Balance of waterproofness, breathability, and higher flexibility of electrospun polyvinylidene fluoride membrane blended graphene for functional garment

Abstract

Flexibility, waterproofness, and breathability are fundamental demands for functional clothing and personal protective equipment. To solve problems caused by the low tensile strength and contradictions between hydraulic pressure and breathability of polyvinylidene fluoride (PVDF) electrospun membrane, graphene was added to PVDF spinning fluid to prepare a graphene/PVDF composite nanofibrous membrane using N, N-dimethylacetamide as a solvent, and the morphological structure, waterproofness, breathability, and mechanical flexibility of the nanofibrous membranes were characterized. The results show that the graphene/PVDF composite nanofibrous membrane was synergistically improved in waterproofness and breathability, and that the moisture permeability of the PVDF membrane increased from 2915.92 g/(m2 24 h) of pristine PVDF nanofibrous membrane to 4415.37 g/(m2 24 h) of 0.15 wt% graphene/PVDF composite nanofibrous membrane. This indicates that the addition of graphene can significantly improve the moisture permeability of PVDF nanofiber membrane. This finding is accompanied with a decrease in the contact angle and hydraulic pressure, from 143.5° and 23.4 kPa, respectively, for the PVDF membrane to 125° and 13.7 kPa, respectively, for the 0.15 wt% graphene/PVDF composite nanofibrous membrane, and indicates that the waterproofing performance was reduced. Controlling the graphene concentration at 0.1125 wt% was beneficial to improving both waterproofness and breathability. The average fiber diameter of the graphene/PVDF composite nanofibrous membrane with different graphene concentrations changed from 317 nm for the PVDF membrane to 355 nm (0.05 wt%) or 1268 nm (0.15 wt%) for the graphene/PVDF composite nanofibrous membrane. The incorporation of graphene in PVDF can satisfactorily change the flexibility of the PVDF nanofibrous membrane: the fracture strength and elongation of the PVDF membrane are 6.7 MPa and 8.3%, respectively, while the fracture strength and elongation of the graphene/PVDF composite nanofibrous membrane are, respectively, 13.2–19.8 MPa and 9.1%–17.9%. This work provides guidance for the preparation of a novel, smart, flexible, waterproof, breathable, wearable PVDF-based nanofiber membrane.