17 research outputs found
A triagem de materiais reciclĂĄveis e as variabilidades inerentes ao processo: estudo de caso em uma cooperativa
Solvolyse de déchets de composites époxyde-verre
La glycolyse des rĂ©seaux tridimensionnels Ă©poxydes rĂ©ticulĂ©s par des anhydrides est assez aisĂ©e. Le tĂ©trabutylorthotitanate sâest rĂ©vĂ©lĂ© un catalyseur efficace. La dĂ©polymĂ©risation est poussĂ©e pratiquement jusquâau stade monomĂšre et le glycolysat est constituĂ© par des esterdiols, des tĂ©trols et lâexcĂšs de glycol. LâexcĂšs de solvant peut ĂȘtre Ă©liminĂ© par distillation sous vide, sans quâil ne se produise de rĂ©actions de rĂ©Ă©quilibrage vers la formation dâespĂšces de masse molaire plus Ă©levĂ©e . La glycolyse des matĂ©riaux composites se produit elle aussi efficacement. Les fibres de verres sont libĂ©rĂ©es aprĂšs dĂ©sagrĂ©gation de la matrice. Des Ă©chantillons de grande taille pouvant ĂȘtre traitĂ©s, on peut rĂ©cupĂ©rer par sĂ©paration solide-liquide, des fibres longues. AprĂšs lavage et sĂ©chage, le taux de contamination organique est infĂ©rieur Ă 0,05 %. Bien que les rĂ©seaux Ă©poxydes rĂ©ticulĂ©s par des aminĂ©s ne contiennent pas de jonctions esters, la glycolyse conduit encore Ă une dĂ©polymĂ©risation, plus aisĂ©e lorsque le durcisseur est une aminĂ© aliphatique. La glycolyse, suivant le mĂȘme mode opĂ©ratoire, de composites Ă matrice DGEBA rĂ©ticulĂ© par une aminĂ© aromatique conduit Ă la libĂ©ration des libres, mais restant polluĂ©es par des rĂ©sidus organiques. Nous avons pu rĂ©duire trĂšs nettement la pollution organique par lâemploi dâautres catalyseur et/ou solvants et espĂ©rons encore progresser dans cette voie
Glycolysis of epoxideâamine hardened networks IIâaminoether model compound
International audienceThe aim of this work was to understand the reactions that appear during glycolytic depolymerization of an epoxide-amine hardened thermoset. A model compound (product of condensation of phenylglycidyl ether to N,N'-dimethylethylenediamine) of the epoxy thermoset was synthesized to simplify the study. By reaction with 1,4-butanediol, a cleavage of the rho-O-C linkage occurs, leading to formation of phenol.A stagnation of the yield in phenol at about 20% was observed for the uncatalysed reaction. Different catalysts were checked (sodium methylate, titanium(IV) n-butoxide, lithium perchlorate and p-toluenesulfonic acid). The most efficient of them are p-toluenesulfonic acid (3 w/w%) and sodium methylate (30 w/w%). The disappearance of the initial model compound was also observed, even for a low yield in phenol.The different reaction products were separated and analysed by NMR spectroscopy. The results are in accordance with a reaction scheme based on two mechanisms of rho-O-C linkage cleavage
Glycolysis of epoxide-amine hardened networks. I. Diglycidylether/aliphatic amines model networks
International audienceEpoxide-amine hardened networks are high performance materials in composites, coatings and adhesives area. Solvolysis is an efficient method of polymer waste valorisation, particularly for fibre-reinforced composites, allowing recovery of inorganic parts (fibres, charges, metals), whereas the matrix yields depolymerization products which may be recycled in useful raw materials for the chemical industry.However, the curing of epoxides with amines results from non-reversible condensation reactions, and then, the controlled depolymerization by chemical reactives seems to be impossible.We have found that the networks from diglycidylether of bisphenol-A (DGEBA) cured with polyamine may be decomposed by glycols, in relatively mild conditions, leading to 'liquefaction' of the matrix. A solvolytic cleavage of ether linkages, originally present in the DGEBA molecular structure, has been identified. Apparently, the reaction is a transetherification one. Depolymerization products are, for a part, aromatic hydroxyl terminated low molecular weight compounds
Le statut d'hybride de Platanus acerifolia confirmé et celui de P. densicoma mis en évidence à l'aide de marqueurs génétiques moléculaires : Conséquences
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