- August 01, 2006, By David J. Bentley Jr. Contributing Editor
The question seems like a good one when we first hear it. Why is there not a universal adhesive, coating, or ink? Such a material certainly would make life considerably easier.
When thinking about an answer, the question obviously requires some explanation. Does it refer to one material that can act as an adhesive, coating, and ink? Or does it mean a universal adhesive, a universal coating, and a universal ink?
We can consider the easiest part of the question first, the part referring to inks. Inks come in a host of different colors. Except for use by people who are totally color blind, a universal ink is therefore impossible. The closest thing to such a material would be a black ink. Having only a black ink would function well, but it would drive graphic designers absolutely crazy by limiting their glitzy choices.
The original question is then simplified: Why is there not a universal adhesive or coating?
The technical answer to the absence of a universal adhesive or coating is that neither one could be removed from its container or processed on any equipment. The adhesive simply would adhere to everything it contacted, and the coating would coat everything it contacted.
Although the answers above are valid for the basic question, perhaps they are too facetious. People who ask the question about universal adhesives, coatings, or inks probably are wondering why such a wide variety of these products are available in the marketplace today. Would it be possible to simplify the number of choices available?
The immediate answer is a resounding no.
The wide variety of materials is available because the applications in which they find use are so diverse. This leads us to the primary point of this column: Do not use any adhesive, coating, or ink for any purpose other than that for which it is intended.
A pressure-sensitive adhesive tape that works well in a masking tape application will never be suitable for use on a paper label that eventually will be used in a freezer application.
A heat-seal coating that functions well when used on a polyester film may not adhere at all to a polyolefin film.
An ink intended to be sandwiched between two films in a flexible packaging application probably will perform unsatisfactorily as a surface-printed ink.
These are but three examples that show adhesives, coatings, and inks are very specific in their applications. Each material has certain characteristics that include adhesion and cohesion properties, application conditions, aging distinctions, etc., that limit it to only the definite uses specified by the manufacturer.
Using an adhesive, coating, or ink that does not fall within its normal range of applications as suggested by the manufacturer is simply asking for trouble. Some totally unexpected development undoubtedly will occur that will lead to product failure.
In addition to avoiding the use of a product for an application other than that intended by the manufacturer, never alter the conditions of use of an adhesive, coating, or ink to something not intended. Do not change coating thickness, drying conditions, choice of diluent, etc.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at firstname.lastname@example.org.