This study aims to examine the effects of N-methylmorpholine-N-oxide (NMMO) swelling-extrusion treatments on the deconstruction behavior and material properties of rice straw fibers. Three strategies were compared: simultaneous swelling and extrusion (CLNE), swelling followed by extrusion (CLNWE), and extrusion followed by swelling (CLEN). A systematic investigation was implemented to clarify the influence of the different treatment sequences on the fiber composition, morphology, crystallinity, hydrogen-bond networks, energy consumption, and tensile performance. The results showed that extrusion alone (CLE) had little effect, whereas the CLNE treatment increased the cellulose and lignin contents, while the hemicellulose was reduced to reflect the preferential disruption of amorphous polysaccharides. CLNWE pretreatment also enhanced the crystallinity to retain the higher hemicellulose, while CLEN facilitated the removal of neutral detergent-soluble fractions at low concentrations. Particle size analysis revealed that CLNE samples also exhibited the concentration-dependent shifts: The moderate NMMO levels promoted the fiber deconstruction, while the high concentrations reduced the mechanical separation, due to the lubrication. CLNWE fibers showed a decreasing mean particle size, indicating the irreversible hydrogen-bond disruption, whereas CLEN fibers remained largely unaffected. Microscopic observations confirmed that CLNE also generated abundant high-aspect-ratio fibers, though excessive NMMO weakened mechanical force transmission. In the CLNWE group, the fibers tended to cluster together at higher NMMO concentrations, whereas the CLEN group maintained the relatively uniform morphology. The XRD analysis demonstrated that all samples retained cellulose I structure. CLNE treatment increased crystallinity by up to 10.41%, compared with the CLE, though the values declined at higher concentrations. CLNWE samples exhibited steadily rising crystallinity, while CLEN samples showed the overall higher crystallinity than that of CLE, with the decreasing trends at elevated concentrations. FTIR analysis confirmed hydrogen-bond restructuring: CLNE promoted the conversion of intrachain to interchain bonds, while CLNWE facilitated chain separation and reformation after water washing, and CLEN primarily altered surface hydrogen-bond networks. Energy consumption indicated that CLNE reduced the average extrusion power by 56.4%~66.77% compared with CLE, due to the decreasing friction with the high fiber mobility. CLNWE and CLEN also lowered the energy demand with the concentration dependence. Mechanical testing revealed that CLNE was achieved in the highest tensile index at 8% NMMO concentration, which was improved by 64.27% over CLE, while simultaneously reducing energy demand. CLNWE and CLEN groups shared the smaller improvements. The CLEN fibers improved the tensile index by 17.21%~23.98% after surface-level regulation rather than bulk structures. Furthermore, the low-concentration trials (0~16% NMMO) confirmed that CLNE also exhibited the most sensitive mechanical response. The tensile index followed a quadratic relationship with the concentration (T₁=3.86+0.66x-0.04x², and R²=0.999), thus reaching the maximum of 6.33 (N·m)/g at 8% NMMO, which was 64.27% higher than CLE, superior to values reported for the rest fiber composites. The tensile index decreased linearly (T₂=5.94-0.05x, R²=0.982) at the higher concentrations (12%~75%). Excessive lubrication weakened fiber separation and reduced performance. Overall, the simultaneous NMMO swelling-extrusion treatment (CLNE) provided synergistic chemical and mechanical effects for the oriented deconstruction of cellulose microfibers, fiber morphology, and tensile strength, with reduced energy consumption. These findings can offer a strong reference for the green and efficient preparation of rice straw fiber composites. The agricultural residues can be valorized into sustainable bio-based materials. Importantly, the insights can be gained for the scalable process in the biomass fiber modification. Practical pathways toward renewable composites can also offer the broader development of the circular bioeconomy.

The application of twin-screw extrusion technology in the field of straw pretreatment is constrained by the closed nature of its structure, and the internal material flow characteristics have yet to be fully elucidated. This has resulted in a paucity of scientific theoretical support for screw configuration design. To address this issue, this study employed the discrete element method (DEM) in conjunction with physical tests to calibrate the simulation model parameters of rice straw powder. The calibration results demonstrate that the discrepancy between the simulation stacking test and the physical test results is 3.68%, thereby indicating that the simulation model parameters are accurate and reliable. Subsequently, an extrusion verification comparison test of rice straw powder was conducted. The results demonstrated that the relative errors between the simulated and actual quality in different regions ranged from 7.95% to 12.45%. This evidence substantiates the applicability and reliability of the established simulation model in simulating the extrusion process of rice straw powder. Furthermore, the variation rules of the parameters of particle motion and their correlation during the extrusion process of rice straw powder were investigated. It was found that the filling degree was significantly correlated with other parameters, and that the screw configuration had a direct influence on the filling degree. Finally, a bench test was conducted to ascertain the viability of the established simulation model in guiding the design of screw configurations. A linear regression equation was derived between the simulated power consumption and the average particle size of extruded samples under different screw configurations. The study offers a particle-scale understanding of the visualization of the extrusion process of rice straw powder and the scientific design of screw configurations, which is of great significance for the industrial application of the extrusion method.

In response to the problems of low efficiency, high labor intensity, and low mechanization in manual tobacco harvesting, a comb-off tobacco picking device for southern hilly tobacco areas was designed following the agronomic requirements and the principle of manual picking of tobacco harvesting in southern China. The device was composed of the power chassis, picking mechanism, and storage mechanism. This study involved the theoretical analysis, structural design, and modeling of the key components, such as chassis structure, combing-type picking mechanism, and power synchronization mechanism. The results of the motion analysis and calculation of the picking process demonstrated that the adjustment range of the comb chain elevation angles was from 12.4° to 20.9°, the comb rod installation distance was 76.2 mm, and the synchronizing mechanism transmission ratio was 3:10. One-factor test and three-factor three-level orthogonal test was performed with the forward speed of the chassis, the distance between the picking device baffles and the elevation angle of the chain with the combing bar as test factors, and the rate of broken and missed tobacco picking as evaluation indicators. It was revealed that the optimal combination of the forward speed of the chassis, the distance between the baffles, and the chain elevation angle were 1.5 km/h, 75 mm, and 12.4°, respectively. Moreover, verification tests suggested that the breakage rate of tobacco leaves was 9.99%, and the probability of missed tobacco picking was 7.31%, both of which satisfy the agriculture requirements and the operational requirements in the agricultural machinery certification syllabus.