Localized radiation grafting of flame retardants to poly(ethylene terephthalate). I. Bromine‐containing monomers

Abstract

Vinyl bromide was used as a model for bromine‐containing flame retardants in developing methodology for localizing flame retardants either on the surface of the filament, uniformly throughout it, or predominantly at the core. SEM–x‐ray microprobe techniques were used in the verification of the location of the flame retardant in the filament. The flame retardance efficiency of PVBr was then correlated with its location in the filament. Grafting other bromine‐containing flame retardants showed a wide range of efficiencies which depended not only upon the location of the grafting within the filament but also upon the structure of the compound. For the various bromine homopolymer grafts, the apparent thermal stability of the graft and its flame retardance efficiency may be simply related to the alpha aliphatic hydrogen‐to‐bromine ratio. The lower this ratio is, the higher the efficiency. VBr copolymers and terpolymers showed wider variation in flame retardance efficiencies. This is attributed to large variations in melt viscosity of the different grafted materials. The grafts showed only small changes in their melting points and minimal changes in tenacity and stiffness. However, grafting induced large increases in the elongation.