| Summary: |
Inorganic fillers (metal oxides included) have been traditionally used in organic coatings, conferring improved mechanical (tensile strength, hardness, abrasion resistance, etc.) and physicochemical properties (thermal stability thermal and electrical conductivity, diffusion-barrier effects, etc.). In recent years, the ability to produce inorganic fillers in nano-sized dispersible dimensions has attracted new attention over an otherwise well established field. Indeed, the performance of the inorganic-organic composites is optimized when the fillers are present in dimensions below 100 nm (i.e., within the "nanoparticle" range). However, this is only effective if the materials are uniformly dispersed throughout the coating film: This brings out the issue of compatibilizing the inorganic particles (hydrophilic) towards the organic matrix (hydrophobic), in order to promote the disaggregation and dispersion of the particles. This can be achieved by surface modification treatments. These may even allow for covalent bonding between the filler and the polymer.
This project intends to look into the use of different commercially available nano-sized metal oxides for improving specific properties of organic coatings. Different surface modification treatments will be tested and compared in terms of procedure complexity and cost, effectiveness of surface modification, facilitation of deagglomeration/dispersion at the time of incorporation in the organic matrix and performance of the final composite coating obtained. Information collected from recent literature will be used in order to compile a systematic and comprehensive approach to the several techniques applicable.
One of the coating systems adopted here as a reference is the epoxy resins used for corrosion resistant applications. The cured epoxy polymer forms a densely cross-linked thermoset, which constitutes an effective barrier to oxygen diffusion and is therefore as excellent protection for metal surfaces  |
Summary
Inorganic fillers (metal oxides included) have been traditionally used in organic coatings, conferring improved mechanical (tensile strength, hardness, abrasion resistance, etc.) and physicochemical properties (thermal stability thermal and electrical conductivity, diffusion-barrier effects, etc.). In recent years, the ability to produce inorganic fillers in nano-sized dispersible dimensions has attracted new attention over an otherwise well established field. Indeed, the performance of the inorganic-organic composites is optimized when the fillers are present in dimensions below 100 nm (i.e., within the "nanoparticle" range). However, this is only effective if the materials are uniformly dispersed throughout the coating film: This brings out the issue of compatibilizing the inorganic particles (hydrophilic) towards the organic matrix (hydrophobic), in order to promote the disaggregation and dispersion of the particles. This can be achieved by surface modification treatments. These may even allow for covalent bonding between the filler and the polymer.
This project intends to look into the use of different commercially available nano-sized metal oxides for improving specific properties of organic coatings. Different surface modification treatments will be tested and compared in terms of procedure complexity and cost, effectiveness of surface modification, facilitation of deagglomeration/dispersion at the time of incorporation in the organic matrix and performance of the final composite coating obtained. Information collected from recent literature will be used in order to compile a systematic and comprehensive approach to the several techniques applicable.
One of the coating systems adopted here as a reference is the epoxy resins used for corrosion resistant applications. The cured epoxy polymer forms a densely cross-linked thermoset, which constitutes an effective barrier to oxygen diffusion and is therefore as excellent protection for metal surfaces. However, these coatings show deficiencies, mainly in terms of resistance to abrasion (associated with wind erosion, for instance) and resistance to UV exposure (which causes chalking due to polymeric decomposition). A combination of properly compatibilized nanometric metal oxides may improve significantly different aspects of the coatings performance.
Another reference system are the architectural coatings based on acrylic or acrylic-styrenic water-based emulsions. Once again, a metal oxide filler may improve relevant properties of the material, but this implies that the nanoparticles become uniformly dispersed throughout the coating film, after coalescence of the organic latex. This is only possible if the inorganic nanoparticles are incorporated into the emulsionated organic phase at the time of polymerization. Otherwise, segregation will occur, leading to aggregation and ineffectiveness of the filler in the final application. Surface modification is, again, paramount in order to allow for the compatibilization of the nano-filler with the organic medium |