Role of the Oxethyl Unit in the Structure of Vegetable Oil-Based Plasticizer for PVC: An Efficient Strategy to Enhance Compatibility and Plasticization

Abstract

Developing vegetable oil-derived primary plasticizers for poly(vinyl chloride) (PVC) is still a challenge because of their insufficient compatibility. As described in this work, we report the synthesis of plasticizers through the esterification of polyethylene glycol methyl ether and dimer acid, in which dimer acid is renewable material prepared via a two-step reaction (1) the hydrolysis of fatty acids from soybean oil at 70 °C and (2) subsequent Diels–Alder reaction at 250 °C. The resulting plasticizers, dimer acid-derived polyethylene glycol methyl ether esters (DA-2n, 2n = 2, 4, 6 or 8 referring to the number of oxethyl units per molecule), were blended with PVC. It was found that the tensile properties, transparency, and thermal stability of plasticized PVC (PVC-DA-2n) increased significantly with an increase in the number of oxyethyl units. Fourier-transform infrared spectroscopy analysis revealed that its good compatibility can be attributed to the strong interaction between oxyethyl units and PVC. As the number of the oxyethyl units of plasticizer increased, the glass transition temperature (Tg) of the corresponding plasticized PVC samples decreased from 62.3 (PVC-DA-2) to 35.4 °C (PVC-DA-8). Owing to the excellent plasticization of DA-8, the performances of PVC-DA-8 were comparable or better than that of the PVC plasticized using commercial dioctyl terephthalate (DOTP). The simple but efficient method of this study provides a new avenue for the preparation of vegetable oil-based plasticizers for PVC.

Recent Attempts in the Design of Efficient PVC Plasticizers with Reduced Migration

“…The most common bio-based plasticizer is epoxidized soybean oil (ESBO) [ 24 , 25 , 84 , 85 ], which is also used as a heat stabilizer in PVC blends because of its ability to scavenge HCl molecules released during heating and is responsible for the propagation of thermal degradation of the polymer [ 86 ]. When ESBO is used as a plasticizer, a content of 25–45 wt% is usually needed to prepare the plastics.…”

“…In 2019, Tan et al [ 24 ] obtained dimer and trimer acid from soybean oil and used it in the esterification reaction with polyethylene glycol methyl ether. The impact of a number of oxethyl units in dimer acid was studied, because of its ability to create hydrogen bonds with a PVC matrix, which implies good plasticizing efficiency.…”

“…An efficient plasticizer interacts with PVC and breaks the extended network of chain-to-chain dipole-induced dipole forces present originally in a polymer that is observed as an attenuation of a signal coming from the covalent bonds. The stronger the interactions, the more prominent the shift of particular peaks to the lower wavenumber [ 24 ]. Signals of a particular interest are methylene groups and carbon-chlorine bonds stretching vibrations at 1450–1400 cm −1 and 650–600 cm −1 , respectively, which are originated from the crystalline domains of PVC.…”

Effect of ketal group in castor oil acid‐based plasticizer on the properties of poly(vinyl chloride)

“…The detailed synthetic routes of plasticizers are showed in Scheme 1. Plasticizer CL was synthesized by esterification of castor oil acid with butanol and acylation with LeA 31,43 . Then CL was further modified by ketalization with ethylene glycol to obtain plasticizer KCL 40,41 …”

Bio-Based Coating Materials Derived from Acetoacetylated Soybean Oil and Aromatic Dicarboxaldehydes

“…Vegetable oil, as a renewable resource, has attracted considerable attention owing to its low cost, availability, low ecotoxicity, and environmental sustainability [4,5]. Vegetable oils contain unsaturated C–C bonds; thus, epoxidation of vegetable oils is commonly employed to graft functional groups by ring-opened reactions [6,7,8].…”