ESTiG - Dissertações de Mestrado Alunos
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Browsing ESTiG - Dissertações de Mestrado Alunos by Author "Adão, Gabilton Caley da Silva"
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- Development of eco-materials for the footwear cluster: isocyanate-terminated prepolymers and cork compositesPublication . Adão, Gabilton Caley da Silva; Barreiro, M.F.; Santamaria-Echart, ArantzazuPrimarily, with the industrial advances that have taken place around the globe since the beginning of the 19th century, many industries have faced various challenges, such as the footwear industry, specifically in producing polyurethane prepolymers. Synthetic raw materials, namely the substitution of petroleum-derived polyols, aromatic isocyanates, and organic solvents, are challenges to overcome. This work aims to develop more sustainable polyurethane products, namely focusing on prepolymers with a high bio- based content (greater than 50%), free of organic solvents, following current legislation, to act as adhesives/binders in cork composites to be used in shoe insoles. The work was divided into two stages, including an initial screening to define the prepolymers’ synthesis conditions (catalyst content, NCO/OH molar ratio, NCO content, ionic nature of the prepolymer) followed by the refinement of the formulations replacing a reference synthetic polyol (PCL2000) by diverse bio-based counterparts (Priplast1838, Priplast 3238, Emerox 14550 and Emerox 14803). Based on the obtained chemical and physical characterisation of the prepolymers (NCO content determination standard, ASTM D2572-97, and Fourier transform infrared spectroscopy, FTIR), in the performed initial screening it was observed that the samples prepared at 5% NCO content samples showed instability during the time, leading to a progressive reduction in the NCO content and the intensity of the NCO peak analysed by FTIR, in contrast, to the 20% NCO content samples that maintained stable. In the refinement phase of the formulations, the obtained results indicated the stability of the NCO content values and the FTIR NCO peak intensity over time, emphasising the durability and stability of the produced prepolymers. To note also that all these formulations contained a bio-based content greater than 50%. The cork-based composites were prepared and mechanically tested, specifically, those prepared with the prepolymers developed at the refinement stage. In particular, the formulations based on Emerox 14803 polyol showed the most promising results, for use in shoe insoles, showing good flexibility and resistance.