Synergistic effects of silicon based material with intumescent flame retardant in thermoplastic polyurethane: Pre-polymerization and dynamic vulcanization based facile approach

A flame retardant thermoplastic polyurethane (TPU) was prepared using the silicon based (Si)-intumescent (IFR) synergistic flame-retardant system, which combined the advantages of additive and reactive types. Silicone rubber was introduced into the matrix of hydroxybutanyl terminated polydimethylsiloxane (PDMS) block TPU via dynamic vulcanization, which enabled the combination of silicon based material and TPU. Then, the IFR system was used to supplement the defects of single Si based flame retardancy, which realized the synergistic flame retardancy of Si-IFR. Under the Si-IFR system, when IFR uses 15%, the TPU reached the V-0 flame retardant level and the limiting oxygen index was 29.6. Moreover, the toughness of the Si-IFR flame-retardant TPU was better than PDMS block TPU. The silicon based material improved the matrix and cooperated with IFR to form a composite carbon layer, which protected the inner material, enhanced the strength of the carbon layer and eliminated dropping.