A Green Synthetic Approach to Glycerol Trihexanoate from Renewable Feedstocks for Enhanced Plasticization across Diverse Polymer Matrices

The increasing demand for sustainable polymer additives has raised attention on the development of biobased plasticizers as alternatives to conventional fossil-derived compounds. In this work, glycerol trihexanoate (GTH) was synthesized via a solvent-free reaction between glycerol and hexanoic acid, two renewable, biobased, and nontoxic building blocks. The plasticizing effect of GTH is investigated on a fully amorphous polymer, such as poly(vinyl chloride) (PVC), and on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a biobased semicrystalline polyester. Through a comprehensive multitechnique approach, the thermal, mechanical, morphological, and surface properties of plasticized films are investigated. GTH demonstrated excellent plasticizing efficiency, significantly lowering the glass transition temperature and improving flexibility in both polymers without causing phase separation. Notably, GTH can promote in PHBH an increase of crystallinity and trigger the formation of beta-phase crystalline domains, typically associated with enhanced ductility and reduced melting temperatures of the material. Migration tests in water reveal minimal plasticizer leaching (<0.6%), underscoring the remarkable retention of GTH regardless of the polymer. These findings support the compatibility and integration of GTH in different polymer systems and highlight its potentialities as a long-lasting, high-performance, and environmentally friendly plasticizer for both conventional and biodegradable plastic formulations.