Polytetrafluoroethylene nano/microfibers by jet blowing

Polytetrafluoroethylene (PTFE) fluoropolymer exhibits extreme chemical and thermal stability, low friction coefficients and many other exceptional properties. Unfortunately, very high molecular weight PTFE has an extremely high melt viscosity (∼10¹⁰-10¹² poise) and negligible solubility in common solvents. Under tensile stress, molten PTFE elongates and breaks rather than forming fibers and processing it is generally laborious and expensive. We have developed a simple, environmentally friendly, single step, solvent-free technique to process very high molecular weight PTFE inside of a high pressure jet of gases such as nitrogen or argon into mats of micro and nanofibers that are up to several millimeter long. Plasticization of PTFE by the hot, high pressure gases within the jet and extensional stretching in the jet nozzle appear to facilitate fiber formation even at temperatures below the melting point. Polarized Raman spectra demonstrate that the PTFE polymer chains exhibit substantial alignment along the fiber axis. The fibers are produced at a rapid rate and adhere to many different materials, allowing for facile fabrication of surface modifying coatings and dense fibrous mats to control properties such as surface hydrophobicity, drag, and biocompatibility. Jet blowing is also suitable for more conventionally processible polymers and formation of polycaprolactone (PCL) fibers is demonstrated.