Biodegradable polyesters as crystallization-accelerating agents of poly(l-lactide).

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials

Background:

• Poly(l-lactide) (PLLA) is a widely used biodegradable polyester with slow crystallization rates.
• Enhancing PLLA crystallization is crucial for optimizing its mechanical properties and processing.
• Biodegradable polyesters offer potential as additives to modify PLLA behavior.

Purpose of the Study:

• To investigate the effects of poly[(R)-3-hydroxybutyrate] (PHB), poly(-caprolactone) (PCL), and polyglycolide (PGA) as crystallization-accelerating agents for PLLA.
• To elucidate the mechanisms behind the accelerated crystallization of PLLA in the presence of these biodegradable polyesters.
• To analyze the impact of these additives on PLLA's crystallization kinetics and morphology.

Main Methods:

• Differential scanning calorimetry (DSC) to analyze thermal properties and crystallization behavior.
• Polarized optical microscopy (POM) to observe and quantify spherulite formation and growth.
• Analysis of crystallization kinetics using parameters like nucleation constant, growth rate, and Avrami exponent.

Main Results:

• PHB, PCL, and PGA effectively accelerated the crystallization of PLLA.
• PCL and PGA acted as nucleation agents, while PHB promoted spherulite growth.
• PHB addition led to decreased PLLA spherulite density but enhanced growth, attributed to PLLA/PHB miscibility and PHB's lower glass transition temperature.
• Crystallization kinetics of PLLA/PHB blends varied during melt cooling, while PLLA/PGA blends showed altered crystallite nucleation and growth during heating.

Conclusions:

• Biodegradable polyesters PHB, PCL, and PGA are effective crystallization accelerators for PLLA.
• The mechanism of acceleration differs among the additives, involving nucleation and/or growth effects.
• These findings provide insights into modifying PLLA crystallization for tailored material properties.