Sara Saraiva, Marta Neves e Daniel Vicente graduate with a M.Sc.
Congratulations to Sara, Marta and Daniel who graduated, in May 2019, with the following M.Sc. theses:
"Microencapsulation of isocyanate compounds assisted by supercritical fluids", by Sara Saraiva. Supervised by Ana C. Marques and Miguel Rodrigues, at IST, in collaboration with CIPADE S.A.
Abstract: Supercritical fluids technology has been used to produce particles of various materials, however no reports exist relating to its application to systems involving spraying and encapsulation by interfacial reaction by polymerization. In this work, a new technique adapted from Particles from Gas Saturated Solutions (PGSS) was successfully employed to enable the encapsulation of isocyanate species using supercritical carbon dioxide as solute. The latter excels by its non-toxic and non-flammable properties, improving furthermore the safety of workers. Further studies were carried on determining the effect of different active hydrogen sources, catalysts, cross-linkers, chain extenders and pressure on the microcapsules physical and chemical properties such as size, morphology and encapsulation yield. Physicochemical characterization of the microcapsules was done via Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).
"Functionalization of lignin for greener carbon fibers", by Marta Neves. Supervised by Ana C. Marques and Dulce Simao at IST, in collaboration with Dr. Paulo Correia from SGL Composites S.A.
Abstract: In this work, a commercial lignin (Kraft lignin) was functionalized using a silane with methacrylate organic functionality, to enable its copolymerization with acrylonitrile and, at the same time, contribute to a higher thermal resistance precursor derived from the presence of silicon. The modified lignin product was characterized by Fourier transformed infrared spectroscopy using an attenuated total reflectance accessory (FTIR-ATR), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and nuclear magnetic resonance spectroscopy (NMR).
"Investigation of submicron particles as emulsion stabilizers", by Daniel Vicente. Supervised by Ana C. Marques and A. Correia Diogo at IST.
Abstract: This work regarded the synthesis of silica submicron particles, developed as emulsion stabilizing agents, their hydrophobization treatment using hexadecyltrimethoxysilane to make them more suitable for water-in-oil emulsions and their comparison with commercial available particles. The submicron particles were tested as emulsion stabilizing agents, at different concentrations, and their effect was compared with that of typical surfactants, namely SPAN 80, currently used in the synthesis of the microspheres, and Pluronic P123, on a water-in-oil emulsion using decahydronaphthalene as oil phase. The emulsion stability was evaluated by visual and microscopy observation, and the emulsion volume fraction was assessed along the time, as well as the evolution of the emulsion droplets size and their distribution. Small silica particles of 200 nm in diameter with a hydrophobization surface treatment at a concentration in the range of ca. 2 to 5 wt% (relative to the organic phase) were the ones exhibiting better performance as emulsion (W/O) stabilizers. .