Waterborne UV Curing is focus of Philadelphia Society.

The September meeting of the Philadelphia Society featured a presentation on "Waterborne UV Curing." Nathan Stuler, of Alberdingk Boley, provided an overview on this technology, and discussed its advantages over conventional solventborne systems. The water-based UV-curing mechanism was contrasted to standard thermal drying, resulting in 100% nonvolatiles. In addition, the lack of conventional solvents used with water-based UV provides formulators with options in meeting VOC compliance, the speaker noted.

Mr. Stuler listed some advantages of using WB UV technology: low or zero VOC, instantaneous speed of cure, immediate development of film properties, and cost-effectiveness. In the liquid phase, additional benefits named were lower susceptibility to skin irritation because of the high molecular weight of polymers used; lower cost; resistance to grain lifting when applied to wood substrates since water is used as the diluent instead of reactive monomers; and formulating flexibility, which provides rheological benefits and better gloss control. In detailing the application phase, Mr. Stuler noted three additional advantages: ease of clean up; the ability to coat vertical surfaces and three-dimensional objects; and, because physical drying precedes final film cure, defects are more readily noticeable and, therefore, repairable. During the cured product phase, formulators can expect a less "plastic-like" wood pore (resulting in a lacquer appearance on wood); the ability to generate "soft-feel" finishes without the use of additives; more uniform appearance; and better adhesion due to less volume shrinkage.

[ILLUSTRATION OMITTED]

Mr. Stuler listed current areas of commerical application for WB UV systems, including wood substrates for furniture, flooring, profiles, and paper coatings; plastic substrates for automotive and electronic components; metal substrates for home siding, facades, and automotive; and leather substrates that include "soft-feel" coatings.

According to the speaker, many types of urethane chemical families exist, such as polyester, polyether, polycarbonate, and caster based backbones. Depending upon the urethane backbone, one can formulate a myriad of end properties. Acrylic and styrenated acrylic chemistry is also available for the WB UV formulator where greater exterior durability, better block resistance, and good adhesion to polyolefins can be expected cost-effectively. Blends of various chemistries are also achievable because of the unique compatibility between these resins.

In conclusion, Mr. Stuler reviewed the components contained within a typical WB UV formulation and performance properties discovered after laboratory evaluation.

--BRUCE MATTA

Philadelphia Society President-Elect