ECTFE foams

Table 11.14. Effect of Nucleating Agent on the ECTFE Foam Properties i ...

In this section, foaming techniques are covered based on the fluoropolymer type, beginning with perfluoroplastics. Next, foaming of partially fluorinated fluoropolymers are reviewed, combining ETFE and ECTFE and separately covering PVDF. Technological reviews are based primarily on patents and publications that focus on potentially commercial methods of foaming fluoroplastics. 

The exterior of foamed wire insulation can be coated with a solid layer (jacket) of ETFE or ECTFE for wires used in telecommunications and fiber optics. This arrangement allows the foamed perfluoro-polymer to provide good electrical properties while the skin layer supplies sufficient mechanical properties. A foamed FEP wire insulation (eore), with a thickness of 0.5 mm, was coatedl with 51 pm of an ETFE jacket it had a dielectric constant of 1.64 and dielectric breakdown strength of 26.6 kV/mm. 

Wires have been insulatedl and jacketed with ETFE and ECTFE resulting in excellent electrical and mechanical properties. A 24-gauge wire was insulated with an ETFE jacket and core. The jacket was solid (25 pm thick) and covered a foam insulation core (0.127 pm). This insulation had 45% void content and a dielectric breakdown voltage of 20 kV/mm. 

Similar to perfluoropolymers (see Sec. 11.6.1), ETFE and ECTFE can be foamedf using carbon dioxide. ECTFE resin was formed into a film and placed in the pressure vessel. The vessel was pressurized with carbon dioxide to 6.9 MPa, then heated to 220°C and held at this temperature for 1 hour. Heating the vessel raised the gas pressure to 18 MPa, which was released by venting. The vessel was eooled to room temperature and the film was removed. The appearance of the film turned opaque from transparent due to foaming it had a void eontent of 56%. 

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