Plastics not subject to viscoelasticity (cold flow)

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In summary, the conversation discusses the need for a machinable plastic or dielectric material that can withstand continuous loading for 20 years, with a stress of approximately 100 KPa and a maximum temperature of 64C. The material must also be able to handle rotating and close clearance applications without expanding and causing frictional failure. The issue of "cold flow" in thermoplastic polymers is raised, and the participants suggest looking into Phenolic material or polyphenylene sulfide as potential options. The Curbell Plastics website is recommended as a good source for comparing and researching different materials.
  • #1
Bcavender
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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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  • #3
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
 
  • #4
Take a look at Phenolic material, sold as Bakelite and Micarta brands.
 
  • #5
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.
 
  • #6
TomG & ChemAir,

Both very good suggestions! I will research both.

Thank you for your assist!

Bruce
 
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Likes Tom.G

1. What are plastics not subject to viscoelasticity?

Plastics not subject to viscoelasticity, also known as non-viscoelastic plastics, are materials that do not exhibit the characteristic of viscoelasticity, which is the tendency of a material to deform under a constant load over time. These plastics have a stable molecular structure and do not exhibit significant changes in shape or properties over time.

2. How are plastics not subject to viscoelasticity different from other plastics?

The main difference between plastics not subject to viscoelasticity and other plastics is their response to external forces. Non-viscoelastic plastics have a more rigid and stable molecular structure, which makes them less susceptible to deformation and creep over time compared to viscoelastic plastics.

3. What are some common examples of plastics not subject to viscoelasticity?

Some examples of plastics not subject to viscoelasticity include polyethylene (PE), polypropylene (PP), and polystyrene (PS). These are commonly used in various industries such as packaging, construction, and automotive due to their durability and resistance to deformation over time.

4. Are there any disadvantages to using plastics not subject to viscoelasticity?

One potential disadvantage of using plastics not subject to viscoelasticity is their stiffness and brittleness compared to viscoelastic plastics. This can make them more prone to cracking or breaking under high stress or impact. Additionally, these plastics may be more difficult to process and mold due to their rigid molecular structure.

5. How can plastics not subject to viscoelasticity be recycled?

Plastics not subject to viscoelasticity can be recycled through mechanical recycling, where they are melted and reformed into new products. However, due to their rigid molecular structure, these plastics may not be as easily recycled as viscoelastic plastics, which can be reprocessed multiple times without significant loss of properties.

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