Thermally unstable polymers such as poly(Me methacrylate) are degraded considerably during industrial processing. This degrdn. and its redn. to a min. were investigated in both lab and continuous pilot-scale expts. A three-step degrdn. mechanism, starting at 180 Deg, was proved by Thermogravimetrical Anal. (TGA) and a kinetic approach to describe it was derived. The knowledge of this degrdn. behavior was then applied to a pilot-scale process with a prodn. 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 org. volatiles concn. (VOC) was drastically reduced to values below 1000 ppm. In order to preserve the mol. wt. of the final product these stabilizers were added into the process, sep., at the end of the polymn. reaction but before the devolatilization step.