UV-laser-induced decomposition of Kapton studied by infrared spectroscopy

The UV-laser (308 nm)-induced decomposition and ablation of polyimide (Kapton) was studied using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The samples were prepared with a special technique (SiC substrates) allowing analysis of surface species of the laser-treated polymer. The first step of photolysis is the simultaneous decomposition of the imide ring, between the nitrogen and carbonyl carbon atom, and of the diaryl ether group. The functional groups belonging to the corresponding amide and carbonyl system are detected. In the next step the aromatic system decomposes, and isocyanates, aliphatic hydrocarbons, nitriles, and alkynes are formed. Volatile species compatible with this decomposition mechanism (CO, CO2, HCN, and C2H2) are detected by additional mass spectrometry measurements.