A period of unusually hot weather across much of Europe this summer has drawn attention to the risks of accelerated degradation of outdoor coatings due to climate change increasing levels of UV exposure.
Global warming is also causing bouts of abnormal heavy rainfall which has triggered demands for protective coatings against the effects of flooding.
As a result, ingredient manufacturers are seeing opportunities for pushing up sales of UV resistant and other protective components in paint. The need for new types of UV safeguards has been bolstered by a swing to low-solvent or solvent-free coatings to comply with European Union legislation on lower emissions of volatile organic compounds (VOCs), due to start coming into effect next year. These coatings could have lower UV resistance.
At the same time there are openings for the wider application of innovations like heat-absorbent pigments and coatings which combat air pollution.
For the moment coatings manufacturers are claiming that climate change has not yet raised UV exposure to levels that endanger the stability of existing coatings-at least in northern Europe.
"So far tests carried out on our coatings on outdoor panels at our laboratory site at Amsterdam in the Netherlands have not found that the effects of sunlight are any different from what they usually are," explained a spokesman for SigmaKalon. "It is the same with the results from our accelerated weathering testing at the site as well."
Also coatings manufacturers in Europe point out many of their products in the region have the same degree of UV resistance as paint sold in areas with hot weather and intense sunlight, like parts of Africa and the Middle East.
"The observed, moderate increase in UV radiation in the northern hemisphere-caused by ozone depletion-is not a specific issue for us," said an Akzo Nobel official. "As a global supplier of coatings for external applications we need to ensure that our products fulfill the weathering standards of all climatic zones, including subtropical and tropical zones in which typically a much higher UV radiation prevails, as compared to Europe and North America."
Nonetheless Akzo Nobel is endeavoring to improve the UV and weathering resistance in its coatings, including safeguards against industrial-based phenomena like acid rain.
"This continuous improvement process has resulted in substantial progress in the weathering resistance of coatings in general," the Akzo official said. "As a result some of our European decorative coatings brands are able to grant long-term warranties for the surface properties of their wood and wall paints. A number of these achievements are based on nanotechnology, for example, the use of nanosized titanium dioxide and other inorganic nanoparticloes as UV filters in clear and top coats."
International Paint, Akzo Nobel's protective coatings producer, has been responding to the needs of the Italian historic city of Venice on the Adriatic Sea, which has been suffering from rising sea levels and increasing incidence of flooding.
The paint company has provided a five-coat anticorrosive system for approximately 32,000 square meters of newly installed large metal walls in Venice's Porto Marghera. The coatings contain a universal primer, an epoxy sealer coat and an acrylic polyurethane finish. "The contract at Porto Marghera is very important to us because it is the first project in a series of regeneration work to be carried out in the Venice lagoon," said Gerard Morganti, International Paint's protective coatings worldwide projects co-ordinator.
Manufacturers of paint ingredients and their pre-cursors are reporting a rising requirement in Europe for components that can give outdoor coatings greater robustness.
"With architectural paints which are not only brush-applied but can also be powder and coil coated, we have noticed an increased demand for high-performance light stabilizers, such as triazines and hindered amine light stabilizers (HALS)," said John Zambounis, global head of industrial and decorative coatings at Ciba Specialty Chemicals. "Wood is another area where there has been a growing demand for outdoor protection, also with ever increasing performance requirements."
Chemical suppliers to the coatings sector are wrestling with the problems of how to provide systems which both lower VOC emissions to comply with new regulations while at least maintaining existing levels of UV resistance.
"The new VOC emission limits can, for example, be reached by reducing the molecular weight of the resins in the coatings but this would cause poor UV resistance," explained Bo Haeggman, global market development manager at Perstorp Specialty Chemicals, Perstorp, Sweden. "The end-users do not want that sort of compromise. They want both lower VOC emissions and the same UV resistance. The big challenge is how to achieve both."
Perstorp's solution has been the development of a new precursor for the preparation of acrylic esters, which is based on a hyperbranched dendritic aliphatic polymer polyols.
"Our dendritic polymers reduce VOCs and at the very least maintain UV resistance with the possibility of even increasing it," said Haeggman. "They are particularly useful with alkyd paints applied to wood because they help to increase the penetration of the coating into the wood while giving it UV resistance. These alkyd paints can also be used as undercoats on wood with acrylic paints which have good UV resistance being applied as the top coats."
Advances have been made in the development of pigments which can reduce the damaging effects of infrared sunlight rays which transmit 50% of the sun's energy compared with UV's five percent. An object with a coating that reflects infrared light will stay cooler than one that absorbs it.
Black outdoor coatings can become especially hot in the sun because carbon black and other black pigments have high absorption in the near infrared (NIR) range causing severe warping and other side effects.
The performance chemicals division of BASF has just introduced a class of functional pigments called Lumogen which are NIR-transparent. The infrared rays pass through the Lumogen coating and are remitted by an underneath coating of titanium dioxide or aluminum. In the infrared range from 750-2500 nanometers, the pigments cut the solar heat buildup by half.
BASF believes that Lumogen will help increase the service life of automotive and decorative coatings. In addition to their heat resistance, they have good color strength, migration stability, chemical resistance and high dispersibility.