Facile strategy and mechanism of preparing high performance intrinsic flame retarding foams based on reactive end-capped liquid crystalline all-aromatic polyester without incorporating additional flame retardants

It is still a big challenge to develop high performance polymer foams with outstanding flame retardancy and high thermal stability through a facile strategy. Herein, starting from synthesizing phenylethynyl end-capped all-aromatic liquid crystalline polyester with good processability, a new kind of flame retarding liquid crystalline thermosetting foam (LCTF) was fabricated without adding additional flame retardant and foaming agent. LCTF simultaneously shows outstanding flame retardancy (UL94-VO grade, 36.4% of limit oxygen index), excellent smoke suppression and high thermal stability, which are the best values reported so far among intrinsic flame retarding foams. The mechanism of outstanding flame retardancy is revealed by investigating chemical and morphological structures with the aid of three-dimensional reconstruction of morphology. Roles from gas phase and condensed phase are proved to be responsible for unique flame retardancy. The application of LCTF in thermal insulation was also evaluated.