matrix. These trends are illustrated by a series of TEM
photomicrographs (Fig. 2) and the cumulative size distribution
shown on the fraction of the dispersed particles that are
below a certain size, i.e. undersize (Fig. 3). The letters in
parenthesis in Fig. 1 correspond to those in Figs. 2 and 3.
Fig. 2a and b shows for the uncompatibilized blends that the
morphology in (a) is similar to that in (b) with regard to the
domain size and the shape; however, the role of the continuous
phase is reversed, i.e. the SAN25 is continuous in (a),
while the nylon 6 is continuous in (b). Fig. 2c and d shows
for the IA compatibilized blends that the morphology in (c)
is signi®cantly different from that in (d). The large elongated
nylon 6 domains in the SAN25 matrix are seen (c);
whereas, the SAN25 dispersed phase forms uniformly
diminished particles in the nylon 6 matrix (d). Fig. 3
shows that the particles of uncompatibilized blends (a)
and (b) have a similar size distribution regardless of
which material forms the dispersed phase; whereas, for
blends compatibilized with IA, SAN25 particles in a
nylon 6 matrix (d) have a much smaller size range compared
to nylon 6 particles in a SAN25 matrix (c).
Fig. 4 shows this asymmetric trend for a broader range of
IA contents. The higher the IA content, the greater the
asymmetry. The asymmetry has been examined as a function
of the polyamide molecular weight and the trends are
similar for all three polyamides. Fig. 5 shows diagrams for
blends based on L-PA (Fig. 5a) and H-PA (Fig. 5b). In all
cases, IA effectively diminishes the size of SAN25 particles
dispersed in a nylon 6 matrix; whereas, IA is not effective in
reducing the nylon 6 domain size in a SAN25 matrix, especially
near the phase inversion composition.