Development and Characterization of Fully Renewable and Biodegradable Polyhydroxyalkanoate Blends with Improved...

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials Engineering

Background:

• Poly(3-hydroxybutyrate-co-3-valerate) (PHBV) is a widely studied biodegradable polymer but suffers from brittleness and a narrow processing window.
• These limitations restrict its application in various plastic products.
• Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is another biodegradable copolyester within the polyhydroxyalkanoate (PHA) family, known for its enhanced ductility.

Purpose of the Study:

• To develop a more processable and potentially applicable biodegradable blend by combining PHBV with PHBH.
• To investigate the effects of PHBH incorporation on the morphology, crystallization, thermal stability, mechanical properties, and thermoformability of PHBV.

Main Methods:

• Melt mixing of PHBV with varying percentages (20%, 30%, 40% wt.) of PHBH.
• Processing of the resulting blends into films via cast extrusion.
• Comprehensive characterization including morphology, crystallization behavior, thermal stability, mechanical testing, and thermoformability assessment.

Main Results:

• Full miscibility was observed in the amorphous phase of the blends, indicated by a single delta transition peak.
• PHBH incorporation hindered PHBV crystallization, reducing the spherulite growth rate.
• Despite PHBH addition, the inherent brittleness of PHBV persisted, dominating the mechanical behavior.
• Thermoformability was significantly enhanced, with the processing window widening by 7 seconds due to increased melt strength.

Conclusions:

• While PHBH addition does not overcome the intrinsic brittleness of PHBV-based materials, it substantially improves their thermoformability.
• The enhanced melt strength and wider processing window make PHBV/PHBH blends more suitable for applications requiring improved processability.
• Further research may explore strategies to mitigate the brittleness while retaining the improved thermoformability for broader applications of these biodegradable polymers.