Improving the flexibility and compostability of starch/poly(butylene cyclohexanedicarboxylate)-based blends

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Materials

Background:

• Thermoplastic starch (TPS) is a renewable polymer but suffers from poor mechanical properties and moisture sensitivity.
• Poly(butylene cyclohexanedicarboxylate) (PBCE) based copolyesters offer tunable properties but require optimization for biobased applications.
• Developing fully biobased materials with enhanced performance and biodegradability is crucial for sustainable packaging and other industries.

Purpose of the Study:

• To create fully biobased blends of thermoplastic starch and a modified poly(butylene cyclohexanedicarboxylate)-based random copolyester (PBCEA).
• To investigate the physicochemical, mechanical, and fragmentation properties of the developed blends.
• To evaluate the impact of adipic acid co-units and citric acid compatibilizer on blend performance.

Main Methods:

• Melt blending of thermoplastic starch and PBCEA.
• Direct extrusion film casting to produce films.
• Physicochemical characterization (e.g., thermal properties, morphology).
• Mechanical testing (e.g., tensile strength, elongation at break).
• Composting tests to assess fragmentation and biodegradation.

Main Results:

• Introduction of 25% adipic acid co-units in PBCE (PBCEA) lowered blending temperature, preventing starch degradation.
• Citric acid acted as a compatibilizer, improving interfacial adhesion and promoting micro-porosity.
• The synergistic effects resulted in elastomeric films with >450% elongation at break and no evident yield point.
• Films demonstrated good moisture resistance and rapid fragmentation under composting conditions.

Conclusions:

• Fully biobased TPS/PBCEA blends offer a promising alternative to conventional plastics.
• The formulation achieves enhanced mechanical properties, including elastomeric behavior, and improved processability.
• The materials exhibit excellent biodegradability, making them suitable for sustainable applications with reduced environmental impact.