There are a number of binding options, including Polyurethane Reactive (PUR), Ethylene Vinyl Acetate (EVA) hotmelt and Polyvinyl Acetate (PVA) cold emulsion adhesives, or Smythe sewing. PUR has only been in bookbinding since about 1989. PUR binding was first adapted by midsize trade binderies for producing many trade journals and annual reports due to short lead times using highly coated and cross-grained papers without sewing. These markets will continue to be the high users of PUR, but publishers are now recognising the benefits of PUR and are requesting the use of PUR binding to ensure quality and longevity to their products.
Since its introduction, PUR use has increased dramatically. PUR is chosen over standard hotmelt adhesives for many reasons, the most important of which are its superior adhesion and the ability of a PUR-bound book to lie flat when open.
It is very important to understand the main differences of the two important binding technologies in the market today.
Advantages of PUR
1) Excellent flexibility and lay-flat quality.
2) Cold and heat resistance enabling books to be bound, stored and used in extremes of temperature.
3) PUR can bind varnished, UV-coated, carton, mylar and other stocks.
4) Impervious to print oils used in the digital print process and binding quality is unaffected by ink migration into the spine.
5) 40% to 60% better page pull results as compared to EVA Hotmelt.
6) Can handle recycled papers.
7) Handles cross-grained stocks better.
8) Square backbone: Because only a small amount of PUR needs to be used for binding, less adhesive is squeezed out when the cover station and side clinchers attach the cover and form the back.
9) PUR is also environmentally friendly due to its low VOC (Volatile Organic Compounds) and the working temperature is set at around 120°C while EVA is at around 170°C.
Advantages of EVA
1) Fast curing (in few seconds) & Quick turn-around time.
2) It is cheaper when compared to PUR glue.
3) Ease of operation, most often it is very easy to handle and maintain PUR gluing system as compared to Hotmelt gluing system.
4) Finished book can be easily handled.
5) Cleaning process of EVA binders is very simple/easy as compared to PUR binders. Most often it takes more time to clean PUR binders.
4) EVA Hotmelt glue still have their place in book-binding, especially when it comes to binding thread-sewn books, as the thicker glue allows for greater penetration into the spine area of the folded sections.
In summary, both processes are still widely used within print finishing. The question’ which is best’, probably needs to be replaced with the question ‘which is most suitable’, as the decision to use one over the other is very much job specific and would involve numerous considerations – from substrate used and thickness of the book, to the intended use of the product and any financial constraints to produce.
International Commercial Marketing