TY  - JOUR
A1  - Schlappa, Stephanie
A1  - Brenker, Lee Josephine
A1  - Bressel, Lena
A1  - Hass, Roland
A1  - Münzberg, Marvin
T1  - Process characterization of polyvinyl acetate emulsions applying inline photon density wave spectroscopy at high solid contents
JF  - Polymers / Molecular Diversity Preservation International
N2  - The high solids semicontinuous emulsion polymerization of polyvinyl acetate using poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated by optical spectroscopy. The suitability of Photon Density Wave (PDW) spectroscopy as inline Process Analytical Technology (PAT) for emulsion polymerization processes at high solid contents (>40% (w/w)) is studied and evaluated. Inline data on absorption and scattering in the dispersion is obtained in real-time. The radical polymerization of vinyl acetate to polyvinyl acetate using ascorbic acid and sodium persulfate as redox initiator system and poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated. Starved-feed radical emulsion polymerization yielded particle sizes in the nanometer size regime. PDW spectroscopy is used to monitor the progress of polymerization by studying the absorption and scattering properties during the synthesis of dispersions with increasing monomer amount and correspondingly decreasing feed rate of protective colloid. Results are compared to particle sizes determined with offline dynamic light scattering (DLS) and static light scattering (SLS) during the synthesis.
KW  - photon density wave spectroscopy
KW  - multiple light scattering
KW  - emulsion
KW  - polymerization
KW  - process analytical technology
KW  - polyvinyl acetate
Y1  - 2021
U6  - https://doi.org/10.3390/polym13040669
SN  - 2073-4360
VL  - 13
IS  - 4
PB  - MDPI
CY  - Basel
ER  - 
TY  - GEN
A1  - Münzberg, Marvin
A1  - Hass, Roland
A1  - Khanh, Ninh Dinh Duc
A1  - Reich, Oliver
T1  - Limitations of turbidity process probes and formazine as their calibration standard
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Turbidity measurements are frequently implemented for the monitoring of heterogeneous chemical, physical, or biotechnological processes. However, for quantitative measurements, turbidity probes need calibration, as is requested and regulated by the ISO 7027:1999. Accordingly, a formazine suspension has to be produced. Despite this regulatory demand, no scientific publication on the stability and reproducibility of this polymerization process is available. In addition, no characterization of the optical properties of this calibration material with other optical methods had been achieved so far. Thus, in this contribution, process conditions such as temperature and concentration have been systematically investigated by turbidity probe measurements and Photon Density Wave (PDW) spectroscopy, revealing an influence on the temporal formazine formation onset. In contrast, different reaction temperatures do not lead to different scattering properties for the final formazine suspensions, but give an access to the activation energy for this condensation reaction. Based on PDW spectroscopy data, the synthesis of formazine is reproducible. However, very strong influences of the ambient conditions on the measurements of the turbidity probe have been observed, limiting its applicability. The restrictions of the turbidity probe with respect to scatterer concentration are examined on the basis of formazine and polystyrene suspensions. Compared to PDW spectroscopy data, signal saturation is observed at already low reduced scattering coefficients.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 831 
KW  - photon density wave spectroscopy
KW  - turbidity probes
KW  - formazine
KW  - calibration standard
KW  - process analytical technology
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-428263
SN  - 1866-8372
IS  - 831
ER  - 
TY  - JOUR
A1  - Hass, Roland
A1  - Reich, Oliver
T1  - Photon density wave spectroscopy for dilution-free sizing of highly concentrated nanoparticles during starved-feed polymerization
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
KW  - analytical methods
KW  - fiber-optical spectroscopy
KW  - nanoparticles
KW  - photon density wave spectroscopy
KW  - polymerization
Y1  - 2011
U6  - https://doi.org/10.1002/cphc.201100323
SN  - 1439-4235
VL  - 12
IS  - 14
SP  - 2572
EP  - 2575
PB  - Wiley-Blackwell
CY  - Malden
ER  -