Study on the preparation and properties of novel transparent fire-resistive coatings

A cyclic polyphosphate (CPPA) was synthesized by the reaction of polyphosphoric acid and pentaerythritol. Polyethylene glycol (PEG) was introduced in the structure of CPPA to improve its solubility in water and ethanol and five kinds of reactive type flame retardants (MCPPA) were obtained. 31P NMR, 1H NMR, FTIR, and TGA were used to characterize the composition and structure of CPPA and MCPPAs. The experimental results showed that there were 25% cyclic P–O–C structures in the product and MCPPA had better carbonization ability than CPPA. Five kinds of transparent fire-resistive coatings were prepared by the mixing of amino resin with five kinds of MCPPAs. The results of the fire protection test showed that both the fire-resistive time of coatings and intumescent factor of char layers decreased with the increase of molecular weight of PEG. The results of TGA and EDS showed that the carbonaceous residue of coatings and the antioxidation ability of char layers also decreased regularly with the increase of molecular weight of PEG. The SEM images demonstrated that the coating prepared with low molecular weight of PEG contributed to dense form structure and narrow distribution of cell size. Above all, the transparent fire-resistive coating prepared with PEG 200 had the best fire retardancy and stable thermal behavior.