PUR PERFECT BINDING FOR THE TRADE

Perfect binding utilizes two types of glue: Polyurethane Reactive (PUR) and Ethylene Vinyl Acetate (EVA). Both are very successful forms of adhesive in perfect binding. The difference in the two is that PUR is the most durable available, offering flexibility for all types of applications including catalogues, manuals, etc.

One of the main concerns with conventional EVA binding is it’s stability in extreme temperatures. PUR adhesive sets quickly when it cools from the melt form to a solid, and at that point has reasonable strength. However, the adhesive will continue to develop strength due to a chemical reaction that occurs between the polyurethane and environmental moisture. Once cure is complete (generally in 18-24 hours), the bond is far superior to ordinary hot melts - by 2.5 times the strength. Due to the cross-linking provided by the moisture reaction, PUR hot melts are highly resistant to re-melting in extreme summer months and cold cracking in harsh winter months.

PUR also uses a smaller amount of glue, and can bind materials that may not have been previously attempted. PUR does not require knocking-out spine ink, coatings and varnishes. Another major advantage of PUR glue is its flexibility once it has fully cured. It is able to withstand heavy usage in demanding conditions.

Some of the benefits of EVA include a faster curing time, ease of operation, cleanup processes are easy when compared to PUR, and is more effective on thread sewn books, as the glue allows greater penetration into the folded sections.

Which is best? - probably needs to be replaced with the question - Which is most suitable? The decision to use one over the other is very much job specific and would involve numerous considerations – substrate used, thickness of book, or intended use of product.

For those that have not had the experience of seeing PUR binding in action, 

please contact us for demonstration!