Low-Flammability Hybrid Polymer Materials Based on Epoxy Oligomers and In Situ-Synthesized Zinc-Containing Microparticles

This study addresses the drawbacks of traditional dispersed fire retardants—such as anisotropy, reduced strength, and poor filler impregnability—by developing in situ-formed hybrid epoxy composites. The materials, based on diglycidyl ether of bisphenol A and triethylenetetramine, were modified with a solution of zinc sulfate heptahydrate in orthophosphoric acid. This approach yielded near-spherical microparticles (6–16 µm) within the polymer matrix. The scientific novelty lies in investigating how such in situ particle formation affects material properties. The modification significantly enhanced fire resistance: char residue increased 1.7–2.2-fold, while total heat release, peak heat release rate, and smoke release were reduced by up to 60.5%, 40.2%, and 70%, respectively. The observed increase in the mass loss rate suggests that accelerated thermal-oxidative degradation promotes char formation. These findings, supported by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy data, demonstrate the efficacy of the in situ strategy for creating high-performance, fire-safe epoxy composites.