Self-replenishing low-adherence coatings

Low-adherence coatings are widely used today since their water/oil repellency makes them easily cleanable (a well-known example is PTFE). The low surface tension is provided by fluorine- or silicon-containing species that are present at the film surface. Low adherence coatings have already been developed via surface segregation of fluorinated species. However, it has been shown that the fluorine-enriched layer is very thin, and the coating may not sustain low adherence upon mechanical abrasion. An approach to develop self-replenishing low surface energy coatings is to distribute long perfluoroalkyl-end-capped chains relatively homogeneously in a coating network. In case of surface damage that leads to the loss of the top layers of the coating, fluorinated tails from sub-layers will be able to reorient themselves to minimize the air/film interfacial energy. In order to study the self-replenishing behavior, model polyester precursors with controlled functionality were synthesized via controlled ring-opening polymerization of e-caprolactone using perfluoroalkyl alcohol or polyol as initiators. The as-prepared precursors were cured with polyisocyanate crosslinker to obtain films with low surface energy. The fluorine depth profile and the self-replenishing behavior have been investigated. The influence of the mobility of polymer spacer and network, as well as temperature, on the self-replenishing behavior will be discussed

Low adherence coating containing polymers with low surface energy

A low adherence coating comprises: (a) a crosslinked polymeric network (N), based on a first polymer (P), (b) a low-surface-energy group (E), coupled to the network via (c) a polymeric spacer (S), having the following relationship between the native surface energies of P, E, and S (resp. sp, se, and ss,, in mN/m): se <ss <sp. The coatings have a low adherence towards different types of contaminants. A coating contained a polycaprolactone terminated with perfluorooctyl ethanol. [on SciFinder (R)

Low adherence coating

The invention relates to a coating having a low adherence towards different types of contaminants. Such a coating comprises a crosslinked polymeric network provided with an end-functionalized dangling chain, as a result of which the surface maintains its low surface energy

Absorption of water and corrosion performance of a clear and pigmented epoxy coating on Al-2024 alloy

The corrosion performance of Al-2024 substrates coated with an epoxy clear coating and a pigmented epoxy coating was investigated. The absorption of water in the pigmented coating was high compared to the clear coating. The clear coating provided a good barrier which is stable beyond 120 days of immersion in a 0.5 M NaCl solution. The shape of the Nyquist plot of the pigmented coating changed with immersion time and reveals the existence of physico-chemical processes in the coating and/or at the interface. Its impedance magnitude at low frequencies remained very high (~ 109 .cm2) after 72 days of immersion in sodium chloride solution. Both coatings exhibited good dry adhesion on Al-2024. The wet adhesion of the clear coating was poor while the stress (~ 9 MPa) required in a pull off adhesion test of the wet pigmented coating remained high

Crushing singularities in spacetimes with spherical, plane and hyperbolic symmetry

It is shown that the initial singularities in spatially compact spacetimes with spherical, plane or hyperbolic symmetry admitting a compact constant mean curvature hypersurface are crushing singularities when the matter content of spacetime is described by the Vlasov equation (collisionless matter) or the wave equation (massless scalar field). In the spherically symmetric case it is further shown that if the spacetime admits a maximal slice then there are crushing singularities both in the past and in the future. The essential properties of the matter models chosen are that their energy-momentum tensors satisfy certain inequalities and that they do not develop singularities in a given regular background spacetime.Comment: 19 page

The Essential Interactions in Oxides and Spectral Weight Transfer in Doped Manganites

We calculate the value of the Fr\"ohlich electron-phonon interaction in manganites, cuprates, and some other charge-transfer insulators and show that this interaction is much stronger than any relevant magnetic interaction. A polaron shift due to the Fr\"ohlich interaction, which is about 1 eV, suggests that carriers in those systems are small (bi)polarons at all temperatures and doping levels, in agreement with the oxygen isotope effect and other data. An opposite conclusion, recently suggested in the literature, is shown to be incorrect. The frequency and temperature dependence of the optical conductivity of ferromagnetic manganites is explained within the framework of the bipolaron theory.Comment: 6 pages, REVTeX 3.1 with 3 eps-figures. Journal versio