ETHYLENE-VINYL ACETATE - BASED COMPOSITESAS A POLYMER MATRIX FOR INTUMESCENT FIRE-PROTECTIVE COATINGS

Abstract

The aim of this work is to investigate the effect of organo-inorganic nanocomposites based on ethylene–vinyl acetate (EVA), montmorillonite (MMT), expanded graphite (EG), and their hybrid combinations on thermal degradation behavior, char formation mechanisms, and the fire-protective performance of intumescent coatings based on the ammonium polyphosphate/melamine/pentaerythritol (APP/MEL/PER) system. The nanocomposites were prepared via preliminary synthesis using solution mixing and melt blending techniques, allowing a comparative assessment of structural organization depending on the preparation method. Structural characterization by FTIR spectroscopy and X-ray diffraction confirmed the formation of intercalated–exfoliated structures with enhanced interfacial interactions between the polymer matrix and nanofillers, particularly pronounced in hybrid systems obtained by solution processing.
It was found that the incorporation of MMT and EG increases the thermal stability of the composites, shifting the onset and main degradation temperatures by 10–25 °C and indicating a modification of degradation pathways. MMT promotes catalytic condensation and carbonization processes, contributing to the formation of a dense and mechanically stable char framework, while expanded graphite enhances the expansion process and facilitates the development of a porous thermally insulating structure. In hybrid EVA-MMT-EG systems, a pronounced synergistic effect is observed, manifested in increased char residue, an extended stability range of the char layer, and improved structural integrity and morphology of the protective barrier.
The results of thermogravimetric analysis, SEM observations, and expansion coefficient measurements are consistent and confirm the formation of a more efficient and stable protective layer. Fire tests of APP/MEL/PER-based intumescent coatings demonstrated an increase in fire resistance from 42 to 53 min (26 %) when hybrid nanocomposites were used as the polymer component. The obtained results indicate the high potential of hybrid organo-inorganic nanocomposites as effective polymer matrices for advanced intumescent fire-protective coatings designed for severe thermal exposure conditions, including hydrocarbon fire scenarios