Theoretically explaining *why* adhesives are able to bond objects together remains a challenging task, as the process involves a complex interplay of numerous factors-including physics, chemistry, and mechanics. However, all adhesives share certain common characteristics: they are applied as a liquid coating to the surfaces intended for bonding; they transition from a liquid to a solid state after application; and once solidified and set, their properties become highly stable, enabling them to withstand external forces.
One popular theory posits that when an adhesive is applied to the microscopic irregularities (peaks and valleys) of the surfaces to be joined, it acts as an anchor. This force-known as the "anchoring effect"-mechanically locks the objects together. However, this perspective struggles to adequately explain the bonding mechanisms involved with extremely smooth surfaces, such as those found on glass or metal.
The bonding of objects like glass relies instead on "intermolecular forces" acting between molecules and atoms. Intermolecular forces are attractive forces that come into play when the molecular-level distance between objects becomes extremely minute; they arise from the electrical polarization within molecules or atoms, causing positive and negative charges to attract one another. When a liquid adhesive coats the surfaces to be joined, the distance between the adhesive's molecules and the objects' molecules is significantly reduced, allowing these intermolecular forces to take effect and bond the objects together.
Currently, instant adhesives are regarded as highly practical and high-performance bonding agents. The instant adhesives widely sold today are synthesized from a compound known as "cyanoacrylate"-a substance accidentally discovered by American researchers during their studies in 1955. Instant adhesives require no additional chemical additives; they simply utilize trace amounts of moisture present in the air to trigger solidification, thereby bonding objects tightly together in a matter of moments. These instant adhesives are compatible with a wide variety of materials (with the exception of wood and fabric) and are particularly well-suited for household use.
