Foamable fluoropolymer compositions

A foamable thermoplastic fluoropolymer composition consisting essentially of:

• at least one melt-processible fluoropolymer [polymer (A)];
• and
• at least one perfluoroalkoxysulphonic derivative selected from the following compounds:
• CF3—(CF2)w—OCF2CF2—SO3−(Zp+)1/p (i)
• wherein w is an integer from 1 to 3, Z is NH4 or an alkaline or alkali-earth metal cation, and
• p is the valence of the cation Z;
• CF3—(CF2)w′OCF2CF2—OCF2CF2—SO3−(Zp+)1/p (ii)
• wherein w′ is an integer from 0 to 2, Z is NH4 or an alkaline or alkali-earth metal cation, and
• p is the valence of the cation Z;
• and
• CF3—(CF2)q—(OCF2CFXF)r—OCF2CF2—SO3−(Zp+)1/p (iii)
• wherein q and r are each independently an integer from 1 to 3, XF is F or CF3, Z is NH4 or an alkaline or alkali-earth metal cation, and p is the valence of the cation Z;
• and
• optionally, at least one additional nucleating agent selected from titanium dioxide, lithium carbonate, calcium carbonate, calcium tetraborate, strontium carbonate, sodium carbonate, sodium tetraborate, sodium sulfite, potassium tetraborate potassium pyrosulfate, potassium sulfate, barium nitrate, aluminum phosphate, sodium fluorosilicate and combinations thereof.