Hybrid coatings based on organic polymers and silicones protect pans, exhaust pipes and wood-burning stoves equally well, and silicone resins add a special degree of heat resistance to such coatings.
Coated aluminum pans are part of the basic equipment of every kitchen: they are lightweight, inexpensive to produce and accommodate the demands of modern, health-conscious consumers – because aluminum pans require less oil than their expensive cast-iron or stainless-steel counterparts, they make it possible to prepare fish, omelets and pancakes with much less fat. Resistance to heat, however, had long been the Achilles heel of aluminum pans, which is why ambitious chefs prefer other metals for techniques such as frying steaks at high temperatures. Aluminum pans have improved in that regard too, however, as they are usually coated on the inside with polytetrafluoroethylene – known by the brand name Teflon – and on the outside with a finish based on silicone polyester resins.
“Organosilicone resins allow us to adjust the properties of coatings to match the needs of a given application quite closely.”Philipp HaasMarketing Manager at WACKER
“Aluminum pans coated on the outside with silicone polyester resins can remain stable at temperatures of up to 250 °C for relatively long periods of time – even up to 300 °C for short periods,” says Walter Göblmeier, a technical service engineer in the WACKER SILICONES Plastics & Coatings business team in Burghausen. He added that, in contrast, heat resistance is limited in conventional surface coating resins based on purely organic polymers, but improves markedly when silicones and polyester resins are bound chemically.
Crosslinking takes place during baking, where the applied coating layer, once it has evaporated, is heated to between 250 °C and 280 °C for around 10 to 15 minutes. Used as a binder, the organosilicone resin envelops the solid particles in the coating – pigments and fillers – and binds them together and to the substrate. This forms a strong coating, which protects the treated object against external influences.
Even greater heat resistance can be achieved in silicone resin coatings formulated with no organic component: if made with pigment fillers, these coatings can even withstand temperatures of over 650 °C for brief periods of time. This works best with silicone resins that have not been organically modified, such as those used in coatings for engine components. Because cookware and other household items are not subjected to the kind of punishment that pure silicone resin binders can take, these qualities – which also come at a higher price – are not absolutely necessary and wouldn’t be the first choice for the application either. “While maintaining excellent adhesion to a substrate, organosilicone resins allow us to adjust the properties of coatings to match the needs of a given application quite closely – and we can do that at competitive prices,” says Philipp Haas, WACKER’s marketing manager responsible for silicone resin intermediates.
“Water-based paints are increasingly in demand in markets where sensitivity to environmental issues is high.”Dr. Tania TrombettaTechnical Manager at Benasedo
The Milan-based Benasedo company, one of Europe’s leading silicone resin producers, likes to use WACKER silicone resins for its modifiers – silicone polyesters that the Italian firm produces on the basis of organic resins. “Benasedo uses our intermediates to modify its organic polymers as a way of improving their properties,” says Göblmeier. These organically modified silicone resins are then sold to major European paints and coatings manufacturers, who use them as binders in their products.
The Italian resin producer has been working with WACKER for over ten years. “Our market is fairly demanding,” explains Dr. Tania Trombetta, technical manager at Benasedo. “The standards of quality are high, products need to be available quickly, and additional quantities sometimes have to be produced on short notice. WACKER has been providing us with reliable support for years. The silicone resin intermediates we produce,” Trombetta goes on to say, “are primarily used in coatings for cookware.” Other applications, of course, such as stoves, ovens and fire pits, benefit from WACKER products as well.