Polymer blend technology has been one of the most investigated areas in pol
ymer science in the past 3 decades. The one area of polymer blends that has
been virtually ignored involves simple emulsion blends, although several a
rticles have recently appeared that address film formation and mechanical c
haracteristics. In this study, we investigated the mechanical property beha
vior of emulsion blends composed of low/high-glass-transition-temperature p
olymers (where low and high mean below and above the test temperature, resp
ectively). The emulsions chosen for this study had similar particle sizes,
and the mixtures were theologically stable. Two conditions were chosen, a b
inary combination of polymers that were thermodynamically immiscible and an
other system that was thermodynamically miscible. The mechanical property r
esults over the entire composition range were compared with the predictions
of the equivalent box model (EBM) with the universal parameters predicted
by percolation theory. An array of randomly mixed and equal-size particles
of differing moduli was expected to show excellent agreement with theory, a
nd the emulsion blends provided an excellent experimental basis for testing
the theory. For the immiscible blend, the EBM prediction for the modulus s
howed excellent agreement with experimental results. With tensile strength,
the agreement between the modulus and theory was good if the yield strengt
h for the higher glass-transition-temperature polymer was employed in compa
rison with the actual tensile strength. The phase inversion point (where bo
th phases were equally continuous) was at a 0.50 volume fraction of each co
mponent (based on an analysis employing Kerner's equation), just as expecte
d for a random mixture of equal-size particles. (C) 2001 John Wiley & Sons,
Inc.