Thermally unstable polymers such as poly(methyl methacrylate) are degraded considerably during industrial processing. This degradation and its reduction to a minimum have been investigated in both lab and continuous pilot-scale experiments. A threestep degradation mechanism, starting at 180 C, was proved by Thermogravimetrical Analysis (TGA) and a kinetic approach to describe it was derived. The knowledge of this degradation behavior was then applied to a pilot-scale process with a production rate of 10 kg/h and the process yield loss during the devolatilization step was investigated. Using heat stabilizers, the overall process yield could be improved by 10 %, whereas the residual organic volatiles concentration (VOC) was drastically reduced to values below 1000 ppm. In order to preserve the molecular weight of the final product these stabilizers were added into the process, separately, at the end of the polymerization reaction but before the devolatilization step.

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Inline conversion measurements in chemical reactions are in general and especially in polymerization reactions necessary for process monitoring and control. For polymerization monitoring, the sound propagation (UPV) can be related to the texture of the bulk with a high accuracy. As the monomer is transformed to polymer, both the density and adiabatic compressibility change, making the UPV closely related to the monomer conversion. This technique is based on the increase of UPV with rising elasticity of the medium due to the polymerization. The application of the UPV technique to follow the composition evolution of the solution during the polymerization reaction in a recycle tubular reactor is presented. The sensor can be directly inserted in the tubular reactor and does not require a sampling circuit. This makes its use particularly simple and suitable for laboratory and industrial purposes.