Computationally-accelerated prediction of polyester-melamine coatings degradation to design sustainable organically-coated steels for outdoor applications.

This work implements computational chemistry as a screening tool to aid in the coating and resin formulation process. Conceptual Density Functional theory (DFT) reactivity descriptors like the global chemical hardness and the dual descriptor Fukui function identify the tendency of polyester-melamine coatings to undergo electrophilic and nucleophilic attack during weathering exposure. Coatings were subjected to natural and accelerated weathering tests, with periodic infrared spectroscopy, colour, and gloss measurements to assess for the degree of changes brought about through photodegradation. It was found that the number of attack sites in the atomistic models, when weighted as a function of the polyester : crosslinker ratio, effectively ranked the degradation of different coating systems upon weathering. This ranking matched the performance of the coatings subjected to both accelerated and natural weathering, showing affinity with naturally weathered samples, and matching in all areas. The results were shown to demonstrate significant correlation, being over R 2 = 0.8 for 7 of the 8 measured areas, and greater than R 2 = 0.9 for 6 compared areas. Comparison of computationally derived and experimentally acquired results showed that the performance of naturally weathered samples was matched across all areas by the computational rankings, showing superior correlation than that observed between natural and accelerated weathering tests. This indicates that the method utilised within this work provides a novel, cost-effective alternative to evaluate the projected performance of selected coatings, while enabling a computationally accelerated platform for more sustainable low-degradation coatings without the requirement of long-term weathering tests.

Improving the Corrosion Performance of Organically Coated Steel Using a Sol-Gel Overcoat.

Organically coated steels are widely used in applications in which they are subjected to the natural environment and therefore require excellent corrosion resistance. Organic clearcoats are typically employed as a barrier that improves the overall corrosion resistance; however, they are typically derived from fossil fuel-based feedstock. A more sustainable alternative could be possible using sol-gel coatings. The application of a simple tetraethoxysilane (TEOS)-based sol-gel was applied to polyurethane-coated steels using a spray coater. The concentration of TEOS was altered to produce coatings containing either 2.5% or 10%. The 10% TEOS resulted in dense, homogeneous coatings that offered a significant improvement in corrosion resistance compared to an uncoated substrate. Whereas the 2.5% TEOS coatings were inhomogeneous and porous, which indicated a limitation of concentration required to produce a uniform coating. The successful demonstration of using a simple TEOS-based coating to improve the corrosion resistance of organically coated steel highlights the potential for further investigation into the use of sol-gels for these applications.

Salivary free concentrations of anti-epileptic drugs: an evaluation in a routine clinical setting.

OBJECTIVE: This study was aimed at correlating the salivary and serum free concentrations of anti-epileptic drugs (carbamazepine, phenytoin and sodium valproate) in a population of neurological patients in a routine clinical setting. METHOD: Twenty-seven paired serum/saliva specimens from 22 patients: 10 for carbamazepine, 8 for phenytoin and 9 for sodium valproate were obtained to study these correlations. Salivary and serum free concentrations of anti-epileptic drugs, anti-epileptic drug dosing history, and associated information were collected prospectively. The salivary and serum free concentrations of the anti-epileptic drugs were simultaneously quantified using fluorescence polarization immunoassay (TDx analyzer). RESULTS: For both carbamazepine and phenytoin there was a strong correlation between the salivary and serum free concentrations, 0.99 and 0.98, respectively. The mean ratio of salivary to serum free carbamazepine concentration was 1.02 +/- 0.11 and 0.82 +/- 0.15 for phenytoin. A poor correlation between salivary and serum free concentration was observed for sodium valproate (0.70) with a mean ratio of salivary to serum free concentration of 0.48 +/- 0.27. CONCLUSION: Monitoring of free salivary concentrations of anti-epileptic drugs, particularly phenytoin and carbamazepine proved to be a realistic alternative in this routine clinical setting.