A molecular dynamics simulation was adopted to investigate the plasticizing effect of polyvinyl chloride (PVC) and its mechanism by blending isosorbide heptylate (SDH) with the traditional plasticizer dioctyl phthalate (DOP) and to explore the feasibility of SDH partially replacing DOP in PVC film. The results demonstrated that the difference in the solubility parameter between SDH and PVC was smaller than that between DOP and PVC, indicating the superior compatibility of SDH with PVC. This enhanced compatibility was further supported by the significantly higher interaction energy between SDH and PVC compared to that between DOP and PVC, primarily attributed to the stronger interactions formed between the polar functional groups in the SDH molecules and the PVC's molecular chains. The analysis of the glass transition temperature demonstrated that the plasticizing effect of the SDH/DOP mixed plasticizer on the PVC exhibited intermediate behavior between that of pure SDH and DOP systems, showing a decreasing trend with an increasing proportion of SDH. An analysis of the radial distribution function further confirmed that the probability of hydrogen bond formation between the SDH and PVC molecules was significantly higher than that between DOP and PVC, contributing to the strong interaction between the SDH and PVC. From the analysis of the plasticizer's diffusion, it was clearly concluded that the migration resistance of SDH was superior to that of DOP. These research findings can provide fundamental data and guidance for the strategy of partially replacing DOP with SDH.
Keywords: PVC; dioctyl phthalate; glass transition temperature; isosorbide diheptanoate; molecular dynamics simulation.