Fire Retardant Action of Layered Double Hydroxides and Zirconium Phosphate Nanocomposites Fillers in Polyisocyanurate Foams

Modern day energy codes are driving the design and multi-layered configuration of exterior wall systems with a significant emphasis on achieving high performance insulation towards improving energy performance of building envelopes. Use of highly insulating polyisocyanurate (PIR) based materials enhanced with eco-friendly lamellar inorganic fillers reinforces energy performance requirements, environmental challenges and cost reduction without compromising the overall building fire safety. The current work assessed the fire behaviour of PIR modified with three layered fillers, namely MgAlCO₃ (PIR-LDH1), MgAl Stearate (PIR-LDH2) and Zirconium Phosphate octadecylamine (PIR-ZrP3). For each of the fillers, three loadings (2, 4 and 6% by weight) were used. Optical analysis by X-ray diffraction patterns (XRD), cone calorimeter (CC), thermogravimetric (TGA) analysis, post-burning morphological evaluation using field emission scanning electron microscope (FESEM) and diffuse reflectance infrared spectroscopy (DRIFT) analysis, were performed. The results indicated that fire reaction properties and thermal stability of foam samples were enhanced with all three different lamellar inorganic smart fillers. The initial degradation temperature of PIR-layered filler samples was increased, demonstrating that incorporation of flame retardants decelerated the degradation of the PIR foam and contributed to significant char formation, from 19.5% in pure PIR samples to 33% in PIR-6%LDH1 samples. Increasing the filler content also resulted in improved char properties and decreased peak Heat Release Rates (HRR) in the cone calorimeter. Due to the development of a stable char layer, samples containing 6% of ZrP3 did not ignite at 20 kW/m² and a reduction of up to 40% in the peak HRR was achieved in PIR-2%ZrP3 samples.