Preparation and performance analysis of palygorskite reinforced silicone-acrylic emulsion-based intumescent coating

Aiming to improve the fire resistance, the synergistic effects of palygorskite and expandable graphite (EG) on water-based intumescent fire retardant (IFR) coatings were investigated in details by fire resistance test, limiting oxygen index (LOI) test, vertical burning (UL-94) tests, thermogravimetry (TGA)-differential scanning calorimeter (DSC) test, and cone calorimeter test. The char residues were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller test (BET). The backside temperature of the substrate of sample 3-3 with 3 wt% of EG and 3 wt% of palygorskite addition (SP3-3) was recorded to be 150 °C after 120 min fire test, 46.5% lower than that of the sample 1 with no addition (SP1). The SP3-3 had the best fire retardant performance reflected by UL-94 V0 flammability rating and the LOI value as high as 35.8%. The TG-DSC analysis showed palygorskite can increase the thermal stability and decrease the decomposition rate of the coatings. The cone calorimeter test demonstrated SP3-3 remarkably reduce the value of peak heat release rate and peak smoke production release by 64.1% and 85.7%, respectively. The XRD analysis confirmed that the decomposition compounds of ammonium polyphosphate, fillers, and palygorskite can react and form a ceramic-like protective barrier, which enhanced the thermal stability and char yield. In addition, the SP3-3 had shown best results in char expansion and char morphology. •Silicone-acrylic emulsion was used to prepare intumescent fire retardant coating.•The synergistic effects of EG and palygorskite apparently promoted the flame retardant and heat insulation performance.•The backside temperature of the coating was kept at ~150 °C after the 120 min fire test.•PHRR and PSPR were reduced by 64.1% and 85.7%, respectively.