Halogen‐Free Coatings Combined with the Synergistic Effect of Phytic Acid and Montmorillonite for Fire Safety Flexible Polyurethane Foam

Abstract

To overcome defects of some synthetic flame retardants, water‐based coatings using ammonium phytate (AP) and montmorillonite (MMT) as low‐cost renewable materials are fabricated to improve the flame retardancy of flexible polyurethane foam (FPUF). The flame‐retardant FPUF with uniform coatings can avoid melt‐dripping during the vertical flame test (UL‐94), and AP5MMT5/FPUF (flame‐retardant FPUF with the 5:5 weight ratio of AP:MMT in the solutions) reaches a UL‐94 V‐0 rating. A remarkable conclusion can be found that AP and MMT present a synergistic effect under the appropriate proportions. The thermal stabilities of flame retardant FPUF at higher temperature zones are enhanced. Furthermore, flame‐retardant samples prevent the flame from spreading on the surface of FPUF. Cone calorimetry results reveal 67% (AP5MMT5/FPUF) reduction of peak heat release rate relative to pure FPUF, and the release of toxic smoke significantly decreases. AP can catalyze the carbonation of FPUF, and MMT is heated and dehydrated to form a silicon‐containing barrier layer. AP/MMT coatings can form stable and solid physical char layers, which act as a barrier to heat and oxygen exchange, and the release of volatiles is delayed and inhibited. This work introduces a green plan for improving the fire safety of FPUF.

Phytic Acid-Iron/Laponite Coatings for Enhanced Flame Retardancy, Antidripping and Mechanical Properties of Flexible Polyurethane Foam

“…FPUF/PA degrades in advance, as evidenced by the movement of onset degradation temperature (T 5% ) and maximum degradation temperature (T max ) towards a lower temperature compared with those of neat FPUF. This is mainly due to the low thermal stability of PA, which degrades into phosphoric acid and polyphosphoric acid to promote matrix degradation and char layers formation [ 29 , 42 ]. The existence of protective layers greatly reduces the maximum degradation rate (R max ) of FPUF/PA compared with neat FPUF, and R max1 is reduced from 6.4%/min to 2.6%/min, and R max2 is reduced from 14.3%/min to 9.1%/min.…”

“…In addition, the time to ignition (TTI) value and T PHRR of FPUF/PA-Fe/LAP are delayed, indicating that it takes longer to be ignited and it can leave more time for people to escape. The ratio of PHRR to T PHRR is equal to the fire growth rate index (FIGRA), which is generally proportional to the fire hazard [ 42 , 52 ]. Notably, the FIGRA values of FPUF/PA (5.0 kW/(m 2 ·s)) and FPUF/PA-Fe/LAP (5.1 kW/(m 2 ·s)) are drastically reduced, compared with that of neat FPUF (10.5 kW/(m 2 ·s)).…”