Nitrogen distribution in polymers determined by proton track counting and 14 MeV neutron activation analysis

Abstract

Bulk and surface nitrogen levels of compression-molded samples of polyacrylonitrile, poly (styrene-co-acrylonitrile), poly(methacrylonitrile), polycaprolactam, polyimide, and a cured epoxy resin (EPON 828 — JEFFAMINE T-403, 100:50) were determined, respectively, by 14 MeV NAA (¹⁴N(n,2n)¹³N) and by analysis of proton tracks registered in cellulose nitrate detectors (CN85) as a result of their exposure to protons from the termal neutron induced reaction,¹⁴N(n,p)¹⁴C. Except for a few polymers, agreement of results obtained for nitrogen levels in the bulk and surface regions is within expected limits. Intrinsic limitations of the method for practical determinations of nitrogen are covered. The spatial homogeneity of materials consisting of nitrogen and non-nitrogen containing segments is easily determined by image analysis of proton track densities. These data are then used to construct nitrogen distribution plots and topographical maps. The potential ability of the proton track image analysis technique for distinguishing phase separation or immiscibility of nitrogen containing polymers is discussed.