Fundamental Studies on the Interactions between Moisture and Textiles V. FT-IR Study on the Moisture Sorption Isotherm of Nylon 6

Abstract

ABSTRACT:The interaction of moisture with nylon 6 was investigated using an FT-IR spectroscopy over a near-infrared range of wavenumbers from 4500 to 8000 em -1 to cover the first overtones of (2vCH) and (2vNH) as well as the water sensitive 5100 and 6900 em -1 bands, a combination of (<10 H)+(v.,0 H) and a combination of (v,0 H)+(v"'0 H), respectively. Two types of differential procedures were performed to separate the contribution of the water sensitive bands from the entire spectrum: i.e., subtracting the spectrum of the test specimen conditioned at dryness of 0% relative humidity from that conditioned at a given relative humidity of x% (procedure A) or the spectrum for x% from that for (x + tl.x)% (procedure B), both as functions of the given relative humidity of x%. From the areas of the water sensitive bands thus separated, the moisture sorption isotherm could be composed in fairly good agreement with that obtained by a gravimetric method. The 6900 em -1 band of bulk water as well as those in the differential spectra, were decomposed into three components of a Lorentzian function, sub-band I, 1-11, and II in the order of descending wavenumber. They were attributed to three kinds of water species differing in the degree of hydrogen-bonding covering singly to doubly hydrogen-bonded water (ice-like water) species. It was found that the water species, which more strongly interact with each other, also more strongly interact with the water accessible sites of nylon 6 to form fewer number of layers of adsorption in the sense of B.E.T.'s multilayer adsorption or the core portion of water cluster in the sense of Hill's multimolecular adsorption. Semi-quantitative comparison was made between the characterization of the sorbed water by the B.E.T.'s multilayer adsorption and that by the present FT-IR spectroscopy.KEY From the temperature dependence of the moisture sorption isotherm, the thermody-

Moisture Effect on Structure and Mechanical Property of Nylon 6 as Studied by the Time-Resolved and Simultaneous Measurements of FT-IR and Dynamic Viscoelasticity under the Controlled Humidity at Constant Scanning Rate

“…The curve separation into components was made as shown in Figure the water molecules or the different strength of the hydrogen bonds. 47 The band assignments to these various states are difficult at the present stage. Even for the basically important liquid water itself, unfortunately, the band assignment has not yet been established because of the complexity of the profile.…”

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

“…[141][142][143] FTIR data as well as the Brunauer-Emmett-Teller model for sorption also support three species of water that differ in the degree of hydrogen-bonding, ranging from singly to doubly hydrogen-bonded (icelike) water. 144 …”

Infrared spectroscopic study of the interactions of nylon‐6 with water

“…The influence of the interactions with water on the properties of polyamides has been studied by several authors 4, 5. Vergelati et al4 reported that water induced the crystalline transition of nylon‐6, 6.…”