Bonding: An Ancient Art

In the Neolithic period, namely ca. 8000 BC, the people used a resin from birch trees to attach the heads of spears and axes. When the glacier man “Ötzi” was discovered, tools and pieces of clothing were found, including an axe made from yew wood whose blade was attached with birch pitch (adhesive) and strips of leather. About 5000 BC, animal blood, protein, various plant resins and asphalt were used as adhesives in Babylon to build houses and temples. In ancient Egypt (about 3500 years ago) bonding was even a profession: the occupation of adhesive-maker was born (Kellopsos). The art of boiling glue which the ancient Egyptians had developed was later taken up by the Greeks and Romans. An indi­cation that the art of bonding was already at an advanced stage of development at the time of the Romans is the oak box from the Roman era that was found in Breslau in about 1886: Five metal coins were bonded onto the top of this oak box. The adhesive that was used is thought to be based on a protein-chalk mixture and must have pos­sessed an extremely high adhesive strength because four of the five coins are still bonded to the wooden surface after almost two thousand years. In the mid 14th century the Aztecs used the adhes­ive properties of blood for construction work. It is the albumin in blood which gives it these bonding properties. The Aztecs mixed this animal blood into cement. The structures built by the Aztecs are even today still in excellent condition and are evidence of the quality of the bonding agents.

Natural rubber was first used as a raw material for adhesives in about 1830. The discovery of rubber vulcanization in 1841 by Goodyear marked the birth of the history of synthetic plastics and hence syn­thetic adhesives. This was the first time in the his­tory of mankind that a natural chemical was altered to make a semi-synthetic material (plastic) having new mechanical and technological properties. In 1864, W. Parks succeeded in making semi-synthetic celluloid. The first “real” synthetic plastics to emerge from chemists’ laboratories which had no parallels in nature were the phenolic resins. They were first used in 1902 and are closely associated with the name Baekeland. Indeed, Baekeland sold the first commercial phenolic resin in 1905 under the name Bakelite. This represented a key step in the chrono­logical development of plastics, namely from natu­ral materials, then on to chemically modified ma­terials and finally to wholly synthetic plastics. Over the next decades the development of synthetic plastics and adhesives experienced a rapid boom. Synthetic rubbers such as polychloroprene, Buna (polybutadiene) and silicone rubber were synthesized. Then followed epoxy resins and the polyurethanes and after the Second World War the methacrylate and the cyanoacrylate adhesives (superglues).

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