| dc.description.abstract | This research is organized into five chapters. The first chapter provides a theoretical overview of key concepts related to resins and wood composites, with emphasis on phenol-based and PMDI-based adhesives. The second chapter describes the synthesis and characterization of a bio-derived novolac resin, in which 50% of the phenol was replaced by bio-oil obtained through pyrolysis. The third chapter focuses on the production of wood composites using both the bio-based novolac resin and a conventional commercial novolac resin. Mini particleboards were fabricated using three resin proportions (20%, 35%, and 50%) to evaluate performance. Mechanical properties such as dry and wet modulus of elasticity (MOE) and internal bonding were assessed, along with complementary analyses such as scanning electron microscopy (SEM) and optical surface observations.
Chapter four explores PMDI-based adhesives modified by partial replacement with bio-oil and polyethylene glycol (PEG 1500), evaluating their adhesive performance through the manufacture of sandwich-type plywood panels. A Box-Behnken experimental design was used with three variables: curing temperature (120°C, 135°C, and 150°C); the percentage molar ratio of hydroxyl (OH) groups from PEG 1500 and bio-oil (0%, 50%, and 100%); and the NCO:OH molar ratio (1:1, 2:1, and 3:1) between PMDI and the OH-rich components. Shear strength tests were conducted in both dry and wet conditions, and further characterization included Soxhlet extraction, contact angle measurement, and SEM imaging to identify optimal adhesive formulations.
In chapter five, the study extended the application of modified PMDI resins to wood composite boards. Another Box-Behnken design was employed using three factors: NCO:OH molar ratio, percentage of PEG 1500, and percentage of bio-oil. Fifteen formulations were tested and evaluated through dry and wet MOE, internal bonding, density, moisture content, and microscopy.
Results indicate that bio-oil contributes to improved dispersion and resin flow through the wood matrix, enhancing mechanical performance, particularly under humid conditions due to its hydrophilic characteristics. PEG 1500 exhibited variable effects: low percentages improved dry performance, while higher amounts reduced mechanical strength under both dry and wet conditions. Overall, both bio-derived novolac resins and modified PMDI formulations demonstrated strong structural potential, with positive implications for mechanical and environmental performance. Saturation thresholds that limit the efficacy of certain modifications were identified, offering valuable insights for the design of sustainable wood adhesives. | en_US |
