Fig. 3

DIC images were used to document the state of particles. The here shown examples were used as the calibration pair for particle recognition, where PA6 particles were exposed to HCl, leading to their complete destruction by polymer hydrolysation. What is left after the treatment are visual marks on the epoxy layer (depressions), where particles sat. For a successful automated image analysis, particles need to be identified in pre- and post-images, while depressions need to be excluded. a: pre-treatment image with high contrast between bright particles and dark background. b: post-treatment image with depressions still recognisable as visual marks of weaker brightness. c, d: equivalent to A and B but after the manual postprocessing step