a) b - École Polytechnique de Montréal

6.4.6 Continuity, Co-continuity, and Tri-continuity of Phases
One very important issue in the selection of a ternary blend for a particular application is the
continuity level of each phase. In this part of the work the effect of the composition of phases on
continuity levels is examined. The same 30 samples examined in the previous section above for
morphology are also examined here for their quantitative PS and PMMA continuity. It was not
possible to obtain the continuity of the HDPE phase since HDPE could not be selectively
extracted. Triangular continuity plots are introduced(Figures 6-9a and 6-9b) to show the
continuity of the PS and PMMA phases respectively. In this HDPE/PS/PMMA system, the
continuity levels of PS and PMMA phases are identified through the selective solvent
extraction/gravimetry of PMMA by acetic acid(Figure 6-9a) and of PS by cyclohexane(Figure 6-
9b). The axes in Figures 6-9a and 6-9b represent the volume fraction of PMMA and PS. Note
that the volume fraction of HDPE for these plots can be estimated by subtracting the combined
volume fractions of PS and PMMA from 100%. For example, in the sample comprising 40%PS
and 40%PMMA the remaining 20% would be HDPE. Figures 6-9a and 6-9b reveal the various
continuity levels for both PS and PMMA in the ternary system. These diagrams show that
increasing the concentration of phases results in increased continuity levels until that phase
becomes the matrix and continuity achieves 100%. In Figure 6-9b there are two regions with a
100% continuity level of the PS phase representing tri-continuous morphologies type I (low PS
concentration) and type II (high PS concentration).
In a binary blend the continuity percolation threshold is only one point. In a ternary blend it
becomes a line due to the simultaneously changing concentration of two of the phases in the
blend. The percolation threshold lines for PS and PMMA are represented in both Figures 6-9a
and 6-9b where the colour changes from purple to blue.
The data from the continuity diagrams for PS and PMMA in Figures 6-9a) and 6-9b), can be
combined with the morphological study shown in the triangular diagram of Figure 6-8c) in
order to produce even more well defined continuity boundaries for the various morphological
states. The new 3-axes triangular diagram is shown in Figure 6-9c). Since it is impossible to
selectively extract HDPE without also extracting PS and PMMA, the upper border of region
191