Maybe your ungrateful family doesn’t value all the thought and care you put into wrapping gifts, but that Scotch tape you’re using is the true underappreciated workhorse: It’s ubiquitous, immensely useful, and largely unrecognized as the modern chemical engineering marvel it is. The magic all started with Richard Drew, a scrappy banjo-playing researcher at 3M. In 1929 he was struggling to create a clear tape for meat-packers and candymakers—the cellophane kept ripping and warping near heat, and the adhesive wouldn’t stick evenly. His work eventually led to today’s Scotch Magic tape, and 3M has kept a tight seal on the recipe for its sandwich of polymers and carefully engineered chemicals ever since. So we did our own research on what likely makes 3M’s tape stick.
The “invisible” film that we know as tape. It starts as cellulose, a long, tough, glucose-laced polymer that gives plants their structure. Typically it’s extracted from cotton or wood and treated with acetic acid, the chemical that makes vinegar vinegary. The process swaps out hydrogens in the cellulose for acetyl groups, which allows the hardy polymer to be dissolved and extruded into a translucent strip that’s strong and water-resistant yet able to be torn off by hand while you’re lovingly (or hastily) wrapping those holiday gifts. Cellulose acetate goes way back: It’s been used for a century as film for photographs and movies.
Although 3M has kept the specific ingredients of its adhesive under wraps for decades, it’s undoubtedly a soup of monomers like butyl acrylate, methyl acrylate, and methyl methacrylate. The acrylic mixture flows onto whatever surface you press the tape on and stays put, thanks to sticky molecular interactions called van der Waals forces.
There’s no water in the tape itself, but water is likely used during manufacturing: The acrylics need to link into chains to form the adhesive, and that often happens in water or another solvent. Tape makers coat the cellulose film with the adhesive-water cocktail, and when the H2O evaporates, it leaves a layer of gluey goo that’s usually 20 microns thick.
Silicone, in other words. To prevent the tape from sticking to itself when it’s rolled up, companies apply a release coating to the nonsticky side. Of course, 3M won’t say what’s in it, but silicone is a usual suspect: It doesn’t really attract other materials, thanks to the stable methyl groups that give it low molecular surface energy. Regardless, the formula is engineered so that the tape unrolls smoothly and quietly—none of those skreeeck noises that packing tape makes.
Styrene Acrylic or Polyurethane
One of these coatings probably helps keep the adhesive stuck to the film so the two don’t just separate when your kid is yanking off that wrapping paper. Styrene acrylic is like the acrylate adhesive but stickier; polyurethane is the main ingredient in some wood finishes and latex-free condoms. No, you should not craft your own mummylike barrier of Scotch tape to use as birth control.
This article appears in the December 2016 issue. Subscribe now.