Process control in UV curing:: In-line, monitoring of the acrylate conversion by near-infrared spectroscopy

the conversion of double bonds in UV-cured acrylic coatings on various substrates was followed in-line by near-infrared (NIR) reflection spectroscopy. Quantitative data were obtained directly from the intensity of the acrylic overtone band at 1620 nm, which allows very easy calibration of the method. The custom-made probe head of the NIR spectrometer was fitted to several pilot-scale coatings and curing lines, and the conversion was determined in clear and pigmented coatings as well as in scratch-resistant nanocomposite layers on the basis of acrylates. was shown that reasonable conversion data can be obtained with sufficient time resolution at line speeds of at least 120 m/min. Furthermore, the method has been proven to be useful for the monitoring of the conversion in layers from hot-melt adhesives for PSA applications. Thus, for the first time there is an analytical method available which can be reliably applied for process and quality control in technical curing processes.