Processing vapour-deposited polyimide

Abstract

Freestanding polyimide (PMDA-ODA) thin films (thickness = 1 to 30 µm) and spherical shells (diameter = 950 to 1100 µm, wall thickness = 0.7 to 11.0 µm) have been fabricated by vapour deposition polymerization (VDP). The deposition process was optimized to obtain smooth and uniform deposition composed of equal-molar PMDA and ODA. The tensile properties, including elastic modulus, tensile strength, and elongation at break, were determined by buckling and bursting the shells and using a nanoindentation test on the films. The gas permeability was measured for He, H2, D2, O2 and N2. The VDP polyimide possessed distinct properties from solution-cast PMDA-ODA polyimide (Kapton®), including better tensile properties and lower permeability, and was insoluble in concentrated sulfuric acid. The differences in the properties were attributed to the presence of physical or chemical cross-linking in the VDP polyimide.