Polymer Seals for Food & Dairy – PTFE and UHMW
Big challenges faced in the Food and Dairy Industry
There are several major issues faced in the food and dairy industry, including:
- Temperature conditions that range from extremely high to cryogenic
- Exposure to harsh chemicals
- Excessive moisture
- Continuous sanitation regimens
- Expensive shutdowns
In these industries, simple thinks like lubrication of seals and bearings become major issues because of potential contamination. Potential contaminants in the food and dairy industry are varied, ranging from lubricants, antimicrobial barrier fluids, insects, splinters of plastic or metal, to coolants. Even contamination at the microbial level can lead to very expensive recalls.
Seals for chemicals that are relatively inert may have to be exposed to harsh sanitizing chemicals on a regular basis. Because of strict sanitation regimens, including processes such as CIP (clean-in-place) and SIP (sterilization-in-place), seals and bearings not only have to exhibit chemical inertness with regard to the liquids and gases that are designed to be exposed to on a daily basis, but also to harsh and potentially corrosive cleaning agents. The operating temperature for a seal or bearing may be well within the range of the material chosen, but it may be exposed to even higher temperatures for sanitation.
Whereas in some applications seal failure may lead to a puddle of oil in the floor, in the food and dairy industries it may lead to disastrous contamination consequences.
To deal with such issues, many engineers have decided to build in hygiene beginning at the design stage of new equipment.
Sanitation is another major consideration in seal design and selection for the food and dairy industries.
Facts about PTFE and UHMW
UHMW is a subset of polyethylene, referred to as ultra-high-molecular weight polyethylene. UHMW is considered one of the toughest plastics, with the highest impact strength of any existing thermoplastic polymer. It combines extremely high abrasion resistance (up to 6x better than steel) with a low coefficient of friction (comparable to that of Teflon), moisture absorption that is almost non-existent, and overall good dimensional stability. It is worthy of note that it is one of the few materials that can resist abrasion so well while still being soft enough for use in sealing applications. UMHW also has low gas permeability. It works well in temperatures ranging from cryogenic applications to regular steam exposure. Unlike many polymers, it does not suffer from cold embrittlement. UMHW is non-toxic and has no odor associated with it. When used in food and dairy applications, its shatter resistant properties are important, as well as its resistance to corrosion and chemical attack. UHMW is also self-lubricating, which means that when used as a seal there is no need for additional lubricants that can act as a contaminant. It also meets USDA, 3-A Dairy, and FDA guidelines. Some people may be more familiar with its use in fiber form, where it is called Spectra or Dyneema.
PTFE is the official acronym for what most people know as Teflon. It has the lowest coefficient of friction of any solid material, probably the best chemical resistance of any polymer, excellent performance under pressures up to 500 psi, a wider temperature range than UHMW. When it comes in contact with foods or dairy products, PTFE never compromises taste. It has very good wear and abrasion resistance. PTFE performs well in applications where it is exposed to thermal cycling. It has excellent dimensional stability, and is self-lubricating. Like UHMW, it can eliminate the need for lubricants that could act as contaminants. Like UHMW, it absorbs almost no water, making it ideal for applications where it is continuously exposed to moisture. One unusual benefit that serves well in some applications is the fact that if it has been under high pressures for extended periods of time, it does not run the risk of shattering when the pressure is removed, like some polymers do. This is known as the saturation of high pressure gas. It also has an unlimited shelf life. PTFE also does not degrade under UV light. Another plus for the food and dairy industry is that Teflon does not absorb dilute benzoic acid and other similar preservatives.
Solving the Problems
With federal oversight, strict standards for hygiene and sanitation, and high competition, it is important that engineers working in the food and dairy industries know their options are when it comes to designing and specifying equipment seals. Get a free slide deck download on
How to Solve Seal Problems in the Food and Dairy Industries with UHMW and PTFE? Get a free copy of the 7 PTFE & UHMW Polymer Solutions for Food & Dairy Equipment Challenges presentation deck.