Although the primary objective of these studies was to investigate stratifi
cation processes in multicomponent coatings, such as butyl acrylate/polyure
thane (BA/PUR) ((C) 1999 by Air Products and Chemicals, Inc.) latex, other
objectives include investigation of step-scan photoacoustic (SS-PA) Fourier
transform infrared (FT-IR) spectroscopy depth profiling capability for ana
lysis of multicomponent systems. These studies show that a combination of s
tep-scan photoacoustic and attenuated total reflectance (ATR) FT-IR spectro
scopy can be successfully utilized to elucidate stratification processes in
BA/PUR latex as well as in other multicomponent systems. ATR FT-IR experim
ents revealed the absence of PUR moieties within the first 0.28 mu m from t
he film/air (F-A) interface, a decrease of the BA component, and the appear
ance of PUR from 0.39 to 2.52 mu m. Coalescence of BA/PUR latex at 149 degr
ees C affects the distribution of these components by driving PUR deeper in
to the bulk and BA closer to the surface. SS-PA FT-IR experiments allowed u
s to monitor stratification processes at greater depths, and in conjunction
with phase rotation analysis, show that the BA component stratifies closer
to the F-A interface, whereas PUR migrates towards the film/substrate (F-S
) interface.