INFLUENCE OF ACID DYES ON THE THERMAL-BEHAVIOR OF NYLON-66

To reveal the effect of acid dyes on the melt processing of recycled n ylon 66, 17 acid dyes with different chemical structures were used to dye a nylon 66 yam. The thermal stability of dyestuffs, the thermal de gradation of the dyed nylon 66 during compression molding, and the mel ting and crystallization of the dyed nylon were investigated. During m elt processing, most dyed nylon 66 changed color strength and color pa ttern. This is attributed to the migration and chemical reactions of d yestuffs. Acid dyes containing metal ions, such as C.I. Acid Black 60, C.I. Acid Red 186, C.I. Acid Yellow 151, and C.I. Acid Black 107, hav e severe impact on the thermal stability of nylon 66. The influence of metal complex acid dyes on the thermal stability of nylon 66 can be e xplained by a mechanism of acid-catalyzed nucleophilic acyl substituti on. It was observed that the existence of acid dye in nylon 66 does no t influence the melting temperature of nylon. However, some metal comp lex dyes reduce the crystallization temperature of molten nylon. (C) 1 998 John Wiley & Sons, Inc.