Depth profiles and free volume in aircraft primer films

• Published in: Journal of physics. Conference series Vol. 618; no. 1; pp. 12023 - 12028
• Main Authors: Van Horn, J D, Chen, H, Jean, Y C, Zhang, W, Jaworowski, M R
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 15.06.2015
• Subjects: Aircraft; Chromates; Heterogeneity; Nondestructive testing; Physics; Polymer films; Positron annihilation; Positron beams; Spectrum analysis; Water vapor
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/618/1/012023

Positron annihilation lifetime spectroscopy (PALS) and associated techniques provide non-destructive methods to study the free volume inside polymeric materials, and to study material characteristics over a depth profile. Cast free films of organic- or aqueous-based, non-chromated aerospace primers, when cured for about one week, had very different water vapour transport (through-plane) behaviour. In addition, both types of primer films showed strong anisotropic behaviour in in-plane versus through-plane water vapour transport rates. We report the differences between the organic- and aqueous-based aircraft primer films samples and their surface depth profiles. In bulk PALS measurements, an aged, organic-based film exhibited typical lifetimes and intensities for a particulate-containing polymer film on both faces. In contrast, aqueous-based films exhibited face oriented-dependent differences. In all aqueous- based samples, the I3 value of the back of the sample was smaller. The primer film samples were also evaluated with mono-energetic positron beam techniques to generate depth profile information. The heterogeneity in the samples was verified by Doppler broadening of energy spectroscopy (DBES). A model for the differences in the faces of the films, and their layered structure is discussed.