Unique bi-continuous phase structure can facilitate the development of fire-resistant surface

Selectively localizing flame retardants and smoke suppressants on the surface can maintain fire resistance properties and other bulky properties while reducing additives usage. However, achieving this with traditional processing techniques remains challenging. In this work, taking immiscible polyvinyl chloride (PVC), ethyl-ene-vinyl acetate (EVA) and expanded graphite (EG) as an example, we attempted to localize EG within single or dual polymer phases, culminating in the development of three bi-continuous ternary composite systems. It was interesting to find that selective EG localization in EVA phase (low smoke emission) gave rise to a distinct fire-resistant surface, showcasing the highest flame retardancy (limiting oxygen index), smoke suppression properties (both experimental and simulation data), mechanical properties, and thermal stability. The formation of such functional surface was attributed to the distinct rheological behaviors between EVA/EG and PVC. These inspiring results proved that the combination of flame retardants/smoke suppressants with a low-smoke-emission polymeric phase in bi-continuous composite systems could create fire-resistant surface via tuning rheological characters, which stands out as universal, efficient, simple, and green methodology compared to more complex synthetic surface chemistry approaches.