Low-Temperature Performance and Migration Behavior of Poly Plasticized with Citrate Esters Bearing Vinyl and Epoxy Groups

Abstract

Carbon–carbon double bonds and epoxy groups in cold-resistant plasticizers play distinct yet insufficiently understood roles in regulating the low-temperature performance of PVC. Herein, two citrate ester derivatives─CA-DB (vinyl-functionalized) and CA-EG (epoxy-functionalized)─were synthesized through a two-step route and incorporated into PVC films. Compared with neat PVC, elongation at break increased by 514% for CA-DB/PVC and 387% for CA-EG/PVC. Migration tests showed that CA-EG/PVC exhibited 3.78% lower mass loss in ethanol and 24.26% lower loss in petroleum ether than CA-DB/PVC, consistent with its higher solubility parameter (9.83 vs 9.36 (cal/cm3)1/2) derived from molecular dynamics (MD) simulations. In situ Raman spectroscopy confirmed that CA-DB/PVC retained compatibility without phase separation down to −60 °C. Further MD analysis revealed that CA-EG/PVC exhibits greater free volume and stronger H-bonding with PVC at subzero temperatures, accounting for its superior low-temperature toughness. These results indicate that epoxy groups more effectively suppress plasticizer migration and retain flexibility under cryogenic conditions, provide guidance for designing biobased plasticizers with excellent low-temperature cold resistance.