Durable hydrophobic structured surface
The present invention relates to a scratch-resistant micro- and/or nanostructured surface comprising a plurality of micro-scale and/or nano-scale surface elements, said surface being essentially unchanged when being subjected to 10 rubbing cycles according to A.A.T.C.C. test method 8-1972 using a cotton cloth and a total stamp weight of 300 g, and comprising a polymeric material having 1) an elongation at break of at least 10%, 2) an irreversible relative plastic deformation (permanent set) of less than 2% and a 3) a tensile strength of at least 5 MPa. The present invention furthermore relates to a hydrophobic micro- and/or nanostructured surface comprising a plurality of micro-scale and/or nano-scale surface elements and having a static contact angle against water of at least 90, said surface comprising a polymeric material having 1) an elongation at break of at least 10%, 2) an irreversible relative plastic deformation (permanent set) of less than 2% and a 3) a tensile strength of at least 5 MPa.
1. A hydrophobic micro- and/or nanostructured surface comprising a plurality of micro-scale and/or nano-scale surface elements and having a static contact angle against water of at least 90°, said surface being essentially unchanged when subjected to 10 rubbing cycles according to A.A.T.C.C. test method 8-1972 using a cotton cloth and a total overlying weight of 300 g, said surface comprising a polymeric material having
1) an elongation at break of at least 10%,
2) an irreversible relative plastic deformation (permanent set) of less than 2% and a
3) a tensile strength of at least 5 MPa,
wherein the polymeric material is obtained by curing a UV- or electron beam curable precursor comprising
a) at least 60 weight % of one or more crosslinkable oligomer and/or polymer compounds selected from a group comprising polyurethanes, polyacrylates, epoxy acrylates, silicone acrylates, and polyether acrylates,
b) 2-40 weight % of one or more reactive diluents selected from a group of UV-curable monomers containing one or more acrylate, methacrylate or vinyl groups,
c) 0.2-5 weight % of one or more hydrophobic additives selected from a group of additives comprising silicones, fluorochemicals and long-chain alkyl compounds, and
d) 0-5 weight % of one or more photoinitiators.
2. Surface according to claim 1 comprising a plurality of micro-scale and, optionally, nano-scale surface elements and having a static contact angle against water of at least 130°.
3. Surface according to claim 1 wherein the polymer material when provided as an unstructured surface has a static contact angle against water of at least 70°.
4. Surface according to claim 1 wherein the hydrophobic additives are selected from a group of additives comprising silicones, fluorochemicals and long-chain alkyl compounds, which contain ethylenically unsaturated groups such as acrylate groups, methacrylate groups or vinyl groups.
5. Surface according to claim 1 wherein the polymeric material comprises one or more additives selected from a group comprising pigments, dyes, colorants, rheology agents, levelling agents, anti-skin agents, UV stabilizers, anti-oxidants, and anti-foam additives.
6. Composite article comprising a surface according to claim 1 wherein the surface is attached to a substrate selected from a group of substrates comprising glass, polymers, metals, wood, concrete, and stone.
7. Method of preparing a hydrophobic micro- and/or nano-structured surface comprising a plurality of micro-scale and/or nano-scale surface elements, said method comprising the steps of
(i) providing a tool surface comprising a plurality of micro- and/or nano-structured surface elements forming the negative of the structured surface, and
(ii) replicating the structured surface from the tool surface by applying a UV- or electron beam curable precursor of a polymeric material onto the tool surface, radiation curing the precursor, and removing the replicated structured surface from the tool surface,
wherein the precursor is selected to provide upon curing a polymer material having
1 an elongation at break of at least 10%,
2 an irreversible plastic deformation (permanent set) of less than 2%, and
3 a tensile strength of at least 5 MPa, and
wherein the structured surface has a static contact angle against water of at least 90°, said surface being essentially unchanged when subjected to 10 rubbing cycles according to A.A.T.C.C. test method 8-1972 using a cotton cloth and a total overlying weight of 300 g, and
wherein the UV- or electron beam curable precursor comprises
a) at least 60 weight % of one or more crosslinkable oligomer and/or polymer compounds selected from a group comprising polyurethanes, polyacrylates, epoxy acrylates, silicone acrylates, and polyether acrylates,
b) 2-40 weight % of one or more reactive diluents selected from a group of UV-curable monomers containing one or more acrylate, methacrylate or vinyl groups,
c) 0.2-5 weight % of one or more hydrophobic additives selected from a group of additives comprising silicones, fluorochemicals and long-chain alkyl compounds, and
d) 0-5 weight % of one or more photoinitiators.
8. Method according to claim 7 wherein the UV- or electron beam curable precursor is supplied continuously to the tool surface, and the replicated structured surface is continuously removed from the tool surface.