In the world of perfect binding there are a wide variety of options when it comes to glue. This may seem like a light decision! But in manufacturing owners are constantly juggling costs, quality, and turnaround time. Every type of glue has certain advantages and disadvantages and researching ahead of time will help you save months of headaches.
Thousands of formulas exist for book binding glue. But we categorize it into two main families: ethyl vinyl acetate (EVA) and polyurethane resin (PUR). Each of the two families of glue have different production factors that should guide your decision. Making these choices early on is critical because machine configurations can vary between glue types.
EVA vs PUR Pros and Cons Table
| Quality Factor | EVA Glue | PUR Glue |
|---|---|---|
| Cost of Glue | Low | Medium |
| Glue Curing Time | Minutes | Hours |
| Thermal Binder Cost | Lower | Higher |
| Lay-Flat Quality | Low | High |
| Survive Extreme Heat | No | Yes |
| Survive Extreme Cold | No | Yes |
| Conclusion | Lower Quality Lower Cost | Higher Quality Higher Cost |
In the early days of bookletmaking, people utilized animal glues as their only option, which were produced from horse, rabbit, and fish byproducts. In modern manufacturing, the industry has transitioned away from animal products and into a category of glue called thermoplastics. Modern thermoplastics used in book binding almost entirely fall under the category of Ethyl Vinyl Acetates (EVA).
Ethyl Vinyl Acetates (EVA)
EVA glue is widely used in the industry for many reasons but mostly because EVA is cost effective general use binding adhesive. EVA bookletmaking machines are considerably more forgiving to operate, require less maintenance, and have a lower cost of investment and operation.
EVA is a clear choice for most applications but there are some limitations. Extreme temperatures will result in the glue re-melting and or cracking. Additional complications include the ability to recycle books made with EVA. In order for these books to be passed through the recycle stream, the spines of the book must be chopped off and discarded.
Poly Urethane Resin (PUR)
PUR glue is slowly becoming more common in the printing industry due to some distinct advantages. PUR is the same chemical family that bowling balls and soccer cleats are made of. It’s incredibly common as a molded plastic for all kinds of manufacturing. It holds up in extreme conditions and a much smaller volume of PUR can get the job done.
The major benefit when it comes to booklet making is adherence. PUR glue chemically bonds to water molecules within the paper itself, where EVA makes a more mechanical bond by intermingling with paper fibers. This chemical bond allows bookletmakers to use smooth coated papers without worry of the book falling apart. PUR is also described as a one-time-melt and holds up better in extreme temperatures. The glue is more flexible meaning books will lay flatter, creating a better experience for the reader. Additionally, PUR glues are more forgiving when it comes time to recycle. Certain properties make it easier for recycling facilities to extract glue from paper pulp.
PUR Downsides
The disadvantage of PUR involves a slightly higher production cost, primarily because it requires additional hardware. PUR systems need Teflon coated tanks, complex extrusion application systems and usually a sealed pre-melter to keep oxygen from setting the glue prematurely. Fortunately, these additional costs are mostly within the initial investment. Once the hardware is in place the cost of operation is very close to that of an EVA based workflow.
PUR glue typically requires a 24-48 curing time before the book can open without damage. Many manufacturers use their shipping time as curing time but there can be situations where the added wait for curing can slow production.
PUR vs EVA Conclusion
There are many factors that surround the decision of what type of glue to use. In every manufacturing purchase the application should drive the purchase:
- Where will the books be going?
- Who will be reading them?
- What quality and delivery time tables does the print buyer expect?
Many modern machines are available as hybrids. The BQ-500 is capable of being configured with a hot-swappable glue tank to quickly switch between glue types without interruptions in production. On the smaller end the BQ-160 is available as an EVA or a PUR model.
Mid-State Litho, Inc.
5459 Fenton Rd.
Grand Blanc, MI 48507
midstatelitho.com