Concept and Properties
Polylactic Acid (PLA) is a thermoplastic polyester produced by ring-opening polymerization of lactide derived from lactic acid. The backbone contains ester bonds, making it hydrolytically degradable. The monomer is produced from renewable resources such as corn, sugarcane, and cassava, giving PLA both renewable and biobased attributes.
- Typical parameters: Tg ≈ 55–65°C, Tm ≈ 150–170°C, tensile modulus ≈ 3–4 GPa.
- Crystallinity is highly sensitive to D-isomer content and thermal history.
- Rapid biodegradation in industrial composting (≈58°C, high humidity, active microbes); much slower in soil and seawater.
Processing Practical Tips
- Dry to ≤ 250 ppm moisture before melt processing.
- Control melt residence time for extrusion and injection molding.
- Avoid amine-containing additives to reduce degradation and discoloration.