Plastics not subject to viscoelasticity (cold flow)

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The discussion focuses on finding a machinable plastic suitable for continuous loading over 20 years, with specific stress and temperature requirements. Concerns about 'cold flow' primarily affecting thermoplastic polymers are raised, highlighting a need for reliable material recommendations. Participants suggest exploring Phenolic materials like Bakelite and Micarta, as well as polyphenylene sulfide, which is a semicrystalline polymer. Resources like the Curbell Plastics website are recommended for detailed material comparisons. The conversation emphasizes the importance of selecting a material that maintains its dimensions to prevent frictional failures.
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I have been asked to find a machinable plastic (or dielectric) that will be subject to continuous loading (20 years) that will be subject to stress of appx 100 KPa at a max temp of 64C. While not a high speed or high energy situation, it is a rotating, close clearance application and the material cannot expand from its original dimensions without creating a potential frictional failure that could generate significant heat.

I have read that 'cold flow' over a long time is primarily a problem with thermoplastic polymers 'only', but the information I have been able to pull up so far is very scarce and gives me little confidence about selecting a material. Not being in materials science, my ignorance is probably has me looking in all the wrong places.

Can anyone shed some light about the cold flow being largely a thermoplastic problem and/or recommend a different source of viscoelastic data that I can use to find a plastic NOT subject to this long term phenomenon?

All comments welcome!
Bruce
 
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JBA,

Thank you for taking the time to link me with the Curbell website. Absolutely the best I have seen for broad comparisons and drill down detail!

Greatly appreciated!
Bruce
 
Take a look at Phenolic material, sold as Bakelite and Micarta brands.
 
This compounder has a wide variety of different types. It may be worth a look.

From previous work, polyphenylene sulfide, a semicrystalline polymer might be an option. Here's the variety of options for that material.

A lot of physical properties are available for this polymer and others on that site.
 
TomG & ChemAir,

Both very good suggestions! I will research both.

Thank you for your assist!

Bruce
 
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