## 4 Conclusions  
Based on the conducted research, it was found that after adjusting the amount, activated carbon from coconut shells can be used as an effective modifier of UF resin. The introduction of activated carbon significantly changes the properties of the adhesive mixture. As the loading increases, the viscosity of the adhesive increases; moreover, the maximum addition of 1.5% also increases the reactivity of the resin. The use of activated carbon in an amount of up to 1.5% does not significantly influence the aesthetic properties and density of the manufactured particleboards. However, it can affect both the physical and mechanical properties of the resultant materials. In the cases of the 0.75 and 1% loadings, the produced particleboards show better mechanical properties (improved internal bond, bending strength, and modulus of elasticity) and delayed degradation in water, as indicated by lower valuesof thickness swelling measured after 2 h of soaking in water. In the case of long-term exposure to water, the modification has no effect. A comparison of the obtained results with the results of other works also indicates that the use of activated carbon as a UF resin modifier is a complex issue, and the expected effect may vary depending on many factors. Furthermore, in the cases of the additions of 1 and  
Figure 6: Water resistance of particleboards after 2 and 24 h of soaking in water: (**a**) thickness swelling, (**b**) water absorption. Error bars represent the standard deviation.  
Figure 7: Formaldehyde content in manufactured particleboard.  
1.5%, a reduced formaldehyde content in the boards is also noted. Based on all of the results, it was concluded that the variant containing 1% activated carbon from coconut shells can be considered optimal, for which increased strength, enhanced water resistance, and reduced formaldehyde content were observed.  
Conceptualization, J.K.; methodology, J.K., D.D. ([PERSON]), P.A., K.S.-S., D.D. ([PERSON]) and R.M.; software, J.K., D.D. ([PERSON]), P.A., K.S.-S., D.D. ([PERSON]) and R.M.; validation, J.K., D.D. ([PERSON]), P.A., K.S.-S., D.D. ([PERSON]) and R.M.; formal analysis, J.K. and D.D. ([PERSON]); investigation, J.K., D.D. ([PERSON]), P.A., K.S.-S., D.D. ([PERSON]) and R.M.; resources, K.S.-S., D.D. ([PERSON]) and R.M.; data curation, J.K. and D.D. ([PERSON]); writing--original draft preparation, J.K.; writing--review and editing, J.K. and P.A.; visualization, J.K. and D.D. ([PERSON]); supervision, P.A., K.S.-S., D.D. ([PERSON]) and R.M.; project administration, R.M.; funding acquisition, K.S.-S. and R.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors would like to thank [PERSON] for performing the spectroscopic analysis. The study was supported by the funding for statutory R&D activities under the research task No. 506.224.02.00 of the Faculty of Forestry and Wood Technology, Poznan University of Life Sciences. This research was also supported by the project \"Development, Exploitation Properties and Application of Eco-Friendly Wood-Based Composites from Alternative Lignocell-Iosic Raw Materials\", project No. HHC-B-1290/19.10.2023, carried out at the University of Forestry, Sofia, Bulgaria.  
The authors declare no conflicts of interest.