- Pressure activates the adhesive on tape. In essence, the harder you press, the more it will stick. Pressure-sensitive adhesives, as they are known, bond with some surfaces better than others. Furthermore, they bond best at moderate temperatures, because the molecular structure of most pressure-sensitive adhesives begins to collapse at extremely high or low temperatures.
- The tape's adhesive strength depends on a molecular bonding phenomenon known as van der Waals force, which is a measure of the force two surfaces exert on one another. Two books, for example, exert minimal van der Waals force on one another. Adhesive tape, on the other hand, is specifically designed--with the aid of applied pressure--to exert maximum van der Waals force.
- A number of factors can affect van der Waals force, and therefore, the effectiveness of adhesive tape. As mentioned, temperature is one key factor. Moisture is another; most pressure-sensitive adhesives do not bond to wet or damp surfaces because the adhesives' molecules will bond with water molecules rather than those of the targeted surface. The type of adhesive can affect bonding power, as well. Duct tape uses far stronger adhesives than masking tape. Likewise, wider tape covers more surface area and has a greater chance of establishing a viable van der Waal bond.
