Near-infrared chemical imaging used for in-line analysis of functional finishes on textiles

Publication date: 1 October 2018
Source:Talanta, Volume 188
Author(s): Gabriele Mirschel, Olesya Daikos, Tom Scherzer, Carsten Steckert
This paper demonstrates for the first time that near-infrared (NIR) chemical imaging can be used for in-line analysis of textile finishing processes based on impregnation. In particular, it was shown that this analytical method is sufficiently sensitive for the quantitative determination of the application weight of rather thin layers of finishing chemicals. Quantitative analysis of the data recorded by a hyperspectral camera (1320–1900 nm) was based on chemometric approaches using the partial least squares (PLS) algorithm. In this work, a flame retardant and a polyvinyl acetate-based stiffening agent applied to polyester or cotton fabrics, respectively, were studied with application weights in the range between about 1 and 50 g m⁻². For both systems, the prediction error (RMSEP) was found to be about 1.5–2 g m⁻². Averaging of the predicted individual values of the application weight of the finishes across the complete surface of the fabric resulted in a very close correlation with the corresponding reference values obtained by gravimetry. Furthermore, NIR chemical imaging was used for the detection of remaining traces of a size (a processing agent) after washing, which had to be washed-out before subsequent processing steps. Results of the present investigations prove that even for very thin size layers between 0.4 and 5.5 g m⁻² the application weight can be predicted with a precision of about 0.4 g m⁻².Apart from the quantitative determination of the application weights, the use of NIR chemical imaging for the analysis of finished textiles was mainly directed towards the investigation of the spatial distribution or the homogeneity of the applied colorless finishes across the surface of the fabrics. It was shown that this method is able to detect and visualize various inhomogeneities on the finished textiles resulting for instance from processing defects or from various technical effects that may influence the drying process and consequently the spatial distribution of the finish. Moreover, the distribution of traces of size that had been sprayed purposely on a washed polyester fabric could be detected.All measurements in the present study were carried under conditions that were very similar to those in typical technical processes (e.g. with respect to line speed). Therefore, the outstanding performance of the method opens an immense potential for application in process and quality control.

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