Abstract
Chlorination and dechlorination of aliphatic and aromatic polyamides such as nylon 66 and poly-m-phenyleneisophthalamide (PMPIPA) were studied. Chemical structures and properties of the chloro-polyamides were examined by means of Cl-analysis, IR and 1H NMR spectroscopies, viscometry, and wide-angle X-ray diffraction (WAXD). Chlorination reactions were carried out with tert-butylhypochlorite at 15°C for nylon 66 and at 30°C for PMPIPA in tetrachloroethane (TCE), and dechlorination reactions were performed with sodium sulfite at 10 °C in formic acid (85 wt%) for nylon 66 and in dimethyl sulfoxide/formic acid (1/1 vol) for PMPIPA. IR and NMR spectra showed that the substitution of chlorine for nylon 66 occurred mainly at the amide groups, whereas for PMPIPA it took place also at the benzene rings. Chloro-nylon 66 was soluble in chloroform and TCE, and chloro-PMPIPA became soluble in dimethylformamide (DMF) without lithium chloride. Both intrinsic viscosities of chloro-nylon 66 in HCOONa (0.1 M)/HCOOH(90 wt%) and chloro-PMPIPA in LiCl(0.25g/dL)/DMF decreased remarkably with increasing chlorine content. The decrease in viscosity of chloro-nylon 66 was attributed to decrease in the degree of polymerization during the reaction, and that of chloro-PMPIPA was caused by increase in poorness of the solvent. WAXD showed that the crystalline structure of nylon 66 was changed with chlorination and it recovered with dechlorination, and that of PMPIPA disappeared with chlorination.
