Evaporative mass loss measurement as a quality control tool for quality assurance in the manufacture of inks suitable for high speed (≥60 m min−1) printing

Abstract

In any manufacturing environment, it is always important to be able to embrace a culture of traceability of any non-conformed product. For the case of ink manufacture, operator confusion, leading to the mixing-up of solvents, or connecting the incorrect solvent drum to solvent lines, can lead to disastrous consequences that are not trivial for a quality control/quality assurance team to unravel. Accordingly, simple methods for assessing whether the correct solvents were added in the correct ratios to products empower this QA/QC requirement. In this paper, we examine the use of a trivial measurement of evaporative mass loss as a protocol for validating the conformance of manufactured ink to specification. Inspired by the transport-limit that occurs at ultramicroelectrodes in electrochemistry, we develop theory to analyse evaporation rate measurements, and illustrate how vaporisation at the liquid | gas interface is dominated by a diffusion anisotropy, owing to natural convection for organic solvents, manufactured resins and commercialised inks that have been used, inter alia, for the underground transport tickets in the cities of London and Paris. We further demonstrate that the use of incorrect solvents is readily seen through evaporation rate transients, thereby enabling this measurement for human factor mitigation during the ink manufacture process.