Polülaktilaat

Polülaktilaat, also known as poly(lactic acid) (PLA), are a class of biodegradable aliphatic polyesters derived from lactic acid. The polymer consists of repeating lactic acid units, with stereochemistry that can be arranged as L-, D-, or a racemic mixture, influencing crystallinity, melting behavior, and mechanical properties.

Production and structure: PLA is typically prepared by ring-opening polymerization of lactide, the cyclic dimer of lactic acid. Industrial routes also include direct polycondensation of lactic acid, though this method is less common due to challenges in removing water. The lactic acid feedstock is commonly produced by fermentation of sugars from renewable resources such as corn or sugarcane.

Properties: PLA is a thermoplastic that is transparent when amorphous and relatively stiff. Its glass transition temperature is around 50–60°C, and semicrystalline grades melt near 150–160°C. It is biodegradable under industrial composting conditions, breaking down into lactic acid, water, and carbon dioxide over time. Mechanical properties are suitable for many packaging and consumer applications but can be brittle unless modified or blended with plasticizers or other polymers.

Applications: PLA is widely used in packaging films and thermoformed containers, disposable tableware, fibers, and increasingly in consumer electronics casings and medical devices. It is also popular in additive manufacturing, where PLA serves as a common 3D-printing filament.

Environmental considerations: PLA is derived from renewable resources, offering potential reductions in fossil-fuel use. Its environmental footprint depends on feedstock sourcing, processing energy, and end-of-life management. Although compostable under appropriate facilities, PLA does not readily biodegrade in standard natural environments, and its recycling requirements differ from those of conventional plastics.

History: Research on polylactic acid dates to the mid-20th century, with commercial production expanding in the early 2000s through joint ventures such as NatureWorks' Ingeo PLA.