Tech Tip Tuesday: What are some of the reasons for poor ink adhesion?
Poor ink adhesion is most commonly a function of mismatching the ink series to the substrate. Where there are many different substrates … there are also multiple ink chemistries, pre-treatments, additives and post cure methods available to meet customer expectations. Appropriate testing should ALWAYS be performed to find a match of ink and substrate that satisfies the end user’s specification for adhesion.
Moving on to inks that have been properly qualified for a process, and “suddenly” show failed adhesion, one should look to contamination, the most common examples of which include mold release, skin oils from handling, upstream processes or blooming of a plasticizer.
One additional item of note, given the time of year, is the use and proper curing of processes that utilize a hardener or catalyst. With the quick turnaround that our customer’s expect today it is frequently forgotten that complete cross linking of a bi-component ink can range from 48 to 72 hours. If’n during this time the printed product sees temperatures in the mid to low 50’s (F) the cross linking process ceases … never to be started again.