Why Use PTFE Seals in Food Industry Applications? - Hennig Gasket

Commercial cooking kettles used for boiling and preparing foods usually have a food grade gasket around the lid. By creating a good seal this helps the vessel build and retain pressure. This raises the boiling point of water, shortening cooking time while also destroying pathogens. A defective gasket can result in food not reaching the required temperature, potentially creating a health hazard. Additionally, the gasket itself can provide places for bacteria to become established.

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This gasket leads a hard life. Not only must it withstand the heat and pressure of cooking, but it’s also expected to go through multiple cleaning cycles. In addition, it’s essential that it not transfer anything or impart any taint to the food being cooked. Several materials are available for such gaskets, but in many situations the best sealing option is PTFE.

A Versatile Sealing Material

Polytetrafluoroethylene, or PTFE, better known by it’s DuPont tradename of Teflon, has a number of properties that make it an excellent choice for a food grade gasket. At the atomic level it consists of a long chain of carbon atoms, each one of which links to two fluorine atoms. This linkage is so strong that PTFE won’t bond to anything else, hence its non-stick properties.

PTFE doesn’t melt until 635°F and is usable at temperatures up to 260°F. At lower temperatures it remains flexible well below freezing, as low as -100°F or even lower, depending on formulation. It’s also a good electrical insulator. Of particular relevance for food industry gasket applications, it doesn’t absorb water and it’s biologically inert. It does however resist attack by almost all chemicals, including aggressive cleaning and disinfecting agents like chlorine dioxide.

PTFE Seal Alternatives

Other materials have properties that are close or superior to PTFE in some regards. Silicone for example is flexible at low temperature, has good compressibility and a higher upper temperature limit. However, silicone does not fare well with steam, which is found in many food preparation environments. It also lacks resistance to acids, alkalies and chlorinated solvents, so is limited in its potential as a food grade gasket.

FDA Approved Seal Material

SOURCES:

Agency for Toxic Substances and Disease Registry: “What are the health effects of PFAS?”

American Cancer Society: “Perfluorooctanoic Acid (PFOA), Teflon, and Related Chemicals.”

Link to JVC

Comparative Medicine: “Polytetrafluoroethylene Toxicosis in Recently Hatched Chickens (Gallus domesticus).”

Environmental science and pollution research international: “PTFE-coated non-stick cookware and toxicity concerns: a perspective.”

Environmental Working Group: “The Toxic Truth About a New Generation of Nonstick and Waterproof Chemicals.”

European Journal of Orthodontics: “The effect of Teflon coating on the resistance to sliding of orthodontics archwires.”

European Respiratory Journal: “Fatal acute pulmonary oedema after inhalation of fumes from polytetrafluoroethylene (PTFE).”

Food Volumes and Contaminants: “Perfluorochemicals: Potential sources of and migration from food packaging.”

Journal of exposure science & environmental epidemiology: “A Review of the Pathways of Human Exposure to Poly- and Perfluoroalkyl Substances (PFASs) and Present Understanding of Health Effects.”

Space: “Apollo Spacesuits Survive Today- in the Roofs Over Your Head.”

Tribology International: “Effect of temperature on the friction and wear behavior of electroless Ni–P–MoS2–CaF2 self-lubricating composite coatings."‌

United States Environmental Protection Agency: “Drinking Water Health Advisories for PFOA and PFOS,” “Risk Management for Per- and Polyfluoroalkyl Substances (PFAS) under TSCA,” “Technical Fact Sheet – Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA).”

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