Utilization of phenol formaldehyde/Fe₃O₄ nanocomposite as microwave preheating amplifier in laminated veneer lumber (LVL) structure

In this study, Phenol Formaldehyde (PF) resin was modified with Fe₃O₄ nanoparticles (NPs) as microwave (MW) absorber nanocomposite in the LVL structure to accelerate MW preheating of the billet. The presence and distribution of Fe₃O₄-NPs in PF substrate was confirmed by Energy Dispersive X-Ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM). Differential Scanning Calorimetry (DSC) analysis also proved that existence of Fe₃O₄-NPs shortened the curing time of PF composite. According to Fourier Transform Infrared (FT-IR) analysis, Fe₃O₄-NPs had no effect on the functional groups of PF nanocomposite. Temperature variations throughout the microwave preheating process were used to monitor the MW absorption performance. Surprisingly, higher temperatures were recorded for samples containing Fe₃O₄-NPs. MW preheated LVL's with 3% Fe₃O₄-NPs were hot-pressed at a higher initial temperature, causing the core layer temperature to reach 100 °C faster. The shear strength and screw withdrawal resistance findings showed that the presence of Fe₃O₄-NPs had a greater impact on the core layers of LVLs than on the surface layers. Remarkably, MW preheated LVLs containing 2% of Fe₃O₄-NPs after 8 min of hot-pressing exhibited comparable mechanical characteristics to control samples after 12 min of hot-pressing. These findings show that the PF/Fe₃O₄-NPs composite improved MW absorption performance while also enhancing LVL mechanical characteristics.