Having recognized the adhesive benefits of naturally occurring materials, the ancient Greeks and Romans both developed early veneer processes using crude glues derived from animal protein. In addition, ancient myths employed adhesives as storytelling devices. For example, the mythical winged horse, Icarus, fell victim to the predictable failure of a hot-melt adhesive when the beeswax holding his wings together softened as he ventured too close to the sun, thus causing his wings to fall apart.
Some of the earliest examples of man's recognition of the adhesive powers natural materials offered were discovered by archeologists near the Dead Sea in what is now Israel. Broken pottery shards seem to have been patched with what is believed to have been tree resins. In Egypt, paintings and drawings found in tombs show what appears to be the use of adhesive materials used in gluing wood objects. Artifacts from Egyptian tombs also reveal objects that appear to have been glued together using animal glues. Other archaeological evidence exists of the use of a number of natural materials as adhesives, including animal collagen, eggs, blood, tree resins, milk byproducts, grains and even the aforementioned beeswax.
In fact, until the 20th century, natural materials were the predominant basis of almost all adhesives. It wasn't until the advent of synthetic polymer chemistry in the 1930s that natural-based adhesives had any real challengers. In the period leading up to World War II, new polymers provided countless building blocks for the modern adhesives industry.
Despite the development of synthetic-based materials and their huge impact on the adhesives industry, natural raw materials continue to play an important role in the formulation of adhesives. They even continue to dominate in certain industrial segments, such as corrugation, where starch- and dextrin-based adhesives reign supreme. In fact, natural-based raw materials represent almost 30% of all raw materials used in modern-day formulated adhesives in the United States. The figure shows the importance of key natural raw materials consumed in adhesive formulations in the United States today. Each key natural raw material is listed as a percentage of the overall U.S. formulated adhesives industry on a dry-pound basis for 2004.
Natural adhesives also find use in a range of end-use market segments, most notably those in woodworking and paper-based industries, including corrugating and package manufacturing. For example, starch-based adhesives represent a significant portion of total U.S. adhesives used in such diverse end-use markets as:
Corrugating - Starch- and dextrin-based adhesives represent about 94% of all the volume of adhesive used in the production of corrugated board. These adhesives are expected to show growth in total volume of a little over 3% annually.
Bookbinding - Animal protein-based adhesives represent just over 10% of the total adhesive consumed in bookbinding applications, with annual growth expected to slightly exceed 4%.
Additionally, many of today's natural-based raw materials find great utility as formulating components in adhesive systems comprised primarily of synthetic materials. Casein is a common component of many water-based adhesives used in packaging and the formulation of pressure-sensitive adhesives. Despite concerns over allergic reactions among certain percentages of the population, natural rubber remains an important formulating tool for PSAs used in medical products, such as self-adhering bandages, and in self-sealing envelope closures. There are few synthetic alternatives capable of effectively duplicating the adhesive properties of these natural materials.
Natural-based adhesives continue to play a major role in global manufacturing and retain a significant share of many end-use applications, particularly in the paper and woodworking industries. It is anticipated that natural-based adhesives will not only continue to grow, but that the current level of sophistication in the formulation of adhesives from these naturally occurring raw materials- even when combined with synthetic compounds- will remain an important part of the adhesives industry on a global basis.
For more information, contact The ChemQuest Group Inc., 8150 Corporate Park Drive, Suite 250, Cincinnati, OH 45242; phone (513) 469-7555; fax (513) 469-7779; or visit http://www.chemquest.com.