Grafting to Achieve Flame Retardancy
Polymer Degradation and Stability
Vinyl monomers, such as methacrylic acid, may be grafted onto styrenebutadiene copolymers, SBS, or onto acrylonitrile-butadiene-styrene terpolymer, ABS, by either a photochemical process or chemical initiation. The amount of grafting is similar using both procedures. Vinyl monomers may not be grafted onto poly(ethylene terephthalate), PET; rather the vinyl monomers homopolymerize within the PET and form a semi-interpenetrating network. All of these copolymers have been analyzed by TGA and TGA-FTIR. For SBS and ABS, the grafted char-former serves to retain the base polymer. There is little difference in the degradation pathway between the grafted and the virgin polymers. Homopolymerization of methacrylic acid within the PET matrix has no effect on the degradation of PET. When one attempts to convert the methacrylic acid contained within the PET into its sodium salt, the entire sample is hydrolyzed. There is good reason to think that the addition of a surface layer of a good char-former onto a polymer will improve the thermal resistance of the polymer.