High capacity surfaces
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Surface of an anodically oxidized aluminium (Fraunhofer IWM Halle) |
Some applications ask for plastic surfaces with a high areal density of a functionalization.
Using anodic oxidation of high purity aluminum, nano structures can be produced on the material surface (figure 1) with dimensions in the range between 30 nm and 250 nm.
For more detail see the annual repot 2008, page 64
Such surfaces were used in cavities of an injection molding machine to produce polypropylene surfaces with the inverse structure.
Using anodic oxidation of high purity aluminum, nano structures can be produced on the material surface (figure 1) with dimensions in the range between 30 nm and 250 nm.
For more detail see the annual repot 2008, page 64
Such surfaces were used in cavities of an injection molding machine to produce polypropylene surfaces with the inverse structure.
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Surface of a flat injection molded PP using a nanostructure tool (Fraunhofer IWM Freiburg) |
The PP surface showed burls and thread-like structures. The aspect ratio is usually higher for flat surfaces than for 3D objects.
We were able to demonstrate that the surface structures are stable for at least 1000 injections. The tendency of the high purity aluminum to deformation can be reduced by an appropriate construction of the tools. A minimum pore size of 60 nm can be used to produce reliably molded parts.
We were able to demonstrate that the surface structures are stable for at least 1000 injections. The tendency of the high purity aluminum to deformation can be reduced by an appropriate construction of the tools. A minimum pore size of 60 nm can be used to produce reliably molded parts.
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Surface of a 3-dimensional injection molded PP using a nanostructure tool (Fraunhofer IWM Halle) |
Finally the surfaces undergo a chemical functionalization. As an example we used poly(ethylene imine) to introduce amino groups. Their concentration was determined using an acidic dye (Functionalized porous materials -> Functionalization with NH2 ). While on the surface of a PP film we found 0.6 nmol/cm² of basic groups, PP samples with nano structures had up to 12 nmol/cm² of basic amino groups on a flat surface and up to 5.7 nmol/cm² on the surface of 3D objects.
If this technology is combined with our surface hydrogel nano coatings (Functionalized porous materials -> Protein Compatible Hydrogel Nanofilms) the specific surface can be increased by a factor of 100 and more.
If this technology is combined with our surface hydrogel nano coatings (Functionalized porous materials -> Protein Compatible Hydrogel Nanofilms) the specific surface can be increased by a factor of 100 and more.
Collaboration with Fraunhofer IWM, Halle
Supported by the Fraunhofer MEF programme
Supported by the Fraunhofer MEF programme
