Iranian Journal of Wood and Paper Industries

Iranian Journal of Wood and Paper Industries

Design and Synthesis of New Ionic Liquids as Pretreatment Agent of Wood Flour, and Studying Its Effects on the Physical, Mechanical and Viscoelastic Properties of Polyethylene-based Composites

Document Type : Research Paper

Authors
Behzad Kord 1
Farnaz Movahedi 2
1 Cellulosic Materials and Packaging Research Group, Research Center of Chemistry and Petrochemistry, Standard Research Institute, Karaj, Iran
2 Cellulosic Materials and Packaging Research Group, Research Center of Chemistry and Petrochemistry, Standard Research Institute, Karaj, Iran.
10.22034/ijwp.2025.2066533.1715
Abstract
Problem definition and objectives: The search for sustainable raw material is of critical importance with the ever-growing environmental concerns together with the diminishing fossil fuel resources. Lignocellulosic biomass is nowadays being considered as one of the most promising alternative feedstocks for the production of engineered composite materials. In this regard, various pretreatment technologies have been employed to increase the efficiency and modify the structure of the lignocellulosic materials but development of an effective and environmental benign innovative pretreatment process remains challenging. Ionic liquids, due to their unique properties, especially high thermal stability and low vapor pressure, have been emerged as environmentally friendly alternatives for the processing of lignocellulosic materials for their effective use in the manufacture of composite materials compared to conventional organic chemical solvents. In this study, the effect of ionic liquids (ILs) pretreatment on the physical and mechanical properties of composite produced from wood flour and high-density polyethylene was investigated.
Methodology: Firstly, two new types of ionic liquids with different anionic charges, namely 1-(3-trimethoxysilylpropyl)-3- methylimidazolium chloride (IL-Cl) and 1-(3-trimethoxysilylpropyl)-3-methylimidazolium thiocyanate (IL-SCN) were designed and synthesized. Then, the validity of the synthesized ionic liquids was checked by Fourier transform infrared spectroscopy (FTIR) and carbon nuclear magnetic resonance (13CNMR) analyses. After that, the pretreatment process of wood flour with ionic liquids was carried out under reflux conditions. Finally, the treated wood flour was mixed with polyethylene at a weight ratio of 50% by melt compounding, and then, the test specimens were produced by compression molding. Further, the mechanical strength, viscoelastic behavior, and water uptake of the specimens prepared from untreated and ionic liquids-treated were evaluated. Besides, the chemical structure of the treated wood, and the anchoring degree of synthesized ionic liquids on the wood surface were tracked by tracked using infrared spectroscopy and elemental analysis, respectively. The morphological aspects of the specimens were characterized using field emission scanning electron microscope (FESEM).
Results: The results of FTIR spectra showed a decrease in the peak intensity of hydroxyl groups (OH) at 3434 cm-1, which indicates the successful modification of wood flour with ionic liquids. Elemental analysis revealed that both types of ionic liquids anchored on the wood surface, but the degree of anchoring was higher in IL-SCN than IL-Cl. It was also found that the strong interaction between the wood flour and high-density polyethylene occurred in the presence of both ionic liquids pretreatment had a noteworthy effect on the mechanical properties of the composite specimens. The composites made from ionic liquids-treated wood flour exhibited higher flexural strength and modulus, tensile strength and modulus, and impact strength as compared to the untreated composites. Besides, the water absorption and thickness swelling of the specimens reduced as a result of the ionic liquids pretreatment, due to the the reduction of the gaps in the interfacial region and block the hydrophilic groups. The results demonstrated that the higher mechanical strength and lower water uptake for the IL-SCN samples compared to the IL-Cl samples, due to the difference in the anchoring degrees. The result of the dynamic mechanical test illustrated that the presence of ionic liquids significantly improved the storage modulus and loss modulus by reducing the mobility of the polymer chain. Also, the tan δ peak was shifted to higher temperature for the modified samples than unmodified ones. Morphological findings showed that the ionic liquid pretreatment method provided better adhesion at the interface by reducing cracks and holes.
Conclusion: Based on the results obtained from physical, mechanical, and viscoelastic tests, as well as morphological observations of the samples, it can be said that the using highly effective and clean ionic liquids-assisted pretreatment technology of lignocellulosic materials for fabrication of the composite panels for outdoor applications.
Keywords
Composites
ionic liquid
pretreatment
spectroscopy
mechanical strength
morphology

Subjects

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Iranian Journal of Wood and Paper Industries
Volume 16, Issue 3
Autumn 2025
Pages 415-435