polylactide

Polylactide, commonly referred to as PLA, is a biodegradable aliphatic polyester derived from lactic acid or its cyclic dimer, lactide. It is a biobased polymer produced from renewable resources such as corn or sugarcane via fermentation to lactic acid, which is then converted to lactide and polymerized.

Polylactide is formed mainly by ring-opening polymerization of lactide. Stereochemistry controls properties: isotactic PLLA (poly-L-lactic acid), PDLA (poly-D-lactic acid), and the atactic PDLLA. Copolymers and blends tailor crystallinity, melting point, and toughness. Common catalysts include tin(II) octanoate and various metal complexes; polymerization can yield high molecular weights suitable for engineering plastics or medical use.

Physical properties depend on tacticity and processing. Tg is about 55–60°C; melting temperatures for crystalline PLLA are around 170–180°C. PLA is relatively stiff and can be brittle, though plasticizers and stereocomplexes improve toughness. It degrades by hydrolysis of ester bonds into lactic acid, with rate influenced by crystallinity, temperature, and enzymes; degradation is faster under industrial composting conditions.

Applications include packaging films and containers, disposable tableware, and 3D-printed components. In medicine, PLA and its copolymers are used for sutures, screws, pins, and drug-delivery systems due to biocompatibility and resorbability.

Environmental aspects: although derived from renewable feedstocks, PLA is not always readily recyclable with conventional plastics, and its compostability requires appropriate facilities. Lifecycle impacts depend on feedstock sourcing, processing energy, and end-of-life management.