Topcoats and clear coats – now self-healing possible

Outstanding properties regarding gloss, flow characteristics as well as high mechanical and chemical resistance contribute to the growing success of one- and two-component polyurethane systems compared to conventional thermosetting-acrylic (TSA) coatings. Today, environmentally friendly waterborne polyurethane coatings are used for automotive finishing as well. Bayer MaterialScience has developed high solids und super high solids for environmentally friendly polyurethane coating systems which meet the highest standards of the automotive industry regarding scratch and weather resistance. Bayer MaterialScience offers Bayhydrol® / Bayhydur® combinations for two-component systems, as well as Bayhydur® BL- and Bayhytherm®-grades for one-component stoving systems. Our experts will gladly assist you if you are interested in this technology.

Polyurethane coatings offer a number of inherent advantages due to their unique chemistry:

High reactivity and complete crosslinking even if cured at low temperatures
Good chemical and weather resistance
Hardness, mechanical resistance and elasticity due to their urethane / urea structure
Hydrogen-bonds allow thermoplastic flow properties and release internal stresses. Therefore they promote the "self-healing" of superficial scratches
Good compatibility with primers
High solids content / low VOC content
Great optical properties – High gloss or wet look

OEM Polyurethane clear coats
A polyurethane clear coat for OEM applications is the reaction product of an isocyante with an acrylate polyol. The subsequent stoving process at 130-140°C lasts about 30 minutes, even though lower temperatures would still allow a complete reaction, so the coating is not sensitive when it comes to the strict maintenance of the stoving conditions. Polyurethane clear coats can be applied to a large variety of primers. They can be formulated as high solids and low VOC coatings.

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Feature: Polyurethane raw material for self-healing coatings
The latest developments at Bayer MaterialScience are raw materials for self-healing coatings. The use of Desmodur® XP 2679 makes it possible to produce chemically resistant coatings, which have short drying times and which are very flexible, but very scratch resistant at the same time.

This is the underlying concept: Mechanical stresses like for instance brushes in a car-wash do not cause this type of polyisocyanate to form micro cracks. Instead it shows plastic deformation. When the coating surface is exposed to higher temperatures it generates a so-called “reflow-effect”.

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Waterborne two-component polyurethane clearcoats for automotive OEM coatings

Waterborne two-component polyurethane clearcoats now provide an alternative to solventborne two-component polyurethane systems. The strict demands made by the automotive industry are met in nearly all respects by hardeners based on aliphatic polyisocyanates in both hydrophobic and hydrophilic form.

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Have a look at this additional information about raw materials for top coats and clear coats:

Brochure:	„On the Road to Improved Scratch Resistance“

Article::	„Kleine Kratzer in Auto's Haut heilen bald von selbst“ (German only)

Article::	„Mit Bravour durch die Tortur“ (German only)

Presentation:	„Fast drying 2K waterborne clearcoat“

Article:	Waterborne from the ground up

Article::	„Shining Prospects for two-component polyurethane clearcoats“