Determination of the residual monomer concentration of ε‐caprolactam in polyamide‐6 using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy gas analysis

For the anionic polymerization of ε‐caprolactam to polyamide‐6 the residual monomer concentration in the final polymer is an important characteristic. To determine this residual ε‐caprolactam monomer concentration, a fast and fail‐safe method was developed, which couples thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FTIR) gas analysis. FTIR allows an identification of the types of gasses released during heat treatment. Calibration of the infrared absorbance of ε‐caprolactam and the corresponding mass loss in TGA allows a quantitative evaluation of the ε‐caprolactam monomer release. Low‐heating rates and powdery samples guarantee high‐precision measurements.