Please use this identifier to cite or link to this item:
https://repositorio.ufu.br/handle/123456789/40952
ORCID: | http://orcid.org/0000-0003-2154-8123 |
Document type: | Tese |
Access type: | Acesso Aberto |
Title: | Preparação e caracterização de fibras de carbono a partir de blendas da lignina carboximetilada e álcool polivinílico |
Alternate title (s): | Preparation and characterization of carbon fibers from carboxymethylated lignin blends and polyvinyl alcohol |
Author: | Pompêu, Gabriela Ciribelli Santos |
First Advisor: | Pasquini, Daniel |
First coorientator: | Ruggiero, Reinaldo |
Second coorientator: | Morais, Luís Carlos |
First member of the Committee: | Driemeier, Carlos Eduardo |
Second member of the Committee: | Matias, Patrícia Gontijo de Melo |
Third member of the Committee: | Assunção, Rosana Maria Nascimento de |
Fourth member of the Committee: | Lopes, Osmando Ferreira |
Summary: | A lignina, apesar da complexidade de sua estrutura, tem um potencial considerável para aplicação em novos produtos com alto valor agregado, especialmente na produção de fibra de carbono. O processo kraft, predominante no setor de papel e celulose, resulta em grandes quantidades de lignina como resíduo industrial mundialmente. Várias metodologias para aplicação de misturas de lignina com polímeros termoplásticos vêm sendo estudadas, principalmente, quando se aplicam modificações químicas para melhorar sua compatibilidade em matriz polimérica. Neste contexto, a lignina resultante do processo kraft foi modificada quimicamente, através da reação de carboximetilação (gerando a carboximetil lignina de sódio - CML-Na) para ser utilizada na formação de blendas, com álcool polivinílico (PVAl), em concentrações de 5, 10, 15, 20% de CML-Na (v/v), o que em porcentual mássico (g/g) corresponde respectivamente à 45,5, 62,5, 71,4 e 76,9%. Assim, determinou-se a quantidade máxima de lignina carboximetilada ideal para a produção de blendas poliméricas com PVAl e CML-Na, visto que as eletrofiações com soluções de concentração 25% (v/v) não foram efetivas. As blendas preparadas foram eletrofiadas sob condições controladas de tensão 15 kV, vazão 0,5 mL h-1 e distância do coletor e a ponta da agulha de 10 cm. As fibras formadas foram visualizadas com auxílio do MEV, evidenciando a existência dos fios, sendo que nas concentrações de 10 e 15% foram obtidas fibras mais homogêneas. Além disso, as blendas eletrofiadas também foram caracterizadas por análises térmicas (TGA e DSC) e estruturais (FTIR), validando-as como materiais precursores de qualidade para produção das fibras de carbono. A partir dos resultados obtidos, as nanofibras eletrofiadas PVAl/CML-Na 5, 10 e 15% foram selecionadas por apresentarem melhores propriedades físico-químicas (melhor estabilidade térmica, morfologia e fiação homogêneas), e submetidas aos processos de termoestabilização (atmosfera oxidante) e carbonização (atmosfera inerte), respectivamente. As fibras carbonizadas foram avaliadas quanto às características morfológicas (MEV), superficiais (AFM) e estruturais (Raman). Após o processo de carbonização, observou-se um aumento na porosidade na superfície das fibras, decorrente do rompimento de algumas fibras superficiais durante o processo de carbonização. Por meio das análises estruturais, identificou-se a ocorrência da modificação na estrutura das fibras durante a etapa de carbonização, confirmando a conversão das fibras de PVAl/CML-Na em fibras de carbono, através das estruturas químicas representativas dos materiais de carbono apresentados nos espectros de Raman. O trabalho demonstra o potencial do uso da lignina modificada como precursor adequado para a preparação de fibra de carbono, nas diversas aplicações tecnológicas importantes e necessárias para a redução do impacto ambiental, e especial, na valorização da lignina como matéria-prima sustentável e de origem renovável para fins mais nobres. |
Abstract: | Lignin, despite the complexity of its structure, has considerable potential for application in new products with high added value, especially in the production of carbon fiber. The kraft process, which is prevalent in the pulp and paper industry, results in large amounts of lignin as industrial waste worldwide. Several methodologies for the application of lignin mixtures with thermoplastic polymers have been studied, especially when chemical modifications are applied to improve their compatibility in a polymeric matrix. In this context, the lignin resulting from the kraft process was chemically modified through the carboxymethylation reaction (generating sodium carboxymethyl lignin - CML-Na) to be used in the formation of blends, with polyvinyl alcohol (PVAl), at concentrations of 5, 10, 15, 20% of CML-Na (v/v), which in mass percentage (g/g) corresponds respectively to 45.5, 62.5, 71.4 and 76.9%. Thus, the maximum amount of carboxymethylated lignin was determined to produce polymeric blends with PVAl and CML-Na since electrospinning with solutions of 25% concentration (v/v) was not effective. The prepared blends were electrospun under controlled conditions of 15 kV voltage, 0.5 mL h-1 flow rate, and distance from the collector and the needle tip of 10 cm. The fibers formed were visualized with the aid of SEM, evidencing the existence of the threads, and at the concentrations of 10 and 15% more homogeneous fibers were obtained. In addition, the electrospun blends were also characterized by thermal (TGA and DSC) and structural (FTIR) analyses, validating them as quality precursor materials to produce carbon fibers. From the results obtained, the electrospun nanofibers PVAl/CML-Na 5, 10, and 15% were selected for their physicochemical properties (better thermal stability, homogeneous morphology, and spinning), and submitted to the processes of thermostabilization (oxidizing atmosphere) and carbonization (inert atmosphere), respectively. The carbonized fibers were evaluated for morphological (SEM), superficial (AFM), and structural (Raman) characteristics. After the carbonization process, an increase in the porosity on the surface of the fibers was observed, due to the rupture of some surface fibers during the carbonization process. By means of structural analyses, it was identified the occurrence of modification in the structure of the fibers during the carbonization stage confirmed the conversion of PVAl/CML-Na fibers into carbon fibers through the chemical structures representative of the carbon materials presented in the Raman spectra. The work demonstrates the potential of the use of modified lignin as a suitable precursor for the preparation of carbon fiber in the various technological applications important and necessary for the reduction of environmental impact, especially in the valorization of lignin as a sustainable raw material of renewable origin for nobler purposes. Lignin, despite the complexity of its structure, has considerable potential for application in new products with high added value, especially in the production of carbon fiber. The kraft process, which is prevalent in the pulp and paper industry, results in large amounts of lignin as industrial waste worldwide. Several methodologies for the application of lignin mixtures with thermoplastic polymers have been studied, especially when chemical modifications are applied to improve their compatibility in a polymeric matrix. In this context, the lignin resulting from the kraft process was chemically modified through the carboxymethylation reaction (generating sodium carboxymethyl lignin - CML-Na) to be used in the formation of blends, with polyvinyl alcohol (PVAl), at concentrations of 5, 10, 15, 20% of CML-Na (v/v), which in mass percentage (g/g) corresponds respectively to 45.5, 62.5, 71.4 and 76.9%. Thus, the maximum amount of carboxymethylated lignin was determined to produce polymeric blends with PVAl and CML-Na since electrospinning with solutions of 25% concentration (v/v) was not effective. The prepared blends were electrospun under controlled conditions of 15 kV voltage, 0.5 mL h-1 flow rate, and distance from the collector and the needle tip of 10 cm. The fibers formed were visualized with the aid of SEM, evidencing the existence of the threads, and at the concentrations of 10 and 15% more homogeneous fibers were obtained. In addition, the electrospun blends were also characterized by thermal (TGA and DSC) and structural (FTIR) analyses, validating them as quality precursor materials to produce carbon fibers. From the results obtained, the electrospun nanofibers PVAl/CML-Na 5, 10, and 15% were selected for their physicochemical properties (better thermal stability, homogeneous morphology, and spinning), and submitted to the processes of thermostabilization (oxidizing atmosphere) and carbonization (inert atmosphere), respectively. The carbonized fibers were evaluated for morphological (SEM), superficial (AFM), and structural (Raman) characteristics. After the carbonization process, an increase in the porosity on the surface of the fibers was observed, due to the rupture of some surface fibers during the carbonization process. By means of structural analyses, it was identified the occurrence of modification in the structure of the fibers during the carbonization stage confirmed the conversion of PVAl/CML-Na fibers into carbon fibers through the chemical structures representative of the carbon materials presented in the Raman spectra. The work demonstrates the potential of the use of modified lignin as a suitable precursor for the preparation of carbon fiber in the various technological applications important and necessary for the reduction of environmental impact, especially in the valorization of lignin as a sustainable raw material of renewable origin for nobler purposes. |
Keywords: | Lignina Carboximetilação Blendas PVAl Eletrofiação Fibra de Carbono Lignin Carboxymethylation Blends Electrospinning Fiber Carbon |
Area (s) of CNPq: | CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
Language: | por |
Country: | Brasil |
Publisher: | Universidade Federal de Uberlândia |
Program: | Programa de Pós-graduação em Biocombustíveis |
Quote: | POMPÊU, Gabriela Ciribelli Santos. Preparação e caracterização de fibras de carbono a partir de Blendas da lignina carboximetilada e álcool polivinílico. 2023. 121f. Tese (Doutorado em Biocombustíveis) - Universidade Federal de Uberlândia, Uberlândia, 2023. DOI. http://doi.org/10.14393/ufu.te.2023.62 |
Document identifier: | http://doi.org/10.14393/ufu.te.2023.623 |
URI: | https://repositorio.ufu.br/handle/123456789/40952 |
Date of defense: | 6-Oct-2023 |
Sustainable Development Goals SDGs: | ODS::ODS 9. Indústria, Inovação e infraestrutura - Construir infraestrutura resiliente, promover a industrialização inclusiva e sustentável, e fomentar a inovação. ODS::ODS 17. Parcerias e meios de implementação - Fortalecer os meios de implementação e revitalizar a parceria global para o desenvolvimento sustentável. |
Appears in Collections: | TESE - Biocombustíveis |
Files in This Item:
File | Description | Size | Format | |
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PreparaçãoCaracterizaçãoFibras.pdf | 4.14 MB | Adobe PDF | View/Open |
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