Polyurethane Reactive (PUR) adhesive has become the adhesive of choice for many printers and trade binderies during the past several years. It has been particularly popular when matched with coated stock projects. One of the most common questions that is posed to us is “When does it make sense to use PUR?”
Allied Bindery was an industry leader for the introduction of PUR and we have experienced a significant growth in the use of PUR during the past several years. We recommend that the following attributes be used as a guideline for choosing PUR for your binding projects:
Coated Stock – particularly 70# basis weight and greater. The heavier the basis weight of the stock, the more stress that is placed on the glue line when pages are flexed (turned) by the end user.
- Cross Grain Stocks – whether coated or uncoated. A short grain stock simply does not have the fiber exposure and fiber length to create a strong page pull or flex result when paired with an Ethyl Vinyl Acetate (EVA) adhesive.
- Mixed Stocks – PUR is the superior choice when a project utilizes mixed text stocks with a variety of fiber characteristics.
- Synthetic Stocks – With no fiber available, an EVA will quickly fail. PUR adheres via a chemical melding versus a “mechanical” glue bind. PUR is the best choice for synthetic stocks.
- Full Ink Coverage – In general, inks and most coatings will not repel PUR as they will EVA adhesives. If your project includes a full ink or coating coverage into the spine grind area, consult with your Allied Bindery representative so that we can guide you with respect to knock outs.
- High Use Products – Catalogs, Directories and Text Books are examples of products subject to a high usage rate, which must also stand the test of time. PUR provides vastly superior page pull and flex results that allow for a high usage rate without the spine breaking down.
- Extreme Heat or Cold – EVA adhesives will cold crack at just less than 40 degrees Fahrenheit and re-soften at 120 degrees Fahrenheit. If you have products that will be stored or used in extreme cold or hot climate conditions, PUR provides superior results.