Tailored flame retardant TPU eco-composites: incorporating phytic acid polyethyleneimine complex and nanoclay

Abstract Incorporating natural sources in flame retardant applications has emerged as an effective strategy for advancing environmentally friendly and sustainable manufacturing practices. This research assesses the flame retardant capabilities of a phytic acid polyethyleneimine polyelectrolyte complex (PA-PEI) in eco-based thermoplastic polyurethane (TPU) composites, while also exploring the adjuvant role of nanoclay (NC). The samples undergo comprehensive characterization using various techniques including thermal gravimetric analysis (TGA), limiting oxygen index (LOI), vertical UL-94 (UL-94 V), mass loss calorimeter (MLC), and tensile testing. With increasing PA-PEI content, there is a gradual enhancement in LOI values alongside reductions in both peak heat release rate (pHRR) and total heat evolved (THE) values. PA-PEI acts in the condensed phase through the formation of moderate intumescent residue structure. When PA-PEI and NC are used together, the highest UL-94 V rating of V0, LOI value of 28%, the lowest peak heat release rate (pHRR) (70 ± 4 kW m −2 ), and total heat evolved (THE) (57 ± 2 MJ m −2 ) values are achieved. NC primarily exhibits an adjuvant effect by increasing the amount, compactness, and intumescent function of the residue in the condensed phase. Tensile test results indicate that PA-PEI addition improves the tensile strength without deteriorating its flexibility due to its reactive and fusible character.