Composite electrospun membranes from cellulose nanocrystals, castor oil, and poly(ethylene terephthalate): Air permeability, thermal stability, and other relevant properties

The study examined the use of cellulose nanocrystals (CNCs) in poly(ethylene terephthalate) (PET)/castor oil (CO) electrospun membranes, focusing on how CNCs influenced membrane properties for aerosol filtration applications. PET membranes were fabricated using 5 wt% and 10 wt% of CNCs and 2.5 wt% CO to assess its effectiveness as a compatibilizing agent, under a solution flow rate of 25.5 μL/min, a voltage of 25 kV, and a needle-collector distance of 8 cm. Nonaligned fiber membranes featured a network of ultrafine and nanofibers, while aligned fibers had an average diameter of over 300 nm (ultrafine fibers). The PET membranes permeability parameters were applied to Forchheimer's equation. All membranes presented values of Darcian (k₁)/non-Darcian (k₂) permeability coefficients in the order of 10⁻¹³ m²/10⁻⁸ m, respectively, near the range reported for commercial high-efficiency particulate air filters. CNCs acted as reinforcing agents, while CO was a compatibilizing agent, improving the material's mechanical behavior. Nonaligned PET/CO/10 wt% CNC presented a storage modulus (E') 2-fold higher/tensile strength 3-fold higher than pristine PET. Aligned PET/CO/5 wt% CNC, characterized in the preferential direction of fiber alignment, had approximately an E' 42-fold higher/tensile strength 6-fold higher than the same membrane, but tested in the perpendicular alignment direction. The glass transition temperature (T_g) values of PET (90–110 °C) did not exhibit any significant impact from membrane composition or fiber alignment. This study demonstrated the promising capability of PET-CNC bio-based electrospun membranes to be used in aerosol filtration or gas-solid and liquid-solid separations.