Overview: All SPI Supplies Brand PTFE beaker covers, which can also be used as watch glasses, are chemically inert, non-contaminating, and are thermally stable in the range of -200°C (390°F) to + 280°C (+536°F). The beaker covers also have a "super smooth" finish making it virtually impossible for anything to "stick" to the surface of these fine laboratory products, making them very easy to clean up for reuse in another experiment. They are especially useful during digestion procedures where it is important to contain the liquid in the beaker. Make sure you understand why we can no longer call these Teflon® beaker covers and must refer to them only as PTFE beaker covers.
Details of the manufacturing: The beaker covers are pressed from pure virgin PTFE resulting in a highly inert material, one that will stand up to nearly every way one might want to use it. The super smooth finish means that virtually nothing will really stick to the covers.
Cautions about over heating: PTFE beakers can not be taken to temperatures as high as glass. The user has to be sure they do not overheat PTFE beakers or their covers. If PTFE is overheated, especially in air, it can start to break down by both thermal decomposition and oxidation, resulting in fumes of HF which should not be inhaled under any circumstances.
