## 4 Conclusions  
Nanoparticle-reinforced flexible bio-based PU foam samples were easily produced using absorption and hydrothermal reduction reaction methods, and they showed to be dependable and delicate with precise control. In total, 15 samples were made using different compositions determined by an RSM central composite design technique. Sample A13 (0.3 wt.%, 0.3 wt.%, and 2.5 wt.% for GNP, ZrO\({}_{2}\), and BC, respectively) depicts a maximum EMI SE of 28.03 dB in the 8-12 GHz frequency band, which is improved compared to regular PU foam without reinforcement. The presence and uniformity of nanoparticles in the PU foam have been authenticated through FESEM and FTIR. Influential parameters have been discovered for statistical computation, and their amounts have been set using ANOVA. The regression equation was persistent, and the EMI SE was obtained using the iterative results of the different samples and the ANOVA for EMI. The difference between the regression equation predicted EMI values and those measured in the experiment are less than 5%. The ideal weight percentage for attaining the highest EMI SE value of 28.61 dB is the combination of 0.1 wt.%, 0.5 wt.%, and 2.5 wt.% for GNP, ZrO\({}_{2}\), and BC, respectively, through the optimization curve.  
Figure 11: Shielding Effectiveness comparison between measured and simulated sample.  
Figure 10: Simulation of Electric Field Intensity through COMSOL Multiphysics.  
The electromagnetic behavior of a geometrically simplified open-cell flexible bio-based polyurethane foam was simulated using the RF module in COMSOL Multiphysics. The results carry a relative error of 2.48% between the EMI SE of the manufactured material, which peaked at 28.03 dB, while the maximum value reached for the simulated model is near 27.35 dB. For specific frequency values, the experimental and simulated results indicate that the sample A13 material can act as a resonance cavity, considerably attenuating the incoming EM radiation. The nanocomposite flexible bio-based PU foam is potentially biodegradable, lightweight, flexible, and low-cost. As a result, it can be utilized as a long-term replacement for traditional PU foam in shielding applications, such as terrestrial data transfer, radio operations, satellite communication body part covering, and radio navigation and positioning. The future scope of this work can be extended with the reinforcement of different nanoparticles for enhancing the EMI shielding.  
V.K.S.: Conceptualization, Methodology, Software, Data curation, Writing--Original draft preparation. J.S.: Supervision, Software, Validation and Editing. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
VIT-Chennai has generously provided us with a seed fund, as well as a fully functional laboratory in which to conduct the trials. We are also grateful to [PERSON] of Acharya Institutes in Bangalore for his assistance and knowledge in analyzing the results and [PERSON], Managing Director of Shaya Polymers Private limited, for the support in material development.  
The authors have no known competing financial interest or personal affiliations that could have influenced the study's findings. As a result, the authors state that no competing interests exist.