Polymer foaming with chemical blowing agents: Experiment and modeling

International audienceAn experimental and theoretical analysis of the polypropylene foaming process using three different chemical blowing agents (CBA) was performed. A simple experiment was designed to analyze the foaming process of polypropylene (PP)/CO2 system under two different pressure conditions. The expansion ratio and final foam structure was measured both by direct observation and from optical measurements and image analysis, showing a good agreement. A single bubble simulation based on relevant differential scanning calorimetry and thermo-gravimetrical analysis experiments, assuming each CBA particles as a nucleation site and accounting for gas diffusion in the surrounding polymer matrix has been built. The sensitivity of the model to physical and processing parameters has been tested. The calculation results are compared to the experiments and open the route to a simplified method for evaluating the efficiency of CBA

Palmitoleic acid prevents palmitic acid-induced macrophage activation and consequent p38 MAPK-mediated-skeletal muscle insulin resistance

Obesity and saturated fatty acid (SFA) treatment are both associated with skeletal muscle insulin resistance (IR) and increased macrophage infiltration. However, the relative effects of SFA and unsaturated fatty acid (UFA)-activated macrophages on muscle are unknown. Here, macrophages were treated with palmitic acid, palmitoleic acid or both and the effects of the conditioned medium (CM) on C2C12 myotubes investigated. CM from palmitic acid-treated J774s (palm-mac-CM) impaired insulin signalling and insulin-stimulated glycogen synthesis, reduced Inhibitor κBα and increased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase in myotubes. p38 MAPK inhibition or siRNA partially ameliorated these defects, as did addition of tumour necrosis factor-α blocking antibody to the CM. Macrophages incubated with both FAs generated CM that did not induce IR, while palmitoleic acid-mac-CM alone was insulin sensitising. Thus UFAs may improve muscle insulin sensitivity and counteract SFA-mediated IR through an effect on macrophage activation

Introduction. La désuétude conceptuelle – abandon ou transformation ?

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Polyvinyl Butyral

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Effect of Compatibilization on Poly-ε-Caprolactone Grafting onto Poly(ethylene-co-vinyl alcohol)

International audienceThe non-miscibility of the reactants during solvent free poly-ε-caprolactone grafting onto poly(ethylene-co-vinyl alcohol) (EVOH) dramatically affects reaction kinetics. Different solutions were proposed to accelerate the exchange reactions between poly(ethylene-co-vinyl alcohol) and poly-ε-caprolactone. Reactions were conducted in a batch reactor or a mini twin-screw extruder. The addition of a poly(ethylene-co-vinyl alcohol)-g-poly-ε-caprolactone copolymer increased the compatibility of the reactants and led to a higher reaction rate. This copolymer was either prepared separately and added at the reaction beginning or prepared in situ grafting caprolactone from EVOH. The reactive system evolution was analyzed using molar mass evolution, microstructure characterization, thermal properties and the reactive blend morphology. The compatibilization effect combined with optimized reaction conditions, such as concentration and nature of catalyst and temperature, resulted in an important increase in reaction rates. Among the tested catalysts, 1,5,7-Triazabicyclo [4.4.0]dec-5-ene was a more efficient catalyst for grafting reactions than Tin (II) 2-ethylhexanoate

Synthesis and characterization of multi-allyl-functionalized polylactic acid and polyhydroxybutyrate polyurethane, and their cross-linking by copolymerization with 2-hydroxylethyl methacrylate

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Blends of Plasticized Polyvinyl Butyral and Polyvinyl Chloride: Morphology Analysis in View of Recycling

International audienceThe morphology development of blends of plasticized polyvinyl butyral (PVB) with plasticized polyvinyl chloride (PVC) is studied to obtain a droplet-in-matrix morphology. Such blends can be used for recycling wastes of plasticized PVB in PVC for flooring because migration of the plasticizer of PVB towards the surface is reduced. Model systems of PVC plasticized with diisodecyl phthalate (DIDP) and of PVB plasticized with dibutyl sebecate (DBS) are used as representatives of common compositions. The percolation threshold of the PVB phase occurs at 22 vol% of plasticized PVB. The morphology results of an equilibrium between break-up and coalescence. The dependence of the characteristic dimension upon the volume fraction is described by a power-law with exponent 1.5 slightly larger than the theoretical value

Antibacterial Textile Based on Hydrolyzed Milk Casein

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Reversible/irreversible networks formation in thermally removable adhesive

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