Enhancing mechanical strength of electrospun nanofibers by coaxial electrospinning and thermal treatment

Abstract Electrospinning of nonwoven nanofibrous mats has received significant attention in recent years due to the high versatility and porosity of electrospun mats. However, electrospun mats generally suffer from low mechanical strength. This work reports a method to improve the mechanical strength of nanofiber mats by coaxial electrospinning combined with thermal treatment, without incurring significant dimensional shrinkage. Coaxial polyacrylonitrile (PAN)/polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) mats showed no shrinkage when tested at temperatures up to 240°C for 20 min, compared to a shrinkage of 94% for the homogenous PVDF‐HFP mats when treated at 190°C for 20 min. When treated at 178°C for up to 30 min, the coaxial fibres consistently showed changes in thickness of less than 10% and no significant change in area. The coaxial PAN/PVDF‐HFP mats showed negligible changes in average porosity after treatment at 178°C for 20 min. The mechanical strength of the coaxial samples heat treated at 178°C for 5 min was 7.72 MPa, a 22% increase from that before heating, and a 54% increase compared to the as‐spun homogenous PVDF‐HFP. Thus, the proposed technique of combining heat treatment with coaxial morphologies demonstrates significant potential for improving mechanical strength without dimensional shrinkage.