Polyurethane clear coats for plastics – high gloss protection from environmental impact

Clear top coats for plastics protect against solvents, UV-damage, dirt and scratching. In addition they can be applied to obtain certain optical effects such as excellent gloss or matting of the desired degree.

Due to their outstanding property profile, polyurethane coatings systems have set the standard for plastic coatings throughout the world. They are crosslinking at low temperatures saving energy and costs. Another reason for their success is that they can be adjusted to the flexibility of the plastic substrate, allowing them to withstand the mechanical stresses of most plastic substrates.

A selection of coating raw materials for waterborne clear coats

Waterbased dispersions:

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Bayhydrol® A 2139/2	Polyester polyacrylate copolymer	48	3.8	1850	In combination with e.g. Bayhydur® 3100 for high-gloss solvent resistant top coats
Bayhydrol® A 2290	Polyester polyacrylate dispersion	45	3.6	< 200	In combination with Bayhydur® 3100 for high-gloss, solvent and tar resistant top coats, overcoatable, good mechanical properties
Bayhydrol® A 2058	Polyacrylate dispersion	42	4.8	1000	In combination with e.g. Bayhydur® 3100 for high-gloss solvent resistant top coats
Bayhydrol® U 241	Polyester polyurethane dispersion	41	2.5	1000	Good pigment wetting, high shearing resistance
Bayhydrol® UH 2606	Polyurethane dispersion	35	-	<100	Binder for 1K plastic clearcoats
Bayhydrol® A 145	Polyester polyurethane dispersion	45	3.3	950	In combination with polyisocyanates for high-gloss two-component polyurethane hydro clearcoats with high film hardness and weather stability
Bayhydrol® A XP 2645	Polyacrylat Dispersion	43	4.5	2000	For waterbased two-component polyurethane hydro clearcoats with good chemical and weather resistance
Bayhydrol® U XP 2750	Polyurethaen Dispersion	43	3.6	1000	For clearcoats and topcoats with very good weather resistance

Polyisocyanate crosslinker for waterbased dispersions:

	Type	Solids in %	% NCO on solids	Viscosity mPas at 23°C	Characteristics
Bayhydur® 3100	HDI polyisocyanate	100	17.4	2800	Hardener for waterborne two component polyurethane systems and additive for waterborne high-quality coating systems
Bayhydur® 304	HDI polyisocyanate	100	18.2	4000	Hardener for waterborne two component polyurethane systems and additive for waterborne high-quality coating systems
Bayhydur® XP 2487/1	HDI polyisocyanate	100	20.6	5400	Cross-linker for waterborne two component polyurethane systems, developed for safe processing. Films with high chemical resistance
Bayhydur® XP 2655	HDI Polyisocyanate	100	21.2	3500	Hardener component for waterborne two-component polyurethane systems (easy mixing) and additive for high-quality waterborne coating systems
Bayhydur® XP 2759	IPDL- Polyisocyanate	70	11,0	6500	Hydrophilic crosslinker, in combination with HDI-based grades to enhance drying properties
Desmodur® N 3600	HDI Polyisocyanat (hydrophobic)	100	23.0	1200	Good chemical and weather resistance, good mechanical resistance

Find all Bayhydur® and Bayhydrol® grades in the "Product Search" section.

Some starting formulations for waterborne clear coats

RR PCO 0038e – CC	One-component polyurethane clear coat, for spraying (Bayhydrol® UH 2606)

RR PCO 0022e – CC	Two-component polyurethane clear coat, hard (Bayhydrol® A 145, Bayhydur® 304)

RR PCO 0023e – CC	Two-component polyurethane clear coat, elastic (Bayhydrol® U 241, Bayhydur® 304)

Some coating raw materials for solventborne clear coats

For one component coating systems:

	Type	Solids in %	% NCO or OH on solids	Viscosity mPas at 23°C	Characteristics
Desmolac® 2100	MDI polyurethane	100 (granules)	-	800 (30%, MEK*)	Non-reactive, for flexible substrates
Desmolac® 4340 X/iB	IPDI polyurethane	40	-	7500	Non-reactive, for flexible substrates and primer for plastics, which are sensitive to solvents, like polycarbonate.

*methyl ethyl ketone

For two component coating systems:

	Type	Solids in %	% NCO or OH on solids	Viscosity mPas at 23°C	Characteristics
Desmophen® 670 BA	Polyester polyol	80	4.4 OH	3000	In combination with Desmodur® N 75 or N 3390 for excellent films, with very good cold weather flexibility, good weathering properties
Desmophen® VP LS 2388	Polyester polyol	80	4.8 OH	3000	For high solid coatings, high gloss, good chemical and weather resistance, lightfast, high flexibility and good tar resistance.
Desmodur® N 3390 BA/SN	HDI trimer	90	21.8 NCO	550	High gloss, good chemical and weather resistance, lightfast, good mechanical resistance
Desmodur® N 75 MPA	HDI biuret	75	22.0 NCO	250	Lightfast, good chemical and weather resistance, high gloss, outstanding mechanical properties

Example of a starting formulation

RR 4822

Two component polyurethane clear coat, very elastic
(Desmophen® 670 / Desmophen® A 365 / Desmodur® N 3390)

UV/EB-curing coating raw materials

If high productivity is key while keeping VOC emissions low and surface quality high, UV/EB-curing systems provide the right solutions. Bayer MaterialScience offers a large number of urethane acrylates, polyester and polyether acrylates, unsaturated polyesters and waterbased polyurethane dispersions. Please look for product information and additional details in the "UV/EB-Technologies" section.

Some UV-curing polyurethane dispersions:

	Type	Solids in %	pH	Viscosity Flow time at 23°C	Characteristics
Bayhydrol® UV 2689/1 XP	Urethane acrylate emulsion	42.0	7.7	~ 33 sec	very good resistance to hydrolysis and cosmetics, for plastic clear coats and pigmented metalic effect coatings
Bayhydrol® UV XP 2736	Polyurethane dispersion	40.0	7.4	~ 3 sec	Flexible and tough, excellent adhesion on plastics and textiles; especially for flexible formulations and base coats

Some UV-crosslinking urethane acrylate:

	Type	Solids in %	Viskosity mPas at 23°C	Characteristics
Desmolux® U 680H	Aliphatic urethane acrylate	80 (HDDA)	29000	For hard, scratch-resistant outdoor applications
Desmolux® XP 2738	Aliphatic urethane acrylate	100	30000	Weather-stable, good resistance to chemicals and mechanical stresses
Desmolux® XP 2740	Aliphatic urethane acrylate	100	8000	Weather-sable, increases the flexibility of UV coatings for outdoor applications

Get more information on our new allophanate technology based products Desmolux® XP 2738 and XP 2740 in this paper presented at the RadTech, Oct. 2009: "Acrylated Allophanates – Low viscous alternatives for outdoor applications"

For more on clearcoats for plastic applications have a detailed look at these brochures and presentations:

	Dispersions - Products and Applications		Polyisocyanates and Prepolymers: Products and Applications
	Bayhydrol® A - designed for high Performance - engineered for Success		Resins - Polyols and Aspartics for reaction with Polyisocyanates
	Toolbox for waterborne 2K Polyurethane-Coating-Systems		UV-Systems: Products and Applications

News:	BMS CAS receives the Ringier Technology Innovation Award 2011 for Coatings Industry
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Presentation:	Bayhydrol® UV XP 2649: UV Soft Touch for industrial plastic coating applications
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Presentation:	The New Frontier: Waterborne UV Coatings for Plastics
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Presentation:	Wässrige UV-Technologie: effizient, vielseitig, umweltfreundlich und zukunftsweisen“ (german)
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Presentation:	Environmentally friendly yet high-performance: New Bayhydrol® U solvent free polyurethane dispersions for high-quality polyurethane surface coatings
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Feature:	Waterborne, highly resistant coatings for plastics - New UV-curing coating materials for mobile phones and other high-quality electronic devices