Water-borne-coatings: “A major improvement lies in designing emulsifier-free emulsions”
Making water-borne coatings more resistant regarding anti-corrosion properties is not easy explains Selim Yetiş: “The root cause of the disadvantages arises from the nature of the water itself, which are very difficult to overcome.” One issue explains Yetis is the sensitivity to on on-site conditions like high humidity or low temperatures.
He also addresses the issue of problems applying water-borne coatings in multiple layers with a high film thickness. “Water is considerably more difficult to evaporate than most organic solvents due to exceptionally strong H-bonding”, he explains.
Tom Vanheertum works as Marketing Manager at Allnex.
Water-borne isociaynate free alternatives
This can lead to a number of issues like sagging or optical problems. A solution to this may be found in 2k isocyanate systems. However, isocyanates are an issue in itself. “With the new water-borne Non-isocyanate development, we think we’ve actually opened up a new path to addressing this problem” says Tom Vanheertum from Allnex.
However, there are possibilities to use water-borne coatings in anti-corrosive applications, depending on the conditions and how good the performance has to be. “At the moment, the market has to find a compromise between corrosion resistance and durability”, says Tom Vanheertum from Allnex. Typically, he explains, hydrophobic systems deliver good anti-corrosive properties since they keep water away from the metal substrate. However, “the difficulty with these polymers however is keeping them dispersed in water, and still achieving good anti-corrosion properties”, explains.
Selim Yetiş works as R&D Director at Kansai Altan.
Corrosion issues of emulsifiers
The problem with hydrophilic and hydrophobic properties is something that Selim Yetiş from Kansai Altan is also seeing as an issue. Since emulsifiers decrease water and corrosion resistance if they stay in dry film, one way could be to have them undergo some kind of transition. “We see emulsion design as the most promising area for future developments in water-borne coatings”, he says. “Another major improvement in water-borne technology lies in designing emulsifier-free emulsion technologies, and macroRAFT techniques in emulsion making”, he adds.
Depending on what you are looking for, there are solutions out there. “We will shortly be launching a new 1K water-borne acrylic system, which can easily pass a C3 standard, together with a new dispersing agent”, says Tom Vanheertum. However, for higher standards like C5 (according to ISO 12944) water-borne technology does not seem to be there yet. And even for C4 there are still issues as Selim Yetiş explains.
This article is based on a more detailed and comprehensive interview in the Euopean Coatings Journal issue 11/2019. The interview is available online for subscribers of European Coatings 360°.
International experts from the coatings industry will meat in March 2020 for the EC Technology Forum | Water-based Coatings in Berlin to discuss the latest developments and trends in water-borne coatings technology