Polyurethane coatings are the perfect solution in many wood coating applications
There are numerous reasons for the popularity of polyurethane coatings for wood applications. One is that their high level of quality and their perfect fit with the natural properties of wood. They combine outstanding resistance to solvents and chemicals with unique toughness and flexibility. It is possible to formulate both clear coats and - because of their good pigment wetting properties - pigmented coatings, which yield high-gloss, high-bodied films with excellent flow properties. The films have outstanding mechanical properties and provide the ideal balance of hardness and flexibility, even at low temperatures. Good scratch resistance is also a feature of polyurethane coatings.
Technology
Polyurethane-Systems for wood coating
1K Systems
2K Systems
Poly-Isocyanate
Polyol
Solvent based
Desmodur® E
Desmodur® L, IL, HL, Desmodur® N
Desmophen®
Waterbased
Bayhydrol®
Bayhydur®
Bayhydrol®
Waterbased and UV-curing
Bayhydrol® UV
High Solids
Desmodur® N
Desmophen® NH
(=Polyaspartics)
UV-curing Urethane Acrylates
Desmolux®
Variable property profiles
The second reason is the high variability of the property profile of polyurethane coatings. The coating system can be tailored for a specific application by varying the molecular structure of the soft segments, the distribution and length of the hard segments or the molecular weight and degree of chain branching. This can be done with the choice of the suitable polyisocyanate and polyol components.
Polyurethane coatings offer a broad variety of perspectives for the future. Based on the well established polyurethane chemistry highly efficient and environmentally friendly alternatives are available:
One and two-component solventbased systems based on highly branched polyester polyols and crosslinkers of the Desmodur® L, IL, HL, and N range set standards for scratch resistant and chemically resistant wood coatings.
Waterborne one and two-component polyurethane coatings consisting of aqueous dispersions, in many cases combined with a waterdispersible polyisocyanate (Bayhydrol®range with their suitable reaction partners Bayhydur®).
Waterborne UV curing polyurethane dispersions containing acrylic double bonds which can in addition be crosslinked by radical polymerisation to achieve high quality coatings with an efficient process. (Bayhydrol® UV range). See also Dual cure process.
Urethane acrylates offering outstanding performance and high productivity (Desmolux® range).
The objective of the development at Bayer MaterialScience is to achieve the property level of conventional polyurethane coatings with low VOC technologies. A basic consideration was that properties as well as application and drying parameters should be maintained or even improved in comparison to solventborne systems.
Bayer MaterialScience offers a wide variety of suitable raw materials and building blocks for the formulation of low VOC wood coatings. They can be applied as spray, brush-, roller- or curtain coating, including those processes where overspray is avoided and high application efficiency is achieved.
