Fabrication and properties of PEI/APP layer-by-layer coated ramie fabric combined with low-temperature plasma treatment

The present work demonstrates a surface pretreatment of reducing assembly layers for flame retardant modification of ramie fabric used by layer-by-layer (LbL) assembly. In order to achieve this goal, low-temperature plasma (LTP) pretreatment was chosen. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscope (SEM) were used to confirm the effect of LTP pretreatment on polyethylenimine/ammonium polyphosphate (PEI/APP) flame retardant coating constructed on the surface of ramie fabric using LbL assembly. The thermal property and flame retardancy of PEI/APP coated ramie fabrics were analyzed by TG, LOI, UL94 vertical burning, and cone calorimeter tests. The results indicated that the decomposition rate of ramie fabrics was reduced and the char forming ability at high temperature was improved by PEI/APP coating on the ramie surface. Its LOI increased markedly to 30.6% and ramie fabric achieved self-extinguishing effect. Meanwhile, LTP-O-2-(PEI/APP)(20) ramie fabric exhibited the low flammability and high fire safety. It was proved that LTP pretreatment under oxygen atmosphere could endow ramie fabric with better flame retardancy due to more PEI/APP adsorbed on its surface. These findings have significant implications for the application of LTP pretreatment to flame retardant modification of ramie fabric by LbL assembly.