Massó, M.; Moré-Ollé, P.; Carrasco, F.; Santana, O.; Maspoch, M.; Bou, J. J. European Meeting on Chemical Industry and Environment p. 351-352 Presentation's date: 2015-06 Presentation of work at congresses
In this study the dynamic viscoelastic properties of three structurally modified poly(lactic acid) (PLA) samples processed through reactive extrusion were analyzed. While classical chromatographic and spectroscopic techniques exhibited limited sensitivity to the presence of topological changes, rheological measurements confirmed the presence of non-uniform branched macromolecules, holding sparsely long chain branches. According to the processing conditions used, the flow activation energy and the thermorheologically simple behavior remained roughly unaffected for PLA-REX containing an amount of modified chains up to 24%. Distinctly separated relaxation processes in a broader transition zone were observed in the complex viscosity function (|¿*(¿)|) of all PLA-REX samples. The “extended Carreau-Yassuda” model and an extension of the Havriliak-Negami model, proposed in this work, were used to capture the main characteristics of |¿*(¿)| experimental data. Both fitted models were inverted to molecular weight distribution (MWD) spectrum using the numerical inversion technique of Shaw and Tuminello and these were compared with size exclusion chromatography (SEC) MWDs. It was shown that the resolution of the predicted bimodal MWDs was enhanced when the model used to fit|¿*(¿)| data was exempted from the Cox-Merz rule and included a complex time dependence. Based on the MWDs deduced from solely melt measurements, a procedure was described to quantitatively estimate the amount of modified chains.
Cyclic butylene terephthalate (CBT (R)) is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT) is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI) as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or exfoliation and flocculated-intercalated structures were observed. The compatibility between the pCBT matrix and clay was further increased by preparing PMDI-tethered intercalated organoclay. The modified organoclay then exfoliated during ring-opening polymerization and yielded true pCBT/clay nanocomposites. This work demonstrates that reactive chain extension of CBT with a polyfunctional isocyanate is an effective method to obtain toughened pCBT nanocomposites. Moreover, isocyanates can enhance the compatibility between pCBT and nanofiller as well as the degree of exfoliation.
Cailloux, J.; Santana, O.; E Franco-Urquiza; Bou, J. J.; Carrasco, F.; Maspoch, M. Journal of materials science Vol. 49, num. 11, p. 4093-4107 DOI: 10.1007/s10853-014-8101-y Date of publication: 2014-06-01 Journal article
The architectural modifications of a linear poly(D,L-Lactide) acid (PD,L-LA) commercial grade were induced by a one-step reactive extrusion-calendering process using a styrene-glycidyl acrylate copolymer as reactive agent. The melt degradation was counteracted by chain extension and branching reactions, leading to a stabilization of the melt properties and an increase in the molecular weight. For such modified samples [poly(lactic acid) (PLA)-reactive extrusion (REX)], the rate of physical aging at 30 A degrees C was investigated during 1 week in order to simulate industrial storage conditions. Fracture behavior of "de-aged" and "controlled aged" (1 week) samples was investigated using the essential work of fracture (EWF) methodology and the critical tip opening displacement at the crack propagation onset, respectively. These analyses were complemented by digital image correlation analysis and inspection of the fractured surfaces by scanning electronic microscopy. As a result of the architectural modifications, the entanglement network density was increased. Those accounted for a slight decrease in the physical aging rate. Under uniaxial loading, aged reactive extrusion (REX) samples exhibited multiple crazing, leading to a slight increase in strain at break. Nevertheless, as a result of a similar dynamic environment of the entangled polymer coils, de-aged REX samples disclosed similar mechanical properties as compared to their neat counterparts. Regarding de-aged samples, the EWF analysis revealed no changes in the work required for the onset of crack propagation. However, the energy consumed up to the onset of crack propagation of aged PLA-REX samples decreased due to an apparently decreased network extensibility, promoting a premature craze-crack transition.
Poly (y-glutamic acid), a novel polyanionic and multifunctional macromolecule synthesized by Bacillus species, has attracted considerable attention because of its eco-friendly, biodegradable and biocompatible characteristics. Recently, its application in a wide range of fields such as food, agriculture, medicine, hygiene, cosmetics and the environment has been explored. This book discusses the chemistry, food sources and health benefits of glutamic acid.
Gamez, J.; Nascimento, L.; Bou, J. J.; E Franco-Urquiza; Santana, O.; Carrasco, F.; Maspoch, M. Journal of applied polymer science Vol. 120, num. 2, p. 896-905 DOI: 10.1002/app.33191 Date of publication: 2011-04-15 Journal article
García Grillasca, G.; Rodríguez-Contreras, A.; Calafell, M.; Bou, J. J.; Almajano, M.P.; Marques, M.S. New biotechnology Vol. 25, num. Supplement 1, p. s129-s130 DOI: 10.1016/j.nbt.2009.06.437 Date of publication: 2009-09 Journal article
Bou, J. J.; Davila, M.; Bover, L.; Diaz, J.; Cañameras, N.; Almajano, M.P. Congreso Nacional de Ciencia y Tecnologia de Alimentos p. 71 Presentation's date: 2009-05-29 Presentation of work at congresses
Bover, L.; Rodriguez-Luna, M.; Davila, M.; Bou, J. J.; Lopez-Perez, D.; Almajano, M.P. Congreso Nacional de Ciencia y Tecnologia de Alimentos p. 79 Presentation's date: 2009-05-27 Presentation of work at congresses