Estabelecimento de rota da síntese da resina furfurílica em meio ácido visando minimizar a exotermia da reação
Data
2022-04-27
Autores
Coimbra, Maria Claudia Ribeiro 
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
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Resumo
A resina furfurílica (RF) é uma bioresina obtida a partir do álcool furfurílico, extraído de fontes renováveis presentes em resíduos agrícolas da produção de cana-de-açúcar e de cereais, como o arroz, milho, aveia e trigo. A resina, quando curada, apresenta excelentes características como elevada dureza, estabilidade química e boa resistência mecânica, que viabilizam sua utilização em diferentes aplicações, destacando-se nos setores aeroespacial e na bioengenharia. No entanto, a sua utilização em larga escala ainda é limitada, devido ao complexo controle do seu processo de síntese, uma vez que a reação de policondensação do álcool furfurílico é extremamente exotérmica. Nesse contexto,o presente trabalho teve como objetivo contribuir com a área de síntese da RF, por meio do estudo de sua obtenção em
meio ácido e em baixa temperatura (~50 ºC), variando os tempos de reação (1, 2 e 3 h), de modo a se obter um maior controle da exotermia do meio reacional. O sucesso das sínteses realizadas foi comprovado por espectroscopia no infravermelho com transformada de Fourier (FT-IR) que evidenciou a obtenção da RF, em concordância com o mecanismo de Dunlop e Peters e a presença de estruturas
dos tipos Diels Alder e cetonas. Medidas de pH comprovaram que as sínteses ocorreram em meios ácidos (~3,0) e com elevados teores de água (7 – 15%), indicando a necessidade de destilar o produto da síntese para diminuir a presença deste subproduto, que pode prejudicar a aplicação da RF. As RFs possuem baixa viscosidade (230 a 470 mPa.s), o que corroboram com as baixas massas molares
obtidas por cromatografia de permeação em gel (GPC) (Mw: ~800 g/mol). As resinas foram curadas com diferentes teores (1-5 % em massa)do ácido p-toluenosulfônico (APTS) afim de verificar o teor mais adequado à cura. Análises termogravimétricas (TGA) mostraram perdas de massa desde o início da análise, devido à presença de água e de frações de baixa massa molar na amostra. Vale ressaltar que as análises sob atmosfera inerte revelaram que as RFs obtidas apresentaram um bom rendimento em resíduo de carbono (50-60%), o que viabiliza o uso na área de materiais carbonosos. Por fim, análises por microscopia eletrônica de varredura(MEV) da resina curada com 2 e 3% em massa de APTS mostraram um elevado volume de poros, o que sugere à presença de voláteis nas RF sintetizadas.
Poly(furfuryl alcohol) (PFA) is a bioresin obtained from furfuryl alcohol extractedfrom renewable sources. This resin, when cured, presents excellent characteristics, such as high hardness, chemical stability, and good mechanical resistance, which enable its use in different applications, especially in the aerospace and bioengineeringsectors. However, its large-scale use is still limited due to the difficult control of its synthesis process, since the polycondensation reaction of furfuryl alcohol is extremelyexothermic. In this context, the present work aims to contribute to the area of PFA synthesis, through the study of its obtainment in acidic medium at low temperature (~50 ºC) and varying the reaction times (1, 2 and 3 h), in order to obtain to have better control of the exothermy of the reaction medium. The success of the syntheses performed was confirmed by Fourier transform infrared spectroscopy, which showed that the PFAwas obtained in agreement with the Dunlop and Peters mechanism and Diels Alder. pH measurements confirmed that the syntheses took place in acidic media (~3.0), and moisture content determinations by the Karl-Fischer method showed high water values (7 - 15%), indicating the need to distill the synthesis product to decreasethe presence of this by-product, which can impair PFA application. Viscosity measurements showed low values (230 to 470 mPa.s), in agreement with the low molar masses obtained by gel permeation chromatography (Mw: ~800 g/mol). The resins were cured with different contents (1-5 % by mass) of p-toluenesulfonic acid (APTS) in order to verify the ideal content. Thermogravimetric analyzes showed masslosses from the beginning of the analysis due to the presence of water and low molar mass fractions in the sample; however, analyses under inert atmosphere revealed thatthe studied PFAs present a good carbon yield (50-60%), which makes their uses in thearea of carbon materials viable. Scanning electron microscopy (SEM) analyses of thecured resin showed a high pore volume due to the synthesized PFA volatiles.
Poly(furfuryl alcohol) (PFA) is a bioresin obtained from furfuryl alcohol extractedfrom renewable sources. This resin, when cured, presents excellent characteristics, such as high hardness, chemical stability, and good mechanical resistance, which enable its use in different applications, especially in the aerospace and bioengineeringsectors. However, its large-scale use is still limited due to the difficult control of its synthesis process, since the polycondensation reaction of furfuryl alcohol is extremelyexothermic. In this context, the present work aims to contribute to the area of PFA synthesis, through the study of its obtainment in acidic medium at low temperature (~50 ºC) and varying the reaction times (1, 2 and 3 h), in order to obtain to have better control of the exothermy of the reaction medium. The success of the syntheses performed was confirmed by Fourier transform infrared spectroscopy, which showed that the PFAwas obtained in agreement with the Dunlop and Peters mechanism and Diels Alder. pH measurements confirmed that the syntheses took place in acidic media (~3.0), and moisture content determinations by the Karl-Fischer method showed high water values (7 - 15%), indicating the need to distill the synthesis product to decreasethe presence of this by-product, which can impair PFA application. Viscosity measurements showed low values (230 to 470 mPa.s), in agreement with the low molar masses obtained by gel permeation chromatography (Mw: ~800 g/mol). The resins were cured with different contents (1-5 % by mass) of p-toluenesulfonic acid (APTS) in order to verify the ideal content. Thermogravimetric analyzes showed masslosses from the beginning of the analysis due to the presence of water and low molar mass fractions in the sample; however, analyses under inert atmosphere revealed thatthe studied PFAs present a good carbon yield (50-60%), which makes their uses in thearea of carbon materials viable. Scanning electron microscopy (SEM) analyses of thecured resin showed a high pore volume due to the synthesized PFA volatiles.