Pressure sensitive adhesives are tacky materials used to bind flat objects together and are activated by light pressure. They do not require the use of heat or solvents to form a viscoelastic bond, but rather a push of the finger or hand. They are used with or without release paper, and are sometimes coated on foil or plastic as well.
Pressure sensitive adhesives require no physical or chemical reaction during the bonding process, and they adhere to almost any surface including wood, paper, metal and plastic. However, they do not perform as polyurethane or silicone adhesives do, because they lose tactility in low or high temperatures. It is not meant to be permanent as the tougher adhesives are.
There are three main types of pressure sensitive adhesives. The first is called hot melt. This adhesive is quite moldable and often used in metal and wood working as well as car repair. Hot melt PSA is often applied with a glue gun. PSA glues are runnier than hot melt, and set almost instantly. They come in aerosol or liquid form and are used in the electric, industrial and medical industries.
Perhaps the most popular type of pressure sensitive adhesive is PSA tape. This tape withstands friction and moderate temperature change well, and is used to bind two flat surfaces together. The adhesive is coated on fabric, metal or plastic. Other pressure sensitive adhesive products include post-it notes, notepads, automobile trim, foil tape for duct work, sound and vibration dampening film, masking tape, price labels, band aids and athletic tape.
The adhesives themselves are made out of non-crosslinked rubber, styrene copolymers or acrylic. A rubber based adhesive, whether natural or synthetic, will be highly flexible and elastic. Styrene copolymer adhesives are commonly used to make hot melt adhesives while acrylic PSA is environmentally friendly and sets fast. Pressure sensitive adhesive products are designed with different bond styles and may be semi-permanent or repositionable.
Permanent pressure sensitive adhesives are not actually permanent, but as close as the type of adhesive comes to it. Therefore, it must be carefully applied because once it has bonded to a surface, it cannot be removed easily. A permanent PSA will set and dry almost instantly. These products keep tactility for years and can last through many different conditions. They are mostly used for industrial applications.
A non-permanent PSA is commonly found around the home or office. This type is usually coated to a material, and while still providing adequate tact, may be relocated if needed. Both types of pressure sensitive adhesives can peel off without damaging the surface or leaving a visible layer of glue, which is why the permanent version is not literally permanent.