What are Non-Stick Coatings?
Non-Stick coatings are a complex mix of lubricating pigments in a continuous matrix of a binder. This is normally a tough coating layer providing a low friction resistance surface between two parts. The lubricating pigments fit into two main categories:
- Crystalline lattice or lamella type structures, for instance Molybdenum Disulphade & Graphite or
- Fluorocarbons, typically PTFE
These varying pigments can be combined with a wide variety of resins to achieve different properties – high load bearing, chemical resistance, high temperature stability, low coefficient of friction.
How might Non-Stick Coatings be used?
Non-Stick coatings are used for many different reasons, but most importantly they are used when a liquid lubricant such as oil or grease cannot be used or it would be beneficial to avoid use. The major problem with liquid lubricants is they have a limited range of use and once exhausted the liquid will often change state (due to temperature, load, wear, migration and debris) becoming a processing or use problem, no longer providing protection.
So take for instance the bread baking process; bread pans might be silicon glaze coated and will require oil/grease to be applied for release of the baked bread. After the baking process the oil/grease will carbonize (burn on) onto the bread pan. Excess oil/grease presents an increase in cleaning requirements and health & safety measures. The baker will need to invest in and maintain oil depositing machinery and finally will incur the extra cost of the oil/grease.
By having the bread pans coated with a Non-Stick Coating all of this can be avoided, bread will be cleaner (not have burnt bits on it), the fat content of the bread will be reduced so making it healthier for consumer and the bakery plant will be a generally cleaner and a safer place to work as well as the financial advantage of not having to purchase oil/grease and the associated coats of running the plant equipment to apply it.
So how does PTFE Coatings really work?
There are 3 factors which give PTFE its unique Non-Stick capabilities:
- PTFE is made from a chain of carbon atoms with 2 large fluorine atoms attached to each carbon atom. The size of the fluorine atoms provides a protective barrier to the carbon atoms and therefore it is almost impossible for chemical structures to gain access to the carbon atom.
- The bond strength between the carbon and fluorine atoms is classified as extremely high bond disassociation strength. The strength is measured typically as 544 kj/mol making them almost unbreakable.
- Fluorine is a naturally ‘anti-social’ atom which wants to repel other atoms.
The combination of these factors makes PTFE coatings very low coefficient of friction coatings which provide chemical resistance.