Design of La-doped SmMn2O5/epoxy composite materials: multifunctional synergy for fire safety and electromagnetic shielding

The development of polymer materials with flame-retardant and microwave-absorbing properties reduced fire risks and mitigated electromagnetic interference, representing an important direction in advanced materials research. In this work, La x Sm 1-x Mn 2 O 5 (xLSMO) mullite with varying La doping levels (molar ratio, x = 0.1, 0.3, 0.5) was synthesized via a co-precipitation method, and the effects of LSMO on the flame-retardant and microwave-absorbing properties of epoxy resin (EP) were investigated. The results demonstrated that LSMO exhibited excellent catalytic charring ability and a pronounced nucleating effect, effectively enhancing the compactness and strength of the char layer and thereby improving the fire safety of EP. When the La doping level was 0.3 and the LSMO loading in EP was 1wt%, the limiting oxygen index (LOI) increased from 24.1% to 32.3%, and a V-1 rating was achieved in the UL-94 test. The peak heat release rate (PHRR) and total heat release (THR) were reduced by 45.32% and 32.69%, respectively. In addition, the incorporation of LSMO endowed EP with favorable electromagnetic wave absorption capability, with a minimum reflection loss reaching −36.87 dB in the frequency range of 1–18 GHz. Therefore, the EP/LSMO composites exhibited considerable potential as multifunctional integrated materials in the fields of public safety and electromagnetic protection technology.