The concept of Neumann's triangle between three liquids was applied to discuss the multi-phase morphology developed by melt-processing of a ternary blend consisting of polymers (A, B, and C) which are immiscible with each other. For a C polymer-rich system, four morphologies were predicted: (a) isolated particles of A and B, (b) particle composed of A and B stuck together, (c) hybrid particle of A encapsulated by B, and (d) hybrid particle of B encapsulated by A; and the morphological variation was shown to depend on the balance between interfacial tensions. To verify the results, we carried out a ‘droplet-sandwich’ experiment for polycarbonate/poly (butylene terephthalate)/ poly(styrene-co-acrylonitrile) system; i.e., small pieces of C polymer were placed between two layers of polymer A and B, and annealed at melt temperature; then after quenching, the cross-section of the sandwich* was observed under a microscope. From the value of cos 6 in Neumann's triangle thus obtained, one could explain the recent results of Hobbs et al. for phase morphology in melt-processed blends [Polymer, 29, 1598 (1988)], indicating that the morphology development is mostly governed by the balance between interfacial tensions and that it is well predictable in the framework of Neumann's triangle concept. © 1990, The Society of Polymer Science, Japan. All rights reserved.
