There are single-sided and double-sided tapes.
Single-sided tapes are those products where adhesive is applied ("coated") on one side only either of the film or of the backing.
Double-sided tapes are those products where adhesive is applied on both sides of the backing; in addition to adhesive and backing, in double-sided tapes and in some single-sided tapes also there is a third component: the liner. As for Sicad tapes, the liner is usually made of siliconized paper but it can also be made of siliconized films.
In double-sided tapes, the outer side is the "free" side of the tape, whilst the adhesive side which appears after removing the liner is identified as the inner side.
Self adhesive tapes can consist of other "components" allowing their production and functionality:
- the release, an antiadhesive material applied on the side without adhesive of single-sided tapes (the "back"); practically it is a substance which makes unwinding of the tape easier avoiding backing's breaking and adhesive's transfer;
- the primer, an "anchor mean", whose function is to increase bond between adhesive and backing.
Primer and release are not always in the tape at the same time; as a matter of fact, there are tapes with the primer only (e.g. natural rubber solvent based PVC tapes), tapes with the release only (e.g. synthetic rubber BOPP tapes), tapes without release nor primer (e.g acrylic BOPP tapes) and tapes where there are both of them (e.g. natural rubber solvent based BOPP tapes).