Electrospinning of ptfe with high viscosity materials

Abstract

An improved process for forming a PTFE mat is described. The process includes providing a dispersion with PTFE, a fiberizing polymer and a solvent wherein said dispersion has a viscosity of at least 50,000 cP. An apparatus is provided which comprises a charge source and a target a distance from the charge source. A voltage source is provided which creates a first charge at the charge source and an opposing charge at the target. The dispersion is electrostatically charged by contact with the charge source. The electrostatically charged dispersion is collected on the target to form a mat precursor which is heated to remove the solvent and the fiberizing polymer thereby forming the PTFE mat.

What is claimed is: 
     
         1 . In combination, a surface formed of metal, ceramic or polymeric material and a coating of spun polytetrafluoroethylene (PTFE) on at least a portion of the surface. 
     
     
         2 . The combination of  claim 1 , wherein the surface is a device, and the coating is sintered in place on the device. 
     
     
         3 . The combination of  claim 1 , wherein the spun PTFE is electrospun PTFE that has been electrospun from a dispersion comprising PTFE, a fiberizing polymer and a solvent. 
     
     
         4 . A nonwoven mat comprising a plurality of spun polytetrafluoroethylene fibers. 
     
     
         5 . The mat of  claim 4 , wherein the plurality of polytetrafluoroethylene fibers exhibit uniform diameter. 
     
     
         6 . The mat of  claim 4  deposited on a cylindrical surface as a coating and sintered in place on the cylindrical surface. 
     
     
         7 . The mat of  claim 4 , wherein the spun polytetrafluoroethylene fibers are electrospun polytetrafluoroethylene fibers. 
     
     
         8 . The mat of  claim 4 , wherein fewer than 20% of the plurality of spun polytetrafluoroethylene fibers are in the form of broken fibers. 
     
     
         9 . The mat of  claim 4 , wherein the polytetrafluoroethylene has an average molecular weight of about 10 6  Da to 10 8  Da. 
     
     
         10 . The mat of  claim 4 , wherein the mat has a tensile strength normalized to 1 mil thickness, calculated by dividing measured tensile strength by thickness of the mat in mils, of about 45 psi or greater. 
     
     
         11 . The mat of  claim 10 , wherein the mat has a normalized tensile strength of between about 45 psi and about 1422 psi. 
     
     
         12 . The mat of  claim 10 , wherein the elongation to failure of the mat is about 100% or greater. 
     
     
         13 . The mat of  claim 10 , wherein the elongation to failure of the mat is between about 100% and about 200%. 
     
     
         14 . The mat of  claim 4 , wherein the spun PTFE fibers have been spun from a dispersion having a viscosity of at least 50,000 cP and comprising PTFE, a fiberizing polymer and a solvent. 
     
     
         15 . The mat of  claim 4 , wherein the density of the mat is between about 2.0 g/cm 3  and about 2.3 g/cm 3 . 
     
     
         16 . The mat of  claim 4 , wherein no beading of the spun polytetrafluoroethylene fibers is observed when the mat is subjected to visual examination under magnification. 
     
     
         17 . The mat of  claim 4 , wherein the bubble point pore diameter of the mat is between about 2 microns and about 10 microns. 
     
     
         18 . A nonwoven mat comprising a plurality of spun polytetrafluoroethylene fibers, characterized by one or more of the following:
 the plurality of polytetrafluoroethylene fibers exhibit uniform diameter;   the spun polytetrafluoroethylene fibers are electrospun polytetrafluoroethylene fibers;   fewer than 20% of the plurality of spun polytetrafluoroethylene fibers are in the form of broken fibers;   the polytetrafluoroethylene has an average molecular weight of about 10 6  Da to 10 8  Da;   the mat has a tensile strength normalized to 1 mil thickness, calculated by dividing measured tensile strength by thickness of the mat in mils, of about 45 psi or greater;   the mat has a normalized tensile strength of between about 45 psi and about 1422 psi;   the elongation to failure of the mat is about 100% or greater;   the elongation to failure of the mat is between about 100% and about 200%;   the spun PTFE fibers have been spun from a dispersion having a viscosity of at least 50,000 cP and comprising PTFE, a fiberizing polymer and a solvent;   the density of the mat is between about 2.0 g/cm 3  and about 2.3 g/cm 3 ;   no beading of the spun polytetrafluoroethylene fibers is observed when the mat is subjected to visual examination under magnification;   the bubble point pore diameter of the mat is between about 2 microns and about 10 microns   
     
     
         19 . The mat of  claim 18 , wherein the spun polytetrafluoroethylene fibers are electrospun polytetrafluoroethylene fibers.