Efeitos de modificações superficiais de nanoplacas de grafeno (GNP) nas propriedades elétricas e eletromagnéticas de nanocompósitos de poli (trimetileno tereftalato)/GNP
Data
2022-01-26
Autores
Wearn, Yves Nicolau 
Orientadores
Passador, Fabio Roberto
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A busca por materiais com elevado desempenho elétrico e eletromagnético para aplicações altamente tecnológicas têm crescido significativamente ao longo das últimas décadas. Nanocompósitos poliméricos atuam como alternativa para o desenvolvimento desses materiais, fazendo-se uso de materiais a base carbono como reforços em matrizes poliméricas, como o grafeno e seus derivados, em especial as nanoplacas de grafeno (GNP). Porém, GNPs possuem forte tendência em se aglomerar, o que dificulta uma boa interação com a matriz polimérica. Assim, a modificação superficial ou funcionalização das GNP é uma alternativa promissora para contornar esse desafio. Com esse intuito, neste projeto foram aplicadas duas técnicas de funcionalização em GNP – via reação com ácido nítrico (HNO3) (GNPÁCIDO) e com o sal 4-nitrobenzeno-diazônio-tetrafluorborato (4-NBD) (GNPSAL). Como matriz polimérica foi escolhido o poli (trimetileno tereftalato) (PTT), um poliéster aromático que possui diversas aplicações que englobam a área têxtil e embalagens. Afim de garantir uma boa homogeneização do sistema, foi preparado o agente compatibilizante PTT graftizado com anidrido maleico (PTT-g-MA) por processamento reativo. Nanocompósitos de PTT com 1% em massa de PTT-g-MA e com teor de nanocarga variando de 1 a 2,5% em massa (GNP ou GNPSAL) foram preparados via extrusão. A análise estrutural e morfológica das GNP foi feita por espectroscopia Raman, difração de raio-X (DRX) e microscopia eletrônica de varredura de alta resolução (MEV-FEG), onde se observou que a modificação com ácido nítrico (HNO3) possivelmente atuou de maneira mais agressiva sobre as nanocargas. Ainda assim, para ambos os tipos de modificação sugere-se que ocorreu com sucesso o acoplamento dos grupamentos funcionais nas GNP. Analisando o comportamento dos nanocompósitos, com a quantidade de nanocargas adicionadas não ocorreu percolação elétrica, como observado pelos ensaios de impedância elétrica e medidas da eficiência da blindagem eletromagnética (EMI SE), visto que os teores de GNP empregados não foram suficientes para formar caminho percolativo. No entanto, foi observado um aumento expressivo da ductilidade, um diferencial para esse tipo de material. A funcionalização das GNPs com o sal de diazônio mostrou-se bastante promissora, sendo capaz de aprimorar propriedades elétricas e eletromagnéticas a maiores concentrações de GNP nos nanocompósitos.
The search for great electrical and magnetic performance materials for highly technological applications has grown significantly over the last decades. Polymer nanocomposites act as an alternative for the development of such products, making use of carbon based materials as reinforcements in polymeric matrices, for instance graphene and its derivatives, mainly graphene nanoplatelets (GNP). Although, they have the tendency to agglomerate, making it difficult to provide good interactions with the polymer matrix. Thus, the application of surface modifications on GNP is a promising alternative to avoid this phenomenon. To that end, in this project two functionalization techniques were carried out on GNP – through treatment with nitric acid and the salt 4-nitrobenze-diazonium-tetraflourborate. As the polymer matrix, it was chosen the poly (trymethylene terephtalate) (PTT), an aromatic polyester that possesses several applications like in packaging. In order to provide an homogenous dispersion in the system, maleic anhydride grafted PTT (PTT-g-MA) was prepared by melt mixing using an extruder. PTT nanocomposites with 1 wt% of PTT-g-MA and 1 to 2.5 wt% of GNP or functionalized GNP with 4-NBD were prepared by extrusion. The structural and morphological analysis of the GNP were evaluated by Raman spectroscopy, Fourier Transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), by which could be observed that the nitric acid modification was possibly more agressive on the nanofillers. Nonetheless, both techniques proved to be successful considering the coupling of the functional groups on the GNP. Investigating the nanocomposites behaviors, with the amount of GNP added there was no electrical threshold, as noted through the impedance and electromagnetic shielding efficiency (EMI SE) characterizations, since the content of GNP wasn’t sufficient to provide such phenomenon. Although, it was noted a significant improve on the ductility, a differential for such material. The diazonium salt surface modification turned out to be very promising being able to provide significant electrical and electromagnetic improvement with higher GNP concentrations on the composites.
The search for great electrical and magnetic performance materials for highly technological applications has grown significantly over the last decades. Polymer nanocomposites act as an alternative for the development of such products, making use of carbon based materials as reinforcements in polymeric matrices, for instance graphene and its derivatives, mainly graphene nanoplatelets (GNP). Although, they have the tendency to agglomerate, making it difficult to provide good interactions with the polymer matrix. Thus, the application of surface modifications on GNP is a promising alternative to avoid this phenomenon. To that end, in this project two functionalization techniques were carried out on GNP – through treatment with nitric acid and the salt 4-nitrobenze-diazonium-tetraflourborate. As the polymer matrix, it was chosen the poly (trymethylene terephtalate) (PTT), an aromatic polyester that possesses several applications like in packaging. In order to provide an homogenous dispersion in the system, maleic anhydride grafted PTT (PTT-g-MA) was prepared by melt mixing using an extruder. PTT nanocomposites with 1 wt% of PTT-g-MA and 1 to 2.5 wt% of GNP or functionalized GNP with 4-NBD were prepared by extrusion. The structural and morphological analysis of the GNP were evaluated by Raman spectroscopy, Fourier Transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), by which could be observed that the nitric acid modification was possibly more agressive on the nanofillers. Nonetheless, both techniques proved to be successful considering the coupling of the functional groups on the GNP. Investigating the nanocomposites behaviors, with the amount of GNP added there was no electrical threshold, as noted through the impedance and electromagnetic shielding efficiency (EMI SE) characterizations, since the content of GNP wasn’t sufficient to provide such phenomenon. Although, it was noted a significant improve on the ductility, a differential for such material. The diazonium salt surface modification turned out to be very promising being able to provide significant electrical and electromagnetic improvement with higher GNP concentrations on the composites.
Descrição
Citação
WEARN, Y. N. Efeitos de modificações superficiais de nanoplacas de grafeno (GNP) nas propriedades elétricas e eletromagnéticas de nanocompósitos de poli (trimetileno tereftalato)/GNP. Orientador: Fabio Roberto Passador. 2022. 103 f. Dissertação (Mestrado em Engenharia e Ciência de Materiais) - Instituto de Ciência e Tecnologia, Universidade Federal de São Paulo, São José dos Campos, 2022.