The Impact of Natural Fiber Science on Manmade Fiber Technology1

Abstract

Analytical methods are described for the chemical characterization of polyamide and polyester fibers. Their origin from natural fiber chemistry is elucidated. End-group data (amino, acylated amino, and carboxyl groups), number-average molecular weights and breaking stress values are given for commercial polyamide fibers produced by several manufacturers. Amino groups were deter mined with 1-fluoro-2,4-dinitrobenzene, using a new technique. Besides its specifity, this chemical method allows the differentiation of primary and secondary amino groups and their determination in the presence of each other. A related topic is the detection of heat damage in polyamides. Heat treatment leads to the formation of basic groups, which can be distinguished spectroscopically from amino groups after reaction with 1-fluoro-2,4-dinitrobenzene. As a practical application the elucidation of the damage of a nylon needle felt, used in a paper machine, is described. Hydrazinolysis was applied for the determination of carboxyl end groups. The use of this new analytical method for polyester studies is described, also its application on several commercial polyethylene terephthalate fibers. Furthermore, hydrazinolysis allows the determination of the amount of 5-sulfo-isophthalic acid in acidic modified fibers. Values ob tained are confirmed by determination of the uptake of a basic dyestuff (methylene blue). The importance of end- group analysis is stressed by its application to the analysis of hydrolytically damaged polyester fibers. The increase in carboxyl groups was determined for steam-treated modified and unmodified polyethylene terephthalate. Results concerning the analysis and generation of oligomers in polyester are added.