Nanocoat system

The manufacture of a nanocoating varies not so much in the processes, but rather in the binder that is utilized. As a rule, the binders used in industrial coatings have an organic structure. But inorganic binders are also utilized in certain applications. Their advantage is in their hardness and chemical durability. But because of their serious drawbacks, including difficult ap plication and brittleness after hardening, these coating materials do not have an extensive field of application.

In nanotechnology-based coatings, the so-called inorganic-organic hybrid polymers come into application. These new binders are a mixture of organic and inorganic binders and bring together numerous advantages from both types of binder. As the nanocoating cures, the inorganic particles begin to form a glasslike network with cross-linked organic elements.

The fundamental chemical reaction behind the manufacture of nanocoat-ings is based on the sol-gel process. This process frequently utilizes silicon-organic compounds, the so-called silanes. The synthesis of these binders is achieved by the hydrolysis of alkoxysilane. In this case study, the product Dynasylan® Glymo from Degussa was utilized. This part of the reaction leads to the formation of the inorganic part of the binder.

At the same time the formation of the organic part of the binder takes place. Organic side chains on the silane compounds undergo reaction to organic chains. As this inorganic-organic network forms, the coating hardens.

The finish condition of the coating, however, remains as it was before hardening. The binder is available as a low-viscosity colloidal suspension, whose particles have a diameter of 40-50 nm. The solvent, at this point, contains unreacted silane, silanol, and partially formed polysiloxane. This colloidal system is chemically in the so-called sol state; followed, after application and hardening of the coating, by the gel state. The entire process is therefore referred to as the sol-gel process (Wagner o.J.).

Base data and assumptions: Summary life cycle assessment data from the study by Harsch and Schuckert (1996) provided the base data for the four existing surface coating technologies. Since no quantified data exists for the primary materials in the nanocoating, specifically for the silane that is used, the data from the dual-component coating was also used for the nanocoating and multiplied by a "safety factor" of 1.5. The base data utilized for each 1 kg of applicable coating are provided in the appendix (Table 43).

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