Umemura, Rodrigo T., et al. Journal of Applied Polymer Science 138.10 (2021): 49990.
Challenge: Poly(3-hydroxybutyrate) (PHB) is a bio-based polymer which is expected to serve as a replacement for synthetic plastics, but has limited use due to its brittleness, narrow process window, and thermal degradation at elevated temperatures during melt processing.
Solution: Triethyl citrate (TEC) was evaluated as a bio-based plasticizer to improve flexibility, toughness and processability of PHB. Mixtures with different TEC mass fractions (0, 0.1, 0.2, 0.3) were prepared. PHB-TEC blends were processed by compounding in a twin-screw microcompounder (175°C, 250 rpm, 1 min). Injection molding of the molten blends was performed (barrel: 175°C, mold: 60°C, pressure: 4.0/4.5 bar).
Key Findings:
· TEC acted as an efficient plasticizer, progressively modifying PHB properties with increasing concentration. It demonstrated significant enhancement in PHB toughness (impact resistance) and flexibility (reduced modulus, increased β-relaxation).
· TEC addition achieved a practical widening of the PHB processing window, enabling safer melt processing.
· TEC impacted the crystallization kinetics of PHB, which changed the crystal structure and spherulite morphology. Nucleation rate was reduced, while an increase of the rate of crystal growth was observed. The crystal structure evolved over time as TEC was expelled from the crystal growth boundary, facilitating interlamellar secondary crystallization.
Zuber, SAN Ahmad, et al. Materials Today: Proceedings 17 (2019): 560-567.