What is meant by porosity of a material?
What does it mean when a material is said to be porous? All materials are porous to a certain degree. The porosity of a material represents the fraction of the volume occupied by the fine holes of its surface (void spaces) compared to the total volume of the surface of the material. Thus, bigger are the holes and higher are their number, the more porous is the material. Its surface will be less smooth and less flat. There are two types of porous structures: closed or open.
In this article, we will focus on open porous structures, in which fine holes are connected to each other; as examples: brick and concrete.
The porosity of a material is represented by a multitude of very fine holes on its surface that may contain gases, liquids, or even bacteria. Those holes will tend to promote the proliferation of bacteria.
What is a food grade finish
Materials designed for the food industry must meet the highest standards at all stages of food and beverage production, processing and food packaging.
These materials must meet the standards set by the FDA (Food and Drug Administration), USDA (U.S. Department of Agriculture), NSF International and Ag Canada (Agriculture and Agri-Food Canada).
Plastic materials designed for the food industry are certified safe for direct contact with food. On the other hand, it is essential to take into account that even if the surface of a raw material may be smooth and non-porous, the way of machining it may change its porosity once the plastic project is finalized. Thus, for a project specific to the food industry, emphasis should be done on the material machining stage, including the quality of welds. Welds should be as smooth as possible in order to make easier the cleaning of surfaces. It will also reduce the risk of potential contaminants (e.g. pathogenic bacteria) in the fine holes of the plastic surface. High-performance plastic materials designed for the food industry must be:
- Smooth and non-porous
- Easy to clean
Applications for non-porous plastics
Nyloil® FG: This material is often used to design mechanical parts of machinery. The abbreviation FG means that this nylon is Food Grade and safe for direct contact with food.
TIVAR® MD: The surface of this UHMW grade improve the sliding properties by reducing friction. The hard, smooth surface of the TIVAR® MD prevents particles from sticking to it and makes cleaning of parts designed with this material much easier. TIVAR® MD is perfect for conveyor guides, wear strips, anti-friction layers on production lines, spouts and rings.
TIVAR® HPV: This very low friction engineered plastic with ultra-smooth surface is an excellent choice for anti-friction strips.