## 3 Results and Discussion
At the same time, diphenyloxyethyl adipate (\(T_{cr}\) = 134 \({}^{\circ}\)C) can theoretically be used as a combined primary plasticizer for elastic materials and PVC products. The good solvent capacity of plasticizers does not guarantee the achievement of the complex properties required for PVC plastics. Another key aspect of plasticizers is the glass transition temperature, \(T_{g}\), of plasticized PVC, which reflects the material's ability to maintain elasticity at lower temperatures. To investigate how synthesized esters influence the properties of PVC, specific compositions were formulated, consisting of 100 parts PVC, 2 parts TBLS, 1.5 parts calcium stearate, 0.25 parts diphenyloprane and 40 parts plasticizer. For comparison, commonly used plasticizers such as dioctyl phthalate and dioctyl adipate were also evaluated. The impact of the synthesized esters on the segmental mobility and thermal transitions of the plasticized compositions was assessed using Dynamic Mechanical Analysis (DMA) (Figures 2-6, Table 5). \begin{table}
\begin{tabular}{c c c} \hline
**Compound** & \(T_{cr}\)\({}^{\circ}\)C & \(A\), \% \\ \hline DBEA & 138 & 81.0 \\ DBPA & 121 & 99.0 \\ DPEA & 134 & 87.0 \\ \hline \end{tabular}
\end{table} 
Table 4: Parameters of compatibility of diesters with PVC. Figure 3: DMA thermogram for PVC, plasticized DPEA. Figure 2: DMA thermogram for PVC, plasticized DBEA. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Plasticizer** & \(\mathbf{E_{r}}\)**MPa** & \(\mathbf{T_{s}}\)\({}^{\circ}\)**C** & \(\mathbf{T_{g^{\prime}}}\)\({}^{\circ}\)**C** & \(\mathbf{T_{f^{\prime}}}\)\({}^{\circ}\)**C** & \(\mathbf{T_{fg^{\prime}}}\)**\({}^{\circ}\)**C** & \(\mathbf{T_{fg^{\prime}}}\)**Max, \({}^{\circ}\)C** & \(\mathbf{T_{f}}\)**\(\mathbf{-T_{s}}\)** \\ \hline DOP & \(5800\) (\(-80\)\({}^{\circ}\)C) & \(-29.0\) & \(-26.2\) & \(23.2\) & \(30.0\) & \(52.6\) \\ DOA & \(3350\) (\(-80\)\({}^{\circ}\)C) & \(-78.4\) & \(-65.7\) & \(3.2\) & \(24.0\) & \(81.6\) \\ DBEA & \(7650\) (\(-80\)\({}^{\circ}\)C) & \(-57.5\) & \(-29.4\) & \(18.4\) & \(23.8\) & \(75.9\) \\ DBPA & \(4450\) (\(-80\)\({}^{\circ}\)C) & \(-77.5\) & \(-37.6\) & \(6.8\) & \(17.1\) & \(84.3\) \\ DPEA & \(4800\) (\(-80\)\({}^{\circ}\)C) & \(-17.2\) & \(7.4\) & \(23.5\) & \(29.6\) & \(40.7\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Thermoanalytical characteristics of plasticized PVC compositions obtained by the DMA method. Single transitions of the tangent of the mechanical loss angle, \(T_{gs}\), can be observed in all the thermograms obtained, which indicates the uniformity of the system and the absence of a second incompatible phase. The structure of the plasticizer has a significant effect on the temperature transitions of PVC plastic (Table 5). The transition of a polymer from a glass-like state to a state of high elasticity is the main relaxation process manifested in the area of major relaxation (\(\alpha\)-relaxation). There is a conditional boundary between these two states--the glass transition temperature. At this temperature, there is a sharp decrease in the mobility of segments of polymer molecules [38; 39; 40]. In the above table, \(T_{S}\) is the temperature at the beginning of the transition from a glassy state to a highly elastic one, \(T_{g}\) is the glass transition temperature, \(T_{f}\) is the temperature at the end of the transition from a glassy state to a highly elastic one, \(T_{f}\)--\(T_{S}\) is the temperature range corresponding to the \(\alpha\)-relaxation region, and \(E\) is the modulus of elasticity. Figure 4: DMA thermogram for PVC, plasticized DBPA. Figure 5: DMA thermogram for PVC, plasticized DOA. A study of the thermomechanical characteristics of PVC-based plastics has shown that the highest glass transition temperature can be observed in a sample with the addition of DPEA.