Inline Process Analytics for high solid content polymer samples using Photon Density Wave spectroscopy
Photon Density Wave (PDW) spectroscopy is a novel measurement technique for the independent determination of the absorption coefficient and the reduced scattering coefficient of highly turbid samples. In contrast to most analytical methods commonly used in inline process analytics, PDW spectroscopy does not saturate at low volume fractions and is applicable for inline measurements both in industrial applications as well as in scientific research. [1,2] Inline and dilution-free analysis of high volume fractions is necessary in the food, cosmetics, paint and coatings industries. PDW spectroscopy is applied to access the chemical as well as the physical properties, such as particle size, volume fraction or absorption of a sample.
PDW spectroscopy uses intensity modulated laser light, transported via optical fibers into samples with volume fractions up to 50 wt-% of scattering material. [3,4] Inline measurements are achieved using a small diameter probe, which is robust against fouling and allows for non-destructive analysis during the process directly through a reactor inlet. The direct inlet of the probe guarantees real-time access to multiple process parameters.
This talk will give insights into PDW spectroscopy, its technical background and applications, focused on polymer chemistry. The monitoring of polymer synthesis and inline particle growth is presented. This enables process control on final particle size, particle size distribution and properties of the product. The study shows very good agreement of inline, dilution-free obtained particle size from PDW spectroscopy with offline dilution based light scattering techniques and optical imaging.
 L. Bressel, R. Hass, and O. Reich, 2013: Particle sizing in highly turbid dispersions by Photon Density Wave spectroscopy. Journal of Quantitative Spectroscopy & Radiative Transfer, 126, 122–129.
 R. Hass, M. Münzberg, L. Bressel, and O. Reich, 2013: Industrial applications of Photon Density Wave spectroscopy for in-line particle sizing [Invited]. Applied Optics, 52, 7, 1423–1431.
 L. Bressel, R. Hass, O. Reich, Particle sizing in highly turbid dispersions by Photon Density Wave spectroscopy, JQSRT, 2013, 126, 122-129.
 R. Hass, M. Muenzberg, L. Bressel, O.Reich: Industrial applications of Photon Density Wave spectroscopy for in-line particle sizing, Appl. Opt., 2013, 52, 1423-1431.