INVESTIGATION OF THE PERFORMANCE OF WOOD COMPOSITES THROUGH ANALYSIS OF METHYLENE AND ETHER BRIDGE FORMATION AND THE INCORPORATION OF ALKYL-SUBSTITUTED UREA COMPOUNDS INTO UREA-FORMALDEHYDE RESIN
S. M. Ashik Abedin
Materials Science and Nano Engineering, MSc. Thesis, July 2025
Thesis Jury
Assoc. Prof. Dr. Bekir Dizman (Thesis Advisor), Prof. Dr. Yusuf Ziya Menceloğlu,
Prof. Dr. Duygu Avcı Semiz
Date & Time: 3 July 2025 – 10.00 AM
Place: FENS G029
Keywords: Modification of urea-formaldehyde resin, formaldehyde emission, wood composites, methylene and ether bridge, urea model compounds.
Abstract
In recent decades, wood-based composite materials, owing to their global sustainability advantages and good surface hardness and dimensional properties, have been utilized in various fields, such as structural applications (construction and architecture), industrial applications (molds and pallets), furniture, and interior design. Wood composites are fabricated by combining and compressing lignocellulosic wood fibers or particles with a suitable resin or binder using a hot press system. Urea-formaldehyde (UF) resin is one of the most popular binders for fabricating wood-based composites, including particleboard and medium-density fiberboard, because of its easy production, low cost, good adhesion properties, and flexibility in the curing process. Although there are several benefits of using UF resin in fabricating wood composites, UF resin-based wood composites exhibit low moisture resistance and formaldehyde emission. Due to their low moisture resistance, UF-bonded wood composites can’t be used in outdoor environments. The gradual formaldehyde emission from the wood composites, attributable to the reversibility of condensation reactions of the UF resin, makes the widespread utilization of UF-bonded wood composites more challenging. Therefore, strategic modifications to its synthesis and crosslinking structure are essential for improving performance, an area that remains underexplored and warrants further research.
In this thesis, eight different UF resin synthesis processes were conducted to investigate the effects of changing the pH, time, temperature, and order of urea and formaldehyde addition on the structure of the UF resin. The methylene and the ether bridge ratio that define the final crosslinking structure were calculated for all synthesis procedures. Additionally, alkyl-substituted urea model compounds (1,1-dimethylurea and 1,3-dimethylurea) were incorporated with the UF resin at 5% and 10% of the original urea. In the first chapter, an introduction was provided to the background and development of UF resin and wood composites, as well as the detailed mechanism of the UF reaction and some modification strategies already explored in the literature. In the second chapter, one UF and one melamine urea formaldehyde (MUF) resin synthesis process were established as reference systems and comprehensively characterized using FTIR, NMR, DSC, and Rheology tests. Then, seven different UF synthesis processes were described, and each was specifically designed to enhance methylene bridge formation through systematic modification of reaction parameters. The methylene and ether bridge ratio was calculated using NMR spectroscopy, and the performance of board tests was also analyzed. In the third chapter, the impact of the incorporation of urea model compound was evaluated in terms of methylene and ether bridge ratio and board performance tests. In the final chapter, the research results and implications were summarized.>
