Zdrojový dokument:Scientific papers of the University of Pardubice. Series A, Faculty of Chemical Technology. 17/2011
ISSN:1211-5541
Abstrakt:
The surface properties of two sets of coated printing papers were studied by the
monitoring of the dynamic behaviour of small drop of standard liquid (water,
ethylene glycol, formamide and methylene iodide) in time region of 20 s after drop
impact on solid surface (“sessile“ drop method). The contact angle 2 formed by
a liquid drop at the three-phase boundary is a quantitative measure of the wetting
of a solid by a liquid. The usual goal of the contact angle measurement is the
calculation of surface free energy (SFE) of solid using the semi-empirical
equations including the estimation of the interfacial interaction between liquid and
solid phases. Using the “cos 2 model”, pseudo-equilibrium contact angle 2
eq,
liquid spreading rate k1 and the rate of liquid penetration k2 were evaluated.
Surface roughness was measured by profilometer and by instrument Parker Print-
Surf TM. The roughness values obtained by both methods correlated well. The
spreading rate parameter k1 decreases and the k2 parameter increases with
increasing roughness of tested papers. The topographical structure of paper
samples was studied by electron microscopy. Polar and disperse components of SFE were evaluated by means of different theoretical approaches to interphase
interactions (Owens–Wendt, van Oss, Good and Chaudhury and Wu). The SFE
calculation based on Owens–Wendt and Wu equations resulted in much higher
values of the total SFE and its polar component than the values calculated by
acido-basic approach derived by van Oss et al.