The Strength of PUR Adhesive
Many adhesive-bound books need to stay together for years, even decades. For an adhesive that delivers the best in both raw strength and flexibility, the preferred choice is PUR (polyurethane reactive) glue. PUR lasts far longer than ordinary hot-melt and cold-emulsion adhesives, endures extreme temperatures, and keeps an iron-clad grip on any difficult coated stock. Did we mention it looks great, too?
This directory was finished using PUR adhesive.
Keep in mind the following tips from Schultz Bindery when planning your next PUR gluing project.
How Does PUR Work?
Once applied to a book’s spine, PUR adhesive cures by drawing moisture from air and paper. This reaction builds a polymer network that, once fully cured, creates a permanent “thermoset” - in other words, the adhesive becomes impervious to temperature extremes. PUR adhesive also maintains a somewhat pliable state, offering much greater flexibility and page-pull strength than EVA hotmelts.
Technical Considerations When Using PUR
Unlike other hot-melt adhesives, which cure within seconds of being applied, PUR glue requires at least six hours curing time. If downstream processes such as shrink-wrapping or packing are performed too soon after binding, books will not exhibit proper appearance or page-pull strength.
When to Specify PUR
When sending out a PUR binding job, it’s helpful to let your bindery know what type of printing press was used. Heatset web presses tend to pull a lot of moisture out of paper. In these cases, web-printed book forms may need time to reabsorb moisture before binding to ensure a faster, more complete PUR curing process.
Ask for PUR if your books...
Unsure whether PUR binding is the best choice for your next book project? Give Schultz Bindery a call; we'd be happy to give you the benefit of our PUR knowledge.
- Feature paper grain perpendicular to the spine
- Include very thick or thin stocks
- Use unusual stocks, such as those with heavy clay content
- Are oblong or landscape format
- Will be digitally printed
- Include inks or coatings bleeding into the spine
- Should lay as flat as possible when opened
- Must look great and last for years!
About Schultz Bindery
For nearly 25 years, Schultz Bindery has provided quality perfect binding solutions to Midwest-area commercial printers. We have two perfect binding lines: Our 33 pocket Muller Martini binder is equipped with the strongest available binding adhesive on the market. Both high capacity perfect binding lines at Schultz Bindery are capable of handling projects of any run length and boasts both inline three-knife trimming and drilling for rapid and efficient production. Cover options include not only a variety of material choices, but pocket covers, gatefold and foldout covers as well.