## 3 Results and Discussion
A well-optimized plasticizer must strike a balance among compatibility, efficiency, non-migration and the durability of the resulting products [30]. The effectiveness of a plasticizer is evaluated based on several key properties: environmental friendliness, odorlessness, compatibility, low volatility, effective plasticization at low temperatures, and minimal sweating or extraction into surrounding media [31]. The main condition for plasticization is the thermodynamic compatibility of the plasticizer with the polymer, i.e., the formation of a true plasticizer solution in the polymer. This makes it possible to vary the concentration of the plasticizer as much as possible. Compatibility depends on the nature of the polymer and plasticizer. This compatibility is largely influenced by the chemical structure of the plasticizer and the proportion of polar groups it contains. In polyvinyl chloride (PVC), strong polar interactions between the C-Cl groups facilitate segment contact. Ester plasticizers exhibit a  
Figure 1: IR spectra of esters. (**a**) The IR spectrum of dibutoxyethyl adipate; (**b**) The IR spectrum of dibhenoxyethyl adipate; (**c**) The IR spectrum of dibutoxypropyl adipate. dual structure, combining polar ester groups with non-polar alkyl chains. This structure not only disrupts polar interactions between polymer segments, enhancing their mobility, but also interacts with the polar groups within the polymer matrix, thereby maintaining certain physical and mechanical properties. Plasticizers can migrate from composite materials through processes like evaporation and diffusion. Notably, an increase in temperature of just 7 \({}^{\circ}\)C can double the migration rate of a plasticizer. The migration process occurs from areas of higher concentration to those of lower concentration and is influenced by the polymer's characteristics. A lower interaction between the plasticizer and PVC correlates with reduced compatibility limits and higher migration rates. When the plasticizer concentration is maintained at or below 10%, it becomes fully solvated by the polymer, minimizing molecular separation. Conversely, increasing the plasticizer content raises the number of fragile bonds within the polymer-plasticizer system, thereby enhancing migration tendencies. Research indicates that when the plasticizer content in PVC compositions ranges from 15% to 35%, there is a nearly linear relationship between migration amounts and plasticizer levels. Understanding compatibility parameters allows for targeted adjustments to both the structure of the plasticizer and the operational characteristics of the final material. This helps mitigate issues such as high volatility and surface migration of impurities, ultimately preserving performance attributes [32; 33]. As the production of plasticizers progressed, a number of technical problems were solved to improve the characteristics of polymer formulations, solve technical problems of end use and meet new requirements. Some of the problems included evaporation, the degradation of plasticizers due to volatility or susceptibility to UV radiation, migration of plasticizers into contact media, insufficient lubrication at subzero temperatures and suspected carcinogenic effects on a number of living organisms. The fundamental foundations of these problems are chemical in nature. They are mainly related to thermodynamic, migration and interphase phenomena [34; 35]. The calculation of Hansen solubility parameters (HSPs) serves as a means of preliminary theoretical assessment of the plasticizing effect of a substance in relation to PVC [36; 37]. According to [PERSON], the solubility region of a polymer is expressed by a sphere of radius, \(R_{0}\). For PVC, this value is 8.2.