Methods of manufacture of multiaxially oriented fluoropolymer films

A method of manufacturing multi-axially oriented fluoropolymer films, the method comprising:

• providing a fluoropolymer film extrudate having a first thickness, first and second orthogonal axes being defined in the plane of the film extrudate;
• calendaring the film extrudate in a first direction parallel to the first orthogonal axis between two parallel rollers spaced apart by a first gap smaller than the first thickness to reduce the film extrudate to a second thickness;
• calendaring the film extrudate having the second thickness in a second direction with respect to the orthogonal axes different than the first direction between two parallel rollers spaced apart by a second gap smaller than the second thickness to reduce few film extrudate to a third thickness;
• and
• drying, expanding, and sintering the film extrudate, wherein the step of expanding comprises radially expanding the multiaxially calendared film extrudate by blown extrusion whereby pressurized gas is blown against the film extrudate to cause radial expansion thereof.

A method of manufacturing multi-axially oriented fluoropolymer films, the method comprising:

• providing a fluoropolymer film extrudate having a first thickness, first and second orthogonal axes being defined in the plane of the film extrudate;
• calendaring the film extrudate in a first direction parallel to the first orthogonal axis between two parallel rollers spaced apart by a first gap smaller than the first thickness to reduce the film extrudate to a second thickness;
• calendaring the film extrudate having the second thickness in a second direction with respect to the orthogonal axes different than the first direction between two parallel rollers spaced apart by a second gap smaller than the second thickness to reduce the film extrudate to a third thickness;
• and
• drying, expanding, and sintering the film extrudate, wherein the multiaxially calendared film extrudate has a middle region and a periphery, and wherein the step of expanding comprises:
• advancing a blunt-ended pusher device against the midregion of the multiaxially calendared film extrudate while holding the periphery thereof in stationary position, thereby causing radial expansion of the multiaxially calendared film extrudate.