Composition‐Dependent Plasticization of Poly(3‐Hydroxybutyrate) Using Glycerol Butyrate Ester Mixtures

ABSTRACT

Poly(3‐hydroxybutyrate) (PHB) is a biodegradable polymer with environmental advantages, although its industrial application is limited by high crystallinity, brittleness, and a narrow thermal processing window. PHB was plasticized with commercial glycerol tributyrate (GTB) and tailored mixtures of di‐ and tri‐butyric glycerol esters (GDB/GTB) obtained by glycerol esterification with butyric acid.

PHB formulations containing 20 and 30 wt% plasticizer were prepared by melt mixing and thermo‐compression and characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. GTB and GTB/GDB mixtures reduced melting (Tm) and crystallization (Tc) temperatures compared to neat PHB, enhancing chain mobility and processability. The GTB/GDB ratio had a negligible effect on Tm, whereas Tc increased at GTB contents above 80 wt%. Crystallinity increased with GTB addition, while mixed‐plasticizer systems showed similar crystallinity values. Thermal stability improved with increasing GTB content. Plasticizers reduced Young's modulus and tensile strength while increasing elongation at break. Increasing GTB proportion slightly reduced tensile strength, whereas elongation increased when GTB exceeded 90 wt%, with almost constant stiffness. Adjusting the GTB/GDB ratio is therefore an effective strategy to tailor the thermo‐mechanical performance and processability of PHB.