Flame retardancy and mechanical properties of polyamide 6 modified by multiple reactions with furan-phosphamide

Polyamide 6 (PA6) has potential safety hazards in many fields due to its intrinsic flammability. In this paper, furan-phosphamide (POCFA) was introduced into PA6 to regulate its flame retardancy and mechanical properties via multiple reactions between them. The results showed that 5 wt% POCFA makes PA6 achieve the UL-94 V0 rating and a LOI 27.2 vol%. The mechanical properties of PA6 were decreased after processing, but these properties can recover after a period of time. This is caused by the multiple reactions between POCFA and PA6 during processing and application. Firstly, POCFA catalyzes the degradation of PA6 resulting in the decrease of molecular weight and the increase of fluidity, which improves the flame retardancy of PA6 by melting-away mode. Secondly, the reactions between POCFA and PA6 graft furan ring onto PA6 chain, thus Diels-Alder addition reactions can occur between different furan rings, which extend the molecular chain of PA6, and improve the mechanical properties. This work provides a good method to balance the flame retardancy and mechanical properties of PA6 composites