Perfect bound books, directories, and catalogs are in demand among a range of demographic groups. Conversely, PUR uses a molecular bond to secure both the cover and pages, which in turn produces a stronger and more flexible spine. Further, EVA has the reputation of failing if roughly handled or exposed to extreme temperatures. EVA continues to be a good general purpose adhesive, however, it is unable to bond properly to certain paper types and ink applications. Therefore, book binding comes down to choosing between Polyurethane Reactive adhesive (PUR) or Ethylene Vinyl Acetate (EVA).
These extreme conditions perform better with PUR binding. Pages could be tugged forcefully, or ripped in some areas, or the spine could be flexed unreasonably, or the books may be subject to extreme temperature variances, from cold-to-hot. When books make their way into the hands of customers, the business, organization or author relinquishes control over how the books are handled. Top bindery vendors employ a state-of-the-art extrusion head system that applies glue directly to the spine of the book, typically with a slot applicator that sprays the adhesive evenly.
That is why the application technique is so critical. Due to the properties designed within the adhesive, moisture is drawn out of the air, thus technically producing PUR as a moisture-curing product. PUR's glue process binds to the book via a chemical reaction. PUR technology has improved over the past decade to greatly shorten that set up time to just a few hours, with current formulations attaining 80% of their green strength during that period. In PURs early inceptions, the glue setup time in many cases was over 24 hours. The resulting fiber is the point where PUR molecularly bonds to a surface during the curing process. As with EVA, the PUR adhesive requires the backbone of the book preparation in similar fashion employing the use of milling knives, notching heads, roughing and equalizing heads to create fiber. As a result, PUR adhesive has become the overwhelming preference within the binding industry. This adhesive which began in 1989 was deemed the perfect binding solution and the clear winner according to industry players. The EVA glue process gave way to the development of the Polyurethane Reactive or PUR as it is commonly known today.
While EVA is acceptable for most offset production requirements, issues can arise in the event more complicated stocks are selected. EVA glue properties provide an allowance for the glue to be re-melted several times and consequently reduces the amount of waste throughout production.ĮVA also provides quick set points that reduce cure time prior to trimming. The EVA glue application is performed with a glue pot via a wheel applicator. This traditional method dubbed "perfect binding" employed a hot melt adhesive which came to be known as EVA. The Ethylene Vinyl Acetate binding process was the abiding standard through the mid-1990s. The second type is sort and bind which uses heat where the spine of the document is set inside of an adhesive spine that is warmed until the binding occurs. First, there's the punch and bind where you create uniform holes and bind the document with either a plastic or metal coil that feeds through the holes.
PUR is the strongest most flexible binding adhesive available and offers several advantages over other binding methods. Today's post, " The Advantages of PUR Binding" clarifies the best type of binding, why it matters, and most importantly how perfect bound books can stand the test of time. Welcome to the Dove Direct Print and Marketing Blog.