Effect of densification on physical and mechanical properties of date palm wood impregnated with melamine formaldehyde Resin

Introduction: The long, thick, and cylindrical trunk of the date palm (Phoenix dactylifera) presents a potential alternative to the large trunks of conventional timber trees for lumber production. However, challenges arise due to its high porosity, incomplete wood structure, and varying density across different sections of the trunk. The aim of this research was to employ wood modification technologies to enhance the performance of date palm trunk wood. The primary objective of this study was to evaluate and improve the physical and mechanical properties of date palm (Phoenix dactylifera) wood through a two-stage treatment process involving impregnation with melamine-formaldehyde resin, followed by compression. This research seeks to offer an effective solution for increasing the added value and enhancing the utility of this agricultural residue as a raw material in the wood industry.
Method: In this study, peripheral wood from date palm trunks in the Behbahan region was collected and prepared. The samples were divided into three main groups: a control group (untreated), a group impregnated with melamine-formaldehyde resin, and a group that was first impregnated with melamine-formaldehyde resin and then densified at compression ratios of 15% and 30%. Following the treatments, key physical and mechanical properties, including the modulus of elasticity in bending, modulus of rupture, compressive strength parallel to the grain, hardness, water absorption, and dimensional stability, were measured and recorded. Microscopic images were taken to confirm resin penetration and examine the internal structure of the treated samples. One-way analysis of variance was used to determine significant differences among treatment means at a 95% confidence level, and, if significant differences were found, Duncan’s multiple range test was employed for group comparisons.
Results: The results indicated that the densification technology, combined with melamine-formaldehyde resin impregnation, significantly improved the physical and mechanical characteristics of the date palm trunk wood. A notable increase in the density of the treated samples was observed. The modulus of rupture, compressive strength parallel to the grain, and hardness of the samples were substantially enhanced, with compressive strength increasing by over 100% and hardness increasing more than threefold. Furthermore, the combined treatment led to a significant reduction in water absorption and thickness swelling, demonstrating a considerable improvement in the hydrophobicity and dimensional stability of the date palm trunk wood. The findings also indicated that shape recovery and springback after densification were negligible, and microscopic observations confirmed the successful penetration of melamine-formaldehyde resin into the pores of the samples.
Conclusion: The findings of this research suggest that the two-stage modification process of resin impregnation and densification can be an effective approach for improving the physical and mechanical properties of date palm trunk wood and increasing its added value. Consequently, the thick and cylindrical trunk of the date palm can be considered a viable alternative to the substantial trunks of timber trees for lumber production.