## 3 Results and Discussion  
### Mechanical Properties of EPS  
EPS is a viscoelastic material and follows a trajectory in the three-dimensional stress-strain-time space. In the SS curve (Figure 2), the material's strength is inferred as the proportional limit and 10% strain strength. As shown in Table 1, both strength indexes clearly increased with density, but no clear temperature dependence was observed for temperatures in the 0-60 \({}^{\circ}\)C range, which was sufficient for statistical verification. Table 2 shows the changes in the density of EPS by temperature condition for the EPS test specimen applied to the measurement of mechanical properties shown in Table 1. Although the density decreased with the temperature increase within the range of 0-60 \({}^{\circ}\)C, the decrease rate was 0.81-1.38%, which does not seem to have significantly affected mechanical properties. However, continuous research is needed on the temperature dependence of EPS strength outside this temperature range. [PERSON] [14] reported that the 10% strain strength of EPS decreased with increasing temperature, for temperatures below 0 \({}^{\circ}\)C and above 45 \({}^{\circ}\)C; however, no effect was observed at other temperatures. However, according to the literature [15; 16], the polystyrene resin (present in raw EPS) is a thermoplastic resin, and it is known that the resin itself softens at high temperatures (>70 \({}^{\circ}\)C) and undergoes displacement (e.g., expansion or contraction), which affects its mechanical properties. However, the effect of the temperature change (\(-\)1743 \({}^{\circ}\)C) on the EPS shock absorption and vibration transmission properties was reportedly significantly smaller than that of expanded polyethylene (EPE) [17]. Figure 6a,b show an example of a SEM image before and after 50% compression, respectively. Table 3 lists the results obtained for various elastic moduli using the raw data in Table 1, with only the density as a parameter. In each case, the elastic modulus increased with density, and in the statistical significance test, all items and sections, except for a specific density section of the tangent modulus, were significant. Compared with the initial tangent modulus of the initial proportional portion (Young's modulus), the secant modulus was approximately 35-38%, and the tangent modulus was approximately 5-9%. This was because the secant and tangent moduli considered the plastic property area of the material. In addition, the error range of the initial tangent modulus was larger than that of the other  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Density (kg/m\({}^{\circ}\))**} & \multicolumn{8}{c}{**Peroperational Limit (kPa)**} & \multicolumn{8}{c}{**10\% Strain Strength (kPa)**} \\ \cline{2-10}  & **0 \({}^{\circ}\)C** & **20 \({}^{\circ}\)C** & **60 \({}^{\circ}\)C** & **Ave.** & **0 \({}^{\circ}\)C** & **20 \({}^{\circ}\)C** & **40 \({}^{\circ}\)C** & **60 \({}^{\circ}\)C** & **Ave.** \\ \hline
16 & 45.17 & 38.00 & 45.17 & 40.83 & 42.29 & 94.45 & 82.49 & 79.64 & 77.15 & 83.97 \\  & (\(\pm\)2.25) \({}^{\mathrm{m}}\) & (\(\pm\)0.71) \({}^{\mathrm{m}}\) & (\(\pm\)2.25) \({}^{\mathrm{m}}\) & (\(\pm\)1.18) \({}^{\mathrm{m}}\) & (\(\pm\)3.50) \({}^{\mathrm{m}}\) & (\(\pm\)2.64) \({}^{\mathrm{m}}\) & (\(\pm\)2.29) \({}^{\mathrm{m}}\) & (\(\pm\)1.94) \({}^{\mathrm{m}}\) & (\(\pm\)1.12) \({}^{\mathrm{mmoduli, which was attributed to the difference in judgment when determining the initial proportional portion of the curve. It has been reported that this initial tangent modulus is also affected by test parameters such as the loading rate and specimen size [14,18]. This value increased as the loading rate decreased or the specimens' dimensions increased. Poisson's ratio quantifies the lateral pressure of the specimen on adjacent structural elements for a given vertical load on the specimen.