Flame Retardancy, Fire Behavior, and Flame Retardant Mechanism of Intumescent Flame Retardant EPDM Containing Ammonium Polyphosphate/Pentaerythrotol and Expandable Graphite.

Junsheng Wang,Xing Jin,Guide Lin,Bi Zhao,Dan Liu,Haibo Zhu,Jinjun Yang,Lei Xue,Ke Shang

doi:10.3390/ma12244035

Abstract

The intumescent flame retardant ethylene–propylene–diene rubber (EPDM) was prepared using intumescent flame retardant (IFR), including ammonium polyphosphate (APP) /pentaerythrotol (PER) and expandable graphite (EG), as the flame retardant agent. The effects of IFR and EG on the flame retardancy, fire behavior, and thermal stability of the EPDM were investigated. The results show that IFR and EG have excellent synergistic flame retardant effects. When the mass ratio of IFR to EG is 3:1 and the total addition content is 40 phr, the limiting oxygen index (LOI) value of the EPDM material (EPDM/IFR/EG) can reach 30.4%, and it can pass a V-0 rating in the vertical combustion (UL-94) test. Meanwhile, during the cone calorimetry test, the heat release rate and total heat release of EPDM/IFR/EG are 69.0% and 33.3% lower than that of the pure EPDM, respectively, and the smoke release of the material also decreases significantly, suggesting that the sample shows good fire safety. In addition, the flame retardant mechanism of IFR and EG is systematically investigated by thermogravimetric analysis/infrared spectrometry (TG-IR), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), and the results indicate that IFR and EG have only physical interaction. Moreover, the reason why IFR exhibits a poor flame retardant effect in EPDM materials is explained.

Highlights

Ethylene–propylene–diene rubber (EPDM), as one of the most useful synthetic rubbers composed of ethylene, propylene, and unsaturated diene, is resistant to heat, light, ozone, and ultraviolet radiation and has been widely used in heat-resistant conveyor belts, cables, wires, gaskets, door and window seals, and so on
The results of the flame retardant tests show that intumescent flame retardant (IFR) exhibits poor flame retardant effect for EPDM, and rather a high loading (60 phr) of flame retardant is required to achieve the necessary flame retardant performance
In order to explain the reason of this phenomenon, the digital photos and microstructures of the flame retardant EPDM materials after burning in the muffle furnace at 300 ◦ C, 350 ◦ C, 400 ◦ C, 450 ◦ C, and 500 ◦ C are conducted by digital camera and scanning electron microscopy (SEM) to analyze the combustion process of the materials, which are presented in Figures 9 and 10, respectively

Summary

Introduction

Ethylene–propylene–diene rubber (EPDM), as one of the most useful synthetic rubbers composed of ethylene, propylene, and unsaturated diene, is resistant to heat, light, ozone, and ultraviolet radiation and has been widely used in heat-resistant conveyor belts, cables, wires, gaskets, door and window seals, and so on. EPDM is a flammable material with a very low limiting oxygen index (LOI). It is necessary to improve the flame retardant performance of EPDM [2,3,4]. The halogenated flame retardant [5,6,7], such as decabromodiphenyl oxide and decabromodiphenyl ethane, has a good flame retardant effect on EPDM, which can significantly improve the LOI of EPDM. Metallic hydroxide has been extensively used as halogen-free flame retardant in polymeric materials due to its higher decomposition temperature and lower smoke and toxic gas production [14,15], but because of its low flame retardant efficiency, rather a high loading of flame retardant is required to achieve the necessary flame retardant effect, which will deteriorate the overall performances of the composites dramatically

Methods

Results

Conclusion