PSA Tapes are designed as following basic physical constructions...
PSA coated on both sides of a carrier protected by a release liner. Provides capability to put the same or different PSA on each side of carrier. Coating weight on each side of carrier can also be varied.
PSA coated on one side of a flexible carrier and may be protected by a suitable release liner. Used where there is only one substrate to be bonded. It is also useful for wet laminating.
There is no carrier. There is nothing to hold the adhesive together except for it's own internal strength. Also know as 'Transfer' Tape. These are used for applications where you need flexibility and stretch and for bonding to irregular surfaces.