Testing for softening temp of thin coatings - by determining the capacitance change beneath an indenter

摘要

The softening temp. of a thin (non-conductive) coating applied to the surface of a conductive substrate is determined by applying an indenting foot with controlled force upon the surface of the coating and monitoring the electrical capacitance of the foot/coating/substrate. The onset of softening is indicated by a sudden increase in the capacitance of the system. Method is used for detg. the softening point of thermoplastic coatings, and is more sensitive than simple mechanical displacement transducer test systems, applicable to thinner coatings, i.e. down to 1-2 mu.