EVA or PUR?

All perfect bound books are bound with either EVA (Ethyl Vinyl Acetate) or PUR (Polyurethane Reactive) adhesives. Here’s a breakdown of each of them.

EVA has been the normal, go-to, adhesive since the beginning of perfect binding and still represents the majority of perfect bound adhesive used in North America. It’s easy to use and inexpensive. Fill the tank with EVA, melt it down to a liquid form and you’re ready for production. Leave it melted all day if need be and when turning the binder off it will return to its solid form. Simply repeat the process the next day.

The EVA drawback? With the onslaught of digital print, we began to realize that EVA adhesives didn’t always adhere well to some of the digital output. The sudden barrage of different substrates, primarily coated, and the increased use of varnishes and fuser oils quickly became the nemesis of EVA adhesives. Book integrity was occasionally compromised! The binders were doing their jobs but the adhesives weren’t. EVA is still an excellent choice for perfect binding as long as you stay away from certain stocks and certain digital outputs. That being said, advancements have indeed been made in regard to more aggressive EVA adhesives.

PUR picks up where EVA leaves off. It will adhere to most anything and makes a nearly bullet-proof perfect bound book. PUR is far and away the norm in the rest of the world and has been for some time. North America, for whatever reason, has lagged in the use of PUR but that is quickly changing. In time, it will become the norm here as well.

Can’t I just put PUR in the adhesive tank rather than EVA? NO. The glue tanks and overall functionality of a PUR binder are different from an EVA binder. The process is slightly different so the binders are different.

PUR reacts to the air it’s exposed to and begins to cure as soon as it’s exposed to air. In an “open tank” system, what goes in the tank is either used or thrown out. Unlike EVA, there is no re-melting it for use the next day. PUR has other quirks as well. It can take up to 24 hours to fully cure. It’s okay to trim and box these books right away but if you take a freshly bound PUR book and open it up you might as well throw it out because you just ruined it.

PUR adhesive can also be as much as three times the cost of EVA adhesives BUT that’s balanced out by the fact that you can use roughly a third of the adhesive amount per bind. With PUR, less is more! This minimal amount of glue also makes for a more flexible and flatter lying finished book. PUR is also impervious to temperature extremes. Unlike EVA, it won’t crack in the bitterest of cold and it won’t get gummy in extreme heat.

While EVA remains a solid part of the current picture, PUR is indeed the future of perfect binding.