Bio-Inspired, Self-Toughening Polymers Enabled by Plasticizer-Releasing Microcapsules.

Area of Science:

• Materials Science
• Polymer Science
• Composite Materials

Background:

• Thermoplastic polymers often exhibit brittleness, limiting their applications.
• Developing effective toughening strategies for rigid polymers is crucial for advanced material design.

Purpose of the Study:

• To introduce a novel concept for self-toughening thermoplastic polymers.
• To demonstrate the efficacy of incorporating plasticizer-filled microcapsules (MCs) into a brittle polymer matrix.

Main Methods:

• Composites were fabricated using a poly(lactic acid) (PLA) matrix with varying percentages of poly(urea-formaldehyde) (PUF) MCs containing hexyl acetate.
• Tensile tests were conducted to evaluate mechanical properties at different strain levels.
• Ballistic impact tests and thermomechanical analyses (dynamic mechanical testing, thermal analysis) were performed to assess performance under high strain rates and understand the toughening mechanism.

Main Results:

• PLA/MC composites maintained rigidity at low strain but exhibited yielding due to MC rupture and plasticizer release at higher strains.
• A significant increase in elongation at break (up to 25-fold) and toughness (up to 20-fold) was observed compared to neat PLA.
• The toughening mechanism was effective at high strain rates, as confirmed by ballistic impact tests and thermomechanical studies.

Conclusions:

• The incorporation of plasticizer-filled MCs provides an effective self-toughening mechanism for brittle polymers like PLA.
• This approach offers a substantial improvement in fracture toughness and ductility with minimal impact on stiffness and strength.
• The developed composites show promise for applications requiring enhanced impact resistance and durability.