Fire Performance of Intumescent Flame Retardant/Nanosilica/Thermoplastic Polyurethane Composite: A Study on Synergism

Document Type : Research Paper

Authors

1 Department of Chemistry, Organic Chemistry, Iran University of Science and Technology, Postal Code, 1674613114, Tehran, Iran

2 IPlastic Processing and Engineering Department, Faculty of Processing, Iran Polymer and Petrochemical Institute, P.O. Box: 14975-112, Tehran, Iran

Abstract

Hypothesis: The aim of this research is to improve the fire behavior of thermoplastic polyurethane (TPU) using an intumescent flame retardant system (IFR) and nanosilica as a synergistic agent 
Methods: A three-component IFR system consisting of ammonium polyphosphate (APP), melamine polyphosphate (MPP), and pentaerythritol (PER) was added to TPU by melt mixing. The flammability of the TPU-IFR was evaluated by UL94 vertical burning test and the efficiency of the IFR was investigated by cone calorimeter test (CCT). A nanosilica as a synergist with low loading was added to the TPU-IFR composite, and fire properties were investigated. Thermal stability and char morphology were investigated by thermal analysis and scanning electron microscopy, respectively.
Findings: The results show that the IFR system is effective with a significant decrease of 62.6% in peak heat release rate (PHRR) and 58.3% in peak smoke production (pSPR). By incorporation of 0.5% (by wt) nanosilica into TPU-IFR, there are decreases in PHRR and pSPR by 75.0% and 79.2%, respectively, compared to the original TPU, while the dripping is removed. This has confirmed the effective synergism of nanosilica in enhancing the flame retardancy of TPU-IFR. Further, the amount of residual char has reached 31.2% and 58.9% for TPU-IFR and TPU-IFR-nanosilica, respectively, compared to 6.2% in a neat TPU. Both TPU composites have reached V0 grade in UL-94 test. FESEM shows an integrated compact char in IFR-TPU-nanosilica, while there are small holes in the char structure of IFR-TPU. Thermal analysis (TGA) has shown enhanced thermal stability in the two TPU composites by formation of a carbon layer as a thermal barrier during burning. This work introduces an efficient intumescent flame retardant system for improving the fire behavior of TPU which can significantly enhance the fire safety of TPU by a low loading of nanosilica as a synergist. 

Keywords

References

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Iranian Journal of Polymer Science and Technology
Volume 36, Issue 1 - Serial Number 183
May and June 2023
Pages 73-86

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