloisite® 30B nanocomposites were studied. The material structure, previously described from XRD and TEM experiments, was more thoroughly characterized in the present work using SEM and FTIR techniques. The FTIR results clearly showed that clay galleries are intercalated by PA chains, which leads to a partially exfoliated nanostructure, confirming the TEM observations and the XRD analysis. However, a few micrometric aggregates are evidenced by SEM analysis, particularly at high clay fractions. TGA and DTA measurements showed that the thermal stability of PA12 matrix is slightly modified by the Cloisite® 30B content. Viscoelastic properties of the nanocomposites in solid-state were analyzed as functions of strain, frequency, and temperature. The extent of the linear response regime of the material is shown to be sensitive to the amount of clay: nonlinearities appear at lower strain values as the clay mass fraction increases. Both relative dynamical moduli also increase with increasing clay mass fraction, with frequency dependence for the viscous modulus and without frequency dependence for the elastic modulus. Finally, similarities have been pointed out between viscoelastic properties of the nanocomposites in solid and melt states. For example, the percolation threshold is highlighted at the same clay mass fraction, â2%, in both states. © 2015 Wiley Periodicals, Inc. Source

The linear viscoelastic properties of immiscible polyethylene/polyamide blends filled with clay nanoparticles or compatibilized by a copolymer, exhibiting identical nodular morphologies, have been studied. The apparent compatibilizing effect of clay nanoparticles, exclusively located at the interface, was evidenced and compared to the more classical organic compatibilization due to the formation of a macromolecular interphase. The results show that there are some analogies between the two types of compatibilization, but mainly highlight significant differences in rheological properties of the two types of interphase involved in the compatibilization mechanisms. The major differences in interphase viscoelastic properties were evidenced not only directly from the experimental data but also indirectly by using the Palierne's model for different clay or compatibilizer contents. © 2013 The Society of Rheology. Source

Louarn S.,LIMATB | Ploteau J.-P.,LIMATB | Glouannec P.,LIMATB | Noel H.,LIMATB
Drying Technology

This article deals with the drying of the waste by-product of an activated sludge manure treatment plant. The studies concern the low temperature drying of planar plates 3 cm thick. The upper face of the sludge is subjected to a tangential air flow controlled for speed, temperature, and humidity. The lower face can be subjected to contact heating. The maximum temperature for air and the bottom of the product is 60 °C. After characterizing the main thermophysical and hygric properties of the product, the laboratory set-up specifically designed for this study is described. Experiments are performed to determine temperature, mass loss, and deformation evolutions for different boundary conditions. These experimental data are used to build a numerical one-dimensional heat and mass transfer model to predict temperature and moisture content fields. Sludge is assimilated with a hygroscopic porous medium, and shrinkage is not taken into account. To validate this model, several comparisons between simulated and measured data are made for different drying methods (hot or fresh air convective drying, contact drying, and combined drying) and various drying conditions. © 2014, Copyright Taylor & Francis Group, LLC. Source

Discover hidden collaborations