Bookbinding is an important application area for adhesives, and requirements are becoming more demanding. With many publishers planning for worldwide distribution, and given today’s competitive market, bookbinding adhesives have to be very versatile. Software publishers, for instance, have to pay particular attention to end use, since their manuals can end up anywhere in the world. They must be able to stand up to a wide range of climates and user habits.
Most books are made by the so-called perfect-binding process. Perfect binding is a relatively simple process whereby the perfect-binding machine collates the pages that make up the text of the book and then clamps the text just above the spine. The collated text passes over a saw that cuts off about 3 mm from the spine of each page. This ensures that each page will contact the adhesive, which is applied next. Adhesive is applied to the entire spine of the book, as well as about 3 mm up the front and back. This “side adhesive” helps keep the cover closed and hides the roughened binding edge of the pages from view. Bookbinding adhesives were traditionally four main types:
- Polyvinyl acetate (PVA) emulsions
- Ethylene-vinyl acetate (EVA) emulsions
- EVA hot melts
- Rubber-based hot melts
Hot melts are the most popular method of bookbinding. They are relatively inexpensive, cure quickly, and form a good strong bond under most conditions. They tend to stiffen when cooled and, thus, do not hold up well under temperature extremes. PVA and EVA emulsions are applied cold. They dry to a semi-soft state, providing a more flexible backbone than hot melts and performing better at low temperatures.
Reactive hot-melt urethanes (RHMUs) are a recent advancement that give instant fixture and then cure to give crosslinked adhesives, which are considered to be the most flexible and durable bookbinding adhesives. They have excellent high-temperature resistance, which prevents pages from falling out in hot climates.
Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.