CHARACTERIZATION OF PARTICLE COALESCENCE IN WATERBORNE COATINGS USINGATOMIC-FORCE MICROSCOPY

Atomic force microscopy (AFM) was used to image coatings formed from b lends containing various ratios of three waterborne acrylic/polyuretha ne hybrid polymers. Tapping and contact mode AFM were evaluated for th is application, and tapping mode proved to be the best method due to t he low friction forces. It was shown that when the tip and feature siz es were similar, the superposition of the tip morphology on the surfac e features in the AFM image was significant. AFM imaging of gold collo ids dispersed on mica and scanning electron microscopy of the tip were used to characterize the AFM tips. A method was developed to estimate the tip radii, in turn, the tip size was accounted for in analyzing t he dimensions of the coating surface features. The degree of particle coalescence was evaluated from the AFM images. The polymer blends were ranked according to the degree of particle coalescence; and the resul ts correlated well with other method of characterization.