Synthesis of aliphatic–aromatic polyamide carbonized system with phosphoramide structure and study on its thermal degradation mechanism and flame retardancy in polypropylene system

Abstract

A novel char-forming agent (PETAP) containing aliphatic–aromatic polyamide and phosphoramide structure was successfully prepared via the high-temperature and high-pressure solution reaction of terephthalic acid, ethylenediamine and phosphorous acid. Meanwhile, polypropylene (PP) composites were prepared by using different proportions of PP, ammonium polyphosphate (APP) and PETAP, and the total load of PETAP and APP was 30%. According to the results of limit oxygen index (LOI), vertical burning test (UL-94) and thermogravimetric analysis, PETAP/APP system can greatly improve the thermal stability and flame retardancy of PP. For the mass ratio of (9 mass%/21 mass%/70 mass%) APP/PETAP/PP sample (PP-4), the LOI value achieved the highest, which is 28.8%. It achieved the UL-94 V-0 rating. Then, the Fourier transform infrared spectroscopy analyzed the thermal degradation mechanism of PP composite’s carbon residue at different temperatures, and the potential relationship between microstructure and flame retardancy was also evaluated and discussed. Moreover, the scanning electron microscopy of residual carbon showed that PETAP and APP were helpful to form denser char layer. This char layer has a compact structure which can effectively prevent heat transfer and plays an important role in flame retardant. Finally, the mechanical properties of PP composites were tested, which indicated the mechanical properties of PP composites have not changed much.

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Acknowledgements

The work was financially supported by the Experiment Center of Polymer Science and Engineering Academy, Sichuan University and National Natural Sciences Foundation of China, Grant No. 50973066.

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Correspondence to Xufu Cai.

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Ma, J., He, L., Huang, L. et al. Synthesis of aliphatic–aromatic polyamide carbonized system with phosphoramide structure and study on its thermal degradation mechanism and flame retardancy in polypropylene system. J Therm Anal Calorim (2020). https://doi.org/10.1007/s10973-020-09879-2

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Keywords

  • Polypropylene (PP)
  • Char-forming agent
  • Composites
  • Thermal degradation