Measurement of adhesion of thin polymer coatings by indentation

Abstract

A microindentation technique was developed to measure the adhesive shear strength of thin polymer coatings on glass substrates. Indentation-induced debonding of the coating was observed to occur under three different conditions: Type I was with the deformations underneath the indenter being essentially elastic; Type II was with the deformations underneath the indenter being plastic; and Type III was after the indenter penetrated the substrate. Stress analyses to calculate the interfacial shear stress for the indentation-induced debonding of thin coatings are presented for the three types of debonding. All three stress analyses are based upon the linear, elastic analysis of the contact stresses arising from indentation of a soft coating on a rigid substrate. These analyses provide a basis for using controlled indentation debonding as a quantitative measure of the interfacial shear strength of thin coatings to rigid substrates.