Forensic Engineering
We investigate the causes of failures in an industrial process or commercial product and propose customized solutions to resolve them.
Problem
Our client has a problem with the adhesion of the inks with which the logos are printed on the surface of the plastic.
Objective
Know at what stage the problem is being generated and propose a solution to improve the current adherence
ATRIA Solution
The surface energy of different samples from each stage of the production process was analyzed. For there to be a correct adhesion between the solid and the liquid, the surface tension of the liquid has to be lower than that of the solid.
In the final samples, a final increase in surface energy, compared to the initial sample, of 5 mN/m was observed. This increase was due to the scattered part. The dispersed phase was higher than the polar phase, so nonpolar liquids, such as solvents, will have better wettability in the sample.
During one of the stages in which the samples contained traces of soap, the surface energy increased, but it was detected that this was only due to product residues. Once clarified (next stage) the surface energy goes down again, but, in some cases, the surface energy was still high.An infrared spectroscopy analysis was performed and it was observed that in one stage of the process there was a variation regarding the chemical bonds. The appearance of a broad band around 3400 cm-1 indicating the presence of an O-H bond or an N-H bond could be observed. Finally, in the analysis of the last phase of the process, this link was no longer present, so it was possible to conclude that no new links were generated during the process.
It was concluded that in some pieces there could be poor adhesion due to poorly rinsed soap residues. This contamination causes better adhesion with water than with solvents.
