Effects of acid dyes on crystallization and mechanical properties of melt-reprocessed nylon 66

Nylon fibers dyed with different types of acid dyes were melt reprocessed using a compression-molding machine. The crystalline structure and mechanical properties of the melt-reprocessed nylon were experimentally evaluated. It was found that metal complex acid dyes showed much more distinct effects on the structure and mechanical properties of melt-reprocessed nylon than nonmetallized acid dyes. They decreased the crystallization rate of the molten nylon and reduced its crystallinity. They also reduced the imperfect form I structure in the crystalline region. Compression-molded nylon samples showed inferior mechanical properties in the presence of metal complex acid dyes. The coordinate bonds between the Cr3+ ions and amide groups are possibly formed in melt-reprocessed nylon, which could be the reason for the changes in the structure and properties of melt-reprocessed nylon. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2386–2396, 1999