Long-range interactions 1,-capping

Fig. 14.5 The dual-shell model for the short- and long-range interactions in nanosolid ferroelectric nanosolid, a Schematic of the high-order exchange bonds loss of an atom in a spherical nanosolid with radius K. Kc is the critical correlation radius. The Vva loss (the shaded portion) is the difference between volumes of the two spherical caps ...

If the viscous forces are significantly smaller than the surface tension (as expressed by a capillary number Ca much less than 1 Ca = U rfljL, with U being the velocity of the contact line and t] the viscosity of the liquid), the shape of a liquid drop can be reasonably well approximated by a spherical cap. Laplace pressure Fl (where Fl = 2 yi K and the curvature K = l/R for a spherical cap of radius R and thus Fl = 2 yiJR) will be able to assure the same curvature everywhere (with the possible exception of the region very close to the contact line, where long-range molecular interactions, e.g., van der Waals forces, may become important). 

On the nanoscale the shape of such droplets can deviate significantly from the macroscopic shape of a spherical cap due to the finite range of the intermolecular interactions involved. As described later, one can actually relate the macroscopic equilibrium contact angle, the character of wetting transitions, and the shape of nanodroplets to the intermolecular interactions by using, for example, classical density functional theory (DFT). But the long range of intermolecular interactions also affects the motion of droplets. In particular it can lead to lateral interactions between droplets and structures, which are absent on the macroscopic scale. 

Hostavin B-CAP from Clariant is a new UV stabiliser for polycarbonate and PET, based on a benzylidene-bis-malonate type UV absorber. It has good absorption in the high-energy range of the UV spectrum, and reduces yellowing. It does not interact with residual metal ions, and therefore does not affect either the colour or transparency of the polymer. Clariant recommends combining this UV absorber with other stabilisers for the long-term protection of polycarbonate and PET. 

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