Pyrolysis of Kapton (R) in air: An in situ DRIFT study

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was use d to study the pyrolysis of polyimide (Kapton (R)). The samples were prepar ed in a KBr matrix, which did not show pronounced interferences, such as in creased emissivity, during the measurements. Tile pyrolysis of Kapton (R) r eveals pronounced differences from laser-induced (CV) decomposition. The po lyimide system decomposes thermally in distinct steps, i.e., first the imid e ring, without elimination of the carbonyl groups, followed by the aromati c system and then the carbonyl groups. Several intermediates, such as nitri les and alkynes, are identified. The quantitative analysis of the spectra s uggests that Kapton (R) decomposes: in two steps, i.e., as a growing partic le with shrinking core followed by a shrinking particle. The growing partic le with shrinking core is the nonreacted polymer as core and a polyamic str ucture as the growing part, while the shrinking particle is the complete py rolysis of the polymer. The activation energies for these two steps were de termined. The reaction rate appears to he diffusion controlled at low tempe ratures and surface reaction controlled at higher temperatures.