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Base-acid catalyzed resorcinol-formaldehyde aerogels

Laskowski, Jessica and Ratke, Lorenz (2013) Base-acid catalyzed resorcinol-formaldehyde aerogels. In: XVII International Sol-Gel Conference. XVII International Sol-Gel Conference, 25.-30. Aug. 2013, Madrid, Spanien.

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Resorcinol-formaldehyde (RF) aerogels were synthesized via a newly developed two-step method. This synthesis combines the base and acid catalyzed routes of the polymerization of resorcinol with formaldehyde, which are well known in single application. For the first step a standard RF-recipe was used with the molar ratio of resorcinol to water (R/W) of 0.04 and of resorcinol to formaldehyde (R/F) of 0.7. In the base catalyzed step sodium carbonate as the catalyst was used and the molar ratio of resorcinol to catalyst (R/C) was varied between 10 and 1500. After a certain time while the RF solution gels, 1 M citric acid was added to initiate the acid catalyzed step. By adding citric acid to the base catalyzed solution, the gels formed could be dried under ambient conditions without large shrinkage. Indeed, in the base catalyzed one-step route with R/C ratios < 1000, heavy shrinkage is observed about more than 50 vol%. Small RF-particles construct the three-dimensional gel structure and therefore the particle chains do not withstand the capillary forces during the drying leading to high shrinkage. With the new method we still obtain small particles, but with an additional coating of a thin layer of RF in the acid catalyzed step. This causes a reinforcing effect allowing the subcritical drying. However, this effect depends on the time of changing the catalyst after starting the polymerization. Aerogels prepared by the new two-step route were characterized by density, thermal conductivity and specific surface and the structure was investigated by scanning electron microscopy.

Item URL in elib:https://elib.dlr.de/85240/
Document Type:Conference or Workshop Item (Poster)
Title:Base-acid catalyzed resorcinol-formaldehyde aerogels
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:29 August 2013
Journal or Publication Title:XVII International Sol-Gel Conference
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:sol-gel; nanoporous materials; organic aerogels; two-step synthesis; base-acid catalysis
Event Title:XVII International Sol-Gel Conference
Event Location:Madrid, Spanien
Event Type:international Conference
Event Dates:25.-30. Aug. 2013
Organizer:ISGS - International Sol-Gel Society
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 - Project Neuartige Fahrzeugkonzepte und -strukturen (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space > Scientific Experiments MP
Deposited By: Laskowski, Jessica
Deposited On:09 Dec 2013 08:46
Last Modified:08 May 2014 23:16

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