Controlling the Properties of Poly(3-hydroxybutyrate) through Lignin-Containing Organogels

Area of Science:

• Polymer Science
• Materials Science
• Biocomposites

Background:

• Poly(3-hydroxybutyrate) (PHB) exhibits slow degradation due to high crystallinity.
• Biodegradable polyesters require modification for tailored applications.
• Lignin, a bio-based polymer, is a potential additive for biocomposites.

Purpose of the Study:

• To investigate the effect of processing and lignin type (softwood vs. hardwood kraft lignin) on PHB-lignin organogels.
• To analyze the structural changes and water stability of these organogels.
• To explore methods for tuning PHB crystallinity and degradation behavior.

Main Methods:

• Preparation of PHB-lignin organogels using the bio-based solvent Cyrene.
• Incorporation of up to 50 wt % softwood kraft lignin (SKL) or hardwood kraft lignin (HKL).
• Analysis using FTIR spectroscopy, SEM, DSC, XRD, and water exposure tests.

Main Results:

• Organogel formation reduced PHB crystallinity by ~10%; lignin further decreased it by up to 84% (SKL) and 73% (HKL).
• Lignin incorporation lowered melting enthalpy and promoted cold crystallization.
• Both SKL and HKL showed similar effects on crystallinity reduction and degradation behavior.
• Water exposure led to increased mass loss due to reduced crystallinity.
• Solvent extraction allowed partial lignin recovery and PHB recrystallization.

Conclusions:

• Processing-based organogel formation effectively reduces PHB crystallinity.
• Lignin incorporation significantly impacts PHB structure and enhances water-induced degradation.
• This approach provides a pathway to tailor the properties of PHB-based biocomposites for various applications.