The fabrication of organic-inorganic hybrid structure towards high mechanical property and improved flame retardancy

In order to design UPR composites with high mechanical property and improved flame retardancy, an organic-inorganic hybrid flame retardant (DA-Si-HNT) was fabricated by grafting silane coupling agent (KH560) and the phosphorus-nitrogen containing structure (DOPA-A, the production of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and adenine) on the surface of halloysite nanotube (HNTs). The UPR/DA-Si-HNT 15 composites exhibited significant improvements in tensile strength , tensile modulus , and flexural strength , with respective increases of 65.6 %, 140.6 %, and 80.2 % compared to neat UPR . These enhancements can be attributed to the enhanced compatibility and interfacial force between the flame retardants and the polymer matrix . Meanwhile, it passed the UL-94 V-0 rating at a limiting oxygen index (LOI) value of 34.5 %. The peak of heat release rate (PHRR) and total heat release (THR) decreased by 49.5 % and 43.5 % comparing to that of UPR, indicating a sharp decline in the heat hazard. Moreover, an obvious catalytic carbonization effect in the condensed phase accompanied with moderate gas-phase effect jointly improved flame retardancy of the UPR/DA-Si-HNT 15 composites.