Correlation of in-situ Raman spectra with isothermal DSC-measurements on radically polymerizing methyl methacrylate
This work discusses the capability of Raman spectroscopy in monitoring the cure reaction and conversion of methyl methacrylate (MMA) in comparison to the conventional differential scanning calorimetry (DSC). In this regard, isothermal DSC measurements have been carried out as standard and compared against in-situ Raman spectra with the same material composition. A novel sample holder has been designed and implemented within the heated Raman chamber to monitor the cure reaction of the highly volatile MMA. The resulting spectra were processed using a custom written Python script, to compare the most significant C=C and C=O peaks. The conversion of monomeric MMA to Poly(methyl methacrylate) (PMMA) was calculated via the relative peak intensity of C=O at 1725 cm-1 to C=C at 1640 cm-1. Small deviations between the different measurement techniques have been observed and discussed in detail. The fundamental principle of Raman based in-situ conversion monitoring is proposed for industrial manufacturing of PMMA. Since these Raman measurements are carried out between 2 transparent glass plates, that are unaffected by the laser used, a simple and analogous setup would suffice industrially for on-line quality control and process optimization.