Multifunctional marine bio-additive with synergistic effect for non-toxic flame-retardancy and anti-microbial performance

Abstract Flame-retardants and biocides are well-established functional additives that enhance key properties of polymer and porous materials. Conventional additives and their secondary emissions may render materials hazardous in the long-term, incrementing human exposure to a toxic load of persistent bio-cumulative substances in the indoor built environment. The present study developed a novel multifunctional green additive formulated for the optimization of thermoplastic-lignocellulose hybrid sheet materials engineered for indoor building applications. The compound was developed from two marine bio-materials, Kelp Macroalgae (Eklonia spp.) and Bivalve mollusc shells (Veneridae spp.), selected due to their exceptional properties for these functions, as result of the complex mixture of biogenic carbonate/halide/oxide inorganic phases intricately connected through a hierarchical structure. Oxidative flame propagation was investigated under fire conditions and thermal degradation coupled with gas analysis was investigated under inert gas purge for the temperature range 30–1300 °C. The microbial biomass was analysed with culture-dependent and independent methods. The marine panel prototypes exhibited superior flame-retardant characteristics as result of synergistic mechanisms occurring at the solid-gas interface through the disruption of volatiles flame reactions in the gas-phase, endothermic reactions, and self-catalytic activation. This resulted in self-extinguishing, flame-inhibition, slow-flame propagation rate; and the formation of hierarchically porous carbonaceous phase of high-adsorptive capacity. The biodegradation and ecotoxicity analyses indicated very low-moisture absorption and a possible inhibitory effect on microbial development due to the CaCO3/alginate destabilizing effect on the cell membrane. This promising result demonstrates that the synergistic effect of the marine additive has high-potential rendering the novel hybrid materials non-toxic, biodegradation resistant, whilst increasing the recyclability potential at their end-of-life.