Morphology evolution and the tri-continuous morphology formation of a PVDF/PS/HDPE ternary blend in melt mixing

Tri-continuous morphology evolution and the formation of a PVDF/PS/HDPE system were studied in this paper. The blends were prepared by melt mixing using an internal mixer. The morphology was analyzed by scanning electron microscopy and optical microscopy. The evolution of the stable morphology would undergo three stages: firstly, most of PS dispersed in HDPE and then all of PS migrated into the interface of PVDF and HDPE; in the end, a portion of PS droplets moved into the HDPE phase and that is the stable morphology. Additionally, the effect of the PS volume fraction on the stable morphology was studied, and the results demonstrated that the PS volume fraction played only a little role on the sub-inclusion structure when the tri-continuous morphology was formed and the thickness of the PS layer shows a clear linear relationship with the content of PS; the viscosity ratio of HDPE/PS is of significant importance on the stable morphology as well as the continuity level of PS, when the viscosity ratio is greater than 1, the tri-continuous morphology cannot form, if the viscosity ratio is about 1, a perfect tri-continuous structure can be observed; when the viscosity ratio is less than 1, the morphology observed is combination of a tri-continuous morphology and sub-inclusion structure.