## 3 Results and Discussion
### Mechanical Performance  
The mechanical properties of thermal insulating PUR foams are crucial for their performance and longevity in various applications. While their primary function is thermal  
Figure 9: The water contact angle of PUR foam composites with different fillers at 5 wt.% and 10 wt.% concentrations. insulation, their ability to withstand mechanical stresses significantly impacts their effectiveness and suitability for specific uses. Therefore, Figures 10 and 11 present the compressive and tensile strengths of control PUR foam and modified PUR foam composites. It can be seen that PUR/Per and PUR/Verm foam composites with 2.5-10 wt.% filler exhibit lower compressive strength values compared to control PUR foam. For instance, 2.5 wt.% and 5 wt.% Per filler (Figure 10a,b) reduces the parameter by 18%, while the same  
Figure 11: Tensile strength of PUR foam composites with different fillers at (**a**) 2.5 wt.%; (**b**) 5 wt.%; (**c**) 7.5 wt.%; and (**d**) 10 wt.%. Figure 10: Compressive strength of PUR foam composites with different fillers at (**a**) 2.5 wt.%; (**b**) 5 wt.%; (**c**) 7.5 wt.%; and (**d**) 10 wt.%. concentration of Verm filler--by 30% and 37%, respectively. With the further addition of 7.5 wt.% and 10 wt.% Per filler (Figure 10c,d), the compressive strength also deteriorates by 19% and 23%, respectively. A similar tendency of the same Verm filler concentrations can also be observed; for example, the parameter reduces by 40% and 45%, respectively. However, [PERSON] and [PERSON] [64] determined that the addition of Verm at concentrations up to 10 wt.% increases the compressive strength of PUR/melamine phenol phosphate composite foams, indicating that the positive results are attributed to fillers' insertion into the cell walls, which then strengthens the cellular matrix. The difference in the results obtained may be due to the size of the fillers used and the varying elasticity of the cellular morphology of PUR foam composites. Thinner cell walls and struts in PUR/Per and PUR/Verm foam composites (Table 3) provide fracture induction. As a result, less energy is absorbed, leading to cell buckling and irreversible damage [65]. Moreover, a decrease in compressive strength was observed in PUR foam composites filled with expandable graphite [66], which causes defects in the analyzed products. The activation of Per and Verm fillers has a significant impact on the compressive strength of all PUR foam composites. Compared to PUR/Per and PUR/Verm foam composites, the maximum increase of 61% and 71% is shown by PUR/PerDex-10 and PUR/VermDex-10, respectively. However, only PUR/PerDex-10 has 24% greater compressive strength than control PUR foam. The positive interaction between Dex-activated fillers and PUR foam can be explained by the FTIR results, which show that hydroxyl groups from Dex form the linkages with silicates in Verm and Per, leading to a more stable and covalent attachment of Dex and anchoring points for attaching polymeric matrix. Therefore, an enhanced interfacial inorganic-organic interaction is observed. Similar conclusions have been drawn by [PERSON] et al. [38], who demonstrated that significant mechanical performance can be achieved by activating inorganic fillers with potato protein, chitosan, and casein. The statistical analysis of compressive strength of PUR foam composites with 2.5 wt.% different fillers showed (Figure 10a) that there are differences between the averages of all PUR foam composites compared to the control PUR. The F-criterion is 42.0, \(p\) = 0, and R\({}^{2}\) = 0.944. Further, the statistical analysis of the compressive strength of PUR foam composites with 5 wt.% different fillers showed (Figure 10b) that there are no differences between the PUR/PerDex-5 and PUR/VermDex-5 foam composites. The F-criterion statistic is 0.15, \(p\) = 0.72, and R\({}^{2}\) = 0.356. When comparing the PUR/PerDex-5 and PUR/VermDex-5 foam composites with the control PUR, the analysis showed that there is no difference between the average values.