Bio-plasticizer from esterification of glycerol and hexanoic acid to tune properties of polymers and bio-polymers

Plasticizers play a crucial role in enhancing the flexibility and mechanical properties of polymeric materials. However, many conventional plasticizers are derived from non-renewable resources and pose significant environmental and health concerns due to their migration and leaching tendencies. This thesis focuses on the synthesis of glycerol trihexanoate (GTH), a bio-based plasticizer, as a sustainable additive for polyvinyl chloride (PVC), polyhydroxybutyrate-co-valerate (PHBV), and polybutylene succinate (PBS). These polymers represent a diverse range of applications and environmental challenges, highlighting the need for innovative and eco-friendly solutions. GTH was synthesized via esterification of glycerol and hexanoic acid under optimized conditions (3% PTSA at 110°C for 7 hours). Reaction progress was monitored using FT-IR and TLC, confirming the formation of ester products. The triester was isolated from the product mixture, achieving a yield of 23%. The chemical structure of GTH was characterized and confirmed using 1D- and 2D-NMR spectroscopy. The plasticization effect of GTH was evaluated by analysing the thermal and mechanical properties of PVC, PHBV, and PBS plasticized films containing different amounts of bio-plasticizer (5, 10, 20 parts by weight per hundred parts of resin). GTH reduced the glass transition temperature (Tg) significantly, particularly in PVC (from 81°C to 44°C at 20 phr). Mechanical tests revealed improved flexibility in PVC, with elongation at break increasing to 317%, while tensile strength and Young's modulus decreased across all polymers, demonstrating an increased flexibility. Stability tests demonstrated low migration and volatility of GTH, indicating its excellent retention within polymer matrices. These findings demonstrate GTH as an effective and environmentally friendly plasticizer, offering a promising alternative to traditional additives in the pursuit of sustainable materials for industrial applications.