Fluoropolymers are ideal for pharmaceutical and biopharmaceutical processing equipment because they have excellent chemical and thermal resistance. Their molecules have continuous non-reactive surfaces and are compatible with virtually all chemicals and solvents. They are far more resistant to chemical attack than conventional chlorinated and hydrocarbon polymers, and have far higher service temperatures. There are a number of materials in the Fluoropolymer family. PTFE (Polytetrafluoroethylene) is the original Fluoropolymer, discovered by DuPont in 1938. From this original development there have been a number of other materials developed – trying to improve on the difficult processing characteristics of PTFE. These have been more or less successful, having to trade properties of PTFE in order to attain other characteristics. The principal materials used in the industries that we serve are:
PCTFE – has many properties similar to other fluoropolymers such as PTFE, FEP or PFA, but is mechanically superior in rigidity (does not deform easily), and has very low gas permeability. Its dimensional stability makes it attractive for use as a component of a structural part where the high temperature and chemical resistance of fluoropolymers is required. PCTFE shows high compressive strength and low deformation under load. However, its relative cost is one of the major considerations in its selection, since it is quite expensive.
Material Properties of Fluoropolymers – A Comparison
In general, the chemical resistance of fluoropolymers is superior to most other families of plastics. This “chemically inert” characteristic accounts for 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 substances than do the partially fluorinated polymers such as CTFE (or PCTFE) and ECTFE. A superior property in one or two areas is accompanied by a diminished property in others (for example PTFE properties are better than PVDF in chemical resistance, but it has lower mechanical properties at normal ambient temperatures. Fully fluorinated polymers (perfluoro polymers) 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 higher tensile strength, toughness, abrasion and cut-through resistance 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.
Typical applications of PCTFE
Moisture barrier in pharmaceutical blister packaging, water vapour barrier for protecting phosphor coatings in electroluminescent lamps, protection in liquid crystal display (LCD) panels which are sensitive to moisture. Protection for sensitive electronic components. Insulation for wires and cables.