Publication Type Journal Article
Title Polyethylene glycol oligomers as siloxane modificators in consolidation of carbonate stones
Authors Bruno Sena da Fonseca Susana Gonçalves Ana Paula Ferreira Pinto Maria F. Montemor
Groups CSSE
Journal PURE AND APPLIED CHEMISTRY
Year 2016
Month December
Volume 88
Number 12
Pages 1117-1128
Abstract The overall performance of alkoxysilanes as stone consolidants is constrained by stone mineralogy (particularly in the carbonate varieties) and by their tendency to crack during drying. In an attempt to overcome these problems, polyethylene glycol chains with two carboxylic acid end-groups (PEG-CA) were introduced in siloxane sols obtained by sol-gel chemistry using tetraethoxysilane (TEOS) as precursor. Different pre-condensation degrees (by varying the stirring times of sol-gel reaction: 10 min, 2, and 24 h) and PEG-CA chains with different molecular weights were studied as variables affecting the initial efficacy of the consolidants when applied into a limestone. The sol containing siloxanes with the lowest pre-condensation degree (10 min stirring) was quite susceptible to the carbonate media and thus a poor consolidation was achieved. The sol with the highest pre-condensation degree (24 h stirring) together with the PEG-CA chains with intermediate molecular weight produced significant and uniform strength gains along the stone depth. The consolidation also showed to be highly dependent on the molecular weight of the PEG-CA chains, the PEG-CA with highest molecular weight produced a non-uniform strength increase with potential harmful side effects. The results confirmed the role of carboxylic acid end-groups as efficient sol-gel catalysts and their ability to be incorporated into the silica matrix in the presence of carbonate stone.
DOI http://dx.doi.org/10.1515/pac-2016-0803
ISBN
Publisher WALTER DE GRUYTER GMBH
Book Title
ISSN 0033-4545
EISSN 1365-3075
Conference Name
Bibtex ID ISI:000393350800003
Observations
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