Rheological determination of the sol–gel transition during the aqueous synthesis of resorcinol-formaldehyde resins

Job, Nathalie; Panariello, Fabian; Crine, Michel; Pirard, Jean‐Paul; Léonard, Angélique

doi:10.1016/j.colsurfa.2006.07.037

Cited by 40 publications

(36 citation statements)

References 31 publications

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“…These authors studied the effect of several combined parameters, gelation and ageing temperature (50, 70 and 90 °C) and ageing time (between 0 and 72 hours), in three series of organic xerogels obtained from precursor solutions with different pH. In all the examples shown, the increase in temperature leads to lower gelation times, which is consistent with other works (Al-Mutasheb & Ritter, 2003;Job et al, 2007a;Kim et al, 2001). Moreover, as the synthesis temperature increases, the ageing time may be shortened (i.e.…”

supporting

confidence: 72%

Designing Nanostructured Carbon Xerogels

Calvo¹,

Menéndez²,

Arenillas³

2011

Nanomaterials

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supporting

confidence: 72%

Designing Nanostructured Carbon Xerogels

Calvo¹,

Menéndez²,

Arenillas³

2011

Nanomaterials

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“…Saliger and co-workers determined the elastic properties of ambiently dried aerogels by sound propagation measurements. The scaling exponent was found to be n = 2.8-3.5 [4].…”

Section: Introductionmentioning

confidence: 97%

“…Due to the nanoporosity (pore size less than 100 nm) the samples were dried with supercritical carbon dioxide to avoid shrinkage otherwise caused by high surface tension gradients [2]. Several investigations have been published on the impact of synthesis and gelation conditions [3][4][5], influence of catalyst type [6] and pH value [7], catalyst and resorcinol amounts [8,9], and drying method [10,11] on the properties of RF aerogels. In contrast, only few studies exist on mechanical properties of RF aerogels [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

From hard to rubber-like: mechanical properties of resorcinol–formaldehyde aerogels

et al. 2015

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Four types of resorcinol-formaldehyde (RF) aerogels, stiff, brittle, low-flexible, and super-flexible are studied in this work. Despite several studies on mechanical properties on RF aerogels their response when exposed to compressive loading and their fracture behavior are not well investigated. Here, we cover aerogels with a very broad density range of 0.08-0.3 g cm -3 and compressive moduli from 0.12 to 28 MPa. We relate the microstructure of the synthesized aerogels and their behavior under uniaxial compression. Additionally, this work is the first, to our knowledge, to implement the usage of digital image correlation for characterizing the deformation of RF aerogels. The comparison of surface strain distribution of four types of aerogels provides an insight to their reaction on compressive loading.

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“…According to literature, the mechanism of formation of R-F gels is initiated by addition reactions between the precursors followed by condensation and cluster growth [3][4][5]. Dynamic viscosity measurements have shown that the initial cluster formation and particle growth takes about one hour [20]; at this stage, the mixture constitutes a colloidal solution of clusters of monomeric particles. This general mechanism depends on the solution pH, the components molar ratios and the temperature, among others [2].…”

Section: Introductionmentioning

confidence: 99%

Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

Isaacs-Páez

Haro

Juárez-Pérez

et al. 2015

Microporous and Mesoporous Materials

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The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically a long process performed throughout several days. In this work, we have explored an experimental approach to reduce the time necessary to obtain porous gels based on mild polymerization conditions and direct drying. We have analyzed the effects of the temperature and time of the gelation/aging step on the porosity of the gels, as well as the impact on the overall energetic cost of the process. Data have shown that well-developed micro-mesoporous architectures can be obtained within less than a day. The temperature of the gelation/aging step mainly affects the mesopore network, whereas the microporosity is determined by the composition of the precursor's mixture. The exclusion of the solvent exchange step yields soft mechanically fragile porous gels with structural limitations upon carbonization at high temperature in inert atmosphere, due to the surface tensions applied to the backbone during the evolution of volatiles. The mesopore structure lost during carbonization is not recovered upon activation in CO 2 atmosphere, but it is preserved upon chemical activation in K 2 CO 3 and the resulting gel exhibits a bimodal micro-mesoporous distribution. Furthermore, the energy savings of this route are similar to those obtained using microwave-heating in terms of grams of xerogel per kilowatt hour of energy consumed for similar textural properties. The correlation between the energy power consumed and the textural parameters is a useful tool to optimize the synthesis.

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Rheological determination of the sol–gel transition during the aqueous synthesis of resorcinol-formaldehyde resins

Cited by 40 publications

References 31 publications

Designing Nanostructured Carbon Xerogels

Designing Nanostructured Carbon Xerogels

From hard to rubber-like: mechanical properties of resorcinol–formaldehyde aerogels

Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

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