Cellulose fibers are promoted for use in various textile applications due their sustainable nature. Cellulose-based fibers vary considerably in their mechanical and flammability properties depending on their chemical composition. The chemical composition of a cellulose-based fiber is further dependent on their source (i.e., seed, leaf, cane, fruit, wood, bast, and grass). Being organic in nature, cellulose fibers, and their products thereof, pose considerable fire risk. In this work we have compared the flammability properties of cellulose fibers obtained from two different sources (i.e., cotton and peat). Compared to cotton cellulose textiles, peat-based cellulose textiles burn longer with a prominent afterglow which can be attributed to the presence of lignin in its structure. A series of phosphoramidates were synthesized and applied on both cellulose textiles. From thermogravimetric and pyrolysis combustion flow analysis of the treated cellulose, we were able to relate the flame retardant efficacy of the synthesized phosphorus compounds to their chemical structure. The phosphoramidates with methyl phosphoester groups exhibited higher condensed phase flame retardant effects on both types of cellulose textiles investigated in this study. In addition, the bis-phosphoramidates exhibited higher flame retardant efficacy compared to the mono-phosphoramidates.

The effects of combining 0.1–5 wt % graphene nanoplatelet (GNP) and 3–30 wt % phosphorous flame retardant, 9,10- dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as fillers in epoxy polymer on the mechanical, flame retardancy, and electrical properties of the epoxy nanocomposites was investigated. GNP was homogeneously dispersed into the epoxy matrix using a solvent-free three-roll milling process, while DOPO was incorporated into the epoxy resin by mechanical stirring at elevated temperature. The incorporation of DOPO reduced the crosslinking density of the epoxy resin. When using polyetheramine as a hardener, the structural rigidity effect of DOPO overshadowed the crosslinking effect and governed the flexural moduli of epoxy/DOPO resins. The flexural moduli of the nanocomposites were improved by adding GNP up to 5 wt % and DOPO up to 30 wt %, whereas the flexural strengths deteriorated when the GNP and DOPO loading were higher than 1 wt % and 10 wt %, respectively. Limited by the adverse effects on mechanical property, the loading combinations of GNP and DOPO within the range of 0–1 wt % and 0–10 wt %, respectively, in epoxy resin were further studied. Flame retardancy index (FRI), which depended on three parameters obtained from cone calorimetry, was considered to evaluate the flame retardancy of the epoxy composites. DOPO showed better performance than GNP as the flame retardant additive, while combining DOPO and GNP could further improve FRI to some extent. With the combination of 0.5 wt % GNP and 10 wt % DOPO, improvement in both mechanical properties and flame retardant efficiency of the nanocomposite was observed. Such a combination did not affect the electrical conductivity of the nanocomposites since the percolation threshold was at 1.6 wt % GNP. Our results enhance the understanding of the structure–property relationship of additive-filled epoxy resin composites and serve as a property constraining guidance for the composite manufacturing.

The role of various additives (emulsifier, anti-dripping agent) and formulation procedures (pre-dispersion of solid additives in polyol via milling) which influence the flame retardancy of 6,6′-[ethan-1,2-diylbis(azandiyl)]bis(6H-dibenzo[c,e][1,2]oxaphosphin-6-oxid) (EDA-DOPO) containing flexible polyurethane foams has been investigated in this work. For comparison, the flame retardancy of two additional structurally-analogous bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based compounds, i.e., ethanolamine-DOPO (ETA-DOPO) and ethylene glycol-DOPO (EG-DOPO) were also evaluated together with EDA-DOPO in flexible PU foams of various formulations. The flame retardancy of these three bridged-DOPO compounds depends on the type of PU formulation. For certain PU formulations containing EDA-DOPO, lower fire performance was observed. Addition of emulsifier and polytetrafluoroethylene (PTFE) to these PU formulations influenced positively the flame retardancy of EDA-DOPO/PU foams. In addition, dispersion of EDA-DOPO and PTFE via milling in polyol improved the flame retardancy of the PU foams. Mechanistic studies performed using a microscale combustion calorimeter (MCC) and its coupling to FTIR showed no difference in the combustion efficiency of the bridged-DOPO compounds in PU foams. From MCC experiments it can be concluded that these bridged-DOPO compounds and their decomposition products may work primarily in the gas phase as flame inhibitors. The physiochemical behavior of additives in PU formulation responsible for the improvement in the flame retardancy of PU foams was further investigated by studying the dripping behavior of the PU foams in the UL 94 HB test. A high-speed camera was used to study the dripping behavior in the UL 94 HB test and results indicate a considerable reduction of the total number of melt drips and flaming drips for the flame retardant formulations. This reduction in melt drips and flaming drips during the UL 94 HB tests help PU foams achieve higher fire classification.

Airborne transmitted as well as multiresistant pathogens can spread rapidly in high traffic enclosed public spaces. Antimicrobial coatings of surfaces are a promising approach limiting the spread of diseases by targeted contact inhibition of microbes. A novel class of light-activated coatings including hydrophobic carbon quantum dots (hCQDs) and up-converter (UPC) are developed for this purpose including Safe-by-Design (SbD) principles. The efficacy against pathogens and the human safety aspects need to be well balanced. In case of fire-related accidents, these additives should not increase flammability, smoke release or the formation of harmful entities. In this work, antimicrobial hCQDs & up-converters are coated onto porous and non-porous substrates, exploring the interplay between substrates and coatings on the release of fume products after incineration. The airborne soot particles were assessed for their polycyclic aromatic hydrocarbon (PAH) content and their potential to cause a pro-inflammatory cytokine response in human lung cells. No significant acute in vitro lung cytotoxicity was detected from nano-coated surfaces after incineration. With this study, an important intermediate goal is reached and provides the rational for further investigations.

Polyamide 6,6 (PA6,6) fabrics are widely used in textiles due to their high mechanical strength and chemical stability. However, their inherent flammability and melting behavior under fire pose significant safety challenges. In this study, a dual-layer flame-retardant system was developed by integrating atomic layer deposition (ALD) of ZnO with a phosphorus–silane-based flame retardant (DOPO-ETES). ALD allowed precise control of ZnO layer thickness (50, 84, and 199 nm), ensuring uniform coating. Thermal analysis (TGA) and microscale combustion calorimetry (MCC) revealed that ZnO altered the degradation pathway of PA6,6 through catalytic effects, promoting char formation and reducing heat release. The combination of ZnO and DOPO-ETES resulted in further reductions in heat release rates. However, direct flame tests showed that self-extinguishing behavior was not achieved, emphasizing the limitations related to the melting of PA6,6. TG-IR and cone calorimetry confirmed that ZnO coatings suppressed the release of smoke-related volatiles and incomplete combustion products. These findings highlight the potential of combining metal-based catalytic flame retardants like ZnO with phosphorus-based coatings to improve flame retardancy while addressing the specific challenges of polyamide textiles. This approach may also be adapted to other fabric types and integrated with additional flame retardants, broadening its relevance for textile applications.

Thermosetting polymers are widely employed in high-performance applications owing to their excellent mechanical properties, thermal stability, and chemical resistance. However, their permanently crosslinked architecture severely limits recyclability, while their intrinsic flammability remains a major concern for safety-critical applications. Herein, hybrid epoxy–amino ester covalent adaptable networks (CANs), incorporating phosphorus-containing polyelectrolyte complex (PEC) micro-particles, are developed to simultaneously address these two challenges. The hybrid network combines associative transesterification and dissociative retro Aza-Michael addition exchange reactions, enabling efficient thermomechanical reprocessing while preserving the crosslinked architecture. The incorporation of PEC, prepared through a simple aqueous process from poly(allylamine hydrochloride) and sodium polyphosphate, provides an environmentally friendly phosphorus-nitrogen flame-retardant additive without altering the curing behavior or dynamic network properties. The resulting materials exhibit stable glass transition temperatures, efficient stress relaxation, and excellent retention of thermal properties after recycling. An optimized phosphorus loading of 3 wt% enables the material to achieve a UL-94 V-0 classification, while maintaining its flame-retardant performance after thermomechanical recycling. In contrast, equivalent formulations containing commercial ammonium polyphosphate (APP) flame retardant failed to achieve a UL-94 V-0 classification, even at 4 wt% phosphorus, demonstrating the superior flame-retardant efficiency of PEC. Finally, carbon-fiber-reinforced composites fabricated using the developed matrix demonstrate excellent flexural properties, highlighting the potential of these recyclable flame-retardant CANs for sustainable structural applications.