Synthesis, green chemistry metrics, and performance of bio-based ketal esters as dual-purpose additive for polyvinyl chloride (PVC)

Abstract

A series of novel bio-based ketal esters were successfully synthesized using glycerol and bio-based dicarboxylic acids varied in their chain length. The performance of the novel modifiers, as plasticizer and thermal stabilizer, and the effect of chain length were examined as poly (vinyl chloride) (PVC) films prepared via the solution casting. Their properties were compared to those modified by a fossil-based additive, di (2-ethylhexyl) phthalate (DOP). Furrier transform infrared (FTIR), Nuclear Magnetic Resonance (¹H- and ¹³C-NMR) spectroscopy confirmed the structures of the synthesized modifiers. The “greenness” and efficiency of the synthesis procedure were evaluated using green chemistry metrics and simplified life-cycle assessments (EcoScale and GREEN MOTION). Based on the greenness assessments, the synthesis process had both high efficiency and environmentally friendly characteristics, aligning with the principles of green chemistry. The films were characterized using dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile strength, and migration testing. The flexibility of the films increased with the enlargement of the dicarboxylic acid moiety, so the film modified by 60% of GC-SEB was the softest showing flexibility similar to the film containing 40% of DOP. On the other hand, the films containing the novel bio-based modifiers demonstrated remarkably high thermal stability as the incorporation of 60% of GC-SUC enhanced the thermal stability of the film up to 34.3 °C comparing to unmodified PVC film. Despite slightly lower plasticizing ability, final products incorporating newly synthesized modifiers exhibited high compatibility, migration resistance and thermal stability, making them more cost-effective and durable when compared to products containing DOP. Overall, the modifiers can be green potential substituents for petroleum-based plasticizers and thermal stabilizers.