Adhesive

Adhesives are non-metallic substances capable of binding separate surfaces through molecular attraction and maintaining resistance to separation. They have long been used to join materials ranging from wood and stone to modern polymers and composite surfaces. Their application offers several advantages over mechanical fasteners or thermal joining techniques, notably the ability to bond dissimilar materials, distribute stress more evenly, and support cost-efficient mass production. Nevertheless, their limitations—such as reduced performance under high temperatures and challenges in dismantling bonded components—remain important considerations in practical use.

Early Development and Prehistoric Uses

The origin of adhesive use can be traced to approximately 200,000 years ago, when early humans produced birch bark tar through dry distillation. This tar served as a binding agent for securing stone points to wooden handles, representing one of the earliest known examples of engineered composite tools. Archaeological findings from central Italy include Middle Palaeolithic implements bearing traces of birch bark tar, indicating the sophistication of early adhesive technology.
Experimental archaeology has demonstrated that birch bark tar could be produced using comparatively simple open-air burning methods, making its discovery accessible even to early populations. However, these natural adhesives, while tacky, were prone to brittleness and environmental degradation.
By around 70,000 years ago, more advanced compound adhesives emerged in southern Africa. At Sibudu, stone segments used for hafted tools were found coated with mixtures of plant gum and ochre, a naturally occurring iron oxide. The addition of ochre strengthened the adhesive, improving its performance under moist conditions. Middle Stone Age populations developed increasing versatility in toolmaking due to these stronger bonding materials.
Further evidence from Le Moustier suggests that Neanderthals combined ochre with bitumen to create functional grips for stone tools. Adhesive use continued to evolve, and by 6,000 years ago, archaeological sites revealed the use of tree resins to repair pottery. Bitumen cements were also employed in ancient Mesopotamia, for example in attaching ivory components to statues within Babylonian temples.
The discovery of the Tyrolean Iceman, dated to approximately 5,200 years ago, has provided additional insight. His arrows and copper hatchet show traces of pitch resin, produced through controlled heating of birch bark in a process known as pyrolysis. Such findings demonstrate a sophisticated understanding of material transformation among prehistoric communities.

Classical and Ancient Civilisations

Adhesives appear in written records from around 2000 BC. Egyptians made significant use of natural adhesives, including animal glues in woodworking and lamination practices. Artifacts from the tomb of Tutankhamun reveal the use of casein-based glues for furniture and bow construction, as well as starch-based pastes for bonding papyrus and textiles. They also developed early gypsum-based bonding plasters resembling plaster of Paris.
From AD 1 to 500, Greek and Roman craftsmen expanded the repertoire of adhesive materials and techniques. Notable developments included wood veneering, marquetry, and refined animal and fish glues. Egg-based binding pastes, enriched with ingredients such as blood, hide, milk or vegetable matter, played an important role in gilding and artistic work. The Greeks first adopted slaked lime mortars, which the Romans improved by mixing volcanic ash and sand to produce Pozzolana, a material central to monumental architecture such as the Pantheon and the Colosseum. Romans also used tar and beeswax as effective sealants in shipbuilding.
In Central Asia, Mongol bowyers around AD 1000 used composite constructions with bamboo, horn and tendon, all secured with strong animal glues. The reliability and elasticity of these adhesive joints contributed to the military success of Mongol mounted archers.

Developments in Europe and the Industrial Period

In Europe, adhesive use declined after antiquity but resurged between AD 1500 and 1700. Renowned furniture makers such as Thomas Chippendale and Duncan Phyfe relied extensively on glue in high-quality joinery. The establishment of Europe’s first commercial glue plant in the Netherlands in 1690 marked an important milestone, focusing on glues derived from animal hides.
Patent activity expanded rapidly during the eighteenth and nineteenth centuries. The first British patent for fish glue was issued in 1750. Casein glue manufacturing grew particularly in German and Swiss industries, and in the United States, the first casein glue patent was issued in 1876. Adhesive technology became increasingly integrated into daily life; for instance, postage stamps introduced gum adhesives in 1847. Dextrin, a starch-derived adhesive, was patented in 1867, further broadening the market for low-cost natural glues.
The introduction of natural rubber into adhesive formulations in about 1830 initiated the development of modern elastomeric adhesives. Subsequent work in metal-rubber bonding, including the electroplating of metals to improve adhesion, was driven by industrial needs such as the development of automobile shock mounts. Cyclised rubber and solvent-based rubber cements emerged in the early twentieth century as durable bonding agents for metal-bending applications.
The invention of pressure-sensitive adhesives in the mid-nineteenth century—first used in medical tapes and later popularised by products such as Scotch Tape and sticky notes—illustrates the growing importance of adhesive convenience materials in domestic and industrial contexts.

The Rise of Synthetic Adhesives

A major transformation occurred in the early twentieth century with the advent of synthetic polymer chemistry. The introduction of Bakelite, a thermosetting phenolic resin, in 1910 marked a turning point. Within two years it was incorporated into plywood coatings, and by the 1930s phenolic adhesives were widely used for structural applications.
The global conflicts of the early twentieth century accelerated innovations in plastic and resin technology, leading to the creation of diverse synthetic adhesives designed for demanding environments. Epoxies, acrylics, polyurethanes and other formulations became indispensable in aerospace, automotive, construction and electronics industries. Despite these advances, natural adhesives remain widely used due to their low cost and ease of production.

Classification of Adhesives

Adhesives may be categorised on several bases, including their mechanism of adhesion, phase of matter at application, natural or synthetic origin, and whether they cure through chemical reaction.

Reactive and Non-Reactive Adhesives

A major distinction lies in whether the adhesive undergoes a chemical reaction to harden (reactive) or sets without such a reaction (non-reactive). Reactive adhesives include epoxies and polyurethanes, which cure through polymerisation or cross-linking. These typically provide strong, durable bonds and are used in high-performance contexts.
Non-reactive adhesives harden through physical processes such as solvent evaporation or cooling. They tend to be easier to apply and are widely used in consumer and craft applications.

Drying Adhesives

Among non-reactive adhesives, drying adhesives constitute an important group. Solvent-based adhesives are formulated by dissolving polymers in volatile solvents; hardening occurs as the solvent evaporates, leaving behind the bonding polymer. Common examples include rubber cements, contact adhesives and polyvinyl acetate (PVA) formulations.
Polymer dispersion adhesives, often known as emulsion adhesives, are another significant category. These milky-white dispersions, frequently based on polyvinyl acetate, cure as water evaporates, allowing the dispersed polymer particles to coalesce into a continuous film. They are widely used in woodworking, paper bonding and packaging.

Broader Applications and Modern Significance

Modern adhesives support a vast range of applications. In engineering, high-strength structural adhesives enable the production of lightweight composite assemblies, critical in aerospace and the automotive industry. In household contexts, adhesives serve for repairs, crafts and packaging. Medical adhesives contribute to wound closure, wearable devices and implantable materials. Digital technologies have also expanded adhesive use in microelectronics, including die-attachment and circuit encapsulation.