Ml. Abel et al., THE ADSORPTION OF ALKOXYSILANES ON OXIDIZED ALUMINUM SUBSTRATES, International journal of adhesion and adhesives, 18(3), 1998, pp. 179-192
As part of an international project on organosilane adhesion promoters
, the interaction of two commercial alkoxysilanes (gamma-glycidoxy pro
pyl trimethoxy silane (GPS) and gamma-amino propyl triethoxy silane (A
PS)) with oxidised aluminium surfaces has been investigated. In the ca
se of GPS, studies have been undertaken to establish the effect of the
water content (0-10 v/v%) in the methanolic solution on the adsorptio
n process. XPS has been employed to construct adsorption isotherms and
it is shown that the uptake of this molecule increases with the water
content. Results have been interpreted in terms of lack of water (les
s than the stoichiometric amount required for hydrolysis of the silane
molecule) or slow kinetics of the hydrolysis reaction. It is shown th
at the mono-hydrolysed molecule yields a diagnostic radical cation at
m/z = 222 in the ToF-SIMS spectra of these specimens. The variation in
the intensity of this ion provides a useful information about the pro
gress of the hydrolysis reaction. APS has been used for preliminary st
udies into the effect of rinsing on the nature of the silane layer dep
osited. The results show very different adsorption behaviour depending
on the rinsing protocol employed (that is water, methanol or no rinsi
ng), and in the thickness of the film which ranges from 2 to >5 nm, an
d chemistry of the deposited layer. Rinsing in water of the APS film l
eads to the formation of a polysiloxane-like layer, as a result of the
rapid hydrolysis, and subsequent polymerisation, of APS molecule. Evi
dence is given that, contrary to other observations, this polymer does
not originate from any source of contamination. (C) British Crown Cop
yright 1998/DERA Published with permission of the Controller of Her Br
itannic Majesty's Stationary Office.