Photon Density Wave spectroscopy to monitor the particle size in seeded semibatch emulsion copolymerization reactions

Abstract

The performance of Photon Density Wave spectroscopy (PDW) is assessed to inline monitor the particle size during the seeded semibatch emulsion copolymerizations of methyl methacrylate, butyl acrylate, methacrylic acid (MMA/BA/MAA = 51/47/2 wt% composition) with particle size and solids content ranges relevant in industrial formulations. Moreover, the suitability of the technique to early detect some of the most probable deviations, such as particle aggregation and secondary nucleation, is studied. It is shown that the PDW can be successfully used to inline monitor the reduced scattering coefficient, and consequently the particle size evolution in emulsion polymerization reactions for a broad range of particle sizes and solids contents. Nevertheless, for particle sizes higher than 350 nm and solids content above 40 %, the low signal to noise ratio together with the characteristic multiple solutions regime of the theoretical reduced scattering versus the particle size curve, produces uncertainties in the determination of the particle size by PDW.