Sticking

Sticking is the ability of two or more surfaces or materials to join and remain united, or the tendency of a substance to adhere to a surface. In materials science, sticking arises from adhesion, cohesion, and friction at the interface, and it can be either temporary or permanent. The term covers both natural phenomena, such as the tack of a glue or the cohesion inside a polymer, and engineered systems designed to bind components together.

Adhesion involves intermolecular forces at the boundary between materials, while cohesion is the internal strength of the adhesive or substrate. Surface energy, cleanliness, roughness, temperature, and curing conditions strongly affect sticking. Common approaches to create sticking include natural and synthetic adhesives, pressure-sensitive tapes, hot melts, epoxies, cyanoacrylates, silicones, and polyurethanes. Mechanical interlocks and composite laminates can also produce sticking through physical interconnection rather than chemical bonding.

Performance is assessed in tests such as peel, shear, and tack tests, and by observing durability under temperature, humidity, and load. Failure modes include adhesive failure at the boundary, cohesive failure within the adhesive, and substrate damage. Proper substrate preparation and compatibility between materials are key to reliable sticking. Applications span packaging, wood and construction, electronics assembly, automotive manufacturing, and medical devices.

In everyday language, sticking also describes something that is tacky or sticky to the touch, and the phrase to stick to something means to remain faithful to a plan or to follow it without deviation. A sticking point refers to a difficult moment or obstacle in a process.