Custom Book Printing: What is PUR Binding?
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PUR Binding
PUR Binding is a popular bookbinding method that uses a
high-performance bonding agent known as Polyurethane Reactive adhesive (abbreviated
as PUR).
PUR Binding is a type of Perfect Binding. Perfect binding involves
applying a strong adhesive to the spinal edge of a book's page block and then affixing
a wrap-around cardstock cover over the page block. The adhesive bonds the cover
and pages together at the spine. After the adhesive cures, the three open sides
of the book are trimmed to give them clean "perfect" edges.
The Evolution of Adhesives used for Perfect Binding
Though the Perfect Binding method was invented in 1895, it
wasn't widely used until paperback books started being mass produced in the
early 1930's. However, these early books used a basic "cold" glue that became
brittle with age.
In 1940, Dupont introduced a hot-melt adhesive that offered better
flexibility. Known as Ethylene Vinyl Acetate (abbreviated as EVA), this glue still
has widespread use today and is considered the traditional perfect binding adhesive.
Unfortunately, EVA glue developed its own share of shortcomings. For
example, it can crack under certain circumstances and often fails to perform in
extreme temperatures. Fortunately for the bookbinding industry (and many other
industries), Polyurethane Reactive adhesive (PUR) was developed in the 1980's and
has been growing in popularity ever since.
What does Polyurethane Reactive mean?
The term "Polyurethane" refers to a string of polymers linked together by urethane bonds, whereas "Reactive" means that the adhesive gains its strength from a chemical reaction.
In the case of PUR, this chemical
reaction is triggered from moisture that naturally exists in the surrounding
air and the material being glued.
The PUR formulation combines the rapid bonding speed of a
hot melt adhesive with the enduring strength of a structural adhesive.
How Is PUR superior to EVA?
Though EVA and PUR are both hot-melt adhesives, PUR is vastly
superior to EVA in many ways…
Stronger Bond -
Unlike EVA glue, PUR will adhere tightly to a wide range of materials,
including heavy cardstocks, synthetic paper, and recycled substrates. Also, PUR adheres
strongly to glossy stocks, including those coated with a varnish, UV coating,
laminate, or Mylar.
Increased Resistance to Page Pullout -
When compared to EVA binding, PUR binding offers up to 60%
more resistance to pages being pulled out. This is particularly important for
books that will see frequent handling, such as manuals, textbooks, workbooks, cookbooks,
or children's books.
Greater Flexibility -
EVA glue might crack at the spine if too much pressure is applied, such as attempting to press an open book down flat. Conversely, PUR glue offers incredible flexibility and will maintain its structural integrity even when the book
is pressed down firmly or opened very wide.
Better Performance in Extreme Temperatures -
EVA glue can become brittle when exposed to cold temperatures.
This can cause the spine to crack. Also, because EVA glue can be reactivated
with heat, it can soften in hot temperatures and the pages can come
loose. However, books bound with PUR glue will remain intact whether the
temperatures are well below zero or 300 degrees Fahrenheit.
Neater Appearance -
The superior binding strength of PUR allows less glue to be
used than its EVA counterpart. This not only helps the spine of a Perfect Bound book maintain a uniformly
square shape, it also minimizes the amount of cured glue that is visible after
the books have been trimmed.
Other Benefits of PUR Adhesive...
> PUR is safe and non-toxic
> PUR is eco-friendly and free from Volatile Organic Compounds (VOCs)
> PUR dries clear and will not shrink
> PUR is resistant to moisture and humidity
> PUR is a one-part adhesive - not having to mix or measure ensures a consistent formulation
For adhesive-bound books, Color Vision uses PUR exclusively
As mentioned above, EVA glue is still widely used
for creating Perfect Bound books. However, because the performance of PUR glue is
vastly superior, Color Vision does not use EVA glue. When
producing adhesive-bound books, Color Vision uses PUR exclusively.
If you are interested in all the benefits PUR adhesive can bring to your next book project, give us a call at 800-543-6299 and we'll
be happy to help.
Or, if you would like to receive a bid for an upcoming project, simply fill out
our Quote Request form and we will email our quote to you.
As always, we look
forward to assisting with your printing and binding needs!
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