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In dieser Arbeit sollen ausgehend von einem Modellsystem notwendige Modifizierungen in Bezug auf die Zusammensetzung des Beschichtungsmaterials zum Erreichen einer abriebfesten, wasser- und chemikalienbeständigen Beschichtung auf Basis des Sol –Gel -Prozesses für PMMA untersucht werden. Zur Erzielung hoher Abriebbeständigkeit soll der Einfluss nanoskaliger Partikel auf die Abriebbeständigkeit untersucht werden. Das Auslaufverhalten des Wassers bzw. die Reinigungsfähigkeit der Wanne soll durch eine niedriege Oberflächenenergie erreicht werden, wozu der Einbau perfluorierter Silane in die Kompositmatrix untersucht wird. Im Anschluss soll eine Anpassung des Systems an die Prozesstechnik des Vakuumverformens durchgeführt werden. Dazu ist sowohl der Aufbau und die Konzeption einer Labortiefziehanlage, wie auch Untersuchungen zur kontrollierten Polymerisation des Ausgangssystems notwendig. Das Ziel ist die Entwicklung eines tiefziehfähigen abriebfesten Beschichtungssystems, welches sich exemplarisch an einer Labortiefziehanlage verformen und aushärten lässt.

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In dieser Arbeit sollen ausgehend von einem Modellsystem notwendige Modifizierungen in Bezug auf die Zusammensetzung des Beschichtungsmaterials zum Erreichen einer abriebfesten, wasser- und chemikalienbeständigen Beschichtung auf Basis des Sol –Gel -Prozesses für PMMA untersucht werden. Zur Erzielung hoher Abriebbeständigkeit soll der Einfluss nanoskaliger Partikel auf die Abriebbeständigkeit untersucht werden. Das Auslaufverhalten des Wassers bzw. die Reinigungsfähigkeit der Wanne soll durch eine niedriege Oberflächenenergie erreicht werden, wozu der Einbau perfluorierter Silane in die Kompositmatrix untersucht wird. Im Anschluss soll eine Anpassung des Systems an die Prozesstechnik des Vakuumverformens durchgeführt werden. Dazu ist sowohl der Aufbau und die Konzeption einer Labortiefziehanlage, wie auch Untersuchungen zur kontrollierten Polymerisation des Ausgangssystems notwendig. Das Ziel ist die Entwicklung eines tiefziehfähigen abriebfesten Beschichtungssystems, welches sich exemplarisch an einer Labortiefziehanlage verformen und aushärten lässt.

Novel corrosion resistant hard-coatings for metal surfaces

Using the sol-gel process, novel inorganic-organic composites (Ormocers) were synthesized. BY controlled hydrolysis and condensation of an epoxy modified alkoxide, a propyl modified alkoxide and an aluminum alkoxide in the presence of fluoride ions, stable sols can be produced. Theses can be applied by conventional coating techniques (e.g. spray-, spin-, dip-coating) on metal surfaces (Al, Zn, Mg) and cured thermally. The high corrosion inhibitant properties are explained by a special metal/coating interface. The transparent coatings show good adhesion, corrosion protection and a high wear resistance avoiding chemical pretreatment (e. g. chromating). These new coatings open a wide field of applications

Novel ormocers and nanomers for coatings

Nanoparticles produced by a microemulsion for a controlled growth precipitation technique (ZrO2, AlOOH) have been surface modified and incorporated into inorganic/organic composite matrices made from epoxy or methacryloxy silanes. For this reason, the nanopowders have been surface modified with carboxylic acids in order to obtain full dispersibility necessary for high optical quality coatings. ZrO2 was used for obtaining high refractive index coatings. By adjusting an appropriate zeta-potential the particles in a not fully cross-linked matrix have been upconcentrated electrophoretically to obtain graded index optical lenses. Methacryloxy grouping containing particles have been used for the preparation of UV curable hard coatings containing particles have been used for the preparation of UV curable hard coatings containing AlOOH. siO2 and TiO2 particles allow the fabrication of antireflective hard coatings on plastic surfaces by UV curing methods

UV curable hard coatings on plastics

A photochemically curable transparent hard coating material has been developed to improve the wear resistance of organic polymers. Methacrylate functionalized silanes and nanoscaled boehmite particles were used for the preparation of the UV curable hard coatings by the sol-gel technique. The inorganic network is formed as a result of the controlled hydrolysis and condensation of the methaclyloxysilanes in the presence of nanoparticles (particle size: 15 nm). The hydrolysis and condensation of the methacryloxy silane, for two hours in presence of boehmite nanoparticles (43 wt.%), at 100°C leads to a degree of condensation of 80% of the inorganic network, as determined by Si-29-NMR spectroscopy. The organic network is formed by photoinitiated polymerisation of the methacrylic-functions in only a few minutes, using UV light from a Hg high pressure lamp. Transparent coatings on plastic substrates (PC, PMMA) were produced by spray coating with good optical quality and thicknesses of several micrometers. The transparent coatings show excellent adhesion on PMMA and PC (GT/TT = 0/0, DIN 53151), even without using primers, and also good abrasion resistance after the Taber abraser test with haze values of 10% after 1000 cycles (CS 10F rolls, 5,4 N, DIN 52347). The water exposition test (65°C, deionized water) and the Suntest, without using filters, did not result in any crack formation, loss of adhesion or yellowing within the test period of two weeks

Nanoscaled filled sol-gel hybrid materials for powder coatings

The sol-gel process has been applied for the synthesis of inorganic-organic powder materials. For this purpose, low reactivity and, for reasons of comparison, nanoscaled sol-gel precursors and nanoscaled silica filler were used to synthesize a low molecular weight inorganic-organic composite which was meltable between 85°C and 100°C and curable at temperatures of 150°C - 200°C. The powders were used for electrostatic coating of aluminum sheets. The resulting coatings of the unfilled system exhibited excellent mechanical properties, e.g. a high abrasion resistance (weight losses between 6 mg and 10 mg per 1000 cycles by taber abrader test (ASTM D1044)) and high values for hardness (universal hardness (DIN 55676): 150 N/mm2). The hardness of the materials was increased up to 210 N/mm2 by the addition of silica, while the abrasion resistance remained unaffected

Aqueous sol-gel derived nanocomposite coating materials

Sol-gel reactions, in general, have to take place in organic solvents in order to control the hydrolysis and condensation reaction. This leads to drawbacks in applications, since the organic solvent vapor concnetration has to be controlled for example in ocoating applications for environmental, health or security reasons. For this reason, a reaction route has been developed to produce coating precursors stable against water as solvent. To achieve this, conventional electrostatically stabilized sols obtained either by hydrolysis and condensation or commercially availabe sols (e.g. SiO2 sols) have been surface modified to reduce the particle-to-particle interaction and electrosterically stabilized precursors compatible to water have been obtained. By use of alkoxy silanes as surface modifiers, water-dispersable nanoparticulate liquid coating systems have been prepared, for example, with boehmite, SiO2 or TiO2 as nanoparticles to be crosslinked after coating thermally by inorganic condensation and organic condensation or polymerization reactions. Thus, aqueous sol-gel coating systems have been prepared with EtOH contents below 5%. In the paper, the basic reaction as well as material properties will be discussed