PUR Binding

PUR is a special adhesive that is similar to traditional hot melt but with much more versatility. It is manufactured with polyurethane reactive (PUR) material which means that as the adhesive dries a natural reaction with the moisture in the air cures the adhesive. The result of this chemical reaction is a superior bond within the fibers of the paper giving the product more strength and flexibility. When the adhesive is finished curing it has a more elastic form than traditional hot melt which allows the pages to move with less resistance and the book to lay flat when open. Some actually refer to PUR binding as Lay Flat binding which is one of its many benefits.

Benefits to utilizing PUR:
 Lay Flat Capabilities
A book that is perfect bound with traditional hot melt glue will not lay open on a surface without being held. The stiffness of the glue on the spine pulls the pages back to the closed position whenever possible, requiring the use of one or both hands at all times. Because PUR glue actually turns into a rubbery material when cured, it allows the pages to move more freely without cracking or coming apart from the adhesive. The book will not lay completely flat on the surface but will stay open on the desired page without being held. Many individuals choose this form of binding for coffee table books, cook books, premium catalogs, and manuals; all of which will be handled repeatedly and may call for hands free reading.
 Resistance to extreme temperatures
PUR glue will not fail in extreme temperatures, which may occur in everyday scenarios more than you think. Consider the temperature inside a car on a hot day; it can climb to 150 degrees – 175 degrees (F) in less than an hour. If someone left a book inside that car with traditional hot melt binding the glue may soften resulting in pages falling out or glue leaking into the margins. The same risk applies in the cold winter months as well, in cold temperatures traditional hot melt glue often cracks and pages may come out of the binding. At temperatures over 200 degrees and as low as – 40 degrees (F) PUR glue will not change its form, giving you a book that can stand up to the elements in almost any situation.
 Adhering to Coated papers
PUR is unique in that it will bond to many different coating materials such as varnish, aqueous, lacquer, UV-cured, and Mylar. Due to the polar nature of the polyurethane molecule, this adhesive also bonds well to clay-coated papers which are many of the #1 and #2 coated sheets we use on a regular basis. If a book has a flood aqueous or varnish throughout, traditional hot melt glue will not bond to the fibers well and pages could start to fall out after limited use. With PUR, the glue bonds to the sealed edge of the coated fibers and holds strong.
 Shear Strength
When testing the strength of perfect binding we utilize a “pull” test which measures the amount of pressure, in pounds, that it takes to pull a page from the book. Traditional hot melt glue usually tests between 30 – 40lbs while PUR holds up to 80lbs. This superior strength is important for books that will go through rough handling and need to last.

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