CELLULOSE CHEMISTRY AND TECHNOLOGY Cellulose Chem. Technol., 58 (1-2), 115-123 (2024) SURFACE FUNCTIONALIZATION OF KENAF FIBERS WITH LAUROYL CHLORIDE: EFFECTS OF ALKALINE PRETREATMENT METHOD PAYLO EBRAHIMI, * MOJTABA KOOSHA, * SEPIDEH HAMEDI, * ELHAM VATANKHAH * and REZA SHIDPOUR ** * Faculty of New Technologies and Aerospace Engineering, Shahid Beheshti University, Tehran, Iran ** Babol Noshirvani University of Technology, Babol, Mazandaran, Iran ✉Corresponding author: M. Koosha, m_koosha@sbu.ac.ir Received November 16, 2023 Surface functionalization of cellulose fibers is the current focus of research seeking to develop composite materials for various applications. One reason is the low compatibility of natural cellulose-based fibers with thermoplastic matrices for the production of wood-plastic composites. In this research, kenaf fibers (KF) were esterified with lauroyl chloride. Before the esterification reaction, two alkaline pretreatment methods were used: Bain-Marie at low temperature, and at high temperature and pressure in the digester. SEM results showed a smoother surface morphology after esterification. ATR-FTIR results confirmed the substitution of hydroxyl groups of cellulose with lauroylate functional groups. Increasing the carbon content in EDX spectroscopy further supported the successful esterification of kenaf fibers, which is in accordance with ATR-FTIR findings. Based on ATR-FTIR and EDX results, the Bain-Marie pretreatment method was more effective for the esterification reaction. According to the XRD results, the crystallinity index of the fibers slightly increased after esterification reaction. However, the fibers pretreated in the digester had a higher crystallinity index, which was related to efficient removal of amorphous regions due to higher temperature and pressure used in the digester process. This research showed that alkaline pretreatment in Bain-Marie was more effective for the surface functionalization of cellulose fibers than the digester process. These results can be applied in future research works for esterification of cellulose fibers. Keywords: kenaf fibers, lauroyl chloride, esterification, digester, pretreatment INTRODUCTION Wood-plastic composites (WPC) generally comprise a thermoplastic polymer, such as polyethylene, polypropylene, PVC, polylactic acid, etc., as a matrix, and a wood-based filler as reinforcement. Wood flour, mainly of softwood, has been used as a reinforcing agent in WPC. Wood fibers can also be replaced by non-wood ones, such as hemp, jute, sisal, and kenaf fibers. 1 Natural fiber-reinforced thermoplastic composites are one of the common methods for obtaining special composites, with desirable properties, that have attracted the attention of many researchers. Natural fibers offer advantages over synthetic ones, such as low cost, low density, less wear in process machines, acceptable strength, biodegradability, and renewability. Hemp, jute, sisal, and kenaf are the most common natural fibers used in the manufacture of thermoset or thermoplastic composites. 2 Kenaf fibers (Hibiscus cannabinus L.) have attracted the researchers’s attention in the past decades. 3-6 Kenaf plants can absorb carbon dioxide at a rate of around 1.5 tons per ton of fiber, which is an environmentally friendly absorption. 7 Kenaf fibers are considered as good candidates for the reinforcement of biodegradable polymer composites. 8 It has been established that the fiber-matrix interface plays an important role in determining the physical and mechanical properties of natural fiber reinforced composites. 9 Most of the natural fibers derived from plant resources are mainly composed of cellulose and hemicelluloses, with a strongly hydrophilic structure, while thermoplastic matrices exhibit hydrophobic chemical structure. 10 Thus, kenaf fibers are largely incompatible with most thermoplastic matrices and cannot make strong fiber-matrix interfaces. 11,12 In this regard, during the preparation of natural fiber reinforced plastic