This study explores how functionalized aromatic P-FRs, specifically phenyl- and phenoxy-based phosphoric acid derivatives, influence the flame retardancy of cotton textiles. By systematically investigating derivatives with varying degrees of phenyl, phenoxy, and acidic hydroxyl terminations, alongside ortho-phosphoric acid as a reference, this work aimed to elucidate the role of aromaticity and functional group composition on both gas- and condensed-phase flame retardant efficacy. Cotton fabrics were treated with comparable phosphorus loadings (~3 g/m²), quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES), to evaluate the gas- and condensed-phase efficacy of the flame retardants. Notably, derivatives with a higher number of acidic hydroxyl terminations exhibited the best flame retardant performance, enhancing char formation through dehydration and condensation reactions during combustion. Thermal analysis (TGA) and microscale combustion calorimetry (MCC) confirmed that phenoxy systems catalyze cotton decomposition more effectively, promoting dehydration through the hydrolysis of phenoxy groups. Furthermore, IR analysis of evolved gases revealed a significant reduction in volatile emissions for phenoxy systems, while this was not observed for phenyl derivatives. These findings underscore the importance of robust condensed-phase mechanisms for achieving effective flame retardancy in cotton textiles.

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.

The conditions under which phosphorus-centered radicals form during the incipient stages of a fire, particularly at ≤600 °C, remain insufficiently understood. Here, we investigate the degradation and flame-retardant action of phosphonate-functionalized silanes featuring distinct P–C linkage motifs: a classical phosphonate (TRI/DPTS(1:3)), a triazine-linked derivative (2DTA), and a carbamoylphosphonate (ID). The compounds were studied both as neat materials and as cotton finishes using a multimethod approach combining standardized flame testing and thermal analysis with steady-state in situ molecular beam mass spectrometry employing mild electron-impact ionization under pyrolytic and oxidative conditions, complemented by transient in situ MS as well as spectroscopic and elemental characterization of evolved gases and residues.,Cotton treated with 2DTA showed the best flame retardancy, consistent with a comparatively stronger condensed-phase contribution. In neat degradation experiments, no detectable volatilization of phosphorus-containing species was observed for 2DTA, whereas TRI/DPTS(1:3) showed minor and ID pronounced volatilization, mirroring the trend in condensed-phase action on cotton. Notably, PO radical formation on cotton under pyrolytic conditions was detected only for 2DTA. Under oxidative conditions 2DTA also exhibited the highest PO emission, indicating competing oxidative and pyrolytic formation pathways. Overall, PO formation correlates inversely with phosphorus volatilization, supporting the hypothesis that low-temperature radical activity (<500 °C) is dominated by condensed-phase collision and transfer reactions. These findings provide a new perspective on the flame-poisoning mechanism of organophosphorus flame retardants.

Polyacrylonitrile (PAN)-derived carbon nanofiber (CNF) nonwovens are promising electrode materials for a wide range of energy-storage applications. However, the relationship between thermal processing, carbon structure, network morphology, and electrical transport remains insufficiently understood. This study examines how stabilization in a temperature range of 220–280 °C and carbonization (800–1500 °C) affect chemical pre-structuring, graphitic-like local ordering, and conductivity in PAN-based nonwovens. Chemical evolution was analyzed by differential scanning calorimetry, Fourier-transform infrared spectroscopy, real-time hot-stage attenuated total reflectance infrared spectroscopy, and X-ray photoelectron spectroscopy. Wide-angle X-ray scattering, scanning electron microscopy, and four-point probe measurements were used to relate carbon structure and morphology to conductivity.Stabilization at 220 °C provided sufficient chemical pre-structuring and yielded the most favorable balance of stacking-related local ordering and conductivity after carbonization at 1000 °C. The 240–260 °C range represented an intermediate regime, whereas the 280 °C condition was associated with stronger oxidative fixation and reduced reorganization capacity. Within the investigated processing range, carbonization temperature had the strongest influence on the final carbon structure and conductivity. The sample treated at 220 °C and 1500 °C reached the smallest interlayer spacing of 3.38 Å and the highest conductivity of 176 S/m while remaining turbostratic. Non-stabilized samples proved that graphitic-like local ordering alone is insufficient for high macroscopic conductivity; preservation of the fibrous transport network is also required. Optimized CNF nonwovens therefore require a balance between stabilization-induced pre-structuring, carbonization-driven reorganization, and network preservation.