In the peel zone: tape's electric gooeyness.
Peeling a strip of adhesive tape off a smooth surface is a violent process. As the adhesive stretches into strands, or fibrils, that suddenly snap apart, electrical activity is generated at the tape-surface juncture junc·ture
The point, line, or surface of union of two parts. , often accompanied by a flickering glow visible in a darkened dark·en
v. dark·ened, dark·en·ing, dark·ens
a. To make dark or darker.
b. To give a darker hue to.
2. To fill with sadness; make gloomy.
Now, J. Thomas dickinson and his coworkers at Washington State University Washington State University, at Pullman; land-grant and state supported; chartered 1890, opened 1892 as an agriculture college. From 1905 to 1959 it was the State College of Washington. in Pullman Pullman.
1 Former town, since 1889 part of Chicago, Ill. It was founded in 1880 by George M. Pullman as a model community for workers of his sleeping-car company; all property was company owned, and administration policies were paternalistic. have investigated the microscopic details of what happens when someone strips a common type of household adhesive tape from a polished copper surface.
The researchers discovered that the electrical current generated by the peeling tape fluctuates erratically. Moreover, the tape's initially smooth but sticky surface ends up pitted with cavities having a wide range of sizes.
"The dance of fibril fibril /fi·bril/ (fi´bril) a minute fiber or filament.fibril´larfib´rillary
collagen fibrils detachment occurring across the entire width of the tape is a chaotic process," Dickinson suggests. "Thus, the forces acting on the adhesive...result in rich void and fibril formation...that greatly influences the way tape peels."
The researchers report their findings in the November JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY.
When adhesive tape comes into contact with a surface, electrons shift from one material to the other to give them opposite electrical charges. The attraction between these oppositely charged surfaces contributes to the adhesive bond.
Peeling stresses the adhesive, creating little cavities in the material. As the process continues, the walls of the cavities stretch into fibrils. At the same time, measurable electrical discharges Noun 1. electrical discharge - a discharge of electricity
discharge - the sudden giving off of energy
nerve impulse, nervous impulse, neural impulse, impulse - the electrical discharge that travels along a nerve fiber; "they demonstrated the transmission of occur between the electrically charged tape and the metal surface near these cavities. Measurements of the resulting electrical currents reveal details of the peeling process on time scales down to nanoseconds.
"The more fibril formation and stretching that you get, the stickier the adhesive is," Dickinson says. Hence, a large proportion of the energy required to peel a strongly adhering tape goes into stretching the fibrils and working the gooey See GUI. adhesive.
This research represents an extension of an earlier effort to study cracking and fracture in brittle materials (SN: 5/4/91, p.279). Fractures may also generate electricity and light.