Our core expertise, and much of the work we do, involves processing of corrosion resistant and high purity fluoropolymers such as PTFE, PFA, FEP, PCTFE and PVDF.

The fluoropolymers industry had its beginnings with PTFE (formerly referred to as TFE) which stands for Polytetrafluoroethylene, the polymer discovered by DuPont in 1938. Since then, other manufacturers entered the market and produce the material under their own trade names. A broad overview of the material can be found in the on-line encyclopedia Wikipedia here.  More specific sources of information come from the manufacturers themselves, including:

3M, who manufactures PTFE under the trade name Dyneon™

DuPont, who manufactures PTFE under the trade name Teflon®

Daikin America, who manufactures PTFE under the trade name DAIKIN-POLYFLON™

AGC Chemicals America, who manufacturers PTFE under the trade name Fluon®

Each manufacturer offers PTFE in a variety of formulations generally referred to as "compounds", differing mostly in the size of the raw powdered resin particles and various added fillers. Fillers can be materials such as carbon to increase electrical conductivity (making parts static dissipative) and glass fibers to enhance certain mechanical properties. Of course, there are always trade-offs to consider in that fillers may adversely affect some material properties. Micromold's years of experience can help you intelligently select the best compound for your particular application.

Since PTFE will not flow above its melting point, it cannot be injection molded and requires special processing techniques. Molded PTFE is processed by first compression molding the powder into preforms, and then sintering the preforms in a process analogous to sintered metal processing. This process creates geometric shapes that can then be machined, fused, and/or welded.

In this product, the three large outer PTFE body parts and two end connection bosses are fillet welded using PFA welding rod. The sealing o-rings are FEP encapsulated and the PTFE inner and outer cartridge cages are snap-fit into the threaded PTFE removable knob. The standard strainer mesh is another fluoropolymer, Tefzel® ETFE. Combining all these materials results in a corrosion resistant assembly where all wetted surfaces are fluoropolymers of one form or another. It can withstand continuous service with hot 98% sulfuric acid, for instance—an environment that would rapidly destroy most metals.

PTFE Y-Strainer cross-sectional view    

Consider the reaction vessel accessories depicted in the figure to the right. These dip pipes and nozzle lines share at least one feature in common. In both cases, Micromold processes the raw PTFE from powder from molding through machining to create the flanges and then fuses the flanges to extruded PTFE tube. Fusion is done using dedicated equipment developed at Micromold to combine carefully calibrated heat and pressure. The proprietary fusion process causes the parts to merge, essentially creating a single seamless product.

PTFE Lined & Jacketed Dip Pipes and
PTFE Nozzle Liners

PFA is similar to PTFE in chemical resistance and temperature capabilities with continuous operating temperature ratings approaching 500 °F (260 °C). FEP has equal chemical resistance, but continuous operating temperature ratings are lower, on the order of 400 °F (204 °C). Both PFA and FEP, unlike PTFE, can be injection molded.

PVDF stands for Polyvinylidene Fluoride and is best known under its trade name, Kynar™ manufactured by Arkema Inc. who offers an on-line source of information here. An overview of the material can also be found in Wikipedia here. Another major source of PVDF is Solvay Solexis who manufacturers it under the trade names Solef® and Hylar® and supplies information here. PVDF is similar to PTFE in that it is resistant to attack from a wide range of chemicals and is able to operate at higher temperatures than most plastics. The range of chemicals it can handle is not as broad as that of PTFE and its continuous operating temperature lower, but it can be injection molded and it is much stronger than PTFE within its operating temperature range. PVDF products can be susceptible to cracking if not properly stress-relieved. Micromold is experienced at stress-relieving in our own ovens with annealing cycles tuned over the years to optimize the strength of our products and our customers' products.

The PVDF Basket strainer shown to the right is another good example of Micromold's ability to mix and match fluoropolymers to optimize products for the end-user. This material is a good choice where the environment is harsh enough to need a fluoropolymer, but doesn't warrant PTFE.

PTFE Basket Strainer cross-sectional view

PCTFE is chemically similar to PTFE, and thus resistant to many corrosive chemicals, but is melt processable and can be injection molded, compression molded or extruded. It has an upper useful temperature rating of 400 °F (204 °C), but it also has value in cryogenic applications down to -400 °F (-200 °C). It can be a difficult material to work with, sometimes requiring annealing, and Micromold has all the needed expertise based on years of experience working with it. Micromold CNC machines PCTFE valve seats and other OEM parts for semiconductor manufacturing, as well as other process industries.

As you can see from the above discussion and examples, we not only apply those same machining skills to our standard and custom fluoropolymer-based products, but add a whole plethora of specialized understanding of these unique and valuable materials.