Archive for the ‘PTFE’ Category

For members of the public PTFE (polytetraflouroethylene) and UHMW (ultra-high molecular weight polyethylene) seem to be very similar materials. They’re both white, soft, food-safe, and widely available from plastic companies. But are they that different? Oh yes they are! The first thing you would notice is the price. PTFE is literally in another category of plastics called the “high performance” plastics. This means the cost is going to be much higher than UHMW. So when do you need PTFE?

It would be an application where slickness is important above all other factors. UHMW, while less expensive, will outwear, outbear, and outperform PTFE in tough mechanical applications like homemade bushings, cutting board, etc. PTFE is very soft, so soft in fact it suffers from something called “cold flow”. This means that PTFE slowly creeps like a semi-solid liquid almost just sitting at rest in room temperature doing nothing. What PTFE does have in addition to outstanding slickness (low coefficient of friction) is that it takes very high temperatures up to 500 degrees Fahrenheit. UHMW does poorly in high temperatures and cannot handle more than 180 degrees Fahrenheit.

To be honest, in most DIY applications that call for a white plastic with balanced properties UHMW is going to be your go to. It’s too available, too cheap, and too balanced to go with PTFE. But in certain situations where very low friction is required (telescope mounts for example) or high heat will be encountered – PTFE may be your only choice.

For more assistance with your application please contact Redwood Plastics and Rubber.

One of the few PTFE applications that brings in the DIY community consistantly to a plastics distributor is the application using sheet material cut into discs as mountings for telescopes. PTFE is the third slickest solid known to man and works well as a sliding surface. It does have very low load-bearing capabilities and is subject to “creep” (dimensional changes at rest) and also cannot handle much wear at all. In short, there are only specific instances the material makes sense – especially due to its high cost compared to most other plastics used in DIY applications.

We recently came across a blog posting from an amateur astronomer (“Chris B.”) chronicling his progress in making telescope mountings from PTFE. He gives some pretty handy tips such as how to cut the material precisely into the desired disc and to keep it from moving around. We don’t really have experience in this area so it’s probably best to let Chris’ work speak for itself. You can find the blog here: https://fullerscopes.blogspot.ca/2016/08/2-shaft-mouting-pt28-ptfe-clutch.html

Machining PTFE

Posted: April 26, 2013 in machining, PTFE
Tags: , , ,

The flouropolymer PTFE (polytetraflouroethylene) AKA “Teflon” is one of the most popular engineering plastics. Considered a bridge plastic to the “High-Performance” plastics it is one of the best plastics readily available for everyday use. PTFE has a number of advantages, including being one of the slickest solids known to us, but it is also very soft and has poor impact resistance. We highly recommend you do your research before selecting it as a material and learn how to work with the material. Mistakes can be costly, as PTFE is one of the most expensive plastics available.

This short video does not provide specific technical assistance but the person hosting the video does a quick rundown on the beneficial properties of the material and he quickly lathes a bearing showing a little of how the material is worked with. We also have a machinist chart which includes PTFE located here.

 

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