| Abstract: | Analysis of phenolphthalein and bisphenol-A copolycarbonates reveals a linear correlation between oxygen index (OI) and char yield (Y): OI = 0.34Y + 19.6, which can be compared with the empirical equation QI = 0.4Y + 17.5 proposed by D. W. Van Krevelen for other polymers. Analysis also suggests that no chemical interction occurs between the two comonomers during pyrolysis, which leads neither to enhanced char yield nor to enhanced oxygen index. Each copolymer component contributes to the char yield and oxygen index on an additive basis. Study of 4,5,6,7-tetrabromophenolphthalein and phenolphthalein copolycarbonates shows that some enhancement of char yield does occur and that the lower the char yield, the higher the oxygen index, which is an indication of the predominance of a vapor-phase bromine effect over that related to char. Study of 4,5,6,7-tetrabromophenolphthalein and bis-phenol-A copolycarbonates is interpreted on the basis of two factors—the char effect that prevails over the vapor phase radical scavenging effect at lower bromine content and the reverse order at higher bromine content. |
