Charring of fire retarded ethylene vinyl acetate copolymer - magnesium hydroxide/zinc borate formulations

Zinc borate has been used as a synergistic agent in EVA-Mg(OH)(2) flame retardant (FR) formulations. Solid state NMR of carbon in the residues collected after thermal treatment allows the study of the charring of the flame retardant system. The study has shown that polymer fragments are in the char layer. It is suggested that zinc borate slows the degradation of the polymer, creating a vitreous protective residual layer which could act as a physical barrier and a glassy cage for polyethylene chains. (C) 2000 Elsevier Science Ltd. All rights reserved.