Study of ε-caprolactone polymerization by NIR spectroscopy

Abstract

Near-infrared (NIR) spectroscopy is proposed for the in-line quantitative and kinetic study of the polymerization of epsilon-caprolactone and eventually to facilitate real-time control of the manufacturing process. Spectra were acquired with a fibre-optic probe operating in transflectance mode immersed in the reactor. The NIR data acquired were processed using a multivariate curve resolution alternating least squares (MCR-ALS) algorithm. The proposed method allows calculation of the concentration and spectral profiles of the species involved in the reaction. The key point of this method is the lack of reference concentrations needed to perform the MCR-ALS method. The use of an extended spectral matrix using both process and pure analyte spectra solves the rank deficiency. The concentration profiles obtained were used to calculate a kinetic fitting of the reaction, but the method was improved by applying kinetic constraints (hard modelling). The rate constants of batches at different temperatures and the energy of activation for this reaction were calculated. Whenever possible, the hard modelling combined with the MCR-ALS method improves the fit of the experimental data: the results show good correlation between the NIR and reference data and allow the collection of high-quality kinetic information on the reaction (rate constants and energy of activation).

In-Line Monitoring of the Thickness of Printed Layers by Near-Infrared (NIR) Spectroscopy at a Printing Press

“…7 In particular, it is used for in-line monitoring of various polymerization reactions. In most cases, the progress of batch polymerization processes was followed, [8][9][10][11][12][13] but also the photopolymerization of thin coatings of acrylates and epoxies has been monitored by this method. [14][15][16] Currently, ultraviolet (UV) curing of functional coatings is a rapidly growing technology.…”

Process Analytical Chemistry

“…Several applications involved batch polymerization processes monitored in the reactor by NIR. MCR using ALS applied to NIR spectra was used to calculate the concentrations and spectral profiles of species involved in the polymerization reaction of ε-caprolactone . Although concentrations of these species could not be provided for MCR, it was possible to compute the concentrations because the spectral matrix was extended using both process and pure analyte spectral to address the problem of rank deficiency.…”

“…MCR using ALS applied to NIR spectra was used to calculate the concentrations and spectral profiles of species involved in the polymerization reaction of ε-caprolactone. 187 Although concentrations of these species could not be provided for MCR, it was possible to compute the concentrations because the spectral matrix was extended using both process and pure analyte spectral to address the problem of rank deficiency. Kinetic information about the reaction (activation energy and rate constants) could be collected from the data which was obtained from a fiber optic probe of the NIR spectrometer which was inserted into the reactor.…”

In-Line Monitoring of the Thickness of Printed Layers by NIR Spectroscopy: Elimination of the Effect of the Varnish Formulation on the Prediction of the Coating Weight

“…Owing to the enormous capability of NIR spectroscopy assisted by chemometrics, this spectroscopy has found numerous applications in process and routine quality control in quite different areas, ,, for example, in waste sorting , and in agriculture − as well as in the food, − petrochemical, , polymer, − pharmaceutical, − and biochemical sectors . More recently, it has been shown that NIR reflection spectroscopy can be also used for the in-line characterization of thin polymer layers.…”