Use of the indentation technique for studying delamination of polymeric coatings

Abstract

The indentation technique is unique in being able to measure the two fracture parameters (interfacial strength and fracture energy) that are required to fully specify the adhesion of polymer coatings. The method is simple to use, requires no special sample size or geometry, and can be used on extremely thin, fragile films. The indentation technique consists in loading a coated surface with an indenter until a critical load is reached to initiate an interfacial crack. Further loading causes the interfacial crack to grow in a stable fashion. Models are discussed to calculate the interfacial shear strength of the coatings from the indenter load that initiates debonding and the interfacial fracture energy from the indenter load vs. debond crack size measurements. Indentation results from four commercial polymer coatings on glass are discussed.