A phosphaphenanthrene-grafted cyclosiloxane in combination with diatomite for flame retardant epoxy resins with excellent comprehensive properties
Xiao Z.-T. Akhmetova M. Shi H.-J. Bekeshev A. Uzakbaeva S. Zhanturina N. Aimaganbetova Z. Hu Y. Wang X.
October 2025Elsevier Ltd
Polymer Degradation and Stability
2025#240
The core shortcomings of commercial epoxy resins (EPs), especially DGEBA-type epoxy thermosets, are their flammability and brittleness, which restrict their applications. Therefore, improving the flame retardancy of EPs has research significance and application value. In this study, an organic -inorganic synergistic flame retardant strategy was applied to improve the flame retardancy of epoxy thermosets. The inorganic flame retardant used was diatomite (DM) before and after modification with a phosphorus-containing silane coupling agent (DOPO-KH560), and phosphorus-containing cyclosiloxane (DOPO-4Si) was used as the organic component. The as-prepared EP composites had excellent comprehensive properties. The limiting oxygen indices (LOIs) of EP/DOPO-4Si-1.0P and EP/(DOPO-4Si+mDM) reached 30.5 % and 28.5 %, respectively, and the V-0 rating in the UL-94 vertical burning test. In addition, the modified EP composites resulted in a lower heat release rate and smoke release rate. Compared with those of EP, the peak heat release rate (PHRR) and total heat release (THR) of EP/(DOPO-4Si+mDM) were 38.9 % and 19.3 % lower, respectively. In addition to their flame retardant properties, the modified epoxy composites also exhibited good strengths. Specifically, the tensile and impact strengths of EP/DOPO-4Si-1.0P reached 47.5 MPa and 52.7 kJ/m2, respectively, whereas those of EP/(DOPO-4Si+mDM) were 42.7 MPa and 27.2 kJ/m2, respectively. In addition, the flame retardancy mechanisms of EP composites were compared via the analysis of char residues and pyrolysis products. This work proposed a new method for the application of organic-inorganic synergistic flame retardant systems in the preparation of high-performance EP composites.
Diatomite , Epoxy resin , P/Si-containing flame retardants , Surface modification
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State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Anhui, Hefei, 230026, China
Department of Physics, K. Zhubanov Aktobe Regional State University, Aliya Moldagulova Avenue 34, Aktobe, 030000, Kazakhstan
Laboratory of Polymer Composites, K. Zhubanov Aktobe Regional State University, Aliya Moldagulova Avenue 34, Aktobe, 030000, Kazakhstan
State Key Laboratory of Fire Science
Department of Physics
Laboratory of Polymer Composites
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