Electrospinnability of PCL-doped eucalyptus kraft lignin and its application for structuring vegetable oils

• Electrospinnability of EKL solutions doped with PCL was investigated for the first time. • Increased viscosity and relaxation time improve nanofiber production and diameter. • SAOS functions of oleo-dispersions depend on the morphology and concentration of nanostructures. • EKL/PCL oleo-dispersions mimic grease rheology, suggesting potential as eco-friendly lubricants. This study explores the utilization of eucalyptus kraft lignin (EKL), extracted from black liquor of the pulp and paper industry, doped with polycaprolactone (PCL) to produce nanofibers with potential applications as vegetable oil structuring agents. Solutions of EKL:PCL in different weight ratios were prepared in a N,N -dimethylformamide/chloroform binary solvent, at concentrations ranging from 10 to 40 wt%, and submitted to electrospinning. Electrospinnability essentially correlates with the shear and extensional rheological properties of the solutions. Resulting electrospun EKL/PCL nanofibers were subsequently dispersed in castor oil at different concentrations (15 and 30 wt%). Stable gel-like dispersions were obtained with electrospun nanostructures predominantly composed of nanofibers or beaded fibers. The rheological properties and microstructure of EKL/PCL nanofiber-based oleo-dispersions were significantly influenced by both the EKL:PCL weight ratio and electrospun nanofiber concentration, with increases in the linear viscoelasticity functions and viscosity correlating with higher nanofiber concentrations and PCL proportions. These findings point out the potential of EKL/PCL nanofibers as eco-friendly vegetable oil structuring agents, in line with the principles of circular economy through the reuse of renewable waste materials.