Biocompósitos de matriz glioxal-fenol reforçada com celulose microcristalina

Abstract

Resumo: Glioxal pode ser obtido a partir de biomassa (como da oxidação de lipídeos) e não é tóxico ou volátil, tendo sido por isso utilizado no presente trabalho como substituto de formaldeído na preparação de resina fenólica do tipo novolaca, sendo usado como catalisador o ácido oxálico, que também pode ser obtido de fontes renováveis. A resina glioxal-fenol foi utilizada na preparação de compósitos reforçados com celulose microcristalina (CM, 30, 50 e 70% em massa), uma celulose com elevada área superficial. As imagens de microscopia eletrônica de varredura (MEV) das superfícies fraturadas demonstraram que os compósitos apresentaram boa interface reforço/matriz, consequência da elevada área superficial da CM e presença de grupos polares (hidroxilas) tanto na matriz como na celulose, o que permitiu a formação de ligações hidrogênio, favorecendo a compatibilidade entre ambas. A análise térmica dinâmico-mecânica (DMTA) demonstrou que todos os compósitos apresentaram elevado módulo de armazenamento à temperatura ambiente. Além disso, o compósito reforçado com 30% de CM apresentou baixa absorção de água, comparável à do termorrígido fenólico, que é utilizado em escala industrial. Os resultados demonstraram que compósitos com boas propriedades podem ser preparados usando elevada proporção de materiais obtidos de biomassa. Palavras-chave: Biocompósitos, glioxal, resina fenólica, celulose microcristalina. Biobased Composites from Glyoxal-Phenol Matrices Reinforced with Microcrystalline CelluloseAbstract: Glyoxal, which can be obtained from biomass (as by lipids oxidation), is non-toxic and non-volatile. It was used as a substitute of formaldehyde, which does not have these properties, in the synthesis of a novolac-type phenolic resin, using oxalic acid as a catalyst, which can also be obtained from renewable sources. The glyoxal-phenol resin was used in the preparation of composites reinforced with microcrystalline cellulose (MCC 30, 50, and 70% w/w). Scanning electron microscopy (SEM) images of the fractured surfaces showed that the composites presented a good reinforcement/matrix interface. This can be attributed to the high surface area of the MCC and also to the presence of polar groups (hydroxyl) in both cellulose and matrix, which allowed the formation of hydrogen bonds, leading to a good adhesion between the components present at the interface. Dynamic mechanical thermoanalysis (DMTA) showed that all of the obtained composites have high storage modulus at room temperature. Moreover, the composite reinforced with 30% of MCC showed the lowest water absorption, almost the same as that of the phenolic thermoset, which is used in industrial applications. The results showed that composites with good properties can be prepared using high proportions of materials obtained from biomass.

Modulating cell response on cellulose surfaces; tunable attachment and scaffold mechanics

“…Previously, we have demonstrated that surface modification, to introduce a positive surface charge to cellulose (Scheme 1), allows cell attachment in the absence of matrix ligands (Courtenay et al 2017). Here we demonstrate the minimal level of surface modification required and combine this with modulation of the mechanical properties of the scaffold material, achieved by crosslinking with glyoxal (Ramires et al 2010), which results in formation of acetal and hemiacetal linkages upon curing (Scheme 2) (Schramm and Rinderer 2000), yielding films with increased elastic moduli depending on degree of crosslinking (Quero et al 2011).…”

“…Glyoxal was chosen in this study as a chemical crosslinker due to its low toxicity to mammalian cells and ability to finely regulate the elastic moduli of the scaffolds (Ramires et al 2010;Wang and Stegemann 2011). Both unmodified and cationic cellulose films were cured in glyoxal solutions (1-12 wt%) to achieve films with a range of crosslinking determined by HPLC (Figs.…”

Progress in the Use of Biosourced Phenolic Molecules for Electrode Manufacturing

“…Other formaldehyde substitutes have proven to be helpful for the formation of phenolic resin with excellent properties. Among all the aldehyde-type alternatives, the role of furfural (Oliveira et al, 2008;Zhang et al, 2020), furfuryl alcohol (Cheng et al, 2018), glyoxal (Ramires et al, 2010) and vanillin (Foyer et al, 2016) should be highlighted. If readers are looking for more details on biosourced precursors to phenolic resins, we encourage them to read the following scientific literature (Sarika et al, 2020).…”

ISOTERMAS DE ADSORÇÃO DE ÍONS CÁLCIO (Ca+2) EM MATERIAIS CELULÓSICOS

“…Segundo Ramires et al (2010), as celuloses microcristalinas são materiais com elevada área superficial e altamente porosos, de forma a justificar a maior adsorção destes se comparada à polpa Kraft de Eucalyptus. Observa-se nas Figuras 10, 11 e 12 a morfologia e as dimensões das amostras de CMC 101, CMC 500 e polpa Kraft, respectivamente.…”