The effect of fibrilation on the tack of pressure sensitive adhesives

The formation and growth of fibrils during debonding seems to be crucial to the peel strength and the tack of polymers to be used as pressure- sensitive adhesives. The objective of this work is to study the influence of a number of parameters such as contact force and time, surface roughness, temperature, and rate of separation on fibrilation, and to establish relations between the nucleation and growth of fibrils and the mechanical behaviour as well as the molecular structure of the adhesives. Measurements of a large number of model polymers lead to the conclusion that the average mass between entanglements, M-e, is an important factor governing fibrilation. Polymers with a high M-e above about 1 x 10(4) g/mol show fibrilation whilst materials with an entanglement length below this limit debond by an apparently homogeneous deformation with lower-energy dissipation. (C) 1998 Elsevier Science Ltd. All rights reserved.