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<p>This study investigated the effect of eight different transition metal oxides (MOx) on the flame retardant, mechanical, and thermal properties of intumescent polypropylene (PP-IFR) composites filled with ammonium polyphosphate (APP) and pentaerythritol (PER). A novel approach is presented through a comprehensive evaluation of the performance characteristics of polypropylene (PP) composites containing various metal oxides. The flame retardant properties of these composites were assessed using both the Limiting Oxygen Index (LOI) and UL-94&#xa0;V tests. For mechanical characterization, tensile strength, flexural strength, and Charpy impact strength tests were conducted. In addition, the heat deflection temperature (HDT) was also examined as an important performance parameter. Ni₂O₃, V₂O₃, MnO₂, and ZrO₂ exhibited a beneficial effect on both mechanical and flame retardant properties (LOI increase of 9–11%). ZnO significantly improved flame retardancy (8% LOI increase) while slightly reducing some mechanical properties. Composites with 2% content of Zn<sub>2</sub>O<sub>3</sub>, Ni<sub>2</sub>O<sub>3</sub>, V<sub>2</sub>O<sub>3</sub>, MnO<sub>2</sub>, and ZrO<sub>2</sub> achieved a V-0 rating in the UL-94&#xa0;V test. V₂O₃ clearly improved HDT (by 12&#xa0;°C). Fe₂O₃ and Cu₂O oxides increased the flammability of PP-IFR composites (N-R vs. V-0). Analyzing the changes in mechanical properties, we observed the expected stiffening effect of the materials, which resulted in increased strength (30% for flexural strength) and moduli (over 50% increase for Young’s modulus and 30% for flexural modulus). The thermal properties and degradation behavior of PP-IFR composites as a function of temperature were investigated using TGA/DSC analysis, along with FTIR to examine interactions. Correlations were observed between the presence of interactions (hydrogen bonds) in the composites and the flammability of the materials, which also depended on the reactivity of the MOx. MOx were found to reduce thermal stability compared to PP-IFR. Their initial decomposition occurred at temperatures of 240–300&#xa0;°C, while the maximum decomposition rate was observed around 400–450&#xa0;°C. This initial thermal decomposition of PP-APP-PER-MOx compounds, synergistically interacting with additives in various ways, can create a barrier, acting as a protective layer against fire. Scanning electron microscopy revealed that the intumescent char surface after combustion of the samples was significantly modified in the presence of metal oxides such as ZnO, Ni₂O₃, and MnO₂.</p>

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Modification of polypropylene composite flammability through synergistic and antagonistic interactions of metal oxides

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月23日

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  • Jacek Iwko,
  • Roman Wróblewski,
  • Beata Anwajler,
  • Mariola Robakowska,
  • Oliwia Trzaska,
  • Przemysław Postawa,
  • Tomasz Jaruga,
  • Anna Nikodem,
  • Daniel Smykowski

摘要

This study investigated the effect of eight different transition metal oxides (MOx) on the flame retardant, mechanical, and thermal properties of intumescent polypropylene (PP-IFR) composites filled with ammonium polyphosphate (APP) and pentaerythritol (PER). A novel approach is presented through a comprehensive evaluation of the performance characteristics of polypropylene (PP) composites containing various metal oxides. The flame retardant properties of these composites were assessed using both the Limiting Oxygen Index (LOI) and UL-94 V tests. For mechanical characterization, tensile strength, flexural strength, and Charpy impact strength tests were conducted. In addition, the heat deflection temperature (HDT) was also examined as an important performance parameter. Ni₂O₃, V₂O₃, MnO₂, and ZrO₂ exhibited a beneficial effect on both mechanical and flame retardant properties (LOI increase of 9–11%). ZnO significantly improved flame retardancy (8% LOI increase) while slightly reducing some mechanical properties. Composites with 2% content of Zn2O3, Ni2O3, V2O3, MnO2, and ZrO2 achieved a V-0 rating in the UL-94 V test. V₂O₃ clearly improved HDT (by 12 °C). Fe₂O₃ and Cu₂O oxides increased the flammability of PP-IFR composites (N-R vs. V-0). Analyzing the changes in mechanical properties, we observed the expected stiffening effect of the materials, which resulted in increased strength (30% for flexural strength) and moduli (over 50% increase for Young’s modulus and 30% for flexural modulus). The thermal properties and degradation behavior of PP-IFR composites as a function of temperature were investigated using TGA/DSC analysis, along with FTIR to examine interactions. Correlations were observed between the presence of interactions (hydrogen bonds) in the composites and the flammability of the materials, which also depended on the reactivity of the MOx. MOx were found to reduce thermal stability compared to PP-IFR. Their initial decomposition occurred at temperatures of 240–300 °C, while the maximum decomposition rate was observed around 400–450 °C. This initial thermal decomposition of PP-APP-PER-MOx compounds, synergistically interacting with additives in various ways, can create a barrier, acting as a protective layer against fire. Scanning electron microscopy revealed that the intumescent char surface after combustion of the samples was significantly modified in the presence of metal oxides such as ZnO, Ni₂O₃, and MnO₂.