Synthesis of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative grafted polyethylene films for improving the flame retardant and anti-dripping properties

Two novel flame retardant and anti-dripping PE films were successfully synthesized in three steps. PE-g-GMA film was first prepared by simultaneous electron beam irradiation to graft glycidyl methacrylate (GMA) onto PE film. 4,4 '-[1,4-phenyl-bis(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl)dimethyneimino)]diphenol (DOPO-t) and 4,4 '-[1,3-phenyl-bis (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl)dimethyneimino)]diphenol (DOPO-m) were then fabricated via a one-pot method. Finally, two DOPO derivative functionalized PE films were obtained through the ring opening reactions of PE-g-GMA film with DOPO-t and DOPO-m, respectively. Combustion properties, flame retardancy, thermal performance, and thermal shrinkage of these films were evaluated. Compared with pure PE film, the burning rate of anti-dripping DOPO-t/DOPO-m functionalized PE films was reduced by 13.2% and 50.0%, and the limiting oxygen index value climbed to 18.5 and 19.5, respectively. The residual chars from DOPO-t/DOPO-m functionalized PE films at 700 degrees C were increased, and the shrinkage ratio decreased remarkably, which could effectively prevent the spread of fire. We also discussed the effect of structural difference between DOPO-t and DOPO-m on the above properties and the flame retardant mechanism of two DOPO derivative functionalized PE films preliminarily. This work provides a method for introducing DOPO derivatives into PE molecules to improve their flame retardancy and anti-dripping properties.