Polilaktyd

Polilaktyd, also known as poly(lactic acid) or PLA, is a biodegradable aliphatic polyester derived from lactic acid. It is typically produced by ring-opening polymerization of lactide, the cyclic dimer of lactic acid, and is commonly sourced from renewable feedstocks such as corn starch or sugarcane.

PLA exists in different stereoisomeric forms: poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), and atactic or racemic poly(lactic acid). The stereochemistry influences crystallinity, thermal behavior, and mechanical performance. By controlling the ratio of enantiomers and processing conditions, materials with a range of properties can be obtained, from rigid, high-strength grades to more flexible variants.

PLA is biodegradable under industrial composting conditions, where heat and humidity accelerate hydrolysis and microbial action. In natural environments such as soil or seawater, degradation is much slower. It has a glass transition temperature around 55–60°C and a melting point around 150–160°C. Crystallinity improves strength and heat resistance but can make processing more challenging; PLA is relatively stiff and can be brittle. It is sensitive to moisture, which affects processing and dimensional stability. Processing methods include extrusion, injection molding, blown film, and fused deposition modeling (3D printing).

Applications span biodegradable packaging and disposable tableware, 3D printing filaments, and medical uses such as absorbable sutures, orthopedic pins, screws, and drug delivery matrices. PLA is generally regarded as safe for food contact and medical applications, though regulatory approvals vary by product and jurisdiction.

End-of-life options include industrial composting and, to a lesser extent, recycling. Mechanical recycling is challenging due to degradation of properties; chemical recycling to lactic acid is an area of research. Compared with conventional plastics, PLA can offer lower greenhouse gas emissions when produced from renewables, but overall sustainability depends on feedstock, energy use, and end-of-life infrastructure.