Der Leim-Talk Blog

Testing Bookbinding Adhesive

How Quickly Can I Test Freshly Bound Books?

Posted 04 Apr 2018 by Gregg Howard, Technical Manager II

A question that comes up frequently in discussions with line operators and other technical personnel at binderies is: “How long should we wait before checking page pulls and flexes on freshly bound books?” The answer is highly dependent on the type of bookbinding adhesive being used in the process.

Typically, in perfect binding, either an EVA-based hot melt adhesive or polyurethane reactive (PUR) adhesive is used as the main bookbinding adhesive on the back of a book. Because the chemical makeup is so different between technologies, the time to wait before checking a book also differs. As a rule of thumb in perfect binding, if running a hot melt for a one-shot system, or a hot/ hot or cold/hot for a two-shot system, you should wait at least one hour before running quality checks on a publication. Waiting one hour gives even the thickest of books adequate time to cool down towards the middle of the book—which is the area that tends to hold heat the longest and will exhibit weak numbers if pulled prematurely.

When running a PUR adhesive (also known as a hot-melt moisture cure), a much longer wait time is necessary because the adhesive needs to cool down and “cure.” Curing, or crosslinking as it is sometimes referred to, is the process of the molecules bonding together with the aid of atmospheric moisture, to form a very strong, flexible adhesive film.

We recommend waiting 24 hours to perform a quality check on PUR adhesives. However, some PUR adhesives have a shorter overall cure rate, which means quality checks can be performed quicker, in some cases in as little as six to eight hours.

If you have any questions on bookbinding adhesive wait times or other bookbinding topics, please contact your local H.B. Fuller representative or visit us online for more information.

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