Advantages of TFM™-PTFE
Table of Contents
Due to its unsurpassed properties, PTFE or TFM™ is particularly suitable for its usage in sample preparation. The brand name TFM™-PTFE refers to a so-called second-generation PTFE in which a modifier has been incorporated into the linear chain of the polymer in small quantities. This modified variant is processed like conventional PTFE, but has a significantly improved property profile. The chemical resistance, thermal stability and wide temperature application range are comparable to those of standard PTFE. However, the modified TFM™-PTFE has a significantly reduced melt viscosity, a considerably reduced microporosity and a lower stretch void index (SVI). This results in pore-free products with low permeability.
The improved material properties are also influenced by the manufacturing process. In addition to uniaxial pressing, PTFE can also be processed using isostatic pressing. The advantages of isostatic pressing can be illustrated by means of SEM images under appropriate magnification. At 2,500x magnification, defects become visible in uniaxially pressed material that no longer occur in isostatically pressed TFM™-PTFE. With isostatically pressed TFM™-PTFE, a significantly finer and smoother structure is achieved. This leads to a significantly reduced risk of contamination and memory effects.
Isostatic pressing
In the conventional, single-axis pressing process, the material is usually compressed vertically in a mold with a punch. Due to the pressure applied on one side and the internal friction, an inhomogeneous compaction of the material is obtained. In the isostatic pressing process, on the other hand, the force acts on the material evenly and simultaneously from all spatial directions via a hydraulic medium and compacts it homogeneously. This achieves optimum compaction, resulting in minimal porosity and an improved surface structure. Preferential directions are not formed and isotropic material properties are maintained. In particular, the tensile and compressive strength of the material is uniform in all spatial directions. In practice, a rubber mold filled with PTFE or TFM™PTFE powder and then sealed in a liquid-tight manner is placed in the pressure vessel of a press system. The pressure acting on all sides of the rubber mold via the liquid in the pressure vessel compresses the enclosed PTFE powder evenly. After pressing, the PTFE pressed part is removed from the rubber mold and subjected to a sintering cycle in the oven.
