Editorial Type: research-article
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Online Publication Date: 24 Sept 2025

SYNTHESIS OF A NEW PHOSPHORUS-NITROGEN FLAME RETARDANT BASED ON SEPIOLITE AND FLAME RETARDANT AND SMOKE SUPPRESSION STUDY ON EPDM

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Article Category: Research Article
Page Range: 539 – 559
DOI: 10.5254/rct.25.00013
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ABSTRACT

To further the design and use of flame retardants with lower environmental impacts, many available, ecofriendly, biobased, and biocompatible flame retardants have begun to be used. This study explores the synthesis of a novel phosphorus-nitrogen synergistic flame retardant (PMO) by using biosourced phytic acid and enteromorpha prolifera, along with mineral-based modified sepiolite and melamine, to investigate its flame retardant and smoke suppression effects on EPDM. Experimental results demonstrate that compared with pure EPDM, EPDM with 50 parts per hundred of rubber PMO achieves a V-0 rating in UL-94 tests, with an increased limiting oxygen index to 31.1%, time to ignition extended from 6 to 29 s, peak heat release rate reduced by 55.8%, and total heat release decreased by 69.4% (particularly total smoke production reduced by >73%), thereby significantly enhancing the flame retardant performance of the rubber composite material. After loading with modified seafoam, a highly efficient PMO flame retardant was successfully prepared that has a broad application prospect in general rubber materials.

Copyright: 2025
Fig. 1.
Fig. 1.

Schematic diagram of the molecular structure of EPDM.

Fig. 2.
Fig. 2.

Structural formula of PA molecule.

Fig. 3.
Fig. 3.

Schematic diagram of the crystal structure of SEP.

Fig. 4.
Fig. 4.

Montmorillonite crystal structure diagram.

Fig. 5.
Fig. 5.

SEM image of montmorillonite.

Fig. 6.
Fig. 6.

SEM image of SEP.

Fig. 7.
Fig. 7.

Synthesis flow chart of PMO.

Fig. 8.
Fig. 8.

(a) FTIR of EP, SEP and MEL and (b) FTIR of PA, PMO1, PMO2, and PMO3.

Fig. 9.
Fig. 9.

CCT results of EPDM, EPDM/EP, EPDM/MEL, EPDM/PMO2, and EPDM/PMO3 composites at 35 kW·m−2 heat flux: (a) HRR, (b) THR, (c) SPR, and (d) TSP.

Fig. 10.
Fig. 10.

Digital photos of char residues for EPDM/EP, EPDM/MEL, EPDM/PMO2, and EPDM/PMO3 composites after CCT test.

Fig. 11.
Fig. 11.

(a) TGA and (b) DTA of EPDM composites in nitrogen atmosphere.

Fig. 12.
Fig. 12.

SEM images of (a1–a3) EPDM/EP and (b1–b3) EPDM/PMO3 carbon residues.

Fig. 13.
Fig. 13.

Raman spectra of (a) EPDM, (b) EPDM/MEL, (c) EPDM/EP, and (d) EPDM/PMO3 carbon residues.

Fig. 14.
Fig. 14.

Tensile strength and tear strength (a), DIN abrasion (b), and Shore A hardness (c) of EPDM composites.

Fig. 15.
Fig. 15.

EPDM-PMO flame retardant mechanism diagram.

Contributor Notes

†

These authors contributed equally to this work.

*Corresponding authors. Ph: 0086+18553282659; email: qustlilin@hotmail.com; Ph: 0086+15954203515; email: lyzhsh@163.com
Received: 11 Mar 2025
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