What is Adhesive Tape?
Adhesive tape (a.k.a. pressure-sensitive tape, PSA tape, self-stick tape or sticky tape) consists of a pressure-sensitive adhesive coated onto a backing material such as paper, plastic film, cloth or metal foil.
Some tapes have removable release liners that protect the adhesive until the liner is removed. Some have layers of adhesives, primers, easy release materials, filaments, printing, etc. made for specific functions.
Pressure-sensitive adhesives (PSAs) do not require water, solvent or heat activation to bond to materials such as paper, plastic, glass, wood, cement, and metal.
PSA tapes are tacky at room temperature in dry form, and they adhere firmly to a variety of surfaces and require only the application of a finger or hand. Technically speaking, that’s a bonding pressure of 14.5 – 29 psi =^ 10 – 20 N/cm² or greater.
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A Brief History of Tape
The history of stickiness didn’t start with tape. It’s credited to the bees. Or rather, woodworkers in ancient Egypt who used glue made from natural, viscous substances like beeswax and resin to hold materials together.
In modern times before tape, glues and epoxies did most of the sticky work. But they had serious drawbacks, especially in household use. Messiness, permanence, and drying to a hard finish all made traditional glues less-than-ideal.
It wasn’t until 1925 that adhesive tape, as we know it today, was invented.
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What Makes Tape Stick?
While the adhesive used on pressure-sensitive tapes might seem alike – they are all tacky, adhere well, and resist stresses – they are actually quite different. There are pros and cons for each tape type, be it rubber/resin, synthetic rubber, acrylic, and silicone-based adhesives.
Rubber/Resin is the oldest type of adhesive based on natural rubber, but it needs a resin to make it into an adhesive.
For many jobs, rubber/resin adhesives offer many advantages:
- It is often a less expensive adhesive.
- It has an initial high tack, as opposed to acrylic which needs time to cure.
- It sticks well to many different surfaces, including some hard-to-stick-to materials.
- Rubber-based adhesives provide highly flexible bonds and are usually based on butadiene-styrene, butyl, polyisobutylene or nitrile compounds.
- It can be formulated to adhere at colder temperatures, but there is a limit, and rubber/resin adhesives have limitations at higher temperatures in its basic form.
- Epoxy resins exhibit high strength and low shrinkage during curing and are known for their toughness and resistance to chemical and environmental damages.
When it comes to disadvantages, rubber/resin’s main weakness is that both the rubber and the resin are prone to oxidation from the air. Therefore, exposure to ultraviolet light from the sun and other light sources can break down in the heat.
Synthetic Rubber can be used in place of natural rubber. Offering much higher adhesion and shear resistance than natural rubber-based adhesives; as a result, it is very good for sealing packages and cartons.
Acrylic Adhesives Most of the weaknesses of rubber/resin adhesives are overcome by a single component of pressure-sensitive adhesive based on “acrylic” chemistry. Acrylic is colourless and is stable to oxidation and exposure to ultraviolet light. The stability to oxidation can give an acrylic adhesive tape many years of protection against ultraviolet light. However, it is more expensive – about twice as much as rubber/resins; it’s not quite so good as natural rubber on harder-to-adhere surfaces, and it needs significant time to cure.
Silicone-based Adhesives give many years of service life. Like acrylics, silicone can be used against the skin, so it has many medical applications as well as uses in the electrical industry where the temperature is a challenge (e.g., jet engines). Silicone adhesives and sealants have a high degree of flexibility and are resistant to very high temperatures. However, silicones are the most expensive adhesives of all, typically twice as much as acrylics.