ECTFE

ECTFE (ethylene-chlorotrifluoroethylene) is an alternating copolymer of ethylene and chlorotrifluoroethylene. It is a semi-crystalline fluoropolymer (a partly fluorinated polymer), with chemical corrosion resistance properties.

Physical and chemical properties 
ECTFE (ethylene chlorotrifluoroethylene) is a polymer known for its chemical resistance, making it suitable for various industrial applications. It is resistant to acids at high concentrations/temperatures, caustic media, oxidizing agents, and many solvents, similar to PTFE (polytetrafluoroethylene). One of the key properties of ECTFE is its permeation resistance to large molecules, which is generally slow and not significant in practical applications. Small molecules, however, may permeate through the polymer matrix. In lining or coating applications using ECTFE, permeability of certain small molecules determines the lifetime of anti-corrosion protection. Small molecules such as H2O, O2, Cl2, H2S, HCl, HF, HBr, N2, H2, and CH3OH are relatively mobile in the polymer matrix and lead to measurable effects. This permeation resistance is particularly critical in lining and coating applications, where the material is used to protect underlying layers, such as fiber-reinforced plastic (FRP) or steel, from corrosive substances. The polymer's resistance to permeation is attributed to the presence of chlorine atoms in the polymer chain, which occupies free volume and restricts the movement of small molecules through the material.

ECTFE finds applications in various industries due to its favorable chemical resistance properties, providing durable and reliable protection in harsh environments.

ECTFE has a continuous usage temperature range between –76°C and +150°C (–105°F to +300°F). It has strong impact resistance and a Young's modulus in the range of 1700 MPa, allowing for self-standing items and pressure piping systems. The polymer maintains high impact strength in cryogenic applications.

In terms of fire resistance, ECTFE shows a limiting oxygen index of 52%. This value places it between the fully fluorinated polymers PTFE, PFA, and FEP with a limiting oxygen index of 95% and other partially fluorinated polymers like PVDF with a limiting oxygen index of 44% or ETFE with a limiting oxygen index of 30%.

ECTFE acts as an electrical insulator, with high resistivity and a low dielectric constant as well as a low dissipation factor, allowing its use for wire and cable primary and secondary jacketing. ECTFE has good ultraviolet (UV) resistance, in particular against UV-A and UV-B. Films made of the polymer can be transparent.

Applications 
ECTFE is applied in several ways:
 By electrostatic powder coating on metal surfaces
 By rotolining on metal surfaces rotolining grade Halar 6012F
 By sheet lining on metal surface or on FRP (glass fiber, carbon fibers, etc.)
 By extrusion or injection molding of self-standing items, in particular pressure pipes
 By rotomolding of self-standing items like tanks or other shapes (rotomolding grade)
 As a protective film using an adequate adhesive

ECTFE powder is most commonly used in electrostatic powder coating.  Such coatings have a typical thickness of 0.8 mm but can be applied up to 2 mm with a special grade for high build up.

Extrusion of ECTFE fabric-backed sheets and subsequent fabrication into vessels, pipes or valves is done in the chemical industry. Thick sheets are compression molded and can be manufactured to 50 mm in thickness. They are used in the semiconductor industry for wet benches or machining other parts.

The most common application of ECTFE is for corrosion protection, for which it is used in industries including:
 Bleaching towers in pulp and paper
 Sulfuric acid production and storage
 Flue gas treatment in particular in the SNOX and WSA processes
 Electrolysis collectors or drying towers in the chlorine industry
 Transport vessels for hazardous goods, in particular class 8 trucks
 Halogen-related industry (bromine, chlorine, fluorine)
 Acid handling (sulfuric acid, nitric acid, phosphoric acid, hydrogen halides, hydrogen sulfide, etc.)
 Mining applications, in particular high pressure heap leaching

ECTFE has been widely used in the semiconductor industry for wet tool and tubing systems for lithographic chemicals.

It is also used in the pharmaceutical industry.

ECTFE is used for primary and secondary jacketing in specialty cables like data cables or self-regulating heating cables, applications where good fire resistance and electrical properties are key properties. It is also used for braiding in that field.

ECTFE in the form of a monofilament fiber is used in flue gas treatment and in certain chemical processes.

Unlike PTFE, ECTFE can be crimped, which allows its production in the form of nonwoven fibers with high surface area and porosity. Even though such material has low chemical reactivity, ECTFE in general has somewhat lower chemical resistance compared to PTFE.

ECTFE is used for manufacturing gaskets to store liquid oxygen and other propellants for aerospace applications.

See also 
 BS 4994 ECTFE as a thermoplastic lining for dual laminate chemical process plant equipment
 RTP-1 ECTFE as a thermoplastic lining for dual laminate ASME stamped vessels

References 

Plastics
Fluoropolymers
Copolymers
Thermoplastics