Comparison of FTIR and Thermal Methods for Analyzing Cure of Polyimides: Part I. Pyralin(R) PI-2555.

We have compared three methods for measuring the degree of cure of a polyimide coating, Pyralin(R) PI-2555, on silicon wafers: fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA). All Three methods gave similar results regarding Du Pont Pyralin(R) PI- 2555 cure in a multi-step oven curing sequence. That is, cure increased with temperature, reaching a maximum at ~300-350C. The results are discussed with regard to applicability of the various methods for analyzing cure of coatings for optical fibers and GC capillaries. In particular, the TGA method, which had previously been used qualitatively to follow cure on optical fiber and capillary coatings, was extended to allow quantification of percent imidization based on an assumption concerning the relative rates of solvent and water evolution. TMA does not directly provide a measure of percent imidization (%I) but may be made semi-quantitative by correlation of softening temperature with %I from FTIR or TGA.