Fire hazard mitigation in bi-continuous phase polymer composites: surface vs. bulk and experimental vs. computational

Abstract

Selective localization of functional additives on the surface of bi-continuous phase polymer composites is proven effective in enhancing bulk properties, such as fire resistance, without additional additive usage. However, the extent and limitations of this functional surface effect on bulk performance remain unclear. To address this, we fabricated polyvinyl chloride (PVC)/high density polyethylene (HDPE) bi-continuous phase polymer composites with tunable surface chlorine, surface expanded graphite (EG), and bulk chlorine contents, systematically evaluating their fire safety through experiments and simulations. It was found that the effect of surface EG content on real combustion is minimal. Instead, bulk chlorine content governs combustion behavior, elevating the limiting oxygen index (from 33.9 to 39.7%) and smoke generation (from 62.8 to 50.3%) while suppressing heat release (from 64.3 to 52.2 MJ m⁻²). Fire dynamics simulation results corroborate experimental findings, and evacuation simulations reveal smoke generation as the dominant factor restricting escape. This study advances the understanding of fire safety mechanisms in polymer composites, offering a foundation for the development of next-generation flame-retardant composite materials with reduced toxic emissions.