How Adhesive Tape Functions

Key Insights

It’s as common as running water, with some even considering it just as convenient. Prior to 1925, when 3M introduced adhesive tape, methods of adhesion were typically permanent and messy.

Masking tape, first created in 1925, was designed to address a specific challenge: creating two-toned paint jobs for cars, which were all the rage at the time.

Prior to masking tape, auto shops used glue and paper to mask off areas for each color application. However, removing the paper often led to ruined paint jobs. Richard Drew, a young research assistant at 3M, witnessed one such disaster and the ensuing frustration. With no prior experience in adhesives, Drew decided to invent an adhesive that could be removed without damaging the dry paint. Two years later, masking tape was born.

Drew would go on to invent clear, cellophane tape, which became known as Scotch® Magic Tape. This invention would forever change the way we wrap gifts.

It also revolutionized everyday household repairs. During the Great Depression, when people had to fix rather than replace things like tablecloths and upholstery, clear tape offered an affordable, quick, and visually pleasing solution. While many businesses struggled or closed, Magic Tape helped 3M not just survive, but thrive.

Today, adhesive tapes are available in various forms: cellophane for wrapping, matte for labeling, and strong duct tape for home repairs. Double-sided tape is used to hang posters, while brown packing tape secures packages, and stretchy tapes find their place in bandages. Taping materials together has become so commonplace that we rarely stop to ask, "How does it work?"

It turns out that tape is quite extraordinary. What makes it so useful in our everyday lives isn't the concept of adhesion itself, but the specific type of adhesive used. The 'stickiness' in sticky tape relies primarily on physical processes rather than chemical ones to bond.

The Science of Stickiness

The concept of adhesion predates tape. In ancient Egypt, woodworkers used a natural glue made from animal collagen. Substances like beeswax and resin have long been effective at binding materials together [source: THToC].

Before the invention of tape, glues and epoxies were used for sticking things together. However, these materials had significant downsides, especially for household use. Their messiness, permanence, and tendency to dry to a hard finish made traditional chemical-based glues less than ideal for quick, small everyday tasks.

The adhesives found in tape behave differently. They are known as pressure-sensitive adhesives (PSA) and are made from materials like silicones, acrylics, and rubbers—polymers with a tacky resin that enhances their stickiness [source: ThomasNet]. These PSAs use physical interactions, not chemical ones, to stick. This is why tape is so flexible and easy to remove—features that make it so useful.

In a pressure-sensitive bond, two processes are at play: wetting and van der Waal's forces. Wetting initiates adhesion, while van der Waal's forces strengthen it [source: Hyperphysics].

Wetting is quite straightforward. It describes how the solid adhesive in tape penetrates the material it's applied to (the substrate). The adhesive in tape is great at wetting because it has a low surface energy, meaning its molecules are highly energetic, resulting in weaker bonds. This allows the adhesive molecules to flow smoothly into the substrate's pores, even in solid form. A small amount of pressure is all that’s needed. The better the flow into the substrate, the stronger the bond.

Some adhesives become even stronger over time as their molecules infiltrate deeper into the substrate. However, right from the start, another physical effect contributes to the strength of pressure-sensitive adhesion. Van der Waal's forces, molecular attractions, come into play even before any pressure is applied to the tape.

Van der Waal's forces are weak attractions between molecules that typically lack positive or negative charges. Some neutral molecules, whose protons and electrons are unevenly distributed, can sometimes exhibit charges, referred to as dipole moments [source: Hyperphysics]. These charges, or polarities, allow them to form physical bonds with other charged molecules; they can even induce charges in nearby neutral molecules just through proximity [source: Hyperphysics].

Molecules in pressure-sensitive adhesives can demonstrate dipole moments and induce similar moments as they approach the surface molecules of the substrate. When the adhesive and substrate molecules with opposite charges make contact, they form physical bonds, enhancing the strength of the adhesion based on wetting.

Adhesion is just one part of the equation. The real appeal of adhesive tape lies in its design as much as in its ability to bond.

Turning Sticky into Sticky Tape

Each time we pull a strip of tape—whether to wrap a gift, hang artwork, temporarily fix a leaking pipe, or seal a package for shipment—we often overlook the brilliance of the tape roll itself. Specifically, how does the adhesive stick to both the backing and the substrate but not to itself?

If tape weren’t rolled up, it might be tricky to throw it in a drawer. Non-tape adhesives are typically glue, which tends to be messy and permanent. The beauty of tape lies in its roll form, making it neat, compact, and easy to handle.

Making tape follows a consistent process. All adhesive tape is made up of four key components [source: ACS].

The layers are applied in large sheets, which are then rolled up and cut into the 1-, 2-, or 3-inch-wide rolls of tape that you find in stores.

The final release coating highlights an interesting difference in the world of stickiness: adhesion versus cohesion. In adhesion, one molecule sticks to another type of molecule; in cohesion, molecules stick to themselves. Tape uses both types of bonding [source: Scientific American]. The adhesive molecules adhere to the substrate molecules, while also cohere with each other to hold together. The release coating stops the adhesive from sticking to itself, making it easy to unroll the tape.

What started as a simple masking tape, much to the delight of auto painters, has evolved into a whole industry. Adhesive tapes have wrapped blimps' metal frames to prevent corrosion, insulated a lunar lander, and assisted the Apollo 11 astronauts in making repairs to their lunar module’s fender on the moon [sources: ACS, NASA]. They secure rearview mirrors on vehicles and prevent millions of scrapbookers from losing their patience when a piece of paper is a fraction of a millimeter off [source: 3M].

Pressure-sensitive adhesives even gave birth to Post-It notes. It might not be flowing water, but it's nearly as essential.