Effect of microencapsulated ammonium polyphosphate on the durability and fire resistance of waterborne intumescent fire-retardant coatings

Large-scale addition of hydrophilic solid filler (i.e., ammonium polyphosphate) into waterborne intumescent fire-retardant coatings can cause many problems such as poor compatibility, easy absorption of moisture, and poor durability. In this work, microencapsulated ammonium polyphosphate with melamine formaldehyde resin (MFAPP) was prepared and applied in intumescent fire-retardant coatings to solve the problems mentioned. Due to the hydrophobicity of melamine formaldehyde (MF) resin, MFAPP exhibited better water resistance, thermal stability, and compatibility with polymer matrix, which was confirmed by Fourier transform infrared spectra, scanning electron microscopy (SEM), particle size test, water solubility, water contact angle, and thermogravimetric analysis (TGA). The effect of the MFAPP on durability and fire resistance of the fire-retardant coatings test were investigated by the static immersion test, fire resistance test, TGA, and SEM. Even immersed in distilled water for 12h, the coatings containing MFAPP did not show obvious damage, indicating microencapsulation improved the water resistance of coatings. Furthermore, the fire-resistant time and thermal stability of the waterborne intumescent fire-retardant coatings were also improved remarkably by utilizing the microencapsulation of ammonium polyphosphate.