Polyurethane primers – a solid base for a perfect plastic coating

Primers are used on many plastics to provide an initial color effect and to smooth surface irregularities caused during the production process, such as ridges, dents or molding marks. And most of all, they improve the adhesion of subsequent coatings to difficult substrates. Also, they form a protective barrier between the substrate and potentially aggressive solvents in the base coats or top coats. When it comes to selecting the binder waterborne products have become more and more important because they do not contain any aggressive substances, which could affect the plastic substrate.

A selection of raw materials for waterborne primers
Waterbased dispersions:

	Type	Solids in %	% OH on solids	Viscosity mPas at 23°C	Characteristics
Bayhydrol® U 241	Polyester polyurethane dispersion	41	6.5	1000	For waterbased two-component polyurethane primers and top coats, good pigment wetting, high shear stability and very good flexibility
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, good adhesion on different plastic substrates
Bayhydrol® UH 2606	Polyurethane dispersion	35	-	< 100	Binder for one-component water-thinnable coatings, good flow characteristics, good weather resistance, tough but elastic
Bayhydrol® UH XP 2648	Polycarbonate/ polyurethane Dispersion	35	-	< 100	For flexible, water-thinnable coatings on metal or plastic substrates like one-component metallic, one and two-component filler and topcoat systems
Bayhydrol® U XP 2750	Polyurethane dispersion	43	3.6	1000	For primers with outstanding adhesion on plastic substrates, particularly for PC and ABS

Crosslinkers for 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 or as an additive for high-quality waterborne one-component 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® 305	HDI polyisocyanate	100	16.2	6500	Hardener for waterborne two-component polyurethane systems or as an additive for high-quality waterborne one-component 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
Desmodur® N 3600	HDI polyisocyanate (hydrophobic)	100	23.0	1200	Chemical and weather resistant, lightfast, good mechanical resistance

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

Some starting formulations for waterborne primers

RR PCO 0009e-PS	One-component polyurethane primer (Bayhydrol® UH 2606)

RR PCO 0012e-PS	Two-component polyurethane primer (Bayhydrol® U 241/ Bayhydur® 3100)

RR PCO 0013e-PS	Two-component polyurethane primer (Bayhydrol® UH 2606 / Bayhydur® XP 2487/1)

RR PCO 0014e-PS	Two-component polyurethane primer Bayhydrol® A 2290 / Bayhydrol® PT 241 / Bayhydur® 3100)

RR PCO 0035e_PS	Two-component polyurethane primer (Bayhydrol® A 2290 / Bayhydur® XP 2487/1)