On-line sensors for monitoring polymer quality

Polymerization rate can be measured by several techniques, although calorimetry (the heat of reaction, Qr, is monitored by solving the energy balances of the reactor and the cooling jacket) is often the most convenient one for industrial reactors. 

This measurement can also be used to evaluate monomer conversion and/or concentration (which is straightforward in homopolymerizations [65], but requires a mathematical model in the case of copolymerizations [66, 67]), as explained in Section 8.3.2.2. 

Other non-invasive (e.g., calorimetry and ultrasounds) and invasive (e.g., densimetry) techniques can also be used for monitoring of monomer concentration in homopolymerization reactions. However, in multimonomer formulations the individual monomer concentrations cannot be obtained with these techniques, meaning that a state estimator is required [66, 67, 69]. The use of reaction calorimetry is appealing because the hardware is very cheap and, when coupled with a state estimator, provides good estimation of the monomer concentration. The performance of calorimetry was compared with that of the Raman spectroscopy in emulsion polymerization to monitor overall and individual monomer conversions [68]. Calorimetry was as good as FT-Raman spectroscopy when monomer concentrations in the reactor were relatively high, but the performance of calorimetry was poorer when monomer concentrations were low. 

Measurement of the MWD of a polymer depends on the nature of the analyzed/produced polymer. The following classes can be distinguished  

Technique Examples Advantages/disadvantages Fields of potential application 

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