Testing Standard
Testing protocols for polyolefin substrates establish the wetting tension of non-polar surfaces. The astm d2578 method identifies the level at which a specific liquid will wet the film without retraction. It provides a numerical value in millinewtons per metre to represent the energy state of the substrate.
This metric allows converters to predict the compatibility of the material with inks and coatings.
Solution Application
Practitioners apply mixtures of formamide and ethyl cellosolve to the material using a cotton swab or a felt tip pen. If the liquid film remains continuous for exactly two seconds, the surface energy matches the rating of that specific solution. Rapid retraction indicates the surface energy is lower than the liquid tension.
Conversely, instantaneous wetting shows the surface energy exceeds the dyne level of the test fluid. This procedure requires controlled environments to prevent evaporation or contamination from skewing the results. Technicians repeat the process with different concentrations until the balance point is found.
Treatment Level
Printing success depends on the substrate meeting a minimum energy threshold to ensure liquid spread. The astm d2578 values help converters determine if corona treatment remains effective after transport. Low wetting tension causes ink rejection and poor adhesion.
Maintaining a high surface energy ensures consistent results.