Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH₃, CO and CO₂. According to the literature review, complex studies on the fire hazard of a system of POSS–phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS–phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

The aim of the research was to investigate the influence of calcium phosphinate (HPCA) and aluminum phosphinate (HPAL) in synergistic systems with organophosphorus compounds, i.e., diphenylcresyl phosphate (CDP) and trichloropropyl phosphate (TCPP), on the thermal stability, flammability, smoke density, and emission of toxic gases during the thermal decomposition of polyurethane (PUR) foams. Thermogravimetric analysis (TGA), along with cone calorimetry and microcalorimetry, were used to assess the influence of fillers on the thermal stability and flammability of PUR foams. The analysis of toxic gas products was performed with the use of a coupled TG–gas analyzer system. The optical density of gases was measured with the use of a smoke density chamber (SDC). The obtained results showed an increase in thermal stability and a decrease in the flammability of the PUR composites. However, the results regarding smoke and gas emissions, as well as toxic combustion by-products, present ambiguity. On one hand, the applied flame retardant systems in the form of PUR-HPCA-CDP and PUR-HPCA-TCPP led to a reduction in the concentration of CO and HCN in the gas by-products. On the other hand, they clearly increased the concentration of CO₂, NOx, and smoke emissions. Microbiological studies indicated that the obtained foam material is completely safe for use and does not exhibit biocidal properties.

The aim of this study was to optimize a method for qualitative and quantitative determination of gaseous degradation products formed in the process of thermal decomposition in the sample. The toxicometric index was determined with the use of the coupled TG-FTIR technique (gas analyzer). The polyurethane (PUR) and polyvinyl chloride (PVC) were used for analytical studies. Based on the obtained results, it was concluded that the sample mass used for analysis, as well as the spectral range of the IR spectrum, has a crucial role in the qualitative and quantitative assessment of gaseous toxic degradation products generated during the thermal decomposition of polymeric materials. Using a gas analyzer, proprietary toxicity indices were developed, i.e., the partial toxicity index (IT_PC) and total toxicity index (IT_GC). It should be noted that the determined toxicity indices refer to a test sample not exceeding 10 mg. The small mass of the sample subjected to analysis allows for high resolution and repeatability of the results reading. The results of this study provide a significant methodological contribution to both the identification of gaseous degradation products formed during the thermal decomposition of materials and their quantitative detection.

In the article we investigated the effectiveness of a synergistic system designed to reduce the fire hazard of flexible polyurethane (PUR) foams. The examined system consisted of a carbon-based filler graphene (G), carbon nanotubes (CNTs), or expanded graphite (EG) combined with melamine polyphosphate (MPP). The investigated polyurethane foams (PUR) were synthesized at room temperature via a polycondensation reaction between a polyol and an isocyanate, with an OH: NCO molar ratio of 2:1. Both the carbon fillers and melamine polyphosphate were homogeneously dispersed within the polyol component. Thermogravimetric analysis (TGA), cone calorimetry, and microcalorimetry were used to evaluate the influence of the fillers on the thermal stability and flammability of the PUR foams. The toxicity of the gaseous products was assessed using a coupled TG-gas analysis system, while the optical density of the evolved gases was determined using a Smoke Density Chamber (SDC). The obtained results demonstrated that the applied synergistic carbon-phosphorus filler system significantly reduced the fire hazard of the tested PUR foams. In particular, the EG5-MPP system enabled the formation of self-extinguishing materials.

In this study, a new approach to improving the fire resistance of flexible polyurethane (PUR) foams is presented, based on the incorporation of cotton chemically modified with boron compounds into the polyurethane matrix. The developed system was additionally modified with melamine polyphosphate (MPP). The effects of the applied modifications on the morphology and chemical structure of the PUR composites were investigated using scanning electron microscopy and infrared spectroscopy. Thermal stability was evaluated by thermogravimetric analysis, whereas fire hazard was assessed using cone calorimetry and a smoke optical density chamber. The toxicometric index (WLC_50SM) was determined using a coupled TG-Omega 5 gas analyzer system. The results provide insight into the mechanism responsible for reducing flammability and limiting the emission of toxic combustion and thermal decomposition products through the modification of PUR foams with chemically modified cotton in combination with MPP. It was observed that, during the combustion of the developed PUR composites, the addition of cotton promotes the formation of a three-dimensional spatial network, which substantially limits heat release and the emission of toxic combustion products. Consequently, the composites exhibited a reduction in heat release of up to 67% in terms of HRR_MAX, together with decreased production of HCN and CO. Nevertheless, the formation of a protective carbon layer contributed to an increase in smoke optical density, which was associated with increased CO₂ emission. Overall, this work demonstrates the development of a new synergistic system capable of reducing both the flammability and toxicity of flexible PUR foams.