Milow, Barbara and Schwan, Marina and Ratke, Lorenz (2013) Synthesis and Properties of Flexible Resorcinol-Formaldehyde Aerogels. Thermosets 2013, 18.-20. Sep. 2013, Berlin.
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Abstract
Organic resorcinol - formaldehyde (RF) aerogels dried under ambient conditions with a large resorcinol (R) to catalyst (C) ratio are usually hard and brittle with strengths about 100 kPa and Young’s-moduli in the range of 1-2 MPa and densities in the range of 0.2 to 0.4 g/cm3. We observe that special conditions of aerogel preparation yield surprisingly flexible aerogels. They can be bent easily (see figure 1), similar to the well-known flexible silica aerogels. They have a low density, a very low elastic modulus of around 70 kPa and are elastically deformable by more than 40% in an almost reversible manner. The procedure of their preparation is simple: The resorcinol is dissolved in deionized water with a very large amount of water (W), close to the gelation limit (molar ratio R/W ≈ 0.008). The R/F molar ratio is fixed at 1:2. The molar ratio R/C is 50:1 usually requiring supercritical drying. The pH is adjusted to be in the range 5.4-5.6. The solution is placed in an oven at 80°C for one week. The gel is washed in acetone and not dried supercritical but in an oven at 80°C. The density of flexible RF-aerogels is about 0.060 g/cm3, a shrinkage is not observed. The thermal conductivity of aerogel is 0.046 W/(mK). The SEM picture in Figure 2 shows the continuous network of particles with sizes of around 1 µm and pores of about 10 µm. The effects of various sol-gel parameters on the flexibility, such as R/W, R/C molar ratios, pH of initial solution, gelation temperature, have been investigated. The aerogels of different densities, microstructures and particle size were obtained by varying the R/W molar ratio. It has been observed that the pH plays a very important role in synthesis of flexible resorcinol-formaldehyde aerogels. The differences between hard and flexible RF aerogels were studied by recording 13C NMR spectra and TGA-FT-IR curves.
Item URL in elib: | https://elib.dlr.de/111255/ | ||||||||||||
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Document Type: | Conference or Workshop Item (Speech, Poster) | ||||||||||||
Title: | Synthesis and Properties of Flexible Resorcinol-Formaldehyde Aerogels | ||||||||||||
Authors: |
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Date: | 2013 | ||||||||||||
Refereed publication: | No | ||||||||||||
Open Access: | Yes | ||||||||||||
Gold Open Access: | No | ||||||||||||
In SCOPUS: | No | ||||||||||||
In ISI Web of Science: | No | ||||||||||||
Status: | Published | ||||||||||||
Keywords: | RF-aerogels, sol-gel process, process Parameter, mechanical strength, rigid to flexible | ||||||||||||
Event Title: | Thermosets 2013 | ||||||||||||
Event Location: | Berlin | ||||||||||||
Event Type: | international Conference | ||||||||||||
Event Dates: | 18.-20. Sep. 2013 | ||||||||||||
Organizer: | Frauenhofer Research Institution for Polymeric and Composites PYCO | ||||||||||||
HGF - Research field: | Aeronautics, Space and Transport | ||||||||||||
HGF - Program: | Transport | ||||||||||||
HGF - Program Themes: | Terrestrial Vehicles (old) | ||||||||||||
DLR - Research area: | Transport | ||||||||||||
DLR - Program: | V BF - Bodengebundene Fahrzeuge | ||||||||||||
DLR - Research theme (Project): | V - NGC Fahrzeugstruktur (old) | ||||||||||||
Location: | Köln-Porz | ||||||||||||
Institutes and Institutions: | Institute of Materials Research > Aerogele | ||||||||||||
Deposited By: | Milow, Dr. Barbara | ||||||||||||
Deposited On: | 28 Feb 2017 07:40 | ||||||||||||
Last Modified: | 31 Jul 2019 20:08 |
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