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Authors
Abstract(s)
A preocupação global com a deterioração do meio ambiente atingiu níveis sem
precedentes, destacando a necessidade crítica de reavaliar e transformar a nossa relação
com os materiais plásticos. O aumento alarmante dos resíduos plásticos e os seus
impactos adversos no ecossistema impulsionam a busca por alternativas sustentáveis e
inovadoras.
A nanocelulose, derivada de fontes renováveis como a celulose vegetal, surge como uma
alternativa promissora e ecológica aos polímeros tradicionais. Neste trabalho foi
realizada a modificação, por via física e via química, da hidrofilia da nanocelulose com o
objetivo de obter um material para embalagem alimentar com fraca afinidade pela água.
Numa primeira fase procedeu-se à seleção, extração e caracterização de ceras e ácidos
gordos naturais que proporcionem hidrofobicidade permanente aos filmes e compósitos
de celulose. Posteriormente, foram desenvolvidos filmes à base de celulose nanofibrilada
(NFC) usando 3 tipos nanocelulose provenientes de pastas químicas distintas e com o
mesmo processo oxidativo TEMPO, variando entre elas em um dos reagentes usados e
ainda no pré-tratamento no homogeneizador (PSSSOTHH2–NC1; PKSOTHH3-NC2;
PKSOTCH2-NC3). O gel da NC3 foi sujeito a funcionalização na tentativa de restringir as
propriedades hidrofílicas do mesmo. Foram realizados espetros de FTIR a fim de
investigar as alterações químicas introduzidas. Adicionalmente, com o objetivo de
melhorar a hidrofobicidade dos filmes das NC’s foi usada a via química recorrendo ao
uso de ceras e a via física através da mimetização micro estruturadas na superfície dos
filmes. Os filmes produzidos foram caracterizados ao nível das principais propriedades
físicas, químicas e estruturais. Os filmes obtidos apresentam elevada transparência, com
91,3% e 94,1% respetivamente para os filmes das NC2 e NC3. Os filmes das três NC’s
exibiram propriedades mecânicas distintas, os da NC3 com uma percentagem de
alongamento mais elevada e baixo valor de Módulo de Young, sendo consequentemente
mais extensíveis. Por outro lado, os filmes das NC1 e NC2 apresentaram valores mais
elevados de módulo de Young e menor alongamento, indicando menos elasticidade e
maior dureza assemelhando-se mais às propriedades do papel. Relativamente à taxa de
permeabilidade, WVTR, destaca-se o valor mais baixo para os filmes da NC1, no entanto
os filmes com menor permeabilidade ao vapor e água foram os da NC2. Adicionalmente,
salienta-se o significativo aumento do ângulo de contacto dos filmes com o tratamento
da cera na superfície, tornando-os hidrofóbicos com ângulo de contacto superior a 100º.
Global concern about protecting the environment has reached unprecedented levels, highlighting the critical need to re-evaluate and transform our relationship with plastic materials. The alarming increase in plastic waste and its adverse impacts on the ecosystem have driven the search for sustainable and innovative alternatives. Nanocellulose, derived from renewable sources such as vegetable cellulose, emerges as a promising and ecological alternative to the traditional polymers. In this work, a chemical and physical modification of the hydrophilicity of nanocellulose was performed, aiming of the obtention of a material for food packaging with low affinity to water. In a first phase, the selection, extraction and characterization of waxes and natural fatty acids that provide permanent hydrophobicity to cellulose films and compounds were performed. Subsequently, films based on nanofibrillated cellulose (NFC) were developed using 3 types of nanocellulose from different chemical paper pulps and with the same oxidative process using TEMPO, varying between them one of the reagents used and in the pre-treatment in the homogenizer (PSSSOTHH2 –NC1; PKSOTHH3-NC2; PKSOTCH2- NC3). The NC3 gel was subjected to functionalization to restrict its hydrophilic properties. FTIR spectra were obtained to investigate the modified chemical changes. Furthermore, with the aim of improving the hydrophobicity of NC films, the chemical route was used using waxes and the physical route was used by mimicking microstructures on the surface of the films. The films produced were characterized in terms of their main physical, chemical and structural properties. The films obtained showed high transparency, with 91.3% and 94.1% respectively for the NC2 and NC3 films. The films from the three NCs exhibited different mechanical properties, those from NC3 with a higher percentage of elongation and a lower Young's Modulus value, being consequently more extensible. Otherwise, the NC1 and NC2 films presented higher Young's Modulus values and lower elongation, reduced elasticity, and greater hardness, more closely resembling the properties of paper. Regarding the permeability rate, WVTR, the lowest value stands out for NC1 films; however, the films with the lowest water vapor permeability were those from NC2. Furthermore, it is worth highlighting the significant increase in the contact angle of the films with the wax treatment on the surface, making them hydrophobic with a contact angle greater than 100º.
Global concern about protecting the environment has reached unprecedented levels, highlighting the critical need to re-evaluate and transform our relationship with plastic materials. The alarming increase in plastic waste and its adverse impacts on the ecosystem have driven the search for sustainable and innovative alternatives. Nanocellulose, derived from renewable sources such as vegetable cellulose, emerges as a promising and ecological alternative to the traditional polymers. In this work, a chemical and physical modification of the hydrophilicity of nanocellulose was performed, aiming of the obtention of a material for food packaging with low affinity to water. In a first phase, the selection, extraction and characterization of waxes and natural fatty acids that provide permanent hydrophobicity to cellulose films and compounds were performed. Subsequently, films based on nanofibrillated cellulose (NFC) were developed using 3 types of nanocellulose from different chemical paper pulps and with the same oxidative process using TEMPO, varying between them one of the reagents used and in the pre-treatment in the homogenizer (PSSSOTHH2 –NC1; PKSOTHH3-NC2; PKSOTCH2- NC3). The NC3 gel was subjected to functionalization to restrict its hydrophilic properties. FTIR spectra were obtained to investigate the modified chemical changes. Furthermore, with the aim of improving the hydrophobicity of NC films, the chemical route was used using waxes and the physical route was used by mimicking microstructures on the surface of the films. The films produced were characterized in terms of their main physical, chemical and structural properties. The films obtained showed high transparency, with 91.3% and 94.1% respectively for the NC2 and NC3 films. The films from the three NCs exhibited different mechanical properties, those from NC3 with a higher percentage of elongation and a lower Young's Modulus value, being consequently more extensible. Otherwise, the NC1 and NC2 films presented higher Young's Modulus values and lower elongation, reduced elasticity, and greater hardness, more closely resembling the properties of paper. Regarding the permeability rate, WVTR, the lowest value stands out for NC1 films; however, the films with the lowest water vapor permeability were those from NC2. Furthermore, it is worth highlighting the significant increase in the contact angle of the films with the wax treatment on the surface, making them hydrophobic with a contact angle greater than 100º.
Description
Keywords
Ácidos Gordos Ceras Filmes Nanocelulose Propriedades Super Hidrofóbicos