Agro-materials : a bibliographic review

Facing the problems of plastic recycling and fossil resources exhaustion, the use of biomass to conceive new materials appears like a reasonable solution. Two axes of research are nowadays developed : on the one hand the synthesis of biodegradable plastics, whichever the methods may be, on the other hand the utilization of raw biopolymers, which is the object of this paper. From this perspective, the “plastic” properties of natural polymers, the caracteristics of the different classes of polymers, the use of charge in vegetable matrix and the possible means of improving the durability of these agro-materials are reviewed

The effect of polymer/plasticiser ratio in film forming solutions on the properties of chitosan films

In this work physical-chemical properties of chitosan/ glycerol film forming solutions (FFS) and the resulting films were analysed. Solutions were prepared using different concentrations of plasticising agent (glycerol) and chitosan. Films were produced by solvent casting and equilibrated in a controlled atmosphere. FFS water activity and rheological behaviour were determined. Films water content, solubility, water vapour and oxygen permeabilities, thickness, and mechanical and thermal properties were determined. Fourier transform infrared (FTIR) spectroscopy was also used to study the chitosan/glycerol interactions. Results demonstrate that FFS chitosan concentration influenced solutions consistency coefficient and this was related with differences in films water retention and structure. Plasticiser addition led to an increase in films moisture content, solubility and water vapour permeability, water affinity and structural changes. Films thermo-mechanical properties are significantly affected by both chitosan and glycerol addition. FTIR experiments confirm these results. This work highlights the importance of glycerol and water plasticisation in films properties.This work was supported by National Funds from FCT - Fundacao para a Ciencia e a Tecnologia, through project PEst-OE/EQB/LA0016/2011.Authors Joana F. Fundo, Andrea C. Galvis-Sanchez and Mafalda A. C. Quintas acknowledge FCT for research grants SFRH/ BD / 62176 / 2009, SFRH/BPD/37890/2007 and SFRH / BPD / 41715 / 2007, respectively

Mechanical behaviour of metal-ceramic bonds

The mechanical behaviour of ceramics bonded with metal is analyzed from the mechanical point of view (interfacial fracture mechanics, applied and residual stress field) and from the physico-chemical point of view taking into account the embrittlement induced by interfacial reactions or diffusion of metal into ceramic and the damages due to the change in interfacial microstructure (segregation, interfacial phases or films, microcracks, ...) during bonding or life. Indeed the behaviour of metal-ceramic bonds is inevitably dependent on the synthesis of all those parameters.Le comportement mécanique des liaisons céramique-métal est analysé du point de vue mécanique (mécanique de la rupture interfaciale, champs des contraintes appliquées et résiduelles) et, du point de vue physicochimique, en tenant compte des effets de fragilisation induits par les réactions interfaciales ou la diffusion du métal dans la céramique et des endommagements dus aux modifications de la microstructure interfaciale (segrégation, phases et films interfaciaux, microfissures ... ) intervenant lors de l'assemblage ou du service. En effet le comportement des assemblages métal-céramique dépend obligatoirement de la synthèse de tous ces paramètres

Viscoelasticity properties of biopolymer composite materials determined using finite element calculation and nanoindentation

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Humidity-Activated Shape Memory Effects on Thermoplastic Starch/EVA Blends and Their Compatibilized Nanocomposites

In this work, a systematic study on the humidity-activated shape memory properties of dual-responsive shape memory bionanocomposites with both humidity- and thermally-activated shape memory effects is reported. The study is performed through humidity-mechanical cycles in an Instron machine with a temperature chamber equipped with an ultrasonic humidity generator. In particular, the bionanocomposites studied are based on blends of ethylene–vinyl acetate (EVA) and thermoplastic starch reinforced with natural bentonite. In our previous work, thermomechanical cycles are performed by using EVA-induced crystallization and a preliminary humidity-activated shape memory test is designed. Herein, the shape memory results of both blends and their nanocomposites reflect the very good ability to humidity-activated recover of the initial shape with values higher than 80%. Moreover, the ability to fix the temporary shape of this systems is very good, especially when nanofillers are added. The compatibilizer effect of natural bentonite is demonstrated by means of different techniques such as scanning emission microscopy and mapping by confocal Raman spectroscopy.The authors are indebted to the Spanish Ministry of Economy, Industry and Competitiveness MINEICO (MAT2013-48059-C2-1-R) and to the Regional Government of Madrid (S2013/MIT-2862) for their economic support. L.P. acknowledges MINEICO for the “Ramon y Cajal” (RYC 2014–15595) contract. J.-M.R. and P.D. are grateful to the “Region Wallonne” and European Community (FEDER, FSE) in the excellence program OPTI2MAT for their financial support. UMONS thanks the “Belgian Federal Government Office Policy of Science (SSTC)” for general support in the frame of the PAI-7/05 and “Région Wallonne for financial support FEDER (LCFM_BIOMAT & BIORGEL). J.-M.R. is an FNRS-FRS research associate (Belgium). The authors thank CSIC for the I-LINK project, I-LINK1149.Peer Reviewe

Biofriendly ionic liquids for starch plasticization: a screening approach

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Damages and cracks in ceramic/metal interfaces

When metal/ceramic junctions are achieved by solid state bonding process, damages and cracks are often observed near by the interface. This paper focuses on the mechanical origin of the embrittlement. The main causes are : - residual stresses due to the mismatch in the mechanical properties of the materials to be joined - friction of metal on the ceramic surface at the interface during bonding - decrease of the toughness of the ceramic close to the interface consecutively to the diffusion of the metallic specie into the ceramic