A Short History of Adhesives and Sealants

We learn from the past -- this week's editorial looks at a short history of adhesives and sealants. It describes where we have been and where we might be going. The list of past accomplishments and innovations are, indeed, quite exceptional. It is no wonder that with a past such as this, it is difficult to keep up with the many advancements in the industry.

With new technology sweeping into business from every avenue, simply keeping up sometimes feels overwhelming. In the article "Innovations in Adhesives - Resins" , I try to mention just a few of the new resin technologies that will hopefully make us more profitable. In 1965, Intel cofounder Gordon Moore stated that computer speed would double every 18 months. Now known as Moore's Law, it is applied to almost every growth area. It also seems to apply to adhesives and sealants. I don't know if my file cabinet (electronic and otherwise) can hold all of the information.

This seems like a good opportunity to look back as well as forward. How did we get here? The history of adhesives and sealants is interesting and probably deserving of a book on its own. It is certainly a winding road, but one that is filled with innovation and excitement.

Adhesives and sealants were first used many thousands of years ago. Early hunters may have seen improvement in their aim by joining 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. 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 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 diary by-product) and soluble sodium silicate adhesive (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 centuries.

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 adhesives and sealants industries. The following table summarizes highlights of the historical development of adhesive and sealant products. The modern adhesives age began about 1910 with the development of phenol formaldehyde adhesives for the plywood industry. Adhesives 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 ratio, the development of modern adhesives and sealants is closely related to the history of the aircraft and aerospace industries. With successful experiences in these entry industries, it was soon realized that adhesives could be used to economically replace mechanical fastening methods such as welding, brazing, or riveting. It was also realized that sealants could be used to provide additional function and value to products in industries ranging from transportation to construction.

The science of adhesion is now well accepted, and the basic rules and methods for achieving high performance joints have been well established. The industry has a strong foundation of formulations and processes. Today, many of the new adhesive and sealant developments are focusing on production cycle time and cost; environmental enhancement; or application to new substrates, such as engineering plastics, advanced composites, and ceramics that are rapidly gaining acceptance.

Development efforts supporting adhesives and sealants are directed to optimizing the manufacturing and assembly processes. For example, automated meter, mixing, and dispensing equipment and weld-bonding adhesives have been perfected to reduce production time in high manufacturing operations. New adhesives and sealants are often applied with robotic equipment to further enhance productivity. UV curable adhesives have been developed to take advantage of their ease of application, elimination of mixing and heat curing, and elimination of liquid solvent. Ultrasonic and other fast thermal welding techniques have found a receptive home in the high-volume transportation industry. Microwave assisted drying of water-based adhesives and new hot melt systems have been developed to make bonding more agreeable to the manufacturing world.