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Near infrared (NIR) spectroscopy compared with thermogravimetric analysis as a tool for on‐line prediction of water diffusion in polyamide 6,6
Author(s) -
Camacho Walker,
Hedenqvist M S,
Karlsson Sigbritt
Publication year - 2002
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1042
Subject(s) - thermogravimetric analysis , thermal diffusivity , sorption , polyamide , diffusion , analytical chemistry (journal) , materials science , spectroscopy , infrared spectroscopy , chemistry , chromatography , composite material , thermodynamics , organic chemistry , physics , adsorption , quantum mechanics
NIR spectroscopy in the transmission mode and thermogravimetric analysis were used to predict diffusion of water into polyamide 6,6 samples immersed in water at 40, 60, 75 and 90 °C for different periods of time. The sorption curves between 40 and 75 were sigmoidal indicating that the surface concentration was time dependent. The sorption curves were readily fitted by the use of a time‐dependent surface concentration and a water‐concentration‐dependent diffusivity. The zero‐concentration water diffusivity decreased non‐linearly and the activation energy of diffusion increased from 24 to 58 kJ mol −1 , with decreasing temperature. The surface concentration relaxation time decreased rapidly. The sorption of water in thick polyamide samples was readily characterized by FT‐NIR spectroscopy. The accuracy and feasibility of this method was similar to conventional thermogravimetric methods. The greatest advantage of FT‐NIR, however, is the possibility of detecting and monitoring the moisture concentration on‐line and in a non‐destructive way. © 2002 Society of Chemical Industry