Coatings World - January 2011

Redefining Surface Coating
Theory and Technology

Researchers are looking to nature to help them create a new generation of coatings.

by Sean Milmo
European Correspondent
milmocw@rodpub.com

Smooth coatings surfaces have traditionally been considered to be best for showing color and for functions like aerodynamics and anti-adhesion. Now results in R&D projects are demonstrating that rough, structured surfaces may be in many circumstances a better option.

Many of these surfaces are already present in nature. So the objective of researchers and developers of coatings has been to mimic biology.

Universities and research institutes and producers of coatings and coatings materials in Europe are beginning to commercialize the outcomes of years of R&D into the biomimetics or mimicking of biological surface structures. The development phase of a lot of the research has been accelerated by advances in nanotechnology, which have enabled natural processes to be reproduced with the help of nanoparticles and materials.

As a result smooth and completely flat coating surfaces may no longer be valued quite so highly as before in some sectors of the market.

However a major challenge facing the developers of the new coatings is ensuring that the creation of one property does not sacrifice another, such as improved aerodynamics diminishing the visual appeal of a vehicle.

“We are at a stage with some innovation
projects in which we know the concept behind
a new coating structure works because it pro-
vides a new function,” said an R&D director at
one research-oriented European coatings com-
pany. “But since it lowers the overall perform-
ance of the product we’re having to find another
category of coating to apply it to.”
One of the latest research initiatives in the
development of coating structures in Europe is a
Swiss-backed project led by Clariant, a major
producer of coatings materials, and by Zurich
University of Applied Sciences (ZHAW). It also
involves the research foundation Gebert Ruef
Stiftung, the Swiss Federal Office of Energy
(SFOE), and the Hamburg-based RETC Re-
newable Energy Technology Centre.

Clariant will be providing its expertise in polymer production and development to help commercialize R&D work by ZHAW’s School of Engineering, which has been working on surface polymers including those with hydrophobic and oleochemical properties with anti-adhesion and easy-to-clean functions.

ZHAW’s researchers have been investigating the antifreeze proteins (AFPs) possessed by plants, insects and fish and other animals to ensure their survival in the Artic and other areas with subzero temperatures. Similar R&D is being done by other European research establishments such as the Fraunhofer Institute and Bochum University in Germany but they have focused on developing coatings and other anti-freeze products incorporating AFPs.

The objective at ZHAW has been to make polymer surface structures mimicking those on the proteins which curb the growth of ice crystals within plants and animals so that they can live in freezing temperatures.

Clariant is hoping that the project with ZHAW will lead to a “breakthrough in anti-freeze technology” enabling polymer-based coatings to be used to reduce the formation of ice on equipment like the rotors of wind turbines. Another aim is the creation of hydrophobic anti-freeze coatings that prevent flowing water freezing so that windscreens and aircraft windows can stay ice-free for extended periods.

“Ice causes major operational problems and costs to businesses and utilities but also to private individuals,” said Achim Stankowiak, Clariant’s head of application engineering and aviation. “The potential for coatings that can prevent or slow down ice formation is therefore enormous.” In the marine sector, a recent completed European Union-funded R&D project on nanostructured surfaces for controlling biofouling concluded that rough heterogeneous nanoscale surfaces are more effective at stopping adhesion by fouling organisms than smooth homogeneous ones. Nanostructured surfaces are also potentially a substitute for biocides in combating fouling, according to a summary of the results of the five-year scheme called AMBIO.