Iodine Treatment of Nylon 6

II. Change in Infrared Spectrum of Nylon 6 by Iodine Treatment

Abstract

Nylon 6 fllm was treated with iodine potassiumiodide aqueous solutions of various concentrations and infrared spectra of these films were measured. The change of the infrared spectra by the treatment agreed with the behavior of the iodine adsorption isotherm and corresponded well to the change in the crystal structure of nylon 6.
It was observed that the amide I band shifts to lower frequencies and the NH stretching band at 3290 cm^-1 shifts to higher frequencies on iodine adsorption and these bands go back to their original position respectively on the removal of iodine. It is supposed from the results that the absorbed iodine coordinates to the CO group in the polymer molecule and the hydrogen bond is released.
Several amide characteristic bands such as amide III, V and VI of nylon 6 (γ-form) was assigned. It was found that the crystalline band at 928 cm^-1 of nylon 6 a-form relates closely to the 977 cm^-1 band of the new crystal structure of nylon 6.