We studied the effects of silicon carbide (SiC) and SiC hybrid systems with different conventional fillers (silica, carbon black, graphene, hydrotalcite, halloysite) on the rheometric measurements, crosslink density, mechanical performance, aging stability, morphology, thermal behaviour, and flammability of ethylene-propylene-diene (EPDM) rubber composites. The hybrid filler systems showed technically promising synergetic effects on the performance of the EPDM composites. A pronounced reinforcing effect in EPDM composites filled with hybrid SiC filler systems was noted. Tensile strength increased in the systems with carbon black, silica, and graphene nanoplatelets, by 21%, 37%, and 68%, respectively, compared to the neat EPDM. Dynamic-mechanical analysis (DMA) revealed a shift of the glass transition temperature (Tg) of EPDM composites towards higher values following the incorporation of hybrid SiC fillers, indicating that the mobility of the macromolecule chains was restricted by the presence of filler particles. Importantly, the application of SiC as a filler in EPDM rubber composites contributed to a considerable reduction in flammability, as demonstrated by microscale combustion calorimetry (MCC). The most promising results were obtained for HAL/SiC and LDH/SiC hybrid systems, which produced final composites with high flame retardancy and good mechanical performance. The study highlights the significant potential of SiC and SiC hybrid systems as effective fillers improving the properties of elastomer composites.

Due to growing restrictions on the use of halogenated flame retardant compounds, there is great research interest in the development of fillers that do not emit toxic compounds during thermal decomposition. Polymeric composite materials with reduced flammability are increasingly in demand. Here, we demonstrate that unmodified graphene and carbon nanotubes as well as basalt fibers or flakes can act as effective flame retardants in polymer composites. We also investigate the effects of mixtures of these carbon and mineral fillers on the thermal, mechanical, and rheological properties of EPDM rubber composites. The thermal properties of the EPDM vulcanizates were analyzed using the thermogravimetric method. Flammability was determined by pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry.

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 smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of lignocellulose filler, we noticeably reduced the fire hazard caused by elastomeric composites. The lignocellulose filler reduced the parameters associated with the flammability of the tested composites, decreased the smoke emission, and limited the toxicity of gaseous decomposition products expressed as a toximetric indicator and the sum of PAHs and PCDDs/Fs. The natural filler also reduced emission of gases that constitute the basis for determination of the value of the toximetric indicator W_LC50SM. The flammability and optical density of the smoke were determined in accordance with the applicable European standards, with the use of a cone calorimeter and a chamber for smoke optical density tests. PCDD/F and PAH were determined using the GCMS-MS technique. The toximetric indicator was determined using the FB-FTIR method (fluidised bed reactor and the infrared spectrum analysis).