Oligomer spin-solvent gel-fiber spinning

Abstract

A fundamental process design for gel-spinning semi-crystalline polymers was developed. An oligomer-spin solvent was shown to fulfill the requirements of an ideal gel-spinning spin-solvent. The concept was tested on two polymers that are difficult to spin into fiber using conventional techniques: POM and PEO. Fibers produced by gel-spinning a PEO/PEG solution achieved tensile strength greater than 0.6 GPa and Young’s modulus greater than 4.3 GPa, significantly stronger and stiffer than PEO fibers spun from conventional spinning techniques. POM gel-spinning with PEG spin-solvent exhibited degradation due to the innate chemistry of the POM molecule. Using caprolactam as the gel-spinning spin-solvent produced a stable spin-dope and yielded fibers with tensile strength greater than 1.8 GPa and Young’s modulus greater than 36 GPa. The efficiency of the gel-spinning process was improved through a mechanical spin-solvent extraction process. Twisting the gel-fiber was shown to remove more than 80% of spin-solvent from the gel-fibers without requiring an additional extraction solvent. The mechanical extraction process was shown to be effective for both volatile and non-volatile spin-solvents. The tensile properties and surface morphology of the mechanically extracted fibers after hot-drawing were shown to be nearly identical to gel-fibers extracted using the conventional chemical extraction process.