Document Type : Research Paper
Authors
1
3. Associate prof. of Wood Science and Technology University of Mohaghegh Ardabili, Faculty of Agriculture and Natural Resources, Ardabil, Iran.
2
Assistant prof. of Wood Science and Technology department of natural resources Faculty of agriculture and natural resources University of Mohaghegh Ardabili Ardabil Iran.
3
2. M.Sc. Student of Wood Science and Technology department of Natural Resources Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil Iran.
10.22034/ijwp.2025.2067054.1718
Abstract
Problem definition and objectives: Cellulose nanofibers (CNF), as an emerging bio-based material with outstanding mechanical, optical, and environmental properties, play a significant role in the development of innovative products in packaging, nanocomposites, and functional papers. However, the industrial production of CNF faces challenges such as high energy consumption and the costly nature of preparation processes including bleaching and refining. On the other hand, the use of non-wood lignocellulosic resources such as wheat straw as a cheap, abundant, and renewable material can be an effective approach to reduce production costs, improve process efficiency, and enhance environmental compatibility. This study aims to investigate the effect of energy consumption in two critical stages mechanical refining and microfluidization on the physical and mechanical properties of CNF derived from wheat straw. The study also seeks to determine optimal energy conditions for producing high-performance CNF while eliminating the need for bleaching in industrial processes.
Methodology: In this study, pulping was performed using the soda process under specific conditions: alkali concentration of 16%, cooking time of 30 minutes, cooking temperature of 160°C, and a liquor-to-wheat straw ratio of 3:1. The resulting unbleached pulp was directly subjected to mechanical refining without any bleaching treatment. This refining was carried out using a disk refiner at four different energy levels: 130, 170, 250, and 500 kWh/t, to evaluate the effect of refining intensity on fiber preparation for microfibrillation. Subsequently, the refined samples were passed through a microfluidizer in six different stages (from one to six successive passes) to complete the final fibrillation process and produce cellulose nanofibers. Ultimately, the mechanical properties including tensile index, burst index, and tear length as well as physical and optical characteristics such as thickness, surface roughness, density, and transparency of the CNF samples were evaluated. All tests were performed according to ISO and TAPPI standards.
Results: The results indicated that increasing energy consumption up to an optimal level led to a significant improvement in the mechanical properties of CNF. The treatment condition using 170 kWh/t in refining and 258 kWh/t in microfluidization showed the best performance. Under these conditions, the tensile index reached 113.5 N·m/g and the tear length reached 11.5 km, representing an improvement of over 220% compared to the control sample. Additionally, the samples under this optimal condition exhibited reduced thickness, increased density, lower surface roughness, and enhanced transparency, indicating a more uniform structure, better nanofiber distribution, and stronger interfiber bonding. In contrast, excessive energy input in the microfluidization stage did not result in further improvements and, in some cases, led to a decline in mechanical performance—likely due to fiber structure degradation caused by over-processing.
Conclusion: The findings of this study demonstrate that it is possible to produce high-quality CNF from unbleached wheat straw pulp without the need for lignin removal. Eliminating the bleaching stage not only reduces energy consumption and production costs but also preserves the structural components of the fibers, thereby enhancing the mechanical performance of the CNF. Moreover, precise control over energy input at each stage is a key factor in optimizing the final product properties. These results can serve as a foundation for the development of industrial-scale CNF production processes from non-wood sources with a cost-effective and resource-efficient approach.
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