Looking for a plastic/ceramic material USDA approved.

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In summary, the material is thermally stable, can maintain a pressure seal, and has a low coefficient of expansion.
  • #1
I have been looking for hours tring to find a material with these properties.
Working Temperature up to 500° F
Low coefiecient of Friction
Chemical Resistance to Costic Cleaners (mainly chlorinated)
Coeffecient of Thermal Expansion around 9.5 μin/in°F
decent machine ability
made in 1/4" flat

The use:
it will bolted to a piece of stainless steel and act as a air seal while a moving piece of stainless is ran along the length of it. The force between the oposing conpents is not great just enough pressure to keep them touching.
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  • #2
So you want a sliding sleeve which can maintain a pressure seal (how much pressure?) Will there be any lubrication? 500 F = 260 C, so not very hot. You could probably use a teflon tube if the air seal will hold.

If you can use MoS2 (dry moly) as the lubricant you could use a ceramic sleeve. Macor is a machinable ceramic:

There are many suppliers, and any experienced machinist can work with it - if they follow the directions! Requires sharp (new) carbide tooling, and obey the speed rules. Or you may be able to order the tube that you need. The coefficient of expansion is much lower than your specification.

Rather than look for something that meets all of your requirements, I would start with a vendor that has a good catalog of materials and sort down the list one property at a time, and see which is the most restrictive.

If you really want to maintain the air seal then the thermal expansion may be the critical issue. As an alternative why not use a bellows made from SS316?

  • #3
Attached is the application, the friction or need of lubrication between the plastic/ceramic and the stainless is not nessecary also the movment is very slow maybe 6.0ft/min. We used Ultem and it is failing due to the chemical concentration of chlorine solution used to clean the machine. We thought about teflon but the cost is high. The length of this unit is 160' x 2 (both sides). Also the max temp is 360°F of this unit, and that is only at start up it drops down lower once all sections are running stable. The other big obsticle I am running into is that it needs to be Food Grade.
  • #4
May be you could consider a nickel-Teflon composite coating, although probably it will not be cheaper than Teflon itself. There are also other low friction composites like the ceramic-teflon coatings used on frying pans but they are not so plastic. If you could use additional lubrication it would be easier for you to find an appropriate material.

1. What does it mean for a plastic/ceramic material to be USDA approved?

Being USDA approved means that the material has been tested and approved by the United States Department of Agriculture for use in food contact or food packaging applications. This ensures that the material is safe for use with food and will not contaminate it.

2. How can I find out if a plastic/ceramic material is USDA approved?

You can check the USDA's list of approved materials or contact the manufacturer of the material to inquire about its USDA approval status. Additionally, the material should have a label or marking indicating its USDA approval.

3. Are there specific requirements for a material to be USDA approved?

Yes, there are specific requirements that a material must meet in order to be USDA approved. These requirements vary depending on the type of material and its intended use, but generally include factors such as non-toxicity, durability, and resistance to chemicals and high temperatures.

4. Can a material lose its USDA approval?

Yes, a material can lose its USDA approval if it no longer meets the necessary requirements or if it is found to be unsafe for use with food. In such cases, the material will be removed from the list of approved materials and will no longer be considered USDA approved.

5. Are there alternatives to USDA approved plastic/ceramic materials?

Yes, there are alternative materials that are considered safe for use with food but may not be USDA approved. These materials may be approved by other regulatory agencies or may have been tested and deemed safe by independent organizations. It is important to research and verify the safety of alternative materials before using them in food contact applications.

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