A pressure-sensitive adhesive (PSA) is a polymeric material applied between two layers to form a bond with the desired cohesive strength upon applying light pressure.1 The ability to form a bond and resist debonding from a substrate determines whether a particular adhesive is appropriate for an application. Commercial PSAs are complex mixtures of polymers, copolymers, tackifiers, stabilizers, etc., designed to provide the required performance for a variety of adhesion applications.
PSAs are highly viscoelastic materials, and their mechanical properties are strongly dependent on strain rate or frequency. The viscoelastic behavior of PSAs is directly related to their performance. If we consider the mechanical response in terms of the storage modulus G' for a typical natural rubber-based PSA as a function of frequency. The storage modulus represents the elastic deformation of a material and is a measure of the hardness at a given temperature and frequency.
For a good PSA with high cohesive strength, the storage modulus G' at room temperature has a value of 5x104 to 2x105 Pa.