PUR is the strongest and most durable form of adhesive binding available. Digital printing has fuser oils on it which can be problematic for EVA perfect binding to create a strong bind. That's why we are going to PUR on digital printing.
There are two tests that measure the strength of perfect binding. The tests are page pulls (how much force does it take to tear a page out of the book) and page flexes (how many times a page is turned back and forth before it comes out of the book). In actual tests, we are getting 10 lbs. per inch (4.5 lbs. is considered excellent) and 1500 flexes (anything over 350 is excellent). Spine strength, ability to resist cracking and superior flexibility are a few more advantages PUR offers over traditional EVA perfect binding adhesives.
What types of digital jobs are perfect for PUR?
Thick books. Books with a lot of heft and bulk benefit from the super strong adhesion of PUR glue.
Oblong books. Books with an oblong (landscape) orientation have more text weight per spine inch than their non-oblong counterparts and therefore can benefit from the durability offered by PUR.
Thin books. Books as thin as 1/16-inch can be bound with PUR for added durability and flexibility.
Difficult stocks. PUR is essential for books containing:
Coated paper stock with lots of clay fillers
Heavy ink, varnish and other press-applied coatings that bleed into the gutter
Cross-grain signature layouts
Fly sheets or other two-page forms in either the first or last position
HOW TO LAYOUT YOUR PERFECT BOUND BOOK.