Simone Pereira da Silva Ribeiro

Timber plays a fundamental role in the fire performance of historic building components, where ageing and environmental exposure can markedly influence its physical and chemical properties. This study presents an experimental investigation of the fire behaviour of Ocotea sp. ( Lauraceae ) wood obtained from a single original historic flooring element preserved in the sacristy of the São Pedro de Alcântara Chapel in Rio de Janeiro, Brazil. The element was not part of the post‐2011 reconstruction and showed no visible fire damage. Both as‐received and oven‐dried samples were analysed to evaluate the effect of moisture content on flammability. Thermal stability and thermal degradation were characterised using thermogravimetric analysis (TGA), highlighting differences in decomposition pathways and residual char yield. Flammability assessments included vertical and horizontal burning tests adapted from UL 94 V and UL 94 HB to examine the influence of specimen orientation on fire propagation. Additionally, limiting oxygen index (LOI) testing quantified the flammability under varying oxygen concentrations, while glow‐wire tests evaluated the response to localised incandescent heating. Under the adopted bench‐scale conditions, the as‐received specimens required a higher oxygen concentration to sustain flaming and yielded higher glow‐wire indices than the oven‐dried specimens. The vertical and horizontal test configurations produced different flame‐propagation outcomes, although the different exposure procedures do not allow this difference to be attributed solely to specimen orientation. These findings provide preliminary material‐level evidence for future element‐scale testing and fire‐dynamics modelling.

This work evaluates the influence of the acidic sites concentration in amorphous silica‐aluminas (ASAs) on the flame‐retardant properties and the thermal stability of intumescent polypropylene (PP) composites. ASAs with different concentrations of alumina and acidic sites were synthesized by surface alumina deposition and coprecipitation methods. The polymeric composites had their flame‐retardant properties evaluated by limiting oxygen index (LOI) and UL‐94. The thermal stability was analyzed by thermogravimetric analysis (TGA). The ASAs had their textural properties evaluated by nitrogen physisorption, their chemical composition by X‐ray fluorescence (XRF) and their acidity by temperature‐programmed ammonia desorption (TPD‐NH ₃ ). The results show that the presence of ASA, regardless of the synthesis method, increased the thermal stability of the composites. Besides, the presence of acidic sites favors the flame‐retardant properties of the intumescent composites, leading to LOI values of 29% and 30%, as well as a V‐0 classification in UL‐94 test. Moreover, after reaching this LOI value threshold, the increase in the acidity of these silica‐aluminas did not promote further increase in the flame‐retardant properties.

The influence of processing intumescent bio-based poly(lactic acid) (PLA) composites by injection and fused filament fabrication (FFF) was evaluated. A raw (ANa) and two acidic-activated (AH2 and AH5) montmorillonites were added to the intumescent formulation, composed by lignin and ammonium polyphosphate, in order to evaluate the influence of the strength and the nature (Brønsted or Lewis) of their acidic sites on the fire behavior of the composites. The thermal stability and the volatile thermal degradation products of the composites were assessed. The injected and 3D-printed composites were submitted to cone calorimeter (CC), limit oxygen index (LOI), and UL-94 flammability tests. A similar tendency was observed for the injected and 3D-printed samples. The high density of strong Lewis sites in AH2 showed to be detrimental to the fire-retarding properties. For the CC test, the addition of the intumescent composite reduced the peak of heat released (pHRR) in approximately 49% when compared to neat PLA, while the composites containing ANa and AH5 presented a reduction of at least 54%. However, the addition of AH2 caused a pHRR reduction of around 47%, close to the one of the composite without clay (49%). In the LOI tests, the composites containing ANa and AH5 achieved the best results: 39% and 35%, respectively, for the injected samples, and 35 and 38% for the 3D-printed samples. For the composite containing AH2 the LOI values were 34% and 32% for injected and 3D-printed samples, respectively. Overall, the best performance in the flammability tests was achieved by the composites containing clays with only weak and moderate strength acidic sites (ANa and AH5).

Biobased flame‐retardant polylactic acid composites were prepared using ammonium polyphosphate (AP), lignin, and a raw montmorillonite (ANa) as the intumescent formulation. The concentration of AP and of ANa was varied in order to study its influence on the flammability properties of the composites. The samples were submitted to cone calorimeter test, thermogravimetric analysis coupled to Fourier‐transform infrared spectroscopy (TGA‐FTIR), limiting oxygen index (LOI), and UL‐94 vertical burn. The cone calorimeter residues were analysed through scanning electronic microscopy, X‐ray diffraction, and FTIR. The results show that the combined addition of the intumescent formulation and the ANa leads to an improvement in the fire behavior of the composites, compared with that of the neat polymer. The best fire‐retardant performance was achieved by using the highest AP concentration (17%) and the lowest ANa concentration (1.2%), reaching a LOI value of 39%.

Summary: This paper presents an experimental investigation of alumina trihydrate (ATH) in glass fibre reinforced polymers (GFRP), aiming to determine the influence of ATH concentration on improved flame‐retardant properties. For this research, different concentrations of ATH: 37 phr (parts per hundred resin), 40, 47.5, 50 and 55 phr, were added in isophthalic polyester matrix composites reinforced with E‐glass fibre through a pultrusion process. These composites were tested for flammability and flame propagation using the mass loss calorimeter cone (MLCC), limiting oxygen index (LOI) and glow wire tests. Simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) was performed to evaluate the thermal stability and enthalpy. These analyses assessed the effectiveness and influence of each ATH concentration. It was observed in the MLCC tests that the ATH concentration of 40 phr reduced the peak heat release rate (PHRR) by 27% compared to a composite with 37 phr. All specimens showed the desired commercial result for wires and cables in the glow wire test since the composites reached the maximum glow wire flammability index (GWFI) of 960 °C and a glow wire ignition temperature (GWIT) above 900 °C. Thus, the addition of ATH above 40 phr leads to an improvement in the flame‐retardant properties of glass fibre reinforced polymers.