Publicação
Production of aerogels from plastic post-consumer residues
| Resumo: | This thesis combines two fields that are currently viewed as relevant scientific topics: aerogels and reuse of post-consumer residues (PCR) from plastics.Three different types of aerogels were prepared: PCR aerogels, fibers-reinforced PCR aerogels, and PCR fibers-reinforced silica aerogels. The PCR aerogels were obtained from a dissolution/precipitation method, from which a gel was obtained. The gel was then dried by freeze-drying. The reinforcement of PCR aerogels was made with commercial fibers. Silica aerogels were prepared by the sol-gel technique, after a two-step acid-base catalyzed procedure, using a well-established method developed by the Computation & Materials (CeM) group, at the Department of Chemical Engineering of University of Coimbra. The PCR fibers were added right before the addition of the base and subsequent gelation. The gels aged for 6 days and were then subjected to a solvent exchange, with heptane, for two days, followed by a silylation step, with Hexamethyldisilazane (HMDZ), for one day. Finally, the samples were dried at ambient pressure and the aerogels were formed. The PCR aerogels showed a highly porous morphology, with macro and mesopores. In the case of the reinforced aerogels, a good interaction between the fibers and the aerogel matrix was observed. Bulk density, skeletal density and porosity were also analyzed. The results obtained are in line with those presented in literature. The values of thermal conductivity and thermal diffusivity of PCR aerogels were slightly higher than those obtained for silica reinforced aerogels. The values of specific heat were close to those found for fiber-reinforced silica aerogels. The mechanical properties of PCR aerogels (both unreinforced and reinforced) were inferior of those presented for other polymer-based aerogels in literature, but slightly better than the verified for the silica aerogels.Regarding silica aerogels reinforced with PCR fibers, from the SEM analysis, it was observed that the silica bounded to the fibers. The values of thermal diffusivity, thermal conductivity and specific heat were in the range of other fiber reinforced-silica aerogels, although the bulk density was higher. |
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| Autores principais: | Pinho, Ricardo Filipe Baptista |
| Assunto: | RPC aerogel fibras silica PCR aerogel fibers silica |
| Ano: | 2022 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade de Coimbra |
| Idioma: | inglês |
| Origem: | Estudo Geral - Universidade de Coimbra |
| Resumo: | This thesis combines two fields that are currently viewed as relevant scientific topics: aerogels and reuse of post-consumer residues (PCR) from plastics.Three different types of aerogels were prepared: PCR aerogels, fibers-reinforced PCR aerogels, and PCR fibers-reinforced silica aerogels. The PCR aerogels were obtained from a dissolution/precipitation method, from which a gel was obtained. The gel was then dried by freeze-drying. The reinforcement of PCR aerogels was made with commercial fibers. Silica aerogels were prepared by the sol-gel technique, after a two-step acid-base catalyzed procedure, using a well-established method developed by the Computation & Materials (CeM) group, at the Department of Chemical Engineering of University of Coimbra. The PCR fibers were added right before the addition of the base and subsequent gelation. The gels aged for 6 days and were then subjected to a solvent exchange, with heptane, for two days, followed by a silylation step, with Hexamethyldisilazane (HMDZ), for one day. Finally, the samples were dried at ambient pressure and the aerogels were formed. The PCR aerogels showed a highly porous morphology, with macro and mesopores. In the case of the reinforced aerogels, a good interaction between the fibers and the aerogel matrix was observed. Bulk density, skeletal density and porosity were also analyzed. The results obtained are in line with those presented in literature. The values of thermal conductivity and thermal diffusivity of PCR aerogels were slightly higher than those obtained for silica reinforced aerogels. The values of specific heat were close to those found for fiber-reinforced silica aerogels. The mechanical properties of PCR aerogels (both unreinforced and reinforced) were inferior of those presented for other polymer-based aerogels in literature, but slightly better than the verified for the silica aerogels.Regarding silica aerogels reinforced with PCR fibers, from the SEM analysis, it was observed that the silica bounded to the fibers. The values of thermal diffusivity, thermal conductivity and specific heat were in the range of other fiber reinforced-silica aerogels, although the bulk density was higher. |
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