V.A highly efficient, bio-ecofriendly, and transparent flame retardant (FR) for cotton fabric was developed and deposited onto the cellulose skeletal structure of cotton fabric through a one-pot sol-gel process. The flame retardant functional coating is composed of ammonium polyphosphate (APP), guar gum (GG), citric acid (CA), and a negligible amount of catalyst. Cotton fabrics were impregnated with different concentrations of ammonium polyphosphate and guar gum, with citric acid as a crosslinking agent. The overall crosslinking and grafting process was proven by FTIR and XPS. Based on the results, the designed coating exhibits over 90 % transmittance in the visible region. A 15 g/m2 flame-retardant coating induces excellent flame retardant efficiency at ultra-low flame-retardant concentrations of less than 6.25 wt%. Only a 5.25 wt% flame retardant concentration demonstrated condensed phase action, which resulted in 58.5 % and 73.6 % reductions in the pHRR and THR, respectively. Moreover, the limiting oxygen index (LOI) value showed a 74 % increase. The mechanical performance of FR coated cotton fibers was slightly reduced.

Previously, it was reported that epoxy resin (EP) filled with ammonium polyphosphate (APP) and copper (I) oxide (Cu2O) at a mass ratio of 8/2 (APP8-Cu2O2) as a self-intumescent system demonstrated promising fire retardancy. To further improve the flame retardant efficiency, the possibility of expandable graphite (EG) as an effective synergist for the self-intumescent EP system was revealed by limiting oxygen index (LOI) test. The results showed that the incorporation of EG increased the LOI value of EP/APP8-Cu2O2 obviously. The highest LOI value was obtained at the EG/APP8-Cu2O2 mass ratio of 3/7, indicating the optimal synergistic effect being achieved. Furthermore, UL-94 test results showed that the excellent synergistic effect resulted in the addition of 13 wt% EG/APP8-Cu2O2 of 3/7 not only endowed EP a relatively high LOI value of 34.3%, but also made it pass UL-94 V-0 rating. Moreover, the main fire hazard parameters obtained from cone calorimeter tests, such as peak heat release rate, total smoke production, and peak CO production were reduced 40.3%, 30.3%, and 46.2%, respectively by the combination effect of EG/APP8-Cu2O2 with mass ratio of 3/7, suggesting the excellent improvement in the fire safety of EP significantly. Finally, a possible action mode, which would be beneficial for developing other flame retardant polymers with high fire safety, was proposed.

This paper focuses on revealing the thermal decomposition behaviors of a self-intumescent flame retardant (IFR) epoxy (EP) resin (EP/15%APP-Cu2O) employing 12 wt% ammonium polyphosphate (APP) as a halogen-free flame retardant and 3 wt% copper (I) oxide (Cu2O) as char forming rate regulator. Initially, the thermal stability of EP/15%APP-Cu2O was analyzed and compared to virgin EP resin and flame retardant EP (EP/15%APP) containing 15 wt% APP as flame retardant by thermogravimetric analysis test at different heating rates under nitrogen atmosphere. It was shown that the incorporation of APP altered the decomposition pathway of EP and decreased the onset decomposition temperature. Luckily, compared to EP/15%APP, the onset decomposition temperature of EP/15%APP-Cu2O was just slightly reduced from 300.4 to 292.8 degrees C. Then, the thermal degradation kinetics of EP, EP/15%APP and EP/15%APP-Cu2O were further evaluated by Kissinger and Flynn-Wall-Ozawa methods. It was worth noted that the addition of APP or APP-Cu2O enhanced the thermal degradation activation energies of EP, which contributed to the protective effect of the char formation. Particularly, the incorporation of 3 wt% Cu2O significantly decreased the thermal degradation activation energies at the early decomposition stage of EP. This may be the main contribution for intumescent char formation, which resulted in higher fire safety of EP/15%APP-Cu2O compared to EP/15%APP. These information can potentially help to develop alternative IFR systems.