There are many properties of plastics that need modifying to suit specific applications. We call these “functional” additives because they are developed to function in a unique way when added to polymer materials. Here we’ll continue our Q&A discussion about functional additives.
Q: What is fogging?
Fogging happens when there is condensation of small water droplets.
Q: Why are brand owners so concerned about fogging?
Fogging generally happens in food container applications; containers that see warm and cold very quickly. It’s not attractive, particularly when most food containers are using a clear polymer material so that the consumer can get a good look at the food inside to allow consumers to make sure the product is fresh. Colorful food products such as strawberries and blueberries, look quite fresh when their colors can be clearly seen through the packaging without water condensation. Additionally, this type of condensation can also cause food spoilage.
Q. What does anti-fogging do from a functional standpoint?
Anti-fog additives are typically non-ionic surfactants that prevent water vapor condensation.
Q. How was anti-fogging developed?
NASA first developed anti-fogging treatments used on glass or plastic surfaces in optical applications such as lenses and goggles.
Q. How do they work?
Anti-fogging treatments – either those that are put onto the surface of optically clear plastic products or those that are put into a Masterbatch format to become an inherent part of the plastic – work by minimizing surface tension, resulting in a non-scattering film of water instead of single droplets. This works by altering the degree of wetting. Anti-fogging entails chemical treatments or additives that prevent condensation of small water droplets on the surface that appear in the form of fog.
Q. Do anti-fogging additives work on all types of polymers?
There are many anti-fog agents for polyolefin systems, as polyolefins are more hydrophobic, but typically not for polyester systems. Polyesters are more polarizing and typically are more compatible with anti-fogging additives.
Q. What is the most difficult type of fogging to prevent?
Hot fogging is the worst. Preventing fogging in hot foods like the roasted chickens that you see in the deli case at the supermarket is the ‘holy grail’ of anti-fogging. Cold fogging is much easier to prevent.