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.


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”.

Have a look at this Flyer

This video (1:40 min.) might also be of interest to you.

Reflow effect

Read also our press release on the "i-mode", a concept car being developed in cooperation with Hyundai
"The bodywork of the "i-mode" shimmers in a stylish silver metallic color called "Topaz Silver". In fact, the coating system used for Hyundai's concept car marks the premiere of a two-component polyurethane topcoat based on new raw materials from Bayer MaterialScience. The special thing about the vehicle's finish is its extreme scratch resistance and its self-healing properties." .... more

Examples of Polyisocyanates for Automotive Clear Coats

	Type	Solids in %	% NCO on solids	Viscosity mPas at 23°C	Characteristics
Desmodur® N 3390 BA	HDI trimer	90	21.8	500	High gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3600	HDI trimer	100	23.0	1200	For High Solid coatings, high gloss, good chemicals and weather resistance, lightfast, good mechanical resistance
Desmodur® N 3900	HDI polyisocyanate	100	23.5	730	Hardener for weather resistant coating systems. For High solid coatings for automotive refinish, large vehicle finishing and plastic coatings
Desmodur® XP 2679	HDI polyisocyanate	80	19.3	500	For self-healing coatings, lightfast, weather resistant, scratch resistant
Desmodur® Z 4470 BA	IPDI trimer	70	17.0	600	Hard, high gloss, good chemical and weather resistance, lightfast, good mechanical resistance, for combination with Desmodur® N
Desmodur® BL 3575/1 MPA/SN	HDI polyisocyanate	75	14.0 bl. NCO on solids	3600	Good chemical and weather, lightfast, very thermo-stable
Desmodur® PL 350, 75%MPA/SN	HDI polyisocyanate	75	14.0 bl.NCO on solids	4300	In combination with polyol components, suitable for lightfast stoving coating systems

Some suggested starting formulations

RR 4210	Two-component polyurethane clear coat, good chemical resistance (Desmodur® N3390 BA / Desmophen® A 665 BA/X)
RR 4211	One-component polyurethane clear coat (Desmophen® A 870 BA / Desmodur® VP LS 2253/1)
RR 4212	One-component polyurethane clear coat (Desmophen® A 870 BA / Desmodur® VP LS 2253/1)

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::	„Total concept for waterborne 2K polyurethane clear coats for automotive finishing“
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“