Double-stretching as an effective and generalizable strategy towards thinner nanofibers in solution blow spinning

Solution blow spinning(SBS)applies high-speed airflow to prepare fibers by generating a strong stretching force.It has the advantages of scalable production,tailorable morphologies,and wide applicability.Yet,the SBS strategy can hardly prepare fibers down to the sub-100 nanometers,which limits its performance in demanding applications.Herein,we overcome the limitation of SBS by introducing a second airflow.This novel strategy is termed double-stretching SBS(DS-SBS)because an extra stretching force is exerted on the fiber when it converges with the second airflow.Polyamide6 nanofibers with an average diameter of 80 nm are successfully prepared with the DS-SBS strategy,while the SBS strategy could only prepare submicron fibers with an average diameter of 120 nm.Further,the generality of the DS-SBS strategy to reduce fiber diameter is verified on numerous solute-solvent pairs.

Processing Nomex Nanofibers by Ionic Solution Blow‑Spinning for Efficient High‑Temperature Exhausts Treatment

Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrin-sically high chemical stability,superior mechanical performance,and excellent high-temperature resistance.However,the mass production of hard-to-dissolve nanofibers still remains a critical challenge.A simple,scalable,and low-cost ionic solu-tion blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm.After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide(LiCl/DMAc)solution system,the conductive solution can be stably and conductivity-independently processed into nanofibers.The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity.Owing to nanofibrous structure and high dipole moment,Nomex nanofibrous filters show a stable high filtration efficiency of 99.92%for PM_(0.3) with a low areal density of 4.6 g m^(-2),as well as a low-pressure drop of 189.47 Pa.Moreover,the flame-retardant filter can work at 250°C and 280°C for a long and short time without shrinking or burning,respectively,exhibiting a high filtration efficiency of 99.50%for PM_(0.3-10.0).The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts,making Nomex nanofi-brous membrane an even more ideal industrial-grade air filter than polypropylene,polytetrafluoroethylene,polyimide,and ceramic nanofibrous filters.