a) b - École Polytechnique de Montréal

case the grey matrix is PS, with dispersed droplets of PMMA (white) and separate dispersed
droplets of HDPE (black). Figure 6-5h shows a micrograph of droplets of PMMA and HDPE
phases in a PS matrix. Since it is hard to distinguish PMMA and HDPE droplets, the PMMA is
selectively extracted showing voids where the PMMA was located and clearly indicating the
presence of HDPE droplets.
6.4.4 Bi-Continuous/Dispersed Phase Morphology
The last case of sub-morphology for HDPE/PS/PMMA is the bi-continuous/dispersed phase
morphology comprised of a co-continuous structure for two phases with the third phase present
as a dispersed phase. This case is generated when the concentration of the middle separating
phase increases resulting in a co-continuous structure of the middle phase with either of the other
two phases. The droplets of the third phase are distributed in the middle separating phase (shown
as a schematic in Figure 6-6a). Two examples of such a morphology are shown in Figures 6-6b)
and 6-6c). 50/40/10 HDPE/PS/PMMA is shown in 6-6b) and it can be seen that the HDPE and
PS phases are continuous with droplets of PMMA in the PS phase. 50/25/25 HDPE/PS/PMMA is
shown in Figure 6-6c).
In a ternary blend with a bi-continuous/dispersed phase structure increasing the amount of inner
dispersed phase and decreasing the extent of continuous outer phase results in an inversion in
morphology. In Figures 6-6 d), e) and f), PMMA and PS have a co-continuous structure and
HDPE is present as droplets. This inversion can be shown in a comparison of 50/25/25
HDPE/PS/PMMA(Figure 6-6c) where droplets of PMMA can be seen in the PS phase which, in
turn, is co-continuous with HDPE, and 10/30/60 HDPE/PS/PMMA(Figure 6-6e) where droplets
of HDPE can be seen in PMMA which is co-continuous with PS. The PS phase is extracted in
Figure 6-6f for the 10/30/60 HDPE/PS/PMMA clearly showing numerous droplets of HDPE
distributed in the PS phase.
Figure 6-7 represents the sub-morphologies in the complete wetting case that can be converted to
each other by varying the phase composition.
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