Fabricating flame retardant polyacrylonitrile fibers modified by sodium lignosulfonate and copper ions

A facile and eco-friendly approach was developed to endow polyacrylonitrile fibers (PAN) with excellent flame retardancy and char-forming capability. First, aminated PAN (A-PAN) was prepared via ethylenediamine treatment. Next, sodium lignosulfonate (SLS) was adsorbed on the surface and interior of A-PAN through strong ionic bonds to obtain the SLS modified A-PAN, i.e., SLS/A-PAN. Afterwards, copper ions (Cu 2+ ) were chelated with SLS/A-PAN to construct Cu/SLS/A-PAN. The modified PAN samples were characterized by solid-state 13 C NMR, FTIR, XPS and SEM. TGA demonstrated that the preferential degradation of Cu/SLS/A-PAN was prone to forming much char residue whether in N 2 or air atmosphere, which acted as an effective barrier to hinder the decomposition of PAN matrix so as to exhibit excellent flame retardancy. Additionally, the char residue of Cu/SLS/A-PAN showed numerous intumescent vesicles with continuous wavy-like char layer and its I D / I G value was 1.28, exhibiting superior degree of graphitization. Particularly, compared to the pristine sample, the peak of heat release rate of Cu/SLS/A-PAN decreased significantly. In addition, TG-IR indicated the volatile products of Cu/SLS/A-PAN were significantly reduced. SLS and Cu 2+ were cooperative in endowing Cu/SLS/A-PAN with excellent flame retardancy and superior char-forming capability.