Objective A high-performance, biodegradable bio-based cushioning packaging material (BCMP) was developed as a sustainable alternative to non-degradable petroleum-based materials such as expanded polystyrene (EPS) and expanded polyethylene (EPE). The primary goal was to leverage natural biopolymers and agricultural waste to create a material that combines excellent cushioning performance with environmental benefits, specifically addressing the issue of “white pollution”. The research focused on enhancing the properties of gelatin, a natural protein, through a novel deep eutectic solvent (DES)-assisted crosslinking strategy, and integrating it with rice straw fiber for reinforcement.

Methods Gelatin was selected as the matrix and modified using a DES system composed of sodium acetate trihydrate and urea (molar ratio of 1∶2). Bis(2-dimethylaminoethyl) ether (BDMAEE) served as the crosslinking agent within this DES medium to facilitate its covalent bonding with gelatin's functional groups. The crosslinked gelatin product (GB_DES) was characterized against a control sample (G-F, prepared in pure water) using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), contact angle measurements, and scanning electron microscopy (SEM). The BCMP was then fabricated by hot-pressing GB_DES with alkali-pretreated rice straw fibers and calcium carbonate filler. The final material's performance was systematically characterized through static compression tests (according to GB/T 8168-2008), rebound rate measurements after three compression cycles, and a 120-day soil burial degradation test to assess its biodegradability.

Results The DES-assisted crosslinking strategy was proved highly effective. DSC analysis showed that the denaturation temperature of the crosslinked film (GB_DES-F) increased significantly to 85.8 ℃ from 73.1 ℃ for the control (G-F), indicating the enhanced thermal stability and crosslinking density Fig.1. FT-IR spectra confirmed the successful covalent crosslinking, with the formation of new amide bonds evidenced by a stronger peak at 1403 cm⁻¹ Fig.2. Contact angle measurements demonstrated the improved hydrophobicity for GB_DES-F (initial angle~99.3°) compared to G-F (~92.8°), which decreased slowly over time, suggesting a more water-resistant and stable network structure Tab.2. SEM images revealed that the crosslinked film possessed a smoother surface and a more uniform, less porous cross-section than the control Fig.3. The resulting BCMP exhibited promising cushioning properties. Its stress-strain behavior was comparable to that of traditional EPE and EPS materials at strains below 60% Fig.4. The material demonstrated good elastic recovery, with rebound rates of 79%, 76%, and 74% over three consecutive compression cycles, meeting the practical standards for cushioning packaging Fig.5. Most importantly, the BCMP showed excellent biodegradability, achieving a degradation rate of 91.3% after 120 days of soil burial. The degradation profile followed a three-stage process, initially slowed by the antimicrobial effect of urea from the DES, then accelerated as microorganisms metabolized the gelatin and hemicellulose components, and finally plateaued during the slower degradation of crystalline cellulose Fig.6.

Conclusions A novel bio-based cushioning material was successfully developed through DES-assisted crosslinking of gelatin with BDMAEE and reinforcement with rice straw fibers. This approach significantly improved the thermal stability, hydrophobicity, and structural integrity of the gelatin matrix. The final BCMP composite demonstrated cushioning and elastic recovery performance on par with conventional petroleum-based materials. Coupled with its high biodegradability (91.3% of degradation rate in 120 days), the BCMP presents a viable and environmentally friendly alternative for sustainable packaging. This work provides a new strategy for valorizing biomass resources and offers a practical solution for developing high-performance, fully biodegradable materials to mitigate plastic pollution.