The design of flame retardant one-component epoxy resin (EP) with long pot life, low curing temperature and fast curing rate has been challenging in the industry. Herein, we synthesized a phosphate-containing imidazole fluid (TA) as the thermal latent curing agent of EP. Based on simple structural design, TA endows EP with excellent curing properties, storage properties, and flame retardant properties. According to DSC results, EP/TA systems exhibit low curing temperature and fast curing rate during operation. The rotary rheometer test confirms that the viscosity curve of EP/TA system maintains longterm stability at 40 C. The X-ray photoelectron spectroscopy (XPS) data reveals that TA releases imidazole intermediates and phosphorous compounds during curing. The former provides conditions for fast curing of EP, while the latter gives EP intrinsic flame retardant properties. With the addition of 20 wt.% TA, EP/TA-4 achieves UL-94 V-0 rating and 28.5% of LOI value. The study of flame retardant mechanism shows that the flame retardancy of TA mainly comes from the protective effect of phosphorus-rich char layer, the dilution effect of non-combustible gas and quenching effect of phosphorous compound. Besides, due to no solvent involved, the synthesis strategy of TA is environmentally friendly, showing a great potential of industrial application.

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Linear low‐density polyethylene (LLDPE) combined with the piperazine pyrophosphate (PAPP) and melamine cyanurate (MCA) was adopted to prepare the flame retardant LLDPE composite by melt blending. The research results showed that the PAPP/MCA mixture with a mass ratio of 4:1 presented the optimal flame retardant effect. With the 25 wt% addition amount, the LLDPE composite passed the UL‐94 V‐0 level (1.6 mm), and the limiting oxygen index (LOI) reached 29.4%. The peak of heat release rate (PHRR) decreased by 78.9% from 877.5 to 185.0 kW/m2, which is attributed to the good synergistic effect between PAPP and MCA, forming the stable and compact char layer. Besides, the thermal behaviors were characterized through thermogravimetric (TG) analysis, and the synergistic mechanism was investigated by scanning electron microscopy (SEM), TG analysis‐infrared spectrometry (TG‐IR), and x‐ray photoelectron spectroscopy (XPS). The results indicate that the good synergistic flame retardant effect can enhance the flame retardancy of LLDPE materials, and with the addition of MCA and PAPP, a flame retardant LLDPE composite with good thermal stability and mechanical properties can be prepared with no molten droplets on combustion, which provides a feasible solution for the application of high‐performance halogen‐free flame retardant LLDPE materials.