Adsorption of Silane Coupling Agents on Glass Fibre Surfaces

G5 Doctoral dissertation (article)


Internal Authors/Editors


Publication Details

List of Authors: Anne Norström
Publisher: Åbo Akademi University
Place: Åbo
Publication year: 2019
ISBN: 978-952-12-3874-1
eISBN: 978-952-12-3875-8


Abstract

Commercial glass fibres are commonly used in reinforced composites. The
importance of such composites is apparent in a number of areas and
applications. Composites have maintained their popularity during several
decades, as the products offered give both strength and modulus at a
reduced weight. Glass fibres used in composites are almost always
pre-treated with coupling agents. Coupling agents are capable of
interacting with both the organic polymer resin as well as the inorganic
glass surface. These coupling agents play a key role in the strength of
a composite.

The overall objective of this work was to characterize glass fibre
surfaces after surface treatment with silane and to gain better
understanding of surface processes at the silane-glass interface of a
composite. Another goal was to investigate how the solvent used in the
surface treatment process affected silane adsorption on the glass fibre
surface.

Adsorption of silane coupling agents from water and organic media on
a glass fibre surface were determined with several analysis methods.
The results indicate that adsorption is dependent on different factors
affecting the monomer dispersion and the formation of a polymer layer on
the glass fibre surface. If the silane adsorbs only physically on the
fibre surface it can lead to a break in the reinforced product. In order
to avoid a breakage the silane treatment must be performed in a way,
that only chemical adsorption of the silane can take place on the fibre
surface.

In this study, adsorption mechanisms of silanes on both pure silica
powders as well as glass fibre surfaces were examined. The experimental
adsorption processes on a silica powder could be described by a
combination of the Henry and Langmuir adsorption isotherms.

Important information on changes in electrokinetic parameters of
heterogeneous glass fibre surfaces was obtained with streaming potential
measurements. The changes introduced by silane adsorption on glass
fibre surface affected the streaming potential and a clear change in the
surface charge was detected. The adsorption was further confirmed by
ESCA measurements by following the carbonyl C3 signal. Information of
the pH dependence of adsorption was detected by streaming potential
measurements.

Furthermore, it was found that treatment of glass fibres with acids
and bases resulted in leaching ions from both the fibre surface as well
as from the fibre bulk. Part of the ions being leached out from the
glass fibre surface were replaced by ions originating from the bulk of
the fibre. This created an ion gradient from the fibre bulk to the
surface.


Last updated on 2020-31-05 at 04:53

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