Blistering failure of elastic coatings with applications to corrosion resistance.

A variety of polymeric surfaces, such as anti-corrosion coatings and polymer-modified asphalts, are prone to blistering when exposed to moisture and air. As water and oxygen diffuse through the material, dissolved species are produced, which generate osmotic pressure that deforms and debonds the coating. These mechanisms are experimentally well-supported; however, comprehensive macroscopic models capable of predicting the formation osmotic blisters, without extensive data-fitting, is scant. Here, we develop a general mathematical theory of blistering and apply it to the failure of anti-corrosion coatings on carbon steel. The model is able to predict the irreversible, nonlinear blister growth dynamics, which eventually reaches a stable state, ruptures, or undergoes runaway delamination, depending on the mechanical and adhesion properties of the coating. For runaway delamination, the theory predicts a critical delamination length, beyond which unstable corrosion-driven growth occurs. The model is able to fit multiple sets of blister growth data with no fitting parameters. Corrosion experiments are also performed to observe undercoat rusting on carbon steel, which yielded trends comparable with model predictions. The theory is used to define three dimensionless numbers which can be used for engineering design of elastic coatings capable of resisting visible deformation, rupture, and delamination.

A comparison of electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization for the liquid chromatography/tandem mass spectrometric analysis of bisphenols. Application to bisphenols in thermal paper receipts and U.S. currency notes.

RATIONALE: Human health concerns have arisen for common bisphenols (BPA and BPS) as well as new structural analogs. While native sulfone bisphenols and sulfone-derivatized bisphenols are amenable to electrospray ionization (ESI), alternative ionization methods such as atmospheric pressure chemical ionization (APCI) and APPI were investigated to analyze non-derivatized, non-sulfone-containing bisphenols. METHODS: Ionization of bisphenols using negative ion APPI was compared to negative ion ESI and negative ion APCI for their relative abilities to produce [M-H]- precursor ions for subsequent collision-induced dissociation (CID) in a triple quadrupole mass analyzer. Multiple reaction monitoring (MRM) transitions were optimized using the most sensitive ion transitions and coupled with high-performance liquid chromatographic (HPLC) separation to detect and quantify BPA, BPB, BPF, BPZ, BPAP, BPS, and BPSIP. RESULTS: APPI provides a more universal sensitivity over ESI toward the classes of bisphenols studied with detection limits of 20-50 pg on-column. The LC/APPI-MS/MS method was used to examine the levels of these seven bisphenols in thermal paper receipts and in U.S. paper currency. In both receipts and currency, BPA and BPS were the dominant bisphenols found in the paper. CONCLUSIONS: The measurement of BPA and bisphenol analogs in thermal paper receipts and transfer of bisphenols from receipts to currency notes is of increasing importance to assess human dermal exposure routes to this class of compounds. Equivalent sensitivity between sulfone- and non-sulfone-containing bisphenols is achievable through the use of alternate ionization sources such as APCI and APPI that circumvents tedious and time-consuming derivatization procedures to render analytical sensitivity by ESI.