PTFE (Polytetrafluoroethylene) dalcon™

PTFE (Polytetrafluoroethylene) dalcon™

PTFE dalcon™ - The chemical structure of fluoropolymers (also called fluoroplastics) primarily consists of carbon and fluorine. The particular combination of these two chemical elements arranged along the molecular chain imparts a unique set of properties to these types of carbon - fluorine based polymers.

PTFE (Poly tetra-fluoro ethylene) dalcon – is a fully fluorinated polymer available in various unmodified and modified grades. PTFE tubing is processed by compacting the powder under pressure at ambient or slightly higher than ambient temperatures. Methods of forming products include paste extrusion, ram extrusion, molding and calendaring between rolls. Many formed PTFE products are consolidated by sintering in an oven or used in unsintered form ( eg: thread sealant tape). Paste extrusion and calendaring methods are used with fine powder PTFE resins while granular PTFE resins are processed by ram extrusion and molding.

Material Properties of Fluoropolymers – A Comparison

In general, the chemical resistance of these materials are superior to most other families of plastics. This “chemically inert” characteristic is closely allied to their superior performance in ultra pure environments. The chemical inertness varies between the fluoropolymers. The fully fluorinated resins such as PTFE, FEP, PFA and MFA exhibit chemical inertness to a wider range of chemicals than do the partially fluorinated polymers such as CTFE (or PCTFE) and ECTFE. A better property in one or two areas is accompanied by a diminished property in others (for example PTFE properties is better than PVDF in chemical resistance but it has lower mechanical properties at normal ambient temperatures. Fully fluorinated polymers (perfluoropolymers) such as PTFE, FEP and PFA offer better thermal (higher use temperature) and chemical resistance properties than their partially fluorinated counterparts like ECTFE or PCTFE. However, partially fluorinated resins posses better mechanical properties, such as tensile strength, toughness, abrasion and cut-through resistance at ambient temperatures.

The flex modulus of PVDF tubing is considerably higher than PTFE (relatively most flexible), FEP, PFA or MFA. This makes PVDF tubing considerably more rigid than the other materials; however it has higher tensile strength at ambient temperatures.

The selection of a resin for a specific use is based on criteria for that application; for example permeability at the use temperature may be a critical requirement and may override other features such as chemical resistance and tensile strength. In each case the choice of material is made by comparing the key property requirements and, of course, cost .

The chemical resistance properties of PTFE (also PFA, MFA and FEP) is so broad that its use is not recommended for only a limited list of chemicals. All of these fluoropolymers are generally acceptable for a wide variety of industrial and commercial applications. Due to lack of additives and extreme chemical inertness these materials also qualify for ultrapure applications, such as using deionized (DI) water in the semiconductor, biological and pharmaceutical industries.

Effect of Fabrication on PTFE, FEP and PFA properties
In general, it is safer to assume that fabrication procedures affect some properties of PTFE, FEP and PFA products. Certain physical properties such as tensile strength, permeability and dielectric strength vary with fabrication conditions. Examples of causes of these may be macroscopic flaws, microporosity (for PTFE properties) and crystallinity. The extent of the variation depends upon the specific conditions of fabrication. Properties of PTFE, FEP and PFA that are relatively unaffected are as follows:

  1. Chemical resistance
  2. Long-term weathering
  3. Non-stick
  4. Non-flammability
  5. Low dielectric constant and low dissipation factor
  6. High arc resistance, surface and volume resistivities
  7. Flexibility at low temperatures and thermal stability at high temperatures
  8. Low coefficient of friction

Typical applications

Bearings, skived film, rotors and clam shells, wafer carrier, tank linings, tubes and fittings, valves, filters.