Materials + Processes

The Isostatic Molding Method in PTFE Processing

Isostatic molding offers the possibility of manufacturing complex molded shapes as well as hollow bodies and liners while, at the same time, offering significant reductions in both the amount of material employed as well as the mechanical rework required.

		The isostatic molding method is based on the physical law that pressure propagates uniformly in all directions in gases and liquids and produces forces on the surfaces under pressure that are directly proportional to these surfaces. In actual PTFE processing, a rubber mold is filled with PTFE powder and then sealed against liquids. This mold is then placed in the pressure vessel of a molding unit.
The pressure which the liquid in the pressure vessel exerts uniformly on all sides of the rubber mold also uniformly compresses the PTFE powder in the mold. After molding, the PTFE part is removed from the rubber mold and sintered in an oven.

Advantages of the Isostatic Molding Method

• Quality advantages thanks to isostatic compression

  		The advantages of isostatic compression molding can be illustrated by means of appropriately enlarged REM images. When magnified 100 times the granulate particles of the original material can still be identified in PTFE if it has been subjected to single-axis compression molding. By contrast, isostatically compression-molded PTFE shows a significantly more consistent surface structure. It is roughly equivalent to single-axis compression-molded TFM™PTFE. However isostatically compression-molded TFM™PTFE achieves a much finer and smoother structure.
  Furthermore, when magnified 2,500 times, in single-axis compression-molded material flaws become visible, which no longer occur in isostaticaly compression-molded TFM™PTFE.

• Lower manufacturing costs
  Minimal material use and either no, or very little, subsequent processing make it much more economical to produce complex parts than is the case with other molding methods..

The possibility of manufacturing parts with sophisticated geometric shapes which cannot be produced using conventional molding techniques opens up many new application areas for PTFE fluoroplastic with its outstanding chemical, mechanical and dielectric properties. In turn, this offers solutions for many problems in areas such as:

• Chemical industrie;
• Mechanical engineering;
• The fittings and pump industry;
• Heavy current engineering;
• Laboratory technology.

Typical examples of isostatically molded PTFE parts include

• Pressure vessels for the chemical trace analysis
• Linings for pumps and valves;
• Hollow bodies such as bottles round-bottomed flasks, floats, etc.;
• T-pieces and elbows for systems carrying aggressive media;
• Thin-walled tubes and tubes with large diameter changes;
• Sheaths for heating pipes and heating tubes for aggressive baths in the chemical, plating, and semiconductor industry.
• Porous PTFE.