Determination of the strength characteristics of ultrathin coatings

A method for evaluation of the tensile strength and the Young modulus of th in coatings is proposed, which is based on analysis of the surface relief a nd the laws of its variation in the course of stretching of a coated sample . The samples (100-mu m-thick polyimide films) bearing a polymeric coating with a thickness of the order of 0.1 mu m were prepared by the method of pl asma activation of a flow of thermal destruction products of a solid polyme r. Stretching of the samples leads to cracking of the coating. A linear rel ationship was established between the average inverse width of the bands of cracked coating fragments and the applied tensile stress, which allows the ultimate strength (breaking stress) and the Young modulus of the coating t o be determined. The method can be used for estimation of the strength char acteristics of ultrathin coatings possessing strong adhesion to substrates.