A quantitative determination of the polymerization of benzoxazine thin coatings by time‐of‐flight secondary ion mass spectrometry

Abstract

Phenol-paraphenylenediamine (P-pPDA) benzoxazines exhibit excellent barrier properties, adequate to protect aluminum alloys from corrosion, and constitute interesting candidates to replace chromate-containing coatings in the aeronautical industry. For the successful application of P-pPDA coatings, it is necessary to decrease the curing temperature to avoid the delamination of the coating while preserving the mechanical properties of the alloy, as well as the barrier properties of the coating. However, decreasing the curing temperature leads to less polymerized films, the extent of which requires a quantitative assessment.While the conversion rate of the polymerization reaction is commonly evaluated for bulk samples using differential scanning calorimetry (DSC), a tool for its evaluation in thin films is missing. Therefore, a new approach was developed for that matter using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The relation between the SIMS data integrated from inside thin films and the DSC results obtained on bulk samples with the same curing cycle allowed to calibrate the SIMS data. With this preliminary calibration of the technique, the polymerization of P-pPDA coatings can be locally determined, at the surface and along the depth of the coating, using dual-beam depth profiling with large argon cluster beam sputtering.

Sealing porous anodic layers on AA2024-T3 with a low viscosity benzoxazine resin for corrosion protection in aeronautical applications

“…Concerning the fully cured system, the high C and N signal on top of the surface is no longer observed and carbon and nitrogen atoms are more homogeneously distributed throughout the anodic layer, conrming the oxide impregnation and the coexistence of both organic and inorganic parts at the same sputtering depth. Both C and N signals are lower in intensity than observed before curing and this can be attributed to the network formation during curing decreasing the sputtering efficiency, as has also been observed during ToF-SIMS analysis of P-pPDA benzoxazine coatings 19,28 The higher intensity of the oxygen signal at the top surface aer curing can probably be explained as a result of oxidation reactions occurring during the thermal curing process in air.…”