Page 40 - Handbook of Adhesives and Sealants

10 Chapter One

The steps necessary to achieve a practical and economic bond or seal
will be developed through insight into the fundamentals of these sci-
ences. The Handbook will attempt to identify solutions to satisfy most
applications or, at least, illuminate the correct path for the end-user.

1.3 Markets and Applications
1.3.1 History
Adhesives and sealants were first used many thousands of years ago.
Early hunters may have seen improvement in their aim by bonding
feathers to arrows with beeswax, a primitive form of adhesive. The
Tower of Babel was probably built with the aid of mortar and tar or
pitch as a sealant. Carvings in Thebes (circa 1300 BC) show a glue
pot and brush to bond veneer to a plank of sycamore. Until relatively
recently, most adhesives and sealants evolved from vegetable, animal,
or mineral substances.
In the early 1900s, synthetic polymeric adhesives began displacing
many of these naturally occurring products owing to their stronger
adhesion, greater formulation possibilities, and superior resistance to
operating environments. However, non-polymeric materials are still
widely used and represent the bulk of the total volume of adhesives
and sealants employed today. Common applications for these non-
polymeric materials include bonding porous substrates such as wood
or paper. Casein adhesive (a dairy by-product) and soluble sodium sil-
icate adhesives (an inorganic, ceramic material) are commonly used
in the cardboard packaging industries. Naturally occurring, bitumen
or asphalt materials have been accepted as sealants for many centu-
ries.
The development of modern polymeric adhesives and sealants began
about the same time as the polymer industry itself, early in the 1900s.
In fact, the polymeric and elastomeric resins industry is bound very
closely to the adhesive and sealant industries. Table 1.2 summarizes
highlights of the historical development of adhesive and sealant prod-
ucts. The modern adhesives age began about 1910 with the develop-
ment of phenol formaldehyde adhesives for the plywood industry. Ad-
hesives and sealants found important markets in the construction
industry, which was providing much of the growing infrastructure in
the U.S. at the time.
Significant growth then again occurred in the 1940s and 1950s with
the development of structural adhesives and sealants for the military
aircraft industry. Because of their exceptional strength-to-weight ra-
tio, the development of modern adhesives and sealants is closely re-
lated to the history of the aircraft and aerospace industries. Durability
of adhesive joints was a problem in aircraft service until advanced