Quantifying Water at the Organic Film/Hydroxylated Substrate Interface.
Quantifying Water at the Organic Film/Hydroxylated
Substrate Interface.
(1676 K)
Nguyen, T.; Byrd, W. E.; Bentz, D. P.
Journal of Adhesion, Vol. 48, 169-194, 1995.
Keywords:
ATR; building technology; FT-IR; interface; internal
reflection spectroscopy; in situ measurement;
quantitative; water
Abstract:
A method, based on Fourier transform infrared-multiple
internal reflection (FTIR-MIR) spectroscopy, for
determining the amount and thickness of water at an
organic film/hydroxylated substrate interface has been
developed. The analysis uses a two-layered model, which
takes into account: (1) water at the organic
film/hydroxylated substrate interface, (2) water taken
up by the organic film within the penetration depth of
the evanescent wave and (3) change of the penetration
depth as water displaces the organic film from the
substrate. Experimentally, the method requires the
application of an organic film, transparent or opaque,
of sufficient thickness on a hydroxylated internal
reflection element, which is used as the substrate. A
water chamber is attached to the organic-coated
specimen. After adding water to the chamber, FTIR-MIR
spectra are taken automatically at specified time
intervals without disturbing the specimen or the
instrument. Water uptake in the organic films and
FTIR-MIR spectra of water on the substrates are also
obtained and used for the analysis. Results of examples
of three organic films: a clear epoxy, and unmodified
asphalt, and a pigmented ester, on a hydroxylated
SiO2-Si substrate were presented to demonstrate the
method. The water layer at the interface for the ester
and asphalt specimens was found to be much thicker than
that for the epoxy, and this was attributed to the
presence of a water-sensitive layer accumulated at the
interface for the formers. The method should be equally
applicable to studies of organic and inorganic compounds
at the organic film/hydroxylated substrate interface and
their transport rates through films adhered to a
substrate.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899