Fire-safe and tough semi-aromatic polyamide enabled by halloysite-based self-assembled microrods

Abstract

High performance flame-retardant engineering plastics are highly desirable in electronic appliances, automotive industry, and aerospace fields. However, traditional flame retardants usually lead to impaired intrinsic properties of plastics, especially mechanical properties. Here, we present a hybrid flame retardant with unique hierarchical microrod structure via self-assembly of halloysite nanotube loaded with phenylphosphinic acid. The resultant hybrid integrates excellent thermal stability (Td = 406 °C), interfacial adhesion, and superior flame-retardant efficiency, that endows semi-aromatic polyamide great mechanical properties (tensile strength 67.3 MPa and 73.2 MPa)，improving by 27% and 38% via 5 wt% and 10 wt% addition, compared to that of pristine resin, and excellent flame retardancy with anti-dripping and self-extinguishing (UL-94 V-0, LOI 30.4%) via 10 wt% addition. Meanwhile this hybrid is demonstrated, with 5 wt% or 10 wt% addition of self-assembly halloysite, the composites can form an effective char barrier, that emphasize its fire-safety properties in simulating fire scenario via approximately halving peak of heat release rate and peak of carbon monoxide release rate of the composites. This self-assembly strategy outlined here paves a novel and facile approach for fabrication and widely application of high performance fire-safety polyamides. This will largely improve the reliability of materials in service, reduce the fire probability of electronic devices and casualties caused by fire.