Silicon containing inherent flame retardant polyamide 6 with anti dripping via introducing ethylene glycol as the chain linker and charring agent
Abstract An inherent flame retardant PA6 (FR PA6) containing polydiphenylsiloxane (PDPS) was synthesized under the action of ethylene glycol (EG) via a facile "2 step" bulk polymerization. Inspiringly, EG acted not only as a 'chain linker' to connect PA6 oligomer with PDPS moiety but also as a charring agent to increase the charring capacity of FR PA6 after combustion. The prepared FR PA6 reached 28.3% of limiting oxygen index (LOI) and passed the V 0 level of UL94 test with suppressed melt dripping. After investigating the char residues and pyrolysis volatiles of FR PA6 after combustion, the formation of silicon rich protective layer was proved to be the essential factor to increase the flame retardancy of FR PA6 via reducing the diffusion of pyrolysis volatiles, restricting the heat transfer and mass loss as well as preventing polymer melts from dripping. This work thus makes a worthwhile contribution to the development of FR PA6 by offering a novel route that is easily accessible to industrial fabrication.