Energy-efficient cellulose acetate nanofilms from hemp hurds for circular packaging and agricultural mulch applications

Abstract This study uniquely demonstrates the valorization of industrial hemp hurds into energy-efficient cellulose acetate (CA) nanofilms tailored for both sustainable packaging and agricultural mulching applications, a dual-purpose approach to address the growing global concern over single-use plastic pollution. The degree of substitution (DS) of CA was tailored by adjusting the soaking time of hurd cellulose in glacial acetic acid. Following acetylation, the resulting CA fibers underwent mechanical nanofibrillation through friction grinding using a Masuko grinder to produce cellulose acetate nanofibers (CAN). Acetylation significantly reduced this energy demand, resulting in up to 81.4% lower energy being required for nanofibril formation compared to unmodified cellulose. The nanofibers were then cast into CAN films via solution casting. The obtained CA fibers were then characterized by using time-of-flight secondary ion mass spectrometry (ToF–SIMS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to evaluate structure, thermal behavior, and morphology. Mechanical and barrier properties of the CAN films were assessed against oxygen, moisture, water, oil, and grease to determine their suitability for high-value packaging and agricultural applications. The films showed excellent oxygen resistance (11.8–60.1 mL/m 2 ·day), high oil and grease resistance (Kit 12), and minimal hot oil absorption (≤ 0.75%). Improved dry (46.17–62.83 Nm/g) and wet (2.19–14.77 Nm/g) tensile strength, reduced water absorption (0.84–6.74%), and 38.63% lower WVTR were also observed. Compared to plastic mulch films, the acetylated films demonstrated excellent moisture retention, promoting seed germination and faster growth rates in preliminary controlled tests. These sustainable films offer a viable alternative to fossil-based plastics, ultimately contributing to food security and a circular economy. Graphical abstract