PTFE (polytetrafluoroethylene) and UHMW (ultra-high molecular weight polyethylene) seem to be remarkably similar materials. They are both white(some PTFE tape is brown and UHMW tape is blue), 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, out bear, and outperform PTFE in tough mechanical applications like homemade bushings, cutting board, etc. PTFE is incredibly 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 extremely high temperatures up to 500 degrees Fahrenheit. UHMW does poorly in high temperatures and cannot handle more than 180 degrees Fahrenheit.
Select your tape!
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 is too available, too cheap, and too balanced to go with PTFE. But in certain situations where exceptionally low friction is required (telescope mounts for example) or high heat will be encountered – PTFE may be your only choice.