Upcycling spent coffee grounds and waste PET bottles into electrospun composite nanofiber mats for oil structuring applications

Abstract

Spent coffee grounds (SCG) and post-consumer PET bottles (PETbot) are major waste materials from the food industry. In this work, their use to obtain electrospun composite nanofibers is explored aiming to develop a new route for their upcycling into high added-value oil-based products. Raising the proportion of PETbot increased the average fiber diameter (from 0.36 to 0.89 μm) and enhanced the tensile properties of the mats. Young's modulus and strain-at-break increased from 5.1 to 32.8 MPa and from 13.8 to 39.4 %, respectively, as the SGC:PETbot weight ratio decreased. Dispersions of the mats in castor oil exhibited shear-thinning and gel-like viscoelastic properties which can be tuned through the SCG:PETbot ratio. Friction coefficient values of resulting oleogels tested in a tribological contact ranged from 0.165 to 0.092. SCG and PETbot can be used to obtain electrospun nanofibers with oil structuring capabilities while resulting oleogels are proposed as environmentally-friendly alternatives to semisolid lubricants.